With the launch of Google Glass and the Samsung Galaxy Gear wristwatch this year, wearable electronics have moved from abstract concepts to tangible products. To integrate these electronic devices seamlessly into clothing, watchbands, and backpacks, some engineers are developing flexible, powerful textile-based batteries. Now researchers in South Korea have built one of the most durable wearable batteries to date on polyester fabric (Nano Lett. 2013, DOI: 10.1021/nl403860k). The battery, which the researchers sewed into a shirt, can be folded 10,000 times without losing function.
Most attempts to make textile batteries have had limited success, says materials scientist Jang Wook Choi of the Korea Advanced Institute of Science and Technology (KAIST).
The problem has been finding battery materials that can retain high function while being bent repeatedly. For example, batteries with metal foils as electrodes can bend only a few times before breaking. Electrodes made by dipping cloth in nanoparticle inks, such as solutions of carbon nanotubes, are more durable than the foils, but the electrical resistance of these cloth electrodes is relatively high, which limits the size of the batteries and the total amount of energy they can store.
To solve these challenges, Choi rethought the entire design of textile batteries, starting with the electrode. He turned to nickel, because it is a fantastic conductor. To make a flexible, but still highly conductive metal electrode, Choi came up with the idea of electroplating nickel onto polyester fabric. The process is simple, and the nickel-coated textile retains the mechanical properties of the fabric. The electrodes had a very low electrical resistance, about 0.35 ohms per square, comparable to that of a pure nickel metal foil.
The other critical component is the polymer used to bind the anode and cathode materials onto the electrodes in the battery. If this binder material fails, the battery will peel apart and stop functioning. Choi found that polyurethane had the right mechanical properties. To complete the battery, Choi’s group used conventional lithium-ion battery materials for the anodes and cathodes.
Choi’s group put the polyester-based batteries through their paces. Other groups have demonstrated bending and flexing of batteries, but the KAIST team thought the real test of mechanical durability would be to fold the device with firm creases. They powered an array of light-emitting diodes with the battery and folded it repeatedly. After 10,000 folding and unfolding cycles, the textile battery still worked. Batteries built with aluminum foil electrodes broke after three cycles and stopped working altogether after 100 cycles.
The KAIST group showed that their textile batteries can be sewn into a sweatshirt and a watchband. They also integrated the batteries with flexible solar cells so the batteries could recharge without needing to be removed from the clothing. “It’s quite comfortable to wear,” Choi says, adding that the battery is sealed so people could wash the fabric with the battery still attached.
“I’m really impressed,” says Yi Cui, a battery researcher at Stanford University. The KAIST group has successfully put their batteries through much harsher mechanical tests than others have been able to, he says.
The next step, Cui says, is to use battery materials that can store more energy to further improve the performance. So far, the KAIST team has used lithium iron phosphate for the cathode and lithium titanium oxide for the anode. Cui says that using a carbon anode material in the textile battery would increase the battery’s voltage, which determines how much power the device can deliver and how fast it can recharge. The voltage of the textile battery is about 2.5 V, and Choi says it should be about 3.8 V for practical applications.
Indeed, Choi’s group is experimenting with other materials, in collaboration with an unnamed South Korean battery maker that is interested in scaling up production of the wearable batteries.
- Chemical & Engineering News
- ISSN 0009-2347
- Copyright © 2013 American Chemical Society
The sun will hopefully be the energy source of the future, but currently, solar power provides less than 1% of global energy. The reason isn’t due to a conspiracy among fossil fuel companies, as some media outlets apparently believe, but because of multiple inherent problems with solar technology. In a nutshell, there is a tradeoff between efficiency and cost.
For example, the current world-record for efficiency (i.e., the ability to convert light into electricity) is 44.7%, held by a multi-junction solar cell used in concentrated photovoltaics. However, for various reasons, such systems are still expensive. Cheaper solar cells, such as the ones you can mount on your roof, are more reasonably priced but have efficiences only around 10 to 20%. Thus, the “holy grail” is to design a solar cell with high efficiency and low cost.
One possible avenue is a design referred to as a dye-sensitized solar cell (DSSC). (Here is a video explaining how DSSCs work.) In a DSSC, dye molecules attached to titanium dioxide absorb photons and release electrons, creating an electric current.
Now, researchers from South Korea have added mobile quantum QTM -0.64% dots to the mix. Quantum dots (QDs) are nanoparticles that have a unique feature: They are able to generate more than one electron for every photon that is absorbed, a phenomenon known as “multiple exciton generation.” QD-DSSCs, therefore, have a higher efficiency than regular DSSCs. (See figure.)
As shown above, DSSCs containing red quantum dots (R-QD) were the best at increasing both light absorption and external quantum efficiency (a measure of how many electrons are generated per photon absorbed).
The authors told RealClearScience in an e-mail that the maximum efficiency of their system is 8.83%, which is obviously lower than most existing solar cell technologies. However, DSSCs are relatively cheap to produce, and with further research, they believe that they can crank up the efficiency way past 33.7% (the Shockley-Queisser limit, which is a theoretical limit on the efficiency of single junction solar cells).
Techies and investors should keep an eye on this emerging technology.
This article originally appeared on RealClearScience.
Source: Gede Widia Pratama Adhyaksa, Ga In Lee, Se-Woong Baek, Jung-Yong Lee & Jeung Ku Kang. “Broadband energy transfer to sensitizing dyes by mobile quantum dot mediators in solar cells.” Scientific Reports 3, Article number: 2711. Published 19-September-2013. doi:10.1038/srep02711
Note To Readers: While monitoring patent activity is neither novel nor “ground breaking”, it is worthy to note the activity as it applies in certains areas of research with burgeoning interest … such as the application of “nanomaterials” in the OLED/ QLED markets, as being “the next generation display material.”
Analysis of Patent Application Trends By country, 93 patents (or 34%) were filed in South Korea, 87 in the U.S., 36 in Japan, 22 in Europe, and 35 under the PCT. By technology, patents on quantum dot light emitting diodes (QLED) technology (188 patents, 69%) were applied the most, followed by those on BLU using the white light source; quantum dot display; and LED-using white light source technologies.
Implications As the quantum dot display has emerged as the next-generation display technology ever since the OLED, the leading companies in the display industry, including Samsung and LG, are making aggressive investment to take a lead in the technology. They not only develop their own technologies, but also purchase patents from; make technology licensing agreements with; or make equity investment in the companies of the field.
The competition to obtain key patents on the quantum dot display is expected to only increase. Monitoring published/issued patents on a regular basis and having a thorough analysis on them have become more important.
Key Patent Report – Quantum Dot Display covers patent application trends and an in-depth analysis.
*** Excerpted from: Flexible OLED/ QLED Screen Markets to Reach $72 Billion by 2016
” … Once freed from today’s relatively heavy, breakable and fixed glass displays, tomorrow’s devices may look very different, with screens that can be rolled out, attached to uneven surfaces, or even stretched. But there’s still some way to go.
“It becomes a product designer’s paradise — once the technology is sorted out,” says Jonathan Melnick, who analyzes display technology for Lux Research.
There is no shortage of prototypes. South Korea’s Samsung Electronics this year showed off a display screen that extends from the side of a device — but obstacles remain: overcoming technical issues, figuring out how to mass produce parts cheaply, and coming up with devices compelling enough for gadget buyers.
Screen technology — with the global small display market expected to more than double to around $72 billion by 2016, according to DisplaySearch — is still dominated by liquid crystal displays (LCDs), which require a backlight and sit between two sheets of glass, making the screen a major contributor to the weight of a device, from laptops to tablets.”
Samsung Galaxy Skin was displayed with a flexible screen
Samsung is pushing the envelope in new areas of smartphone design, as it displayed devices with screens that bend. Samsung Galaxy Skin is reported to feature a flexible AMOLED, which uses a plastic polymer instead of glass. The new range of Samsung’s flexible phones will come in handy for clumsy hands as the device is reported to survive falls and blows.
The devices with flexible screens from Samsung are reported to be in the last phase of development and are rumoured to be released in the first half of next year. The flexibility of the screen is a result of the use of organic light emitting diodes (OLEDs), which are thin and can be applied on flexible material, like plastic or metal foil.
Samsung is not the only company which has tried to create something unique like the flexible screens as companies like Japan’s Sony and South Korea’s LG Display have launched prototypes of the flexible screens. Samsung had previously promised flexible displays this year, but the date has passed with no confirmation from the South Korean manufacturer.
The prototypes of the flexible devices were displayed at the 2012 Plastics show in Birmingham this week. With the flexible devices, Samsung might be looking to create a unique pedestal for the South Korean company and the bendy devices might prove to be the factor, which pushes Samsung ahead.
Lee Chang-hoon, Vice President of Samsung’s display division, told the Journal that the South Korean company has sent out samples of the new displays to a few select customers.
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Published on October 14th, 2010 by ecopolitology
The South Korean government has announced that it intends to invest $35.4 billion in the renewable energy sector over the next five years as it aims at reducing its dependence on fossil fuels and build a green economy for the future.
The announcement was made by a presidential task force which is responsible for the drafting the country’s green energy policy. According to the announced plans, the green energy thrust to the economy would be provided through a combination of public and private initiatives.
The South Korean government announced the ‘Green Korea‘ plan in September 2008 which identified nine key areas for green investment: solar and wind power, light-emitting diodes (LED), hydrogen fuel cells, gas-to-liquid energy, integrated gasification combined cycle (IGCC) and energy storage.
The South Korean government plans to increase the solar power generation capacity to 400 MW by 2012. In addition to large-scale power plants the government is also looking to investment in home-basedsolar power systems. According to the ministry of Knowledge Economy, a total of 100,000 homes will have solar power systems installed by 2012 these will include all government-planned buildings and 60 percent of privately-owned homes will have solar power systems.
And seeing a local market opportunity, South Korean manufacturing giants like Hyundai, Samsung and LG have also invested heavily in solar.
The country aims at increasing the installed wind energy capacity to 1000 MW by 2012. There are plans for creating local manufacturing hubs which would supply wind turbine components to the local as well as foreign markets. The aim is to grab 10 percent share of the world’s wind energy technology supply chain by 2020.
The local companies like Hanjin Corporation are installing there own medium-sized wind turbines in the existing wind farms and are also looking to develop wind turbines of more than 5 MW generation capacity.
The new automobile policy has been designed keeping in mind Korea’s strong automobile sector. The government has outlined a policy which targets development of next-generation engines which are fuel flexible, that is, can be operated with several combinations of fuels. Several automakers in Korea are preparing to launch fuel cell-based cars in the near future and many, including Hyundai Motors, have launched hybrid cars which runs on cleaner fuels like natural gas.
The government will invest $5.6 billion in the automobile sector by 2013 as it aims at becoming one of the four largest green cars manufacturing nations.
The government believes that the green industry can generate more jobs than conventional industries. If these projects are executed as per plans the government expects to generate more than 100,000 jobs by 2012 which can increase to 950,000 by 2030.