The MEMS Industry Group, a trade association representing the MEMS and microstructures industries, has launched a MEMS Marketplace online “matchmaking” portal that enables MEMS companies to connect with prospective customers and partners.

The portal is designed for companies in the entire MEMS supply chain, from material suppliers to original equipment manufacturers. It also provides a networking forum for MEMS companies interested in collaborative or customer relationships. Users can search for specific products and services offered by MEMS device manufacturers, foundries, wafer suppliers, equipment suppliers, MEMS-specific software providers and market research analysts. Information is broken down into four search options: by category, product, company, and industry.

Participating companies can manage their profiles, update product/service listings, and post recent press releases by logging in to the profile management area of MEMS Marketplace.

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Nano to fight flying fish? USGS seeks funding

Advanced BioNutrition Corp. and the US Geological Survey are looking to partner on a project to evaluate whether nanotechnology can control flying carp in Wisconsin waterways.

According to the local Onalaska Holmen Courier-Life, a USGS biologist asked the Lake Onalaska Protection and Rehabilitation District if it could test MicroMatrix, a product that delivers a range of bioactive compounds in animals and human foods, at its French Island facility to see if it will work with flying carp and other aquatic invasive species. The USGS doesn’t have the roughly $3 million it would cost to fund the first year of the three- to five-year study; while Advanced BioNutrition builds a working prototype the USGS can test, local officials are writing to congressional reps, fishing for funding.

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Winners, losers in 2008 MEMS standings

Overall sales for the top 30 MEMS manufacturers inched up 2% in 2008 to $5.5B, held back in large part (and little surprise) to the global economic malaise, according to a recent report by Yole Développement. A closer look, however, reveals more distinct shifts and patterns among suppliers and product segments.

The top two suppliers, HP and Texas Instruments, both saw sales decline, but held onto their positions still by a wide margin. New No. 3 STMicroelectronics moved ahead of Robert Bosch, followed by Canon, and Seiko Epson (all separated by ~$16M); Freeescale came in seventh, with the top 10 rounded out by Lexmark, Analog Devices, and Avago (all separated by a small margin, ~$19M or <10% of sales). On the other end of the scale, Kionix and Micralyne entered the top 30 rankings for the first time; Delphi and Sanyo were bumped out. (Yole notes its rankings only include providers of silicon MEMS chips.)

Preliminary top 30 worldwide MEMS manufacturers based on estimated 2008 MEMS revenues. Click here to enlarge image

Top growth in 2008 went to Kionix (70%), with 18 of the top 30 MEMS manufacturers showing sales growth vs. 2008. FormFactor (-51%) suffered the biggest declines among the 12 firms who saw sales slide year-on-year.

The economic crisis was felt across the MEMS spectrum, but its depth varied among product sectors. Automotive was likely hurt the worst (-10% to -20%), though within this sector emerging devices such as tire pressure monitoring systems fared better than mature products, such as airbag accelerometers. And individual companies within sectors fared differently, too. Systron Donner sunk -14% to 13th place, and VTI lost -10% (in euros) attributed to a slowdown in the automotive market. Bosch, meanwhile, though it also suffered a -10% decrease, is better positioned with a new 200mm fab ready to start production when conditions improve, Yole surmised.

Consumer markets obviously were hurt too, but also varied by sector. Makers of ink-jet heads saw a -15% decreased in sales and saw units decline too. Inertial MEMS products, however, in general saw growth “in the range of several %), with STM and ADI pacing this sector. ST got a boost from a 42% (in euros) jump in its accelerometer business.

Other snippets from the Yole report:

• Avago’s 2008 sales ($183M, #10 overall) don’t include the $38M (Yole estimate) attributed to Infineon’s former the bulk acoustic wave (BAW) filter business, which it bought in September – that would probably be enough to leapfrog #9 ADI. Measurement Systems, meanwhile, enjoyed a five-spot boost through integration of Intersema (in January 2008, adding ~$17M).
• Boeringher Ingelheim microParts enjoyed 9% growth (in euros) thanks to the biomedical market.
• Texas Instruments saw its DLP chip sales sink about 13% (in US $).
• Panasonic (#16, $124M, up three spots) likely has taken market share in gyroscopes from Murata (#20, $86M, -4%) and SSS (#30, $30M, -14%), Yole says.
• As for the two who fell off the list: Sanyo stopped its foundry activity, and Delphi “has dramatically reduced its MEMS staff,” Yole pointed out.

Editor’s note: Yole and SEMI will again publish their MEMS supply chain market report as a benefit for SEMI members, detailing key developments impacting equipment and materials suppliers, and the market outlook for these sectors.

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MEMS sector takes hit from auto, economy slump

As the economy slogs along, big-ticket consumer purchases such as cars have dried up; shipments slipped 8% in 2008 and are expected to sink 19% in 2009. And that’s bad news for, among others, suppliers of automotive electronics, noted iSuppli in a pair of reports tracking the sector.

A notable casualty of the hurting auto sector are MEMS sensor suppliers, whose technology is used for applications such as vehicle stability control, airbags, and satellites. MEMS sensor companies saw sales decay more than the actual auto industry in 2008 (-6% to -15%). Industry leader Robert Bosch GmbH led the pack with $429M in sales (~80% of that for internal consumption in its automotive subsystems) and a -6.1% Y/Y decline (Figure 1).

Figure 1. Global automotive MEMS supplier sales. Click here to enlarge image

The strain on automotive MEMS suppliers has caused casualties. Systron Donner Automotive, the world’s second-largest supplier of car quartz MEMS gyroscopes (behind Bosch), was shut down by French parent Schneider Electric, laying off all engineers and leaving a skeleton crew to meet contractual commitments. “This is major turnaround for a company that sold nearly $105 million worth of MEMS vehicle dynamics gyroscopes in 2008,” noted Richard Dixon, iSuppli senior analyst for MEMS, in a statement. “The company was under competitive siege and already was beginning to lose market share at its key long-time customer, Continental, to Panasonic, which is offering a cheaper product.”

Meanwhile, Infineon has said it wants to sell off its Norwegian unit Sensonor to private investors. “The recent downturn […] has especially hit the market for tire pressure monitors sensors (TPMS),” Dixon said. Shedding its unit “will help balance Infineon’s books in the short term and has little impact on its market-leading position.” Some process steps done in Sensonor’s site in Horten, Norway, will be merged with Infineon’s TPMS production in Austria, simplifying the supply chain, he said. “But the major impact is to Infineon’s capability to innovate, as the Sensonor group represented an R&D team par excellence.”

Government mandates for multiple MEMS-driven capabilities such as gyroscopes, accelerometers, and pressure sensors for tires and brakes have kept the sector from sliding any further. “In the past TPMS has been presented as the new El Dorado of the automotive MEMS market,” wrote Richard Dixon, senior analyst for MEMS at iSuppli. “Today TPMS is a US market due to a mandate that required fitment in all cars by the end of 2007.” He forecasts the auto MEMS sector will return to “healthy” growth in 2010, and double-digit revenue growth in 2011, as such systems will become mandatory on vehicles in the US starting in 2012, and in the EU starting 2014 (Figure 2).

