Category Archives: Materials and Equipment

The Semiconductor Industry Association (SIA), representing U.S. leadership in semiconductor manufacturing, design, and research, today announced worldwide sales of semiconductors reached $30.5 billion for the month of October 2016, an increase of 3.4 percent from last month’s total of $29.5 billion and 5.1 percent higher than the October 2015 total of $29.0 billion. All monthly sales numbers are compiled by the World Semiconductor Trade Statistics (WSTS) organization and represent a three-month moving average. Additionally, a new WSTS industry forecast projects roughly flat annual semiconductor sales in 2016, followed by slight market growth in 2017 and 2018.

“The global semiconductor market has rebounded in recent months, with October marking the largest year-to-year sales increase since March 2015,” said John Neuffer, president and CEO, Semiconductor Industry Association. “Sales increased compared to last month across all regional markets and nearly every major semiconductor product category. Meanwhile, the latest industry forecast has been revised upward and now calls for flat annual sales in 2016 and small increases in 2017 and 2018. All told, the industry is well-positioned for a strong close to 2016.

Regionally, year-to-year sales increased in China (14.0 percent), Japan (7.2 percent), Asia Pacific/All Other (1.9 percent), and the Americas (0.1 percent), but decreased in Europe (-3.0 percent). Compared with last month, sales were up across all regional markets: the Americas (6.5 percent), China (3.2 percent), Japan (3.0 percent), Europe (2.2 percent), and Asia Pacific/All Other (2.0 percent).

Additionally, SIA today endorsed the WSTS Autumn 2016 global semiconductor sales forecast, which projects the industry’s worldwide sales will be $335.0 billion in 2016, a 0.1 percent decrease from the 2015 sales total. WSTS projects a year-to-year increase in Japan (3.2 percent) and Asia Pacific (2.5 percent), with decreases expected in Europe (-4.9 percent) and the Americas (-6.5 percent). Among major semiconductor product categories, WSTS forecasts growth in 2016 for sensors (22.6 percent), discretes (4.2 percent), analog (4.8 percent) and MOS micro ICs (2.3 percent), which include microprocessors and microcontrollers.

Beyond 2016, the semiconductor market is expected to grow at a modest pace across all regions. WSTS forecasts 3.3 percent growth globally for 2017 ($346.1 billion in total sales) and 2.3 percent growth for 2018 ($354.0 billion). WSTS tabulates its semi-annual industry forecast by convening an extensive group of global semiconductor companies that provide accurate and timely indicators of semiconductor trends.

ClassOne Technology, manufacturer of cost-efficient wet processing equipment for ≤200mm substrates, has reported its best-ever sales quarter and is currently doubling its Kalispell manufacturing capacity to meet the demand.

“We’ve been seeing a steady increase in market interest and sales,” said ClassOne Technology President, Kevin Witt. “Most of these users are now focusing on capabilities they couldn’t get before, like wafer-level packaging and More than Moore technologies.”

Witt explained that wafer-level packaging (WLP) has been used for some time with 300mm and larger substrates — but the equipment has not been available for 200mm. “Fortunately, ClassOne focuses specifically on the smaller-wafer markets,” said Witt. “At a very affordable price, we deliver the new technology and advanced 3D features they’re looking for. For example, our Solstice® line of multifunctional electroplating systems enables high-efficiency Cu Through Silicon Via (TSV), Pillar, Bump and Barrier Plating and other capabilities that WLP requires. And that’s one major reason they’re coming to us.”

ClassOne reports that many of the new buyers are keenly interested in More than Moore (MtM) technologies to increase functionality while reducing cost per device. They are producing compound semiconductors, LEDs, MEMS, RF, Wi-Fi and a range of IoT-related sensors and other devices. ClassOne cites the combination of ≤200mm-specific tools, advanced capabilities and affordable pricing as the primary driver behind the current equipment-buying surge in emerging markets.

ClassOne Technology offers a selection of new-technology wet processing tools designed for 75mm to 200mm wafer users. These include three different models of Solstice electroplating systems for production and development as well as the Trident families of Spin-Rinse-Dryers and Spray Solvent Tools. All are priced at less than half of what similarly configured systems from the larger manufacturers would cost — which is why the ClassOne lines are often described as delivering “Advanced Wet Processing for the Rest of Us.”

Vigorous M&A activity in 2015 and 2016 has reshaped the landscape of the semiconductor industry, with the top companies now controlling a much greater percentage of marketshare.  Not including foundries, IC Insights forecasts to top five semiconductor suppliers—Intel, Samsung, Qualcomm, Broadcom, and SK Hynix— will account for 41% marketshare in 2016 (Figure 1).  This represents a nine-point increase from the 32% marketshare held by the top five suppliers ten years ago. Furthermore, the top 10 semiconductor suppliers are forecast to account for 56% marketshare in 2016, an 11-point swing from 45% in 2006, and the top 25 companies are forecast to account for more than three-quarters of all semiconductor sales this year.

semiconductor sales leaders

Figure 1

Following an historic surge in semiconductor merger and acquisition agreements in 2015, the torrid pace of transactions eased a bit in the first half of 2016.  However, 2016 is now forecast to be the second-largest year ever for chip industry M&A announcements, thanks to three major deals struck in 3Q16 that have a combined total value of $51.0 billion.  These deals were SoftBank’s purchase of ARM, Analog Devices’ intended purchase of Linear Technology, and Renesas’ potential acquisition of Intersil. With the surge in mergers and acquisitions expected to continue over the next few years, IC Insights believes that the consolidation will raise the shares of the top suppliers to even loftier levels.

TriLumina Corp., a developer of semiconductor laser illuminators for solid-state LiDAR systems that enable autonomous vehicles and new automotive safety systems, announced that Brian Wong has been named as the company’s new President and Chief Executive Officer and as a member of the board of directors. Mr. Wong is an experienced leader and highly respected in the semiconductor industry with an impressive record of building and growing profitable technology companies.

“As TriLumina continues to solidify its position in the automotive sensing market building customer relationships and strategic partnerships, we are pleased to have Brian join the Company to lead us into this exciting next phase,” said Ray Quintana, TriLumina board member and Partner with Cottonwood Technology Fund.  “Brian brings the experience and leadership necessary to drive TriLumina from technology developer to a key supplier of enabling products to the rapidly expanding automotive sensing, illumination and depth sensing markets.”

With over 30 years’ experience in optical, semiconductor, and energy storage segments for automotive, aerospace, and consumer customers, Mr. Wong’s background dovetails well with TriLumina’s technology and target markets. In previous CEO roles, he has introduced complex technologies into high volume production for mission critical applications, formed strategic partnerships with over a dozen international companies, and raised significant equity financing.  Most recently, Mr. Wong was CEO of Enevate Corp, a Silicon-Anode based Li-Ion battery company.

“I’m excited to join TriLumina and lead the company as we commercialize our technology for key markets,” Mr. Wong said, “particularly now as TriLumina focuses and accelerates its development efforts in the solid-state LiDAR space. LiDAR sensors, enabled by TriLumina lasers, are driving the development of today’s new safety systems and tomorrow’s autonomous vehicles. The technology will make our roads much safer, more efficient and are expected to save millions of lives.”

“Brian Wong is the ideal person for the CEO position at TriLumina given his long track record in developing and deploying semiconductor technologies in automotive and other extremely demanding customer segments.  Brian has a successful history of growing cutting-edge and innovative companies and is a perfect match for TriLumina,” said Lee Rand, a TriLumina board member and Partner at Sun Mountain Capital.

According to the latest market study released by Technavio, the global fan-in wafer-level packaging (WLP) market is expected to reach USD 4.75 billion by 2020, growing at a CAGR of almost 10%.

This research report titled ‘Global Fan-In WLP Market 2016-2020’ provides an in-depth analysis of the market in terms of revenue and emerging market trends. The report also presents a corresponding detailed analysis of the major vendors manufacturing fan-in wafer-level packages in North America, APAC, and Europe.

The increasing number of fabs globally has pushed the demand for IC packaging solutions. The vendors are setting up new fabs in different countries to produce memory devices like dynamic random access memory (DRAM) and not AND (NAND). The transition of semiconductor industry such as miniaturized semiconductor electronics, because of emerging technology such as the Internet of Things (IoT), is also driving the global fan-in WLP market.

The surging demand for compact electronic devices in sectors such as telecommunications, automotive, industrial manufacturing, and healthcare has generated the need for miniaturized semiconductor ICs. With the emergence of products such as 3D ICs and MEMS devices, the electronic equipment is becoming compact and user-friendly, which involves changes in IC designing such as finer patterning.

Technavio’s sample reports are free of charge and contain multiple sections of the report including the market size and forecast, drivers, challenges, trends, and more.

Technavio’s hardware and semiconductor analysts categorize the global fan-in WLP market into five major segments by application. They are:

  •    CMOS image sensor
  •    Wireless connectivity
  •    Logic and memory IC
  •    MEMS and sensor
  •    Analog and mixed IC

The top three segments by application for the fan-in WLP market are:

Analog and mixed ICs

The global analog and mixed IC shipments amounted to 27.57 billion units in 2015 and will reach 40.93 billion units by 2020, growing at a CAGR of 8.22% during the forecast period.

The demand for analog ICs from different segments (such as consumer electronics, communications, and automotive) is gradual but significant. The rising demand for smartphones, phablets, and tablets worldwide is driving their demand in the communications segment. The increasing pace of new product development, the declining cost per function of ICs, and the reduced product replacement cycle have contributed to the high demand for semiconductor ICs and, therefore, analog ICs. The rapid technological developments in the semiconductor industry and the development of efficient analog ICs (which deliver optimized performance) have also increased the proliferation of analog ICs in the global market space.

Wireless connectivity

The global shipments in the wireless connectivity segment amounted to 2.71 billion units in 2015 and will reach 4.79 billion units by 2020, growing at a CAGR of 12.07% during the forecast period.

The wireless connectivity segment includes the demand for fan-in WLP solutions from technologies such as Wi-Fi, RF transceivers, Bluetooth, DC/DC converters, audio/video codecs, RF filters, gyroscopes, and accelerometers, which assist in providing optimum wireless connectivity. Wi-Fi technology is adapting to new protocol versions such as Wi-Fi Direct, 802.11ac, and 801.11ad. With continuous evolution of new technologies and continuous integration of Wi-Fi capability into mobile devices, the demand for wireless connectivity solutions will increase during the forecast period.

According to Sunil Kumar Singh, a lead semiconductor equipment analyst from Technavio, “The global Wi-Fi chipset market is experiencing the transition to 5th Wi-Fi generation, the 802.11ac with MIMO. An increasing number of customers are likely to adopt the technology due to an improvement in speed by up to 1.3 GHz over a long distance.”

Logic and memory ICs

The global shipments in the logic and memory IC segment amounted to 3.51 billion units in 2015 and will reach 4.79 billion units by 2020, growing at a CAGR of 6.42% during the forecast period.

Technological development has led to the introduction of better electronic devices across sectors, such as high-powered smartphones, performance-packed automobiles, automated machinery in the industrial sector, and electronic devices in the healthcare sector for better monitoring of patients. This has increased the demand for better processing to ensure efficient background operations.

The demand for high-powered processors has increased the demand for logic ICs, especially for automation purposes. This will trigger the demand for fan-in WLP solutions in the logic IC segment as they constitute an integral part of IC packaging at the manufacturing level.

The top vendors highlighted by Technavio’s research analysts in this report are:

  •    STATS ChipPAC
  •    STMicroelectronics
  •    TSMC
  •    Texas Instruments

About Technavio

Technavio is a leading global technology research and advisory company. The company develops over 2000 pieces of research every year, covering more than 500 technologies across 80 countries. Technavio has about 300 analysts globally who specialize in customized consulting and business research assignments across the latest leading edge technologies.

In 2015, more than US$1 billion was invested in China’s advanced packaging ecosystem, announces Yole Développement (Yole) in its report Status and Prospects for the Advanced Packaging Industry. And right now, more than 100 companies are involved in assembly & packaging activities in China. Almost all key global IDMs and OSATs have a packaging facility in China to take advantage of low costs.

But what are the strategies of these companies? How do they ensure their market positioning and their development in the Chinese advanced packaging industry? Is there a specific approach according to their business model?

advanced packaging china

“Global OSATs are working on their strategies to thwart challenges and exploit opportunities in China’s advanced packaging market,” details for example, Santosh Kumar, Senior, Technology & Market Analyst, Advanced Packaging & Semiconductor Manufacturing at Yole. And in parallel, Chinese players may acquire or invest in others with complimentary packaging technology/services/customers.

Status and Prospects for the Advanced Packaging Industry in China report presents the Chinese semiconductor market outlook as well as the advanced packaging ecosystem in China. This analysis details the global and local players as well as the Chinese backend equipment & materials suppliers. It also covers supply chain evolution, OSAT strategy and business opportunities for local and global players in China’s advanced packaging space. Some results will be presented by Santosh Kumar at the China International Semiconductor Executive Summit taking place from November 1 to 2, 2016 in Shanghai, China.

The advanced packaging market in China is reaching about US$2.5 billion in 2016. And Yole’s analysts expect an impressive 16% CAGR between 2016 and 2020, scoring US$4.6 billion at the end of this period. Under this imposing growth, advanced packaging companies are deploying complex strategies to ensure their business and develop their activities. For example, some companies collaborate with local IC design & foundries and invest in R&D and manufacturing capacity in China. Others invest in Chinese capital.

Technical innovation is also a priority for all China-based companies. Companies are investing a lot to secure important R&D activities and develop disruptive technologies. In parallel, advanced packaging players protect their IP and company’s core value. From a human resources point of view, they reserve key employees through incentives and educate employees to not release confidential information.

China’s advanced packaging industry took a giant leap when JCET acquired STATSChipPAC in 2015 for US$780 million. This deal propelled JCET into 4th place amongst OSAT companies. “JCET-STATS ChipPAC is clearly the game changer in China AP ecosystem,” comments Santosh Kumar from Yole. And he adds: “JCET-STATS ChipPAC results in operational, revenue & capex synergy”.
Other notable acquisitions are:

•  Huatian acquiring FCI
•  Nantong Fujitsu acquiring AMD backend facilities in China and Malaysia.

While Chinese OSATs and foundries are rapidly acquiring advanced packaging capabilities, the local equipment and materials supply chains are still far behind compared to global players, who still dominate the advanced packaging equipment and materials space.

Will this remain true over the next five years? Do global suppliers see China’s advanced packaging market as an opportunity or a threat from local supplier)? In Yole’s report’s equipment/materials section, the advanced packaging team addresses these questions as well as other issues.

CMOS image sensor update


October 30, 2016

BY DR. PHIL GARROU, Contributing Editor

Toshiba was the first to commercially implement CMOS image sensors with backside TSV last technologies in 2007. Many of us stated in 2007 that further advances could be obtained by removing the CMOS circuitry to a separate layer and forming a true 3D chip stack, but the technology imple- mentation had to wait while the industry first converted to back side imaging technology.

With a conventional front-illumination structure, the metal wiring above the sensor’s photo-diodes impede photon gathering. A back-illuminated structure increases the amount of light that enters each pixel due to the lack of obstacles such as metal wiring and transistors that have been moved to the reverse of the silicon substrate.

The next generation, as expected, combined both BSI and stacking. Conventional CMOS image sensor technology creates the pixel function and analog logic circuitry on the same chip. The motivations for stacked chip CIS include: optimization of each function in the stack, adding function- ality to the stack and decreasing form factor.

Since the pixel section and circuit section are formed as independent chips, each function can be separately optimized, enabling the pixel section to deliver higher image quality while the circuit section can be specialized for higher functionality. In addition, faster signal processing and lower power consumption can also be achieved through the use of leading process for the chip containing the circuits.

The 2014 image sensor market was estimated by Techno Systems Research with Sony as the top seller of image sensors with 40.2% market share, followed by OmniVision (15.7%), Samsung (15.2%) and others with 28.9%.

Sony is clearly leading in commercializing the latest CIS packaging technologies. Some of the biggest names in tech use Sony sensors: The iPhone 6 camera has a Sony sensor, as does the Samsung Galaxy S6, Motorola phones, Nikon DSLRs, and Olympus mirrorless cameras.
Earlier in 2016 it was reported that there are two versions of the Samsung Galaxy S7. One has a Samsung stacked ISOCELL sensor (S5K2L1) and the other a special Sony stacked sensor (IMX260).

The recent Chipworks teardown of the Samsung Galaxy S7 with a Sony IMX 260 revealed BSI stacked technology. Furthermore, it revealed the first reported use of the Ziptronix (now Tessera) Direct Bond interconnect (DBI) technology rather than prior oxide –oxide bonding with subsequent TSVs connecting through the oxide interface. This BSI-stacked DBI technology is possibly the next step in the CIS roadmap.

The Chipworks cross-section reveals a 5 metal (Cu) CMOS image sensor (CIS) die and a 7 metal (6 Cu + 1 Al) image signal processor (ISP) die. The Cu-Cu vias are 3.0 μm wide and have a 14 μm pitch in the peripheral regions. In the active pixel array they are also 3.0 μm wide, but have a pitch of 6.0 μm.
Omnivision was the first to sample BSI in 2007 but costs were too high and adoption was thus very low. In 2015 Omnivision announced their OV 16880 a 16-megapixel image sensor built on OmniVision’s PureCel-STM stacked die technology.

Samsung’s first entrant into stacked technology with TSV was also at 16MP with the Samsung S5K3P3SX in late 2014. The CIS die is face-to-face bonded to a 65nm Samsung image signal processor die and connected with W based TSV. The CIS die is fabricated on a 65nm CMOS process with 5 levels of interconnect.

In early 2015 On Semiconductor (Aptina) introduced its first stacked CMOS sensor the AR 1335 with 1.1μm pixels. It resulted in a smaller die footprint, higher pixel performance and better power consumption compared to their traditional monolithic non-stacked designs. They announced that it would be introduced in commercial products in late 2015.

In late 2015, Olympus announced the OL 20150702-1 a new 3D stacked 16MP CMOS image sensor.

ams AG (SIX: AMS), a provider of high performance sensors and analog ICs, a provider of high performance sensors and analog ICs, has announced its fast and cost-efficient IC prototyping service, known as Multi-Project Wafer (MPW) or shuttle run, with an updated schedule for 2017. The prototyping service, which combines several IC designs from different customers onto a single wafer, offers significant cost advantages for foundry customers as the costs for wafers and masks are shared among all shuttle participants.

ams’ best in class MPW service offers the whole range of 180nm and 0.35μm specialty processes including the recently introduced 180nm CMOS technology (“aC18”). The aC18 process supports a large number of 1.8V and 5.0V NMOS and PMOS devices (substrate based, floating, low leakage and high threshold voltage options) and fully characterised passives including various capacitors. Area-optimised high-density and low-power digital libraries with gate densities up to 152kGates/mm², updated digital and analog I/O libraries with up to 6 metal layers as well as ESD protection cells with up to 8kV HBM level complete the offering. ams’ aC18 process is ideally suited for sensor and sensor interface devices in a wide variety of applications. All 2017 MPW runs in aC18 technology will be manufactured in ams’ state of the art 200mm fabrication facility in Austria ensuring very low defect densities and high yields.

In addition to the four aC18 MPW runs, ams will also offer four MPW runs in its advanced 180nm High-Voltage CMOS (aH18) technology supporting 1.8V, 5V, 20V and 50V devices. For its 0.35μm specialty processes a total of 14 runs are offered in 2017. ams’ 0.35μm High-Voltage CMOS process family, optimised for high-voltage designs in automotive and industrial applications, supports 20V, 50V and 120V devices as well as truly voltage scalable transistors. The advanced High-Voltage CMOS process with embedded EEPROM functionality as well as the 0.35μm SiGe-BiCMOS technology S35 are fully compatible with the base CMOS process and complete ams’ MPW service portfolio.

Overall, ams will offer almost 150 MPW start dates in 2017, enabled by co-operations with worldwide partner organisations such as CMP, Europractice, Fraunhofer IIS and Mosis. Customers located in APAC region may also participate via our local MPW program partners Toppan Technical Design Center Co., Ltd (TDC) and MEDs Technologies.

The complete schedule for 2017 has now been released and detailed start dates per process are available on the web atwww.ams.com/MPW.

To take advantage of the MPW service, ams’ foundry customers deliver their completed GDSII-data on specific dates and receive untested packaged samples or dies within a short lead-time of typically 8 weeks for CMOS and 12 weeks for High-Voltage CMOS, SiGe-BiCMOS and Embedded Flash processes.

All process technologies are supported by the well-known hitkit, ams’ industry benchmark process design kit based on Cadence, Mentor Graphics or Keysight ADS design environments. The hitkit comes complete with fully silicon-qualified standard cells, periphery cells and general purpose analog cells such as comparators, operational amplifiers, low power A/D and D/A converters. Custom analog and RF devices, physical verification rule sets for Assura and Calibre, as well as precisely characterised circuit simulation models enable rapid design starts of complex high performance mixed-signal ICs. In addition to standard prototype services, ams also offers advanced analog IP blocks, a memory (RAM/ROM) generation service and packaging services in ceramic or plastic.

Learn more about the comprehensive service and technology portfolio of Full Service Foundry at www.ams.com/foundry.

A new type of atomic force microscope (AFM) uses nanowires as tiny sensors. Unlike standard AFM, the device with a nanowire sensor enables measurements of both the size and direction of forces. Physicists at the University of Basel and at the EPF Lausanne have described these results in the recent issue of Nature Nanotechnology.

A nanowire sensor measures size and direction of forces. Credit: University of Basel, Department of Physics

A nanowire sensor measures size and direction of forces. Credit: University of Basel, Department of Physics

Nanowires are extremely tiny filamentary crystals which are built-up molecule by molecule from various materials and which are now being very actively studied by scientists all around the world because of their exceptional properties.

The wires normally have a diameter of 100 nanometers and therefore possess only about one thousandth of a hair thickness. Because of this tiny dimension, they have a very large surface in comparison to their volume. This fact, their small mass and flawless crystal lattice make them very attractive in a variety of nanometer-scale sensing applications, including as sensors of biological and chemical samples, and as pressure or charge sensors.

Measurement of direction and size

The team of Argovia Professor Martino Poggio from the Swiss Nanoscience Institute (SNI) and the Department of Physics at the University of Basel has now demonstrated that nanowires can also be used as force sensors in atomic force microscopes. Based on their special mechanical properties, nanowires vibrate along two perpendicular axes at nearly the same frequency. When they are integrated into an AFM, the researchers can measure changes in the perpendicular vibrations caused by different forces. Essentially, they use the nanowires like tiny mechanical compasses that point out both the direction and size of the surrounding forces.

Image of the two-dimensional force field

The scientists from Basel describe how they imaged a patterned sample surface using a nanowire sensor. Together with colleagues from the EPF Lausanne, who grew the nanowires, they mapped the two-dimensional force field above the sample surface using their nanowire “compass”. As a proof-of-principle, they also mapped out test force fields produced by tiny electrodes.

The most challenging technical aspect of the experiments was the realization of an apparatus that could simultaneously scan a nanowire above a surface and monitor its vibration along two perpendicular directions. With their study, the scientists have demonstrated a new type of AFM that could extend the technique’s numerous applications even further.

AFM – today widely used

The development of AFM 30 years ago was honored with the conferment of the Kavli-Prize beginning of September this year. Professor Christoph Gerber of the SNI and Department of Physics at the University of Basel is one of the awardees, who has substantially contributed to the wide use of AFM in different fields, including solid-state physics, materials science, biology, and medicine.

The various different types of AFM are most often carried out using cantilevers made from crystalline Si as the mechanical sensor. “Moving to much smaller nanowire sensors may now allow for even further improvements on an already amazingly successful technique”, Martino Poggio comments his approach.

Scientists have created a material that could make reading biological signals, from heartbeats to brainwaves, much more sensitive.

Organic electrochemical transistors (OECTs) are designed to measure signals created by electrical impulses in the body, such as heartbeats or brainwaves. However, they are currently only able to measure certain signals.

Now researchers led by a team from Imperial College London have created a material that measures signals in a different way to traditional OECTs that they believe could be used in complementary circuits, paving the way for new biological sensor technologies.

Semiconducting materials can conduct electronic signals, carried by either electrons or their positively charged counterparts, called holes. Holes in this sense are the absence of electrons – the spaces within atoms that can be filled by them.

Electrons can be passed between atoms but so can holes. Materials that use primarily hole-driven transport are called ‘p-type’ materials, and those that use primarily electron-driven transport are called, and ‘n-type’ materials.

An ‘ambipolar’ material is the combination of both types, allowing the transport of holes and electrons within the same material, leading to potentially more sensitive devices. However, it has not previously been possible to create ambipolar materials that work in the body.

The current most sensitive OECTs use a material where only holes are transported. Electron transport in these devices however has not been possible, since n-type materials readily break down in water-based environments like the human body.

But in research published today in Nature Communications, the team have demonstrated the first ambipolar OECT that can conduct electrons as well as holes with high stability in water-based solutions.

The team overcame the seemingly inherent instability of n-type materials in water by designing new structures that prevent electrons from engaging in side-reactions, which would otherwise degrade the device.

These new devices can detect positively charged sodium and potassium ions, important for neuron activities in the body, particularly in the brain. In the future, the team hope to be able to create materials tuned to detect particular ions, allowing ion-specific signals to be detected.

Lead author Alexander Giovannitti, a PhD student under the supervision of Professor Iain McCulloch, from the Department of Chemistry and Centre for Plastic Electronics at Imperial said: “Proving that an n-type organic electrochemical transistor can operate in water paves the way for new sensor electronics with improved sensitivity.

“It will also allow new applications, particularly in the sensing of biologically important positive ions, which are not feasible with current devices. For example, these materials might be able to detect abnormalities in sodium and potassium ion concentrations in the brain, responsible for neuron diseases such as epilepsy.”