Category Archives: LEDs

Seoul Semiconductor Co., Ltd. announced on Sept. 19, 2017 that it has filed a patent infringement lawsuit, together with its affiliate, Seoul Viosys Co., Ltd., against Archipelago Lighting, Inc. in the U.S. District Court for the Central District of California.

In its complaint, Seoul asserts that Archipelago Lighting is selling various LED bulb products, including filament LED bulbs, that infringe on “twelve” (12) patents covering aspects of Seoul’s long-established Acrich technology. These Acrich patents include fundamental LED technologies, such as LED driver technology for high-voltage operation, MJT (Multi-Junction Technology), filament LED bulb structure, LED packaging, LED epitaxial growth, LED chip fabrication, etc.

In conventional LED products, one LED unit usually operates at a low voltage (3V) and high current. In order to increase brightness, one must connect many LED units through wire-bonding, but this can lead to other issues, such as an oversized, costly operating circuit, a substantial increase in manufacturing costs and defects caused by multiple wire-bonding connections.

Seoul’s Acrich technology resolves such problems by enabling the design of a high-voltage product with a high power output that relies on only a small number of LED units. Acrich technology does so by utilizing its innovative LED driver technology to enable high-voltage operation, as well as its unique MJT technology for mounting and integrating many LEDs within a small area. Seoul’s Acrich technology enables LED products to operate using AC power without requiring conversion to DC, minimizing power dissipation and reducing overall component count. This maximizes the available space in LED products, facilitating a simple circuit design and significantly reducing the size and cost of LED products. Acrich technology has become widely adopted for general lighting, as well as electronic products, including televisions.

For example, in the general lighting market, 12V/18V high-voltage products have become increasingly popular, and there has been a significant increase in the demand for 36V/48V products. To manufacture such high-voltage products, Acrich technology is necessary to support LED driver technology for high-voltage operations with MJT technology. The innovative benefits of Acrich technology have resulted in its being applied in street lights and commercial lights in countries throughout the world, including locations as diverse as Korea, the United States, China, Europe, Southeast Asia, Mongolia and Kazakhstan.

In electronic products, Acrich technology is being increasingly used for valuable product lines such as large-area television displays. Acrich technology enables a dramatic enhancement in the service life and efficiency of such displays by simplifying their internal system. It also dramatically reduces the size and thickness of the final product, rendering it more pleasing to consumers, by reducing the amount of internal space previously reserved for complicated electric circuits. In particular, Acrich enables full-array local dimming that enhances the contrast range of the latest ultra-thin UHD display products by providing the next generation of backlighting solutions for high-definition displays.

Acrich technology is also expanding its application to other product areas that require high LED light output, such as landscape lighting, vehicle headlamps and daylight running lamps as well as mobile phone flash units.

Seoul began to develop its unique Acrich technology in the mid-1990s and has continued to launch advanced, innovative Acrich products every year following its successful volume production in 2005. Based on its decades of investment in research and development, Seoul has established a large patent portfolio for Acrich technology, including rights to approximately 1,000 Acrich patents. However, with the recent increase in the demand for high-voltage LED products, several companies have begun to manufacture products that infringe on Seoul’s Acrich patents. In order to protect its hard-earned investment against such infringement, Seoul will actively enforce its patent rights against any infringers.

Dr. Ki-bum Nam, head of Seoul’s R&D Center and chief technology officer said, “We have extensively investigated copycat products infringing on Acrich technology with various LED TVs, general lighting and automotive lighting products. In order to protect Acrich technology, which has been developed with considerable resources over many decades, we will continuously take any and all legal action against infringers that disregard our valuable intellectual property.” Nam added: “Creating a fair market that respects intellectual property is important for all innovative entrepreneurs and businesses.”

