Cho+Byung+Jin
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Thermoelectric generator on glass fabric for wearable electronic devices
Wearable computers or devices have been hailed as the next generation of mobile electronic gadgets, from smart watches to smart glasses to smart pacemakers. For electronics to be worn by a user, they must be light, flexible, and equipped with a power source, which could be a portable, long-lasting battery or no battery at all but a generator. How to supply power in a stable and reliable manner is one of the most critical issues to commercialize wearable devices.
A team of KAIST researchers headed by Byung Jin Cho, a professor of electrical engineering, proposed a solution to this problem by developing a glass fabric-based thermoelectric (TE) generator that is extremely light and flexible and produces electricity from the heat of the human body. In fact, it is so flexible that the allowable bending radius of the generator is as low as 20 mm. There are no changes in performance even if the generator bends upward and downward for up to 120 cycles.
To date, two types of TE generators have been developed based either on organic or inorganic materials. The organic-based TE generators use polymers that are highly flexible and compatible with human skin, ideal for wearable electronics. The polymers, however, have a low power output. Inorganic-based TE generators produce a high electrical energy, but they are heavy, rigid, and bulky.
Professor Cho came up with a new concept and design technique to build a flexible TE generator that minimizes thermal energy loss but maximizes power output. His team synthesized liquid-like pastes of n-type (Bi2Te3) and p-type (Sb2Te3) TE materials and printed them onto a glass fabric by applying a screen printing technique. The pastes permeated through the meshes of the fabric and formed films of TE materials in a range of thickness of several hundreds of microns. As a result, hundreds of TE material dots (in combination of n and p types) were printed and well arranged on a specific area of the glass fabric.
Professor Cho explained that his TE generator has a self-sustaining structure, eliminating thick external substrates (usually made of ceramic or alumina) that hold inorganic TE materials. These substrates have taken away a great portion of thermal energy, a serious setback which causes low output power.
He also commented,
"For our case, the glass fabric itself serves as the upper and lower substrates of a TE generator, keeping the inorganic TE materials in between. This is quite a revolutionary approach to design a generator. In so doing, we were able to significantly reduce the weight of our generator (~0.13g/cm2), which is an essential element for wearable electronics."
When using KAIST's TE generator (with a size of 10 cm x 10 cm) for a wearable wristband device, it will produce around 40 mW electric power based on the temperature difference of 31 °F between human skin and the surrounding air.
Professor Cho further described about the merits of the new generator:
"Our technology presents an easy and simple way of fabricating an extremely flexible, light, and high-performance TE generator. We expect that this technology will find further applications in scale-up systems such as automobiles, factories, aircrafts, and vessels where we see abundant thermal energy being wasted."
This research result was published online in the March 14th issue of Energy & Environmental Science and was entitled "Wearable Thermoelectric Generator Fabricated on Glass Fabric."
Youtube Link: http://www.youtube.com/watch?v=BlN9lvEzCuw&feature=youtu.be
[Picture Captions]
Caption 1: The picture shows a high-performance wearable thermoelectric generator that is extremely flexible and light.
Caption 2: A thermoelectric generator developed as a wristband. The generator can be easily curved along with the shape of human body.
Caption 3: KAIST’s thermoelectric generator can be bent as many as 120 times, but it still shows the same high performance.
2014.04.21 View 19798 -
Inexpensive Separation Method of Graphene Developed
The problem with commercializing graphene that is synthesized onto metals over a wide area is that it can not be separated from the metal. However, a groundbreaking separation technology which is both cheap and environment friendly has been developed.
Prof. Taek soo Kim and Prof. Byung Jin Cho"s research teams have conducted this research under the support of the Global Frontier program and Researcher Support Program initiated by The Ministry of Education and Science and Korea Research Foundation. The research results have been posted on the online news flash of Nano Letters on februrary 29th. (Thesis title: Direct Measurement of Adhesion Energy of Monolayer Graphene As-Grown on Copper and Its Application to Renewable Transfer Process)
The research has generated exact results on the interfacial adhesive energy of graphene and its surface material for the first time. Through this, the catalyst metal are no longer to be used just once, but will be used for an infinite number of times, thereby being ecofriendly and efficient.
Wide area graphine synthesized onto the catalyst meatal are used in various ways such as for display and for solar cells. There has been much research going on in this field. However, in order to use this wide area graphene, the graphene must be removed from the catalyst metal without damage.
Until now, the metal had been melted away through the use of chemical substances in order to separate the graphene. However, this method has been very problematic. The metal can not be reused, the costs are very high, much harmful wastes were created in the process of melting the metals, and the process was very complicated.
The research teams of Professors Taek Su Kim and Byung Jin Cho measured the interfacial adhesive energy of the synthesized graphene and learned that it could be easily removed.
Also, the mechanically removed graphene was successfully used in creating molecular electronic devices directly. This has thus innovatively shortened the graphene manufacturing process. Also, it has been confirmed that the metalic board can be reused multiple times after the graphene is removed. A new, ecofriendly and cost friendly method of graphene manufacturing has been paved.
Through this discovery, it is expected that graphene will become easier to manufacture and that the period til the commercialization date of graphene will therefore be greatly reduced
Prof. Cho stated " This reserach has much academical meaning significance in that it has successfully defined the surfacial adhesive energy between the graphene and its catalyst material and it should receive much attention in that it solved the largest technical problem involved in the production of graphene.
2012.04.04 View 12601