Figure 2. MEMS market in US $M for automotive applications, 2006-2013.Click here to enlarge image

One key point about that growth hinges on what type of TPMS will be adopted. “Indirect” TPMS systems use an algorithm to model wheel rotation speed, this requiring only one sensor (which makes the system less expensive). Direct TPMS systems, now being employed in the US, use separate sensors inside each tire to detect pressure levels (and are more accurate, and expensive). The EU is still working on its regulations, and this point of which system to require is yet undecided; final regulations are due in November. “Much of the growth in the future market will hinge on whether or indirect systems can meet the accuracy requirements of the European mandates,” Dixon wrote.

Government mandates aren’t just key to growth in the auto MEMS sector, they’ve significantly reshaped the landscape of suppliers. “Taking a technology that has only been used in luxury cars in the past and putting it into every car, including those that cost less than $10,000, is a big challenge for the major established players in the MEMS market,” Dixon noted (citing as Exhibit A the Schneider Electric/Systron Donner shuttering).

Another key factor to auto MEMS growth is China, which is poised to become the global leader in auto production in 2009. “Unlike India, China is not a low-cost market for cars and there is a higher sensor content in the cars it makes,” pointed out Jérémie Bouchaud, iSuppli principal analyst for MEMS, adding that China also imports a lot of cars. Biggest opportunities are in power-train sensors; “safety is not expected to be the biggest driver in terms of sensor suppliers,” he noted.

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NYU touts DNA-enabled nanoparticle glue

Researchers at New York University say they’ve created a method to precisely bind nanoparticles into larger structures that overcomes a “sticky” problem and enables creation of stable, sophisticated microscopic and macroscopic structures.

The work, reported in an advanced online publication by Nature Materials, describes confronting the problem of self-replication: when the number of objects doubles in each cycle it presents a linear challenge when trying to fabricate things microscopic objects with a sophisticated architecture.

Their solution? Coat micrometer particles with short stretches of DNA (“sticky ends”), each with a particular sequence of DNA building blocks; those with complimentary sequences form reversible bonds when a certain temperature is applied. Thus, the particles can be organized in a controlled fashion onto a template, and then released again.

The novel DNA ‘sticky ends’ can form intra-particle loops and hairpins (e.g. schemes II & III), giving more control over the particles’ interactions than conventional sticky ends that can only form inter-particle bridges (scheme Ia). Click here to enlarge image

DNA-mediated interactions are known, but binding only subsets of a particle (not the whole thing) into structures has proven difficult. So the researchers at NYU’s Center for Soft Matter Research and in the university’s Department of Chemistry focused on a particular type of DNA sequence that can fold like a hairpin and bind to neighboring “sticky ends.” Lowering the temperature, they determined, rapidly caused the sticky ends to fold up on the particle before they could bind to other sticky ends. This occurred long enough (a few minutes) for the sticky ends to find binding partners on other particles moved around by optical traps, thus building a structure (see video above). “We can finely tune and even switch off the attractions between particles, rendering them inert unless they are heated or held together–like a nano-contact glue,” said Mirjam Leunissen, the study’s lead author, in a statement.

Micrometer-sized particles, functionalized with self-protective scheme II sticky ends, are collected in a circular array of point-like optical traps. Relatively low system temperature gives good self-protection of the sticky ends and thus ample time to release superfluous particles from doubly occupied traps without forming unwanted doublets. Near the end of the movie, we shrink the array to bring the particles in close proximity. Click here to enlarge image

Potential applications include ordering arrays of these particles into optical devices such as sensors and photonic crystals. The same organizational principles also apply to smaller nanoparticles, which have a range of useful electrical, optical, and magnetic properties, NYU noted.

The work was supported by the NSF’s Materials Research Science and Engineering Center (MRSEC) program, the Keck Foundation, and the Netherlands Organization for Scientific Research.

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Russian officials at odds over nanotech success

Recent media reports indicate Russia wants to better track its nanotech production, and is traveling the globe to press its interests and grow its position in the worldwide market–but a top government official isn’t convinced that current efforts are up to the job.

Nobody currently knows how much “nanotechnology production” there is in the country, pointed out Anatoly Chubais, the head of state-owned nanotech business group RUSNANO, which is teaming with the State Statistics Service to develop a tracking system. RUSNANO reportedly wants to help Russian companies win 3% of the global nanotechnology market by 2015 as part of the government’s drive to diversify the economy, according to the Moscow Times.

Russia isn’t just examining its own domestic capabilities. It’s proposed to pump at least $10M into Canada’s nanotech industry, according to a report by Canwest News Service; the investment could inject life into the sector, according to Neil Gordon, former head of the now-defunct Canadian NanoBusiness Alliance, who told Small Times contributing editor Howard Lovy that the “Canadian government [has] ignored the massive economic development opportunity from nanotechnology.”

RUSNANO’s Chubais also reportedly was in Israel in March to deepen discussions about ways the two countries can cooperate in nanotechnology development, meeting with President Shimon Peres (a longtime nanotech-development advocate) and Prime Minister-designate Benjamin Netanyahu, reported the Itar-Tass news service. RUSNANO representatives met with Israeli scientists and businessmen last fall.

But Russia’s top government official isn’t fully on board with the idea that state-owned corporations are up to the job in nanotech. “[Rusnano] is the kind of instrum×ent that sometimes works and sometimes doesn’t work at all,” said Russian President Dmitry Medvedev, quoted by the Moscow Times. The group, he added, is a “large structure that has a lot of money and that still has to understand how to correctly spend it,” so that it is not blamed for wasting it in the future.

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Ears have nanoscale ‘flexoelectric’ motors

Utah and Texas researchers have discovered what they call a “nanoscale motor” in the human ear: hair-like tubes atop “hair cells” that dance back and forth, acting as “flexoelectric motors” that amplify sound mechanically.

Previous research elsewhere indicated that hair cells (each ~10µm × 30-100µm) within the cochlea of the inner ear can “dance” (elongate and contract) to help amplify sounds. The new study by Richard Rabbitt, the study’s principal author and a professor and chair of bioengineering at the University of Utah College of Engineering, and colleagues at Utah and Baylor College of Medicine in Houston, shows sounds also may be amplified by the back-and-forth flexing or “dancing” of “stereocilia,” the 50-300 hair-like nanotubes (1-10µm × ~200nm) projecting from the top of each hair cell. This flexing converts an electric signal generated by incoming sound into mechanical work (more flexing of the stereocilia), thereby amplifying the sound by a “flexoelectric effect.”

The tops of the stereocilia tubes are connected by protein filaments; at those connection points is an “ion channel” that opens and closes as the bundle of stereocilia sway back and forth. When the channel opens, electrically charged calcium and potassium ions flow into the tubes, which changes the electric voltage across the membrane encasing each stereocilium, making the tubes flex and dance even more. Such flexoelectricity amplifies the sound and ultimately releases neurotransmitter chemicals from the bottom of the hair cells, sending the sound’s nerve signal to the brain.

Cross-section of part of the cochlea, the fluid-filled part of the inner ear that converts vibrations from incoming sounds into nerve signals that travel to the brain via the auditory nerve. University of Utah and Baylor College of Medicine researchers found evidence that stereocilia–bundles of tiny hair-like tubes atop “hair cells” in the cochlea–dance back and forth to mechanically amplify incoming sounds via what is known as the “flexoelectric effect.” Click here to enlarge image

The researchers estimate the combined flexoelectric amplification by hair cells and the stereocilia atop them enables humans to hear the quietest 35-40 dB of their range of hearing. Rabbitt says the flexoelectric amplifiers are needed to hear sounds quieter than the level of comfortable conversation; the cells are said to be sensitive enough to detect sounds almost as small as those caused by Brownian motion.

The researchers’ calculations and computer simulations deduced that “a longer stereocilium was more efficient if it was receiving low-frequency sounds,” while shorter stereocilia most efficiently amplified high-frequency sound.

In addition, the researchers speculate that flexoelectrical conversion of electricity into mechanical work also might be involved in processes such as memory formation and food digestion. The stereocilia involved in amplifying hearing are similar to other tube-like structures in the human body, such as villi in the gut, dendritic spines on the signal-receiving ends of nerve cells, and growth cones on the signal-transmitting axon ends of growing nerve cells.

The study, part of an effort by researchers to understand the amazing sensitivity of human hearing, is published in PLoS ONE, a journal published by the Public Library of Science.

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IMEC paves way to deep-brain stimulation

IMEC says it has created a prototype multi-electrode stimulation and recording probe for deep-brain stimulation, which beyond the medical applications highlights the opportunities in the healthcare market for design tool developers.

Brain implants for electrical stimulation of specific brain areas are used as a last-resort therapy for brain disorders such as Parkinson’s disease, tremor, or obsessive-compulsive disorder. Conventional deep-brain stimulation probes use millimeter-size electrodes which stimulate a large area of the brain, “and have significant unwanted side effects,” IMEC notes. However, more precise stimulation and recording is achievable with electrodes as small as neurons built using semiconductor process technology, design tools, and electronic signal processing, notes Wolfgang Eberle, senior scientist and project manager at IMEC’s bioelectronics research group.

IMEC’s design and modeling strategy relies on finite-element modeling of the electrical field distribution around the brain probe (using multiphysics simulation software COMSOL); this also enabled investigation of the mechanical properties of the probe during surgical insertion and the effects of temperature. Results indicate that adapting the penetration depth and field asymmetry allows steering the electrical field around the probe, which results in high-precision stimulation. Another key was development of a mixed-signal compensation scheme enabling multi-electrode probes capable of stimulation as well as recording, needed to realize closed-loop systems.

A prototype multi-electrode stimulation and recording probe for deep-brain stimulation. Click here to enlarge image

The result of IMEC’s work is creation of brain implants consisting of multiple electrodes with simultaneous stimulation and recording. Prototype probes with 10µm-size electrodes and various electrode topologies have been built; the new design approaches also point to ways to achieve more effective stimulation with fewer side effects, reduced energy consumption (due to focusing the stimulation current on the desired brain target), and closed-loop control adapting the stimulation based on the recorded effect.

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Ex-EPA official calls for new agency to oversee nanotech

Existing health and safety agencies are unable to cope with the risk assessment, standard setting, and oversight challenges of advancing nanotechnology–so J. Clarence (Terry) Davies, in a recent paper, “Oversight of Next Generation Nanotechnology,” calls for a new Department of Environmental and Consumer Protection to oversee product regulation, pollution control, and monitoring and technology assessment.

The proposed agency would foster more integrated oversight and a unified mechanism for product regulation to deal with current problems like toxics in children’s toys and newer challenges like nanotechnology. A more integrated approach to pollution control was necessary even before EPA was created, and since that time the need has only increased, according to Davies.

“Federal regulatory agencies already suffer from under-funding and bureaucratic ossification, but they will require more than just increased budgets and minor rule changes to deal adequately with the potential adverse effects of new technologies,” he says. “New thinking, new laws, and new organizational forms are necessary. Many of these changes will take a decade or more to accomplish, but there is an urgent need given the rapid pace of technological change to start thinking about them now.”

Davies served during the George H.W. Bush administration as Assistant Administrator for Policy, Planning and Evaluation at the US Environmental Protection Agency. In 1970, as a consultant to the President’s Advisory Council on Executive Organization, he co-authored the plan that created EPA. As a senior staff member at the Council on Environmental Quality, he wrote the original version of what became the Toxic Substances Control Act (TSCA).

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MIT virus battery could power cars

MIT researchers have genetically engineered viruses to build both the positively and negatively charged ends of a lithium-ion battery, with comparable energy capacity/power as batteries in hybrid cars, and could also be used for personal electronic devices.

The new batteries, described in the April 2 online edition of Science, could be manufactured with a cheap and environmentally benign process: The synthesis takes place at/below room temperature and requires no harmful organic solvents, and the materials that go into the battery are non-toxic.

In a traditional lithium-ion battery, lithium ions flow between a negatively charged anode (usually graphite) and the positively charged cathode (usually cobalt oxide or lithium iron phosphate). Angela Belcher and co-researchers already had engineered viruses that coat themselves with cobalt oxide and gold and self-assemble to form a nanowire.

Their latest work extends the work by building a cathode to pair up with that anode. Because most candidate materials for cathodes are highly insulating (non-conductive), the team genetically engineered viruses (a common bacteriophage) that first coat themselves with iron phosphate, then grab hold of carbon nanotubes to create a network of highly conductive material. As the viruses recognize and bind specifically to the CNTs, each iron phosphate nanowire can be electrically “wired” to conducting carbon nanotube networks. Electrons travel along the CNT networks, percolating throughout the electrodes to the iron phosphate and transferring energy.

In lab tests, batteries with the new cathode material could be charged and discharged at least 100× without losing any capacitance; that’s fewer charge cycles than currently available lithium-ion batteries, but Belcher predicts “much longer” lifetimes. The prototype is packaged as a typical coin cell battery, but the technology allows for the assembly of very lightweight, flexible, and conformable batteries that can take the shape of their container. Future work will pursue better batteries using materials with higher voltage and capacitance, such as manganese phosphate and nickel phosphate, and from there look to improve the technology and processes for commercial production.

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Catilin, Ames develop algae ‘nanofarming’

Algae as a biofuel catalyst is a promising field. Up to 10,000 gallons of oil can be produced on a single acre of land; the US Department of Energy extrapolates that replacing all the petroleum fuel in the US would require 15,000 sq. miles, less than 1/7 the area devoted to corn production (and just a tad bigger than Maryland). One of the challenges in creating promising biofuels from algae is that extracting the oil from the algae tends to kill the organisms. To this end, researchers at Iowa State University and the DoE’s Ames Laboratory say they have developed a “nanofarming” technology that safely harvests oil from the algae so the pond-based “crop” can keep on producing–and keep costs low.

The “nanofarming” technology uses nanoparticles to extract oil from the algae; once the algal oil is extracted, a separate solid catalyst from Catilin will be used to produce ASTM (American Society for Testing and Materials) and EN certified biodiesel.

Ames Labs, Iowa State, and Ames spinoff Catilin are involved in a three-year cooperative R&D project; phases one and two will cover the culturing and selection of microalgae as well as development of the specific nanoparticle-based extraction of algal oil, and catalyst technologies for production of biodiesel. Phase three will focus on scale-up of the catalyst and pilot plant testing on conversion to biodiesel.

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Stanford sets new record for smallest letters

A novel technique is enabling Stanford researchers to push individual molecules into specifically arranged patterns, and reclaim their title of producers of the world’s smallest letters.

The researchers encoded 35 bits of information per electron and wrote the letters “S” and “U” (of course) composed of 0.3nm bits, a feat that edges out researchers at Japan’s Hitachi, who in 1991 set the record for microscopic calligraphy by chiseling 1.5nm-tall letters into a crystal. The demonstration suggests information could be stored more densely providing greater speed and storage capacity for modern computers.

Using a scanning tunneling microscope, researchers Hari Manoharan and Christopher Moon arranged individual carbon monoxide molecules on a copper surface in a complicated 2D pattern with a void in the middle, into which was projected electronic versions of the letters. The constant flow of electrons naturally present on the copper surface scattered any carbon monoxide molecules and worked to project holographic patterns of the letters into the void. Essentially, the pattern functioned as a molecular hologram, illuminated with electrons instead of light, they claim.

Molecular holograms are fashioned with scanning tunneling microscope manipulation. When illuminated by two-dimensional electron gas, a three-dimensional holographic projection is created.Click here to enlarge image

“Imagine the copper as a very shallow pool of water into which we put some rocks [the carbon monoxide molecules],” said Manoharan, in a statement. “The water waves scatter and interfere off the rocks, making well-defined standing wave patterns.” If the rocks are positioned just right, the wave patterns will form into letters.

The research, supported by the National Science Foundation, the DoE’s SLAC National Accelerator Laboratory, the Stanford Institute for Materials and Energy Science, the Office of Naval Research, and the Stanford-IBM Center for Probing the Nanoscale, was published online in Nature Nanotechnology.

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Gold nanoparticles could ‘cook’ cancer cells

Researchers presenting at the American Chemical Society’s 237th National Meeting in March, and in Clinical Cancer Research in February, described an advance in the nanotech-enabled fight against cancer: the first hollow gold nanospheres that can search out and “cook” cancer cells, showing particular promise as a minimally invasive future treatment for malignant melanoma, the most serious form of skin cancer.

The nanospheres are equipped with a special “peptide” to a protein receptor abundant in melanoma cells, which draws the spheres to the cancer cells while avoiding healthy skin cells. After collecting inside the cancer the nanospheres heat up when exposed to near-infrared light. Studies in mice showed the hollow gold nanospheres did 8× more damage to skin tumors than the same nanospheres without the targeting peptides.

“It’s basically like putting a cancer cell in hot water and boiling it to death. The more heat the metal nanospheres generate, the better,” explained study co-author Jin Zhang, a professor of chemistry and biochemistry at the University of California in Santa Cruz, in a statement. Zhang’s team worked with Chun Li at the University of Texas M.D. Anderson Cancer Center in Houston.

Transmission electron microscope images, showing (A) hollow gold nanospheres with average size of ~30nm, and (B) an individual hollow gold nanosphere with diameter 29.1nm and wall thickness ~5nm. (Image courtesy of Jin Zhang)Click here to enlarge image

This form of cancer therapy is a variation of photothermal ablation (photoablation therapy or PAT), a technique that uses light to burn tumors–but also can destroy healthy skin cells, so it requires careful control of duration and intensity. Applying a light absorbing material such as metal nanoparticles to the tumor greatly enhances the PAT treatment, but ideal candidates must have both good penetration into the cells and limited heat-carrying capacity. Solid gold nanoparticles and nanorods don’t possess both qualities; Zhang’s creation in 2006 of gold nanoshells (30-50nm in size) did, and were safer than other metal nanoparticles, he noted.

Li emphasized, though, that the next step is human trials, which will require “extensive preclinical toxicity studies,” and that “there is a long way to go before it can be put into clinical practice.”

Nanoscale properties enable improved thermoelectrics, NEMS gas sensors

By Dr. Paula Doe, contributing editor

The much-hyped properties of materials at the nanoscale are finally starting to be applied to some real electronics applications, ranging from near-ideal thermoelectric material based on spray-on semiconductor nanocrystals, to transparent conductive films made from on carbon nanotubes and self assembled silver nanoparticles, to ultrasensitive nanoscale MEMS gas sensors.

Nanoscale materials properties are enabling efficient, low-cost thermoelectric materials. Though long studied, thermoelectric conversion of heat to electricity have never been efficient enough to be practical for most applications. “They were stuck with natural materials,” says Evident Technologies CEO Clinton Ballinger. “But with nano-structured materials you have a lot more materials to work with. You can change the thermal properties.” That means it is possible to design something that approximates the ideal thermoelectric material, conducting electricity well but not heat. Modeling suggests that the most efficient structure would be point sources of excited electrons distributed evenly in a matrix–and that ideal efficient material can be approximated quite well by a low-cost solution, using colloidal ink containing semiconductor nanocrystals to create a bulk material while retaining the nano properties.

Ballinger suggests that some of the first markets for this technology will be in the semiconductor industry, where it could enable efficient, flexible, solid-state cooling for integrated circuits and LEDs. This could greatly reduce the size or need for a heat sink, he argues, and potentially improve performance. “Right now we’re just spraying it on with an airbrush,” he notes. “So it could likely be coated right on the chip for thermoelectric cooling.”

First application is likely to be for less sophisticated solid-state cooling, though, such as spot cooling for things like wine coolers. But eventual markets for low-cost roll-to-roll coated thermoelectric films could also include waste heat recovery in automobiles and central power stations, general heating and cooling, and even power generation.

Likely closer to market are transparent conductive films using innovative nanomaterials to potentially challenge ITO. Unidym is sampling a transparent conductive film based on carbon nanotubes for touch panel displays and readying production capacity. CimaNanotech is similarly sampling its flexible film product based on self assemble of silver nano particles, for which Toray Advanced Films is the production coating partner.

Pushing MEMS to the nanoscale opens up new potential as well. “The advantages go beyond scaling,” says Caltech professor Michael Roukes, whose lab has been driving developments for the last 15 years. “The physics scales in a profound way.” This means MEMS-based detectors in an electronic nose can be made significantly more sensitive, as well as scaled down in size by about a million fold, compared to the existing state-of-the-art–and made with efficient wafer-scale processes.

Roukes’ lab and CEA-Leti are now routinely mass producing arrays of these nano MEMS sensors on 8-in. wafers, and recruiting corporate partners to their Alliance for Nanosystems VLSI for the final stage of developing the MEMS and CMOS processes to integrate them into practical low-cost gas-phase chemical sensors, to monitor toxic industrial gases and gas phase processes, or to analyze human breath to detect diseases.

The detectors are essentially arrays of nanoscale MEMS resonators–fancy versions of guitar strings–set within MEMS flow channels. The resonators are coated with a kind of chemical sponge that absorbs the target material, which changes the mass of the resonator. The gas is first sent through a chipscale version of a gas chromotograph process, to simplify the identification problem.

Though first markets will likely be military and industrial, the most interesting potential may be in medical diagnostics. “There are a few validated tests for detecting lung cancer and other diseases from the gases in the breath, enough to suggest this is a fertile area,” says Roukes, even though studies so far require large-scale lab instrumentation, so are hard to do. “The more easily and routinely this could be deployed, the more deeply it could be studied,” he notes.

All these structures can be made at 90nm, though 45nm would be preferable, says Roukes. He notes that with the device arrays successfully being produced at wafer-scale, current efforts are directed towards precursor systems including surface chemical functionalization and integration en masse with both MEMS flow channels and CMOS circuits for data post processing.

These companies will be among those discussing their latest developments in the program on Emerging Commercial Applications of Nanoelectronics at SEMICON West, July 14-16 in San Francisco. SRC Nano Electronics Initiative director Jeff Welser will also give a mini keynote on the interesting properties of graphene and spin wave transistors with potential to impact the semiconductor industry further out. The program is part of the Extreme Electronics series on emerging technology opportunities for the semiconductor manufacturing supply chain. For details, see www.semiconwest.org.

by Gerhard Lammel and Julia Patzelt, Bosch SensorTech

Inside of buildings, even the newest GPS navigation units quickly hit their limits–their navigational abilities are so inexact that a few floors can stand between the goal they indicate and the actual one. These are extremely poor qualifications for location-based services. An experimental study recently proved that the BMP085 pressure sensor can resolve not only the imprecision of GPS indoor navigation in a cost-efficient manner and without requiring additional infrastructure, it can also substantially improve locating in urban canyons.

In order for a navigation unit with GPS to provide exact positioning information within a few meters, the device has to receive data simultaneously from as many GPS satellites as possible. This requirement is fulfilled most easily on flat land under the open sky. However, as soon as obstacles block the unit’s view of the satellites, and it receives data from fewer than four satellites, the 3D positioning quickly becomes a game of chance.

Older GPS units are practically blind inside of buildings. A single wall within a structure generally damps a GPS signal in the 1.5GHz range by 20–30dB (factor of 100 to 1000), while reinforced concrete has the greatest dampening impact. The weak, useful signal is then drowned in the static of broadband HF receiving modules in these situations; a signal-to-noise ratio sufficient for determining position can no longer be reached using correction algorithms, and the navigation unit fails.

Indoor navigation: More than comfort

Unerring navigation within buildings is as advantageous for pedestrians as outdoor navigation is for drivers. In large foreign airports, for example, passengers could effortlessly find the correct check-in counter and from thence their departure gate. In large shopping centers and malls, they could be guided directly to businesses or restaurant without detours. New forms of location-based services, linked to GPS-equipped cell phones, could be offered for these environments. Imagine a note about a special sale at a certain store, or a restaurant’s reasonably priced lunch menu; once a person expresses interest, a GPS-equipped cell phone could immediately provide navigation to the new goal. For professional usage, examples include various types of support–a maintenance technician unfamiliar with the plant could traverse an extensive industrial complex, or merchandise could be unerringly delivered, even by someone not well acquainted with the locale. The possibilities for use by first responders are of incalculable value–no longer would they have to fumble through complex corridors, instead they could be directly guided to the location where they were needed.

Small errors have embarrassing effects without floor accuracy

All of the uses for indoor navigation listed are based on the concept that navigation within buildings decisively requires vertical “floor accuracy” (along the z-axis). If one assumes that building floors are 4m in height, then a positional accuracy of only 10 vertical meters for a GPS unit can easily steer one to the wrong floor. The people so affected would, however, only notice the error when they had arrived at the putative goal, then have to retrace their steps, perhaps along both floors in question, in order to finally arrive at their destination. This type of indoor navigation is both worthless and counterproductive. A positioning error of 10m has far less impact when it occurs horizontally (along the x- or y-axis); in the former case, floors and ceilings do not bar one’s view of the goal, which can generally be quickly reached by traveling a few more steps.

Figure 1. Indoor altitude measurement values comprised using a modern GPS navigation device in an office building. The fluctuations from the actual value (30m) are substantial over time.Click here to enlarge image

A limited type of GPS navigation within buildings has only become possible with the most recent navigation devices, equipped with new, highly sensitive receivers. However, multipath reception is omnipresent in buildings, caused by repeated signal reflections off walls, ceilings and floors; distortions of the signal propagation time significantly reduce the accuracy of positioning within buildings, especially in comparison with navigation under the open sky. Figure 1 quantifies the quintessential positioning error along the z-axis. The statistical measuring point was located at a height of 30m in the third floor of a three-story office building. The navigational unit used for the test could determine the elevation within the building, but without great accuracy. Over the course of the observation time of ~13min, during which time the actual position of the device at 30m did not change, the position measured along the z-axis fluctuated between 10–50m. Despite the most modern reception technology, the indoor positioning error of ±20m greatly exceeded that which is acceptable for floor-accurate navigation (=4m).

Pressure sensor for floor-accurate GPS indoor navigation

With its BMP085 pressure sensor, Bosch SensorTech already has the solution to the “floor-accurate GPS navigation” problem, with a very small (5mm × 1.2mm), yet highly exact digital barometric pressure sensor, constructed using MEMS (microelectromechanical systems) technology. At every point in the earth’s atmosphere, air pressure and elevation (as it relates to sea level) have a fixed relationship; by measuring the air pressure, the exact altitude of a measuring point can be calculated. The BMP085 has extremely high-pressure resolution of max. ±0.03 hPa (RMS), which when converted to altitude corresponds to a resolution of ±0.25m (at sea level). At this level of accuracy, the sensor can essentially recognize the difference in altitude that a person undergoes as they move from one step to the next on a flight of stairs.

Figure 2. The SiRFstarIII chip set offers a user input function for storing altitude information gained using a separate pressure sensor.Click here to enlarge image

A prerequisite for transmitting exact knowledge of momentary elevation to a chip set is excluding the less exact altitude information, generated in parallel via GPS. Bosch SensorTech’s SiRFstarIII chip set (Figure 2) incorporates the usual NMEA protocol, plus a proprietary binary protocol that enables settings that reach deeper on the chip set, making it possible to influence the type of positional calculation. In normal operation, the chip set decides automatically about the best type of calculation (four possibilities are available) with regard to the situation, independent from the number of satellites the receiver can see at the moment. The “2D fix” type of calculation is the most favorable for inputting barometrically measured altitude; the chip set normally uses this when it only has reception from three satellites. By this means it sets the elevation to a fixed value in order to reduce the number of unknowns in its formula for calculating position.

Results of an experimental study using a BPM085/GPS coupling

An “Alt Hold Mode” feature with the SiRF technology enables storage of the navigating engine in the SiRFstarIII chip with the measured values of the BMP085. Bosch SensorTech conducted an experimental study using practical tests to examine which results this BMP-GPS coupling would involve. The goal was to determine if the coupling of the GPS chip set with the pressure sensor provided not only a better level of accuracy for vertical navigation, but also whether this positively affected horizontal navigation.

The barometric pressure measurement increases the accuracy of GPS navigation: vertically, in every condition horizontally, and only in urban canyons.Click here to enlarge image

After setting the Alt Hold Mode parameter to “always use input altitude,” the SiRF chip set adopted the barometrically measured elevation as the new input variable. Also, a software interface was installed between the pressure sensor and the GPS chip set to turn off several negative influences on the positioning accuracy:

Recognition of climatic and artificial pressure fluctuations. Weather can cause strong fluctuations in air pressure (up to ±40hPa) that should not be interpreted as changes in elevation. An already extant algorithm analyzed the course of pressure fluctuations, and excluded rather slow changes typical of weather influences (<2.5hPa/h) from measured values. It similarly resolved abrupt, artificial pressure fluctuations, caused by air conditioning, ventilation systems, or a strong wind through open windows.

Statistical reduction of measurement errors. A BMP085 can perform up to 128 pressure measurements per second. Averaging over several measured values eliminates statistical outliers.

Figure 3. Principle of dynamic zero compensation. During indoor navigation, the high-resolution BMP085 signal replaces the weak, inexact GPS signal (left). During periods of strong reception, the highly accurate GPS signal calibrates the pressure sensor (middle). In urban canyons, the pressure sensor again replaces the GPS altitude signal, which has become unreliable due to multipath reception.Click here to enlarge image

Calibration compensates for absolute measurement errors. Independent of its height resolution, the BMP085 has an absolute measurement error of ±2.5hPa (±20m). This error was demonstrated to be easily compensated for–at good GPS reception, i.e. at the maximum GPS positional accuracy, height values determined via GPS by the navigation device were used automatically as calibration values for the pressure sensor. If the GPS reception deteriorated, then the high-resolution barometric altitude values–based on the most recently calibrated values–came into play (Figure 3). A Kalman filter determined whether or not to use situational calibration in this example.

The results of the experimental study of a SiRFstarIII with a BMP085 as external user altitude input are compiled (see table on p.22). The pressure sensor guaranteed indoor navigation at a floor-accurate level, thereby allowing the user to reach his or her destination; it also significantly increased the vertical positioning accuracy when used outdoors. In addition to a drastic reduction in the altitude error (visible only in the bar graph), the error in horizontal direction due to sensor support is also significantly smaller, with a standard deviation reduced by ~60%. This unexpected positive effect on horizontal positioning could, however, only be observed in comparable situations, such as in “urban canyons”.

BMP085 pressure sensor

Introduced in 2008, the BMP085 in an LCC-8 housing has a measuring range of 300–1100hPa and high over-pressure resistance at 10,000 hPa. Specifically developed for use in consumer electronic mobile devices, the sensor requires only 3µA of power (in ultra-low-power mode), with a low idle current consumption in stand-by mode of 0.1µA. The minimum supply voltage was also reduced to its current 1.8V. A 19-bit measurement operation on applications takes place inclusive of calibration data for temperature compensation in serial via an I2C 2-wire interface, which simplifies the integration of the BMP085 into already extant applications and eliminates the need for additional external components for wiring. At its slowest, a new measured value is ready for collection every 7.5ms.

---

Dr. Gerhard Lammel is manager of engineering at Bosch SensorTech GmbH, a wholly owned subsidiary of Bosch SensorTech.
Julia Patzelt is responsible for marketing communication and public relations at Bosch SensorTech GmbH.

---

No infrastructure required

At present, alternatives to satellite navigation are being developed and tested globally for indoor and urban navigation. Locating takes place by cross bearing, determining position by using the distance-dependent intensity of HF signals, which can be emitted by terrestrial transmitters from exactly known locations. The specific advantage is that the current transmission networks for cellular structures can be used for this form of navigation, without requiring a completely new system of transmitters.

This type of system, which functions using currently available WLAN islands, was developed by the Fraunhofer Institute for Integrated Circuits (IIS). The navigation unit constantly analyzes the reception field strength of nearby WLAN spots, and by means of their SSIDs, obtains the exact location of the WLAN transmitter from a central databank, which it then uses to navigate. However, this is not sufficient to also navigate within buildings with a sufficient degree of accuracy. For indoor navigation to function correctly, the navigation unit has to recognize the additional field strength divisions in every building, which in turn requires preliminary mapping measurements. Solutions related to this one convert the same navigational principle, but use different radio systems, such as GSM or DECT.

A communications network infrastructure is imperative for each of these solutions, which in turn requires an (at least periodic) administrative expenditure (e.g. mapping) which is not insignificant. The combination of the BMP085 pressure sensor and GPS is completely different does not require any foreign infrastructure; it functions everywhere, all over the planet, and is completely autarchic, in that the pressure sensor can fundamentally increase the vertical resolution of each of the alternative navigation systems.

Quicker 3D simulation, more practical dry etch, and automated die inspection

By Dr. Paula Doe, contributing editor

Though the MEMS market has remained essentially flat in 2008 and 2009, as plenty of new consumer and medical applications continued healthy growth (see page 6), equipment demand is another story. The MEMS equipment market (new specialty MEMS tools) likely reached less than $200 million in 2008, down from $330 million in 2007, says Yole Développement CEO Jean-Christophe Eloy, and 2009 looks about the same, though visibility is very limited. However, “several specialty MEMS tool suppliers are adding capacity in light of strong order intake so far this year,” he notes. “This growth is driven by the diffusion of MEMS technologies into other markets like 3D ICs, image sensors, and new applications for nanoimprint.”

Virtual fabrication of a MEMS accelerometer by the X-Fab SOI process. Click here to enlarge image

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Click here to enlarge image

Suppliers also see potential in offering new approaches to improve tricky MEMS yields in manufacturing faster, and at lower cost, with solutions for quicker simulation, more practical dry etch, and smarter package inspection.

One option for getting those MEMS devices to yield would be to find design problems by simulation. Some fabs are using Coventor Inc.’s 3D virtual fabrication software to find design flaws or process problems before fabrication, reports Stephen Breit, Coventor VP of product development. Using voxels (cubic 3D equivalents of pixels) instead of traditional compute-intensive CAD-like solid modeling techniques–plus some elegant compression algorithms–allows fast modeling of the entire process sequence. The virtual prototype that results shows real engineering information on how the 2D layout will translate to a 3D device, revealing things like gaps in film coverage or cavities in underlying layers.

Users specify the parameters that impact the MEMS device geometry, like layer thickness, snowfall or conformal deposition, or etch rate ratios between different materials, for each step in the sequence. The modeler then applies a series of strictly geometric operations to generate a realistic virtual prototype of the device. The parameters must be experimentally calibrated, but the simpler modeling process can then simulate the entire fabrication sequence over a large part of the die within a few hours on a desktop computer.

X-Fab now regularly uses the tool throughout design and process development to validate MEMS designs before tape out, saving test wafers, and speeding time to yield.

More practical dry etch

Though wet etch remains the workhorse technology for etching away sacrificial layers to release the functional MEMS structures, at smaller geometries the surface tension effects of trapped moisture tend to stick down the released structures. Dry etch processes prevent this stiction, but they’ve yet to see wide adoption in production. Vapor phase HF etchers still require careful control of the condensation from the water used as a catalyst, and have been relatively low throughput, and the option of using XeF₂ is extremely expensive.

Primaxx proposes to avoid stiction at lower cost with a batch vapor HF system that better keeps water out of the process. It uses low cost anhydrous HF, with low-water electronic grade alcohol for the catalyst, to minimize the H₂O content of reagents going in, control H₂O byproducts and keep them in gas phase, and draw the H₂O away from the etch interface with the alcohol properties. The process also runs at minimal power at 45°C. CEO Paul Hammond says etch rates range from 0.05-5µm/minute, depending on oxide type, and with <10% variability within wafer, wafer to wafer, and batch to batch, on 25-wafer batches of 200mm wafers.

Air Products and Chemicals, meanwhile, is bringing down the cost of using XeF₂ by reclaiming the xenon. Increasing demand for xenon for new applications in flat-panel displays and other electronics is pushing prices up, but the rare gas is also simply costly to extract and distill. It occurs naturally in air only in minute quantities of 87 parts per billion–so manufacturing typically requires some 220 watt-hours to extract one liter of Xe from air, then further purification by cryogenic distillation. This energy-intensive extraction process only makes sense on very large air plant, mostly associated with steel mills, and with the economic downturn they’ve curtailed production, further tightening supplies.

Air Products’ system for the fab reclaims the xenon by-product of the XeF₂ etch process, then sends it back to an Air Products facility for manufacturing into more XeF₂, explains commercial development manager Eugene Karawacki.

Automated package die inspection

Printed circuit board inspection tool supplier Vi Technology is entering the MEMS market by applying its automated optical inspection expertise to automating the inspection of MEMS dies before encapsulation. First customer for the new product started full volume production in mid-May.

The tool replaces traditional inspection by an operator with a microscope with a quick, two-step automated process. The first pass uses a laser to measure the tilt of each die in the package, to make sure products like inertial sensors are correctly seated so they work. It also measures the exact focal distance of the die in the package, adjusting to make sure the optical system can see from the top to the bottom of the dimensional MEMS device. The second pass comes back with a high-end camera and telecentric lens to take pictures of the die with different fields of view. After stitching the pictures together to reconstruct an image, it compares that to a reference image to identify any differences, and flags the ones that are actually real defects, down to 3µm in size. Both passes take about 2-5 seconds per die, depending on size and types of defects.

“This ensures that only the known good dies go on to the next step, usually encapsulation, therefore saving costs,” says product line manager David Richard. “It also enables for the first time a real tilt measurement, which is a key functional criterion for accelerometers and gyros, and no electrical test can measure this.”

These ideas are some that will be discussed in the MEMS programs at SEMICON West in San Francisco, July 14-16. Yole will present it latest market forecast for the supply chain, and leading European development foundries IMEC, CEA Leti, and Silex Microsystems will discuss their progress in using standard processes to cut development time and costs. The sessions are part of a series on key developments in disruptive semiconductor technologies featured this year in the Extreme Electronics program. See www.semiconwest.org for details.

by Gerhard Lammel and Julia Patzelt, Bosch SensorTech

Inside of buildings, even the newest GPS navigation units quickly hit their limits–their navigational abilities are so inexact that a few floors can stand between the goal they indicate and the actual one. These are extremely poor qualifications for location-based services. An experimental study recently proved that the BMP085 pressure sensor can resolve not only the imprecision of GPS indoor navigation in a cost-efficient manner and without requiring additional infrastructure, it can also substantially improve locating in urban canyons.

In order for a navigation unit with GPS to provide exact positioning information within a few meters, the device has to receive data simultaneously from as many GPS satellites as possible. This requirement is fulfilled most easily on flat land under the open sky. However, as soon as obstacles block the unit’s view of the satellites, and it receives data from fewer than four satellites, the 3D positioning quickly becomes a game of chance.

Older GPS units are practically blind inside of buildings. A single wall within a structure generally damps a GPS signal in the 1.5GHz range by 20–30dB (factor of 100 to 1000), while reinforced concrete has the greatest dampening impact. The weak, useful signal is then drowned in the static of broadband HF receiving modules in these situations; a signal-to-noise ratio sufficient for determining position can no longer be reached using correction algorithms, and the navigation unit fails.

Indoor navigation: More than comfort

Unerring navigation within buildings is as advantageous for pedestrians as outdoor navigation is for drivers. In large foreign airports, for example, passengers could effortlessly find the correct check-in counter and from thence their departure gate. In large shopping centers and malls, they could be guided directly to businesses or restaurant without detours. New forms of location-based services, linked to GPS-equipped cell phones, could be offered for these environments. Imagine a note about a special sale at a certain store, or a restaurant’s reasonably priced lunch menu; once a person expresses interest, a GPS-equipped cell phone could immediately provide navigation to the new goal. For professional usage, examples include various types of support–a maintenance technician unfamiliar with the plant could traverse an extensive industrial complex, or merchandise could be unerringly delivered, even by someone not well acquainted with the locale. The possibilities for use by first responders are of incalculable value–no longer would they have to fumble through complex corridors, instead they could be directly guided to the location where they were needed.

Small errors have embarrassing effects without floor accuracy

All of the uses for indoor navigation listed are based on the concept that navigation within buildings decisively requires vertical “floor accuracy” (along the z-axis). If one assumes that building floors are 4m in height, then a positional accuracy of only 10 vertical meters for a GPS unit can easily steer one to the wrong floor. The people so affected would, however, only notice the error when they had arrived at the putative goal, then have to retrace their steps, perhaps along both floors in question, in order to finally arrive at their destination. This type of indoor navigation is both worthless and counterproductive. A positioning error of 10m has far less impact when it occurs horizontally (along the x- or y-axis); in the former case, floors and ceilings do not bar one’s view of the goal, which can generally be quickly reached by traveling a few more steps.

Figure 1. Indoor altitude measurement values comprised using a modern GPS navigation device in an office building. The fluctuations from the actual value (30m) are substantial over time.Click here to enlarge image

A limited type of GPS navigation within buildings has only become possible with the most recent navigation devices, equipped with new, highly sensitive receivers. However, multipath reception is omnipresent in buildings, caused by repeated signal reflections off walls, ceilings and floors; distortions of the signal propagation time significantly reduce the accuracy of positioning within buildings, especially in comparison with navigation under the open sky. Figure 1 quantifies the quintessential positioning error along the z-axis. The statistical measuring point was located at a height of 30m in the third floor of a three-story office building. The navigational unit used for the test could determine the elevation within the building, but without great accuracy. Over the course of the observation time of ~13min, during which time the actual position of the device at 30m did not change, the position measured along the z-axis fluctuated between 10–50m. Despite the most modern reception technology, the indoor positioning error of ±20m greatly exceeded that which is acceptable for floor-accurate navigation (=4m).

Pressure sensor for floor-accurate GPS indoor navigation

With its BMP085 pressure sensor, Bosch SensorTech already has the solution to the “floor-accurate GPS navigation” problem, with a very small (5mm × 1.2mm), yet highly exact digital barometric pressure sensor, constructed using MEMS (microelectromechanical systems) technology. At every point in the earth’s atmosphere, air pressure and elevation (as it relates to sea level) have a fixed relationship; by measuring the air pressure, the exact altitude of a measuring point can be calculated. The BMP085 has extremely high-pressure resolution of max. ±0.03 hPa (RMS), which when converted to altitude corresponds to a resolution of ±0.25m (at sea level). At this level of accuracy, the sensor can essentially recognize the difference in altitude that a person undergoes as they move from one step to the next on a flight of stairs.

Figure 2. The SiRFstarIII chip set offers a user input function for storing altitude information gained using a separate pressure sensor.Click here to enlarge image

A prerequisite for transmitting exact knowledge of momentary elevation to a chip set is excluding the less exact altitude information, generated in parallel via GPS. Bosch SensorTech’s SiRFstarIII chip set (Figure 2) incorporates the usual NMEA protocol, plus a proprietary binary protocol that enables settings that reach deeper on the chip set, making it possible to influence the type of positional calculation. In normal operation, the chip set decides automatically about the best type of calculation (four possibilities are available) with regard to the situation, independent from the number of satellites the receiver can see at the moment. The “2D fix” type of calculation is the most favorable for inputting barometrically measured altitude; the chip set normally uses this when it only has reception from three satellites. By this means it sets the elevation to a fixed value in order to reduce the number of unknowns in its formula for calculating position.

Results of an experimental study using a BPM085/GPS coupling

An “Alt Hold Mode” feature with the SiRF technology enables storage of the navigating engine in the SiRFstarIII chip with the measured values of the BMP085. Bosch SensorTech conducted an experimental study using practical tests to examine which results this BMP-GPS coupling would involve. The goal was to determine if the coupling of the GPS chip set with the pressure sensor provided not only a better level of accuracy for vertical navigation, but also whether this positively affected horizontal navigation.

The barometric pressure measurement increases the accuracy of GPS navigation: vertically, in every condition horizontally, and only in urban canyons.Click here to enlarge image

After setting the Alt Hold Mode parameter to “always use input altitude,” the SiRF chip set adopted the barometrically measured elevation as the new input variable. Also, a software interface was installed between the pressure sensor and the GPS chip set to turn off several negative influences on the positioning accuracy:

Recognition of climatic and artificial pressure fluctuations. Weather can cause strong fluctuations in air pressure (up to ±40hPa) that should not be interpreted as changes in elevation. An already extant algorithm analyzed the course of pressure fluctuations, and excluded rather slow changes typical of weather influences (<2.5hPa/h) from measured values. It similarly resolved abrupt, artificial pressure fluctuations, caused by air conditioning, ventilation systems, or a strong wind through open windows.

Statistical reduction of measurement errors. A BMP085 can perform up to 128 pressure measurements per second. Averaging over several measured values eliminates statistical outliers.

Figure 3. Principle of dynamic zero compensation. During indoor navigation, the high-resolution BMP085 signal replaces the weak, inexact GPS signal (left). During periods of strong reception, the highly accurate GPS signal calibrates the pressure sensor (middle). In urban canyons, the pressure sensor again replaces the GPS altitude signal, which has become unreliable due to multipath reception.Click here to enlarge image

Calibration compensates for absolute measurement errors. Independent of its height resolution, the BMP085 has an absolute measurement error of ±2.5hPa (±20m). This error was demonstrated to be easily compensated for–at good GPS reception, i.e. at the maximum GPS positional accuracy, height values determined via GPS by the navigation device were used automatically as calibration values for the pressure sensor. If the GPS reception deteriorated, then the high-resolution barometric altitude values–based on the most recently calibrated values–came into play (Figure 3). A Kalman filter determined whether or not to use situational calibration in this example.

The results of the experimental study of a SiRFstarIII with a BMP085 as external user altitude input are compiled (see table on p.22). The pressure sensor guaranteed indoor navigation at a floor-accurate level, thereby allowing the user to reach his or her destination; it also significantly increased the vertical positioning accuracy when used outdoors. In addition to a drastic reduction in the altitude error (visible only in the bar graph), the error in horizontal direction due to sensor support is also significantly smaller, with a standard deviation reduced by ~60%. This unexpected positive effect on horizontal positioning could, however, only be observed in comparable situations, such as in “urban canyons”.

BMP085 pressure sensor

Introduced in 2008, the BMP085 in an LCC-8 housing has a measuring range of 300–1100hPa and high over-pressure resistance at 10,000 hPa. Specifically developed for use in consumer electronic mobile devices, the sensor requires only 3µA of power (in ultra-low-power mode), with a low idle current consumption in stand-by mode of 0.1µA. The minimum supply voltage was also reduced to its current 1.8V. A 19-bit measurement operation on applications takes place inclusive of calibration data for temperature compensation in serial via an I2C 2-wire interface, which simplifies the integration of the BMP085 into already extant applications and eliminates the need for additional external components for wiring. At its slowest, a new measured value is ready for collection every 7.5ms.

---

Dr. Gerhard Lammel is manager of engineering at Bosch SensorTech GmbH, a wholly owned subsidiary of Bosch SensorTech.
Julia Patzelt is responsible for marketing communication and public relations at Bosch SensorTech GmbH.

---

No infrastructure required

At present, alternatives to satellite navigation are being developed and tested globally for indoor and urban navigation. Locating takes place by cross bearing, determining position by using the distance-dependent intensity of HF signals, which can be emitted by terrestrial transmitters from exactly known locations. The specific advantage is that the current transmission networks for cellular structures can be used for this form of navigation, without requiring a completely new system of transmitters.

This type of system, which functions using currently available WLAN islands, was developed by the Fraunhofer Institute for Integrated Circuits (IIS). The navigation unit constantly analyzes the reception field strength of nearby WLAN spots, and by means of their SSIDs, obtains the exact location of the WLAN transmitter from a central databank, which it then uses to navigate. However, this is not sufficient to also navigate within buildings with a sufficient degree of accuracy. For indoor navigation to function correctly, the navigation unit has to recognize the additional field strength divisions in every building, which in turn requires preliminary mapping measurements. Solutions related to this one convert the same navigational principle, but use different radio systems, such as GSM or DECT.

A communications network infrastructure is imperative for each of these solutions, which in turn requires an (at least periodic) administrative expenditure (e.g. mapping) which is not insignificant. The combination of the BMP085 pressure sensor and GPS is completely different does not require any foreign infrastructure; it functions everywhere, all over the planet, and is completely autarchic, in that the pressure sensor can fundamentally increase the vertical resolution of each of the alternative navigation systems.