Upbeat about the growth prospects of Taiwan’s electronics sector, more than 45,000 visitors are expected to attend SEMICON Taiwan 2017 which opens tomorrow at Taipei’s Nangang Exhibition Center.  SEMICON Taiwan (September 13-15), the premier tradeshow and event for the electronics manufacturing supply chain, aims to connect the electronics manufacturing ecosystem─ both vertically and horizontally. The event will provide an overview of market trends and leading technologies in the industry, with forums and business-matching activities which will enable collaboration and new opportunities. The three-day event features 700 exhibitors covering over 1,800 booths.

Taiwan is forecast to spend US$12.3 billion in 2017, making it the second largest fab equipment spending region, according to the SEMI World Fab Forecast report just issued.  Taiwan is home to the leading share of the world’s IC foundry, and has the largest share of installed capacity ─ more than 20 percent. With 2017’s large semiconductor equipment investment, Taiwan’s semiconductor industry is booming and is also the world’s largest consumer of semiconductor materials ($9.8 billion in 2016) for the seventh consecutive year, bringing new opportunities in this increasingly critical sector.

Covering the hottest electronics topics like smart manufacturing and automation, high-tech facility, materials, laser, and emerging semiconductor technology, more than 70 presentations will be given on TechXPOT stages, providing the latest technology updates plus opportunities to meet potential partners and customers. To further connect attendees and exhibitors, SEMICON Taiwan will facilitate a series of networking events, like the Materials, High-Tech Facility, Laser, and Smart Manufacturing “Get Togethers” and the Supplier Search Program, creating business opportunities.

This year SEMICON Taiwan has added new theme pavilions including Circular Economy, Compound Semiconductor, Laser, and Opto Semiconductor.  In addition, 12 theme pavilions and eight country/region pavilions are featured.

This is the first year that the International Test Conference (ITC) will be co-located with SEMICON Taiwan 2017, also marking the first time that ITC is held in Asia. The conference will focus on the rapid growth of emerging applications like IoT and automotive electronics, and how testing technologies are challenged by rapid advancements of manufacturing processes, 3D stacking and SiP.

Also co-located with SEMICON Taiwan 2017, the SiP Global Summit will discuss three key system-in-package topics:

  •  Package Innovation in Automotive
  •  3D IC, 3D interconnection for AI and High-end Computing
  •  Innovative Embedded Substrate and Fan-Out Technology to Enable 3D-SiP Devices

The Jing Jing Lucky Draw is always an anticipated show activity with excellent prizes like the Dyson 3-in-1 smart fan, iPad Pro, and Nintendo Switch.

For more information about SEMICON Taiwan 2017, please visit http://www.semicontaiwan.org.

The latest update to the World Fab Forecast report, published on September 5, 2017 by SEMI, again reveals record spending for fab equipment. Out of the 296 Front End facilities and lines tracked by SEMI, the report shows 30 facilities and lines with over $500 million in fab equipment spending.  2017 fab equipment spending (new and refurbished) is expected to increase by 37 percent, reaching a new annual spending record of about US$55 billion. The SEMI World Fab Forecast also forecasts that in 2018, fab equipment spending will increase even more, another 5 percent, for another record high of about $58 billion. The last record spending was in 2011 with about $40 billion. The spending in 2017 is now expected to top that by about $15 billion.

fab equipment spending

Figure 1: Fab equipment spending (new and refurbished) for Front End facilities

Examining 2017 spending by region, SEMI reports that the largest equipment spending region is Korea, which increases to about $19.5 billion in spending for 2017 from the $8.5 billion reported in 2016. This represents 130 percent growth year-over-year. In 2018, the World Fab Forecast report predicts that Korea will remain the largest spending region, while China will move up to second place with $12.5 billion (66 percent growth YoY) in equipment spending. Double-digit growth is also projected for Americas, Japan, and Europe/Mideast, while other regions growth is projected to remain below 10 percent.

The World Fab Forecast report estimates that Samsung is expected to more than double its fab equipment spending in 2017, to $16-$17 billion for Front End equipment, with another $15 billion in spending for 2018. Other memory companies are also forecast to make major spending increases, accounting for a total of $30 billion in memory-related spending for the year. Other market segments, such as Foundry ($17.8 billion), MPU ($3 billion), Logic ($1.8 billion), and Discrete with Power and LED ($1.8 billion), will also invest huge amounts on equipment. These same product segments also dominate spending into 2018.

In both 2017 and 2018, Samsung will drive the largest level in fab spending the industry has ever seen. While a single company can dominate spending trends, SEMI’s World Fab Forecast report also shows that a single region, China, can surge ahead and significantly impact spending. Worldwide, the World Fab Forecast tracks 62 active construction projects in 2017 and 42 projects for 2018, with many of these in China.

For insight into semiconductor manufacturing in 2017 and 2018 with more details about capex for construction projects, fab equipping, technology levels, and products, visit the SEMI Fab Database webpage (www.semi.org/en/MarketInfo/FabDatabase) and order the SEMI World Fab Forecast Report. The report, in Excel format, tracks spending and capacities for over 1,200 facilities including over 80 future facilities, across industry segments from Analog, Power, Logic, MPU, Memory, and Foundry to MEMS and LEDs facilities.

Researchers have shown that defects in the molecular structure of perovskites – a material which could revolutionise the solar cell industry – can be “healed” by exposing it to light and just the right amount of humidity.

The international team of researchers demonstrated in 2016 that defects in the crystalline structure of perovskites could be healed by exposing them to light, but the effects were temporary.

Now, an expanded team, from Cambridge, MIT, Oxford, Bath and Delft, have shown that these defects can be permanently healed, which could further accelerate the development of cheap, high-performance perovskite-based solar cells that rival the efficiency of silicon. Their results are reported in the inaugural edition of the journal Joule, published by Cell Press.

The concoction of light with water and oxygen molecules leads to substantial defect-healing in metal halide perovskite semiconductors. Credit: Dr. Matthew T. Klug

The concoction of light with water and oxygen molecules leads to substantial defect-healing in metal halide perovskite semiconductors. Credit: Dr. Matthew T. Klug

Most solar cells on the market today are silicon-based, but since they are expensive and energy-intensive to produce, researchers have been searching for alternative materials for solar cells and other photovoltaics. Perovskites are perhaps the most promising of these alternatives: they are cheap and easy to produce, and in just a few short years of development, perovskites have become almost as efficient as silicon at converting sunlight into electricity.

Despite the potential of perovskites, some limitations have hampered their efficiency and consistency. Tiny defects in the crystalline structure of perovskites, called traps, can cause electrons to get “stuck” before their energy can be harnessed. The easier that electrons can move around in a solar cell material, the more efficient that material will be at converting photons, particles of light, into electricity.

“In perovskite solar cells and LEDs, you tend to lose a lot of efficiency through defects,” said Dr Sam Stranks, who led the research while he was a Marie Curie Fellow jointly at MIT and Cambridge. “We want to know the origins of the defects so that we can eliminate them and make perovskites more efficient.”

In a 2016 paper, Stranks and his colleagues found that when perovskites were exposed to illumination, iodide ions – atoms stripped of an electron so that they carry an electric charge – migrated away from the illuminated region, and in the process swept away most of the defects in that region along with them. However, these effects, while promising, were temporary because the ions migrated back to similar positions when the light was removed.

In the new study, the team made a perovskite-based device, printed using techniques compatible with scalable roll-to-roll processes, but before the device was completed, they exposed it to light, oxygen and humidity. Perovskites often start to degrade when exposed to humidity, but the team found that when humidity levels were between 40 and 50 percent, and the exposure was limited to 30 minutes, degradation did not occur. Once the exposure was complete, the remaining layers were deposited to finish the device.

When the light was applied, electrons bound with oxygen, forming a superoxide that could very effectively bind to electron traps and prevent these traps from hindering electrons. In the accompanying presence of water, the perovskite surface also gets converted to a protective shell. The shell coating removes traps from the surfaces but also locks in the superoxide, meaning that the performance improvements in the perovskites are now long-lived.

“It’s counter-intuitive, but applying humidity and light makes the perovskite solar cells more luminescent, a property which is extremely important if you want efficient solar cells,” said Stranks, who is now based at Cambridge’s Cavendish Laboratory. “We’ve seen an increase in luminescence efficiency from one percent to 89 percent, and we think we could get it all the way to 100 percent, which means we could have no voltage loss – but there’s still a lot of work to be done.”

BY PETE SINGER, Editor-in-Chief

At a SEMICON West press conference, SEMI released its Mid-year Forecast. Worldwide sales of new semiconductor manufacturing equipment are projected to increase 19.8 percent to total $49.4 billion in 2017, marking the first time that the semiconductor equipment market has exceeded the market high of $47.7 billion set in 2000. In 2018, 7.7 percent growth is expected, resulting in another record-breaking year—totaling $53.2 billion for the global semiconductor equipment market.

“It’s really an exciting time for the industry in the terms of technology, the growth in information and data and that’s all going to require semiconductors to enable that growth,” said Dan Tracy, senior director, IR&S at SEMI.

The average of various analysts forecast the semiconductor industry in general 12% growth for the year. “It’s a very good growth year for the industry,” Tracy said. “In January, the consensus was about 5% growth for the year and with the improvement in the market and the firmer pricing for memory we see an increase in the outlook for the market.”

The SEMI Mid-year Forecast predicts wafer processing equipment is anticipated to increase 21.7 percent in 2017 to total $39.8 billion. The other front-end segment, which consists of fab facilities equipment, wafer manufacturing, and mask/reticle equipment, will increase 25.6 percent to total $2.3 billion. The assembly and packaging equipment segment is projected to grow by 12.8 percent to $3.4 billion in 2017 while semiconductor test equipment is forecast to increase by 6.4 percent, to a total of $3.9 billion this year.

“Based on the May outlook, we are looking at a record year in terms of tracking equipment spending. This is for new equipment, used equipment, and spending related to the facility that installed the equipment. It will be about a $49 billion market this year. Next year, it’s going to grow to $54 billion, so we have two years in a row of back to back record spending,” Tracy said.

In 2017, South Korea will be the largest equipment market for the first time. After maintaining the top spot for five years, Taiwan will place second, while China will come in third. All regions tracked will experience growth, with the exception of Rest of World (primarily Southeast Asia). South Korea will lead in growth with 68.7 percent, followed by Europe at 58.6 percent, and North America at 16.3 percent.

SEMI forecasts that in 2018, equipment sales in China will climb the most, 61.4 percent, to a total of $11.0 billion, following 5.9 percent growth in 2017. In 2018, South Korea, Taiwan, and China are forecast to remain the top three markets, with South Korea maintaining the top spot to total $13.4 billion. China is forecasted to become the second largest market at $11.0 billion, while equipment sales to Taiwan are expected to reach $10.9 billion.

SparkLabs Group, a network of accelerators and funds, is launching a $50 million early-stage fund (Series A & B) primarily focused on South Korea. The fund will be led by Brian Kang, who was a founding member of Samsung’s first venture capital arm and later led Korea Venture Fund, which was Korea’s first VC fund of funds. He has over 20 years of experience as an investment professional and several years as an entrepreneur and operator. He was CEO & Chairman of the Board at Gravity, a Softbank affliated gaming company, and then went on to launch his own gaming startup.

Brian is joined by Chris Koh, Co-founder of Coupang which is the leading ecommerce player in South Korea and received $1 billion investment from Softbank in 2015. Chris started Coupang with a classmate from Harvard Business School and their friend at Harvard Law. He was vice president of the company for five years focusing on operations and growth.

“We are grateful to SeAH who was one of the first investors in SparkLabs Global Ventures, our global seed fund, and now the anchor investor along with Korea Development Bank/Multi-Asset in our new Series A fund for South Korea. We believe we have assembled the best team to service entrepreneurs in Korea since all of us have built companies from the ground up in Korea and the U.S.,” stated HanJoo Lee, co-founder of SparkLabs.

SeAH is a top 50 business group in South Korea and Korea Development Bank/Multi-Asset is subsidiary of Mirae Asset, which is the largest asset manager in South Korea with over US$100 billion assets under management.

Brian Kang and Chris Koh are joined by Venture Partners (part-time partners) Rob Das, Co-founder and former Chief Architect of Splunk, and John Suh, CEO of Legalzoom. Splunk is a $8 billion market cap company that Rob helped grow from concept to its IPO in 2012. John has served as CEO since 2007 to help grow Legalzoom into the leading provider of online legal document services in the U.S. that has serviced almost 4 million customers.

“We are excited to launch this new early-stage fund to help Korea’s rapidly growing startup ecosystem. I believe the venture capital business must evolve as the startup environment is changing fast in Korea. Finding companies of global capacity, generating rich deal flow, adding real values post investment are becoming more and more critical to the success of venture investments. Chris and I look forward to working with other investors to help nurture the next generation of impact entrepreneurs in South Korea,” said Brian Kang, Co-founder and Managing Partner of SparkLabs Ventures.

SparkLabs Ventures is also supported by a heavy hitting advisory board that includes former Congressman Mike Honda, who served in the U.S. Congress from 2001 to 2017 (represented Silicon Valley in the 17th congressional district from 2013 to 2017); David Lee, Co-founder and Managing Partner of Refactor Capital; and Nadiem Makarim, Co-founder and CEO of Go-Jek, which recently raised $1.2 billion from Tencent and others.

The fund will focus primarily on South Korea startups at their Series A or B rounds, and will not be limited to graduates of SparkLabs accelerator in Seoul. The fund will focus its investments on companies that have potential to expand abroad to different markets and have the ability to take advantage of the global reach of the SparkLabs’ network. A secondary target region is SE Asia, so the fund will be open to startups within this region who have global ambitions.

Samsung Electronics Co., Ltd. today announced the launch of the “Q-series,” a new line-up of LED linear modules for use in premium indoor luminaire applications where an exceptionally high level of light efficacy* is required.

The Q-series features 200 lumens per watt (lm/W) of light efficacy, which is the highest efficacy level among current LED linear modules. The new modules are the first to incorporate the LM301B, Samsung’s recently announced mid-power LED package.

This allows LED lighting fixtures using the new modules to reach more than 150lm/W, enabled through an optical efficiency level of approximately 86 percent and LED driver efficiency of about 88 percent. The Q-series’ performance levels are ideally suited to meet DLC** Premium technical standards, which require higher efficacy and lumen maintenance specifications than the DLC Standard classification.

The new Q-series modules come in one-, two- and four-foot sizes, and can be combined linearly to achieve any desired length. There are two sets of modules: Q-series modules for the North American market are UL certified, while those for the European market have CE certification.

With the addition of the premium Q-series line-up, Samsung now offers five families of LED lighting modules (Q-, H-, M-, S- and V-series) to meet most indoor LED lighting needs. The Q-series has the same form factor as Samsung’s other modules for easy retrofitting with existing LED luminaires and is now available through Samsung’s worldwide LED sales network.

Samsung’s Q-series line-up includes:

(@ tp = 40 ºC, 4000K)
Region Type Model Luminous Flux Efficacy Conditions
US

4 ft.

LT-QB22A

4,000 lm

 203 lm/W

450 mA, 43.8 V
2 ft. LT-Q562A

2,000 lm

 450 mA, 21.9 V
1 ft. LT-Q282A

1,000 lm

 450 mA, 11.0 V
Europe 2 ft. LT-Q562B 2,000 lm 180 mA, 54.8 V
1 ft. LT-Q282B 1,000 lm 180 mA, 27.4 V

ROHM has recently announced the availability of the industry’s smallest class (1608 size) of 2-color chip LEDs. In addition to their breakthrough size, the SML-D22MUW features a special design that improves reliability along with a backside electrode configuration that supports high-resolution displays.

In recent years, chip LEDs are being increasingly used for numerical displays in industrial equipment and consumer devices. Conventional numerical displays utilize a single color to indicate numbers, but there is a growing need to change the color to make it easier to recognize abnormalities. However, this typically entails utilizing two separate LEDs, which doubles the mounting area along with development costs, or opting for a standard 2-color LED that also increases board size.

In contrast, proprietary technologies and processes allowed ROHM to integrate 2 chips in the same package size as conventional single-color LEDs, making it possible to emit multiple colors in a smaller footprint. Board space is reduced by 35% over standard 1.5 x 1.3mm 2-color LEDs, contributing to thinner displays. And after taking into consideration usage conditions during reflow, countermeasures were adopted that prevents solder penetration within the resin package to ensure greater reliability.

In a depressed visible LED industry, manufacturers are looking at new opportunities to increase their revenues and margins. In this context, the IR LED market is perceived as a potential new ‘blue ocean’ with attractive opportunities for those players.

While LEDs are important, VCSEL technology is the hot topic. “IR LEDs represented around 65% of the IR light source market in 2016, but this figure is likely to decrease to 45% in 2022,” commented Pierrick Boulay, Technology & Market Analyst at Yole Développement (Yole). Development of 3D cameras and autofocus applications, associated with the sensor fusion trend in smartphones and automotive, will strongly drive growth of the IR VCSEL market in the future (1).

All these topics will be discussed during the First Executive Forum on Laser Technologies created by Yole’s analysts, in collaboration with CIOE. Taking place on September 6&7 in Shenzhen, China, the Forum proposes an impressive agenda composed of 4 sessions, 19 presentations, debates and networking. All along the Forum, industrial experts will debate about the latest innovations, market trends and business opportunities. They will make a special focus on laser manufacturing and analyze the emerging applications. The agenda is now available: LASER FORUM AGENDA.

What are the technologies perspectives? What are the latest advances in semiconductor manufacturing? What will be the next applications? Innovation enables the identification of new business opportunities. It has further accelerated the adoption of laser solutions in many areas.

ir light sources

IR VCSEL represents a good compromise between traditional laser diodes, providing coherent and directional light, and IR LEDs, offering lower manufacturing cost and ease of integration. Additionally, IR VCSELs allow new sensing approaches, such as ToF . In this context, the IR VCSEL industry will be at the center of the attention and should experience strong growth in coming years. It is also likely that some players will work on both IR LEDs and lasers to maximize their revenues.

“Opportunities for both technologies will also be dependent on developments to overcome current limitations, towards longer wavelengths, higher performance, multi-spectral functionality and lower cost,” analyzed Yole’s expert, Pierrick Boulay. Typically, most current IR LEDs are in the 850nm or 940nm range. To enable emerging applications such as gas sensors or portable/integrated spectroscopy systems, longer wavelengths will be mandatory. In addition, integration of these light sources into sensors and modules will also be part of the challenge to be handled by the photonics industry.

Pierrick Boulay from Yole is one of the key speaker of the Emerging Applications session in the First Executive Forum on Laser Technologies agenda. Based on his strong expertise on LED lighting (general lighting, automotive lighting…) and OLED lighting, Pierrick proposes a relevant presentation, titled “IR laser: At the heart of the industry in coming years”. He will highlight the status of laser technologies and emerging applications including 3D camera, LIDAR, proximity sensors… This session also welcome other experts of the industry:
•  Rainer Paetzel, Director of Marketing, Coherent
•  Steven Hsieh, Senior Industry Analyst, ITRI
•  Hans van der Tang, Director Sales & Marketing – APAC Region, ElectroniCast Consultants

First Executive Forum’s program is also offering several networking times to discuss with industrial leaders and identify business opportunities… Discover the agenda and register today: LASER FORUM REGISTRATION 

A team of engineers has developed stretchable fuel cells that extract energy from sweat and are capable of powering electronics, such as LEDs and Bluetooth radios. The biofuel cells generate 10 times more power per surface area than any existing wearable biofuel cells. The devices could be used to power a range of wearable devices.

The epidermal biofuel cells are a major breakthrough in the field, which has been struggling with making the devices that are stretchable enough and powerful enough. Engineers from the University of California San Diego were able to achieve this breakthrough thanks to a combination of clever chemistry, advanced materials and electronic interfaces. This allowed them to build a stretchable electronic foundation by using lithography and by using screen-printing to make 3D carbon nanotube-based cathode and anode arrays.

The biofuel cells are equipped with an enzyme that oxidizes the lactic acid present in human sweat to generate current. This turns the sweat into a source of power.

Engineers report their results in the June issue of Energy & Environmental Science. In the paper, they describe how they connected the biofuel cells to a custom-made circuit board and demonstrated the device was able to power an LED while a person wearing it exercised on a stationary bike. Professor Joseph Wang, who directs the Center for Wearable Sensors at UC San Diego, led the research, in collaboration with electrical engineering professor and center co-director Patrick Mercier and nanoegnineering professor Sheng Xu, both also at the Jacobs School of Engineering UC San Diego.

The biofuel cell can stretch and flex, conforming to the human body. Credit: University of California San Diego

The biofuel cell can stretch and flex, conforming to the human body. Credit: University of California San Diego

Islands and bridges

To be compatible with wearable devices, the biofuel cell needs to be flexible and stretchable. So engineers decided to use what they call a “bridge and island” structure developed in Xu’s research group. Essentially, the cell is made up of rows of dots that are each connected by spring-shaped structures. Half of the dots make up the cell’s anode; the other half are the cathode. The spring-like structures can stretch and bend, making the cell flexible without deforming the anode and cathode.

The basis for the islands and bridges structure was manufactured via lithography and is made of gold. As a second step, researchers used screen printing to deposit layers of biofuel materials on top of the anode and cathode dots.

Increasing energy density

The researchers’ biggest challenge was increasing the biofuel cell’s energy density, meaning the amount of energy it can generate per surface area. Increasing energy density is key to increasing performance for the biofuel cells. The more energy the cells can generate, the more powerful they can be.

“We needed to figure out the best combination of materials to use and in what ratio to use them,” said Amay Bandodkar, one of the paper’s first authors, who was then a Ph.D. student in Wang’s research group. He is now a postdoctoral researcher at Northwestern University.

To increase power density, engineers screen printed a 3D carbon nanotube structure on top the anodes and cathodes. The structure allows engineers to load each anodic dot with more of the enzyme that reacts to lactic acid and silver oxide at the cathode dots. In addition, the tubes allow easier electron transfer, which improves biofuel cell performance.

Testing applications

The biofuel cell was connected to a custom-made circuit board manufactured in Mercier’s research group. The board is a DC/DC converter that evens out the power generated by the fuel cells, which fluctuates with the amount of sweat produced by a user, and turns it into constant power with a constant voltage.

Researchers equipped four subjects with the biofuel cell-board combination and had them exercise on a stationary bike. The subjects were able to power a blue LED for about four minutes.

Next steps

Future work is needed in two areas. First, the silver oxide used at the cathode is light sensitive and degrades over time. In the long run, researchers will need to find a more stable material.

Also, the concentration of lactic acid in a person’s sweat gets diluted over time. That is why subjects were able to light up an LED for only four minutes while biking. The team is exploring a way to store the energy produced while the concentration of lactate is high enough and then release it gradually.