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Recent Technological Advances In Flexible Electronics RECENT TECHNOLOGICAL ADVANCES IN FLEXIBLE
ELECTRONICS
1AKSHAT JARIWALA, 2SHIJIN RAMESH
Department of Electronics and Telecommunication engineering, Rajiv Gandhi Institute of Technology, India Department of Electronics and Telecommunication engineering, Rajiv Gandhi Institute of Technology, India
Abstract: Flexible electronics is a new field of research that is becoming popular day by day. The arrival of new era of
foldable power sources in integration with electronics has led to growing demand for portable, flexible roll-up displays,
biomedical sensors and wearable devices. Devices that are bendable or even wearable are unique in their functionality and
convenience. Not only do they have excellent electrochemical performance but also there is a drastic reduction in the devices
tendency to break or damage under pressure. We shall discuss about some of the latest technological innovations in foldable
electronics like flexible solar cells and place special focus on cable-type flexible batteries. We shall also introduce various
functional electrodes explored for flexible lithium ion batteries based on carbon nanotubes, graphene paper and also on a
newly advanced technology of using inkjet printable ink based on graphene(or prepared from graphene) and flexible LEDs.
A comprehensive discussion on supercapacitors and Proton Exchange Membrane Fuel Cells (PEMFCs) which are at the
forefront of present day energy storage technologies is dealt within this paper. These devices are high in demand in the
modern world and provide an avenue for extensive research to obtain superior next generation technologies.
Keywords: cable-type, carbon nanotubes, cable-type, graphene, inkjet, LEDs, PEMFCs, supercapacitors.
INTRODUCTION
considerable advancement in conventional battery In recent times, the new emerging trend of flexible energy storage systems in integration with FLEXIBLE ENERGY STORAGE
electronic equipment’s has taken a rapid growth and have garnered to become the cynosure of all eyes. There has always been a strong interest in portable and flexible electronic equipment such as roll up displays and wearable devices. In order to achieve The various functional electrodes explored for functionality of these devices in flexible form, compliant battery units with high energy and power density should be considered. The main purpose of this invention is to free the development of innovative energy storage systems from design limitation which Carbon nanotubes have unique electrical, is considered to be the most important technical pre- optical, mechanical and thermal properties which requisite. This paper includes discussion on recent make them very attractive for a wide range of progress made in the development of next generation applications. They have high electrical conductivity flexible energy storage systems such as lithium-ion and electron mobility which has paved way for an batteries, along with an overview of the progress extensive study for their possible use in diverse made in supercapacitors and flexible proton exchange applications of flexible electronic devices. A structure of thin, flexible lithium-ion battery was developed using plain paper as a separator and free standing In this paper, the present status and future CNT thin films as current collectors. The current development of each energy storage system such as collectors and battery materials were integrated onto lithium ion batteries, supercapacitors and proton a single sheet of paper through a lamination process. exchange membrane fuel cells is described based on The thin lithium-ion paper battery was very thin of approximately 300 micrometer thickness, had robust conformable solid electrolytes and soft current mechanical flexibility that could be bent up to a collectors. A more focus has been dedicated to the radius less than 6mm and a high energy density of technological advances in flexible lithium ion approximately 108 mAh/g. Despite of their excellent batteries and supercapacitors which have managed to performance, it was observed that direct coating of gain maximum attraction and smartly expanded their electrode slurry onto plain paper led to the occasional application scope. The second half of the paper internal shorting of the device due to the leakage of describes the development of a new design concept the electrode material through a large sized hole in called cable type flexible lithium ion battery with the paper. Therefore, an additional lamination process Omni-directional flexibility that represents a was required to apply a thin layer of polyvinylidene Proceedings of Fifth IRAJ International Conference, 15th September 2013, Pune, India, ISBN: 978-93-82702-29-0 Recent Technological Advances In Flexible Electronics extremely conductive electrodes. The resulting flexible and binder free electrodes of approximately patterns were found highly conductive and could lead to low cost applications in flexible energy storage interpenetrative nanocomposites of very long CNTs systems. Inkjet printing is one of the most vanadium oxide (V2O5) nanowires. These electrodes sophisticated printing methods that is relatively exhibit excellent electrochemical performance due to inexpensive and highly scalable. It has been their strong architecture that enables effective charge previously explored as a method for fabricating transportation and electrode integrity. The only challenge to this is the use lithium metal as a counter components. It is capable of printing large areas and can create variety of substrates making it suitable for next generation electronics. Inkjet printing with graphene is extremely promising, but it is a tedious task because it is difficult to produce an adequate In a new approach to flexible energy storage amount of graphene without compromising its systems, the use of flexible electrode based on free- electronic properties. Graphene is basic structural standing graphene paper to be applied in lithium element of graphite. Graphite often requires oxidizing rechargeable batteries has been suggested. Graphene conditions that makes the resulting graphene oxide paper is a functional material which not only acts as material less conductive than pure carbon. Pure conducting agent but also as a current collector. The unoxidizedgraphene can be achieved through properties of graphene are attractive and intriguing to exfoliation but the process requires solvents whose engineers, in particular to designers and developers of next generation electronic devices. It has a unique combination of outstanding properties such as high mechanical strength, large surface area and high electrical conductivity which makes graphene paper a suitable base material for flexible energy storage devices. Graphene based flexible electrode can deliver significantly improved performances in electrochemical properties such as in energy density and power density and also has a better life cycle compared to non-flexible conventional electrode. This unique graphene paper of diameter 10 cm and thickness of 10 micrometer was prepared by mechanically pressing a graphene aerogel. A distinctive characteristic of the resulting graphene Fig.1. Graphene based ink
paper was that it allowed graphene sheet folding which could effectively enhance the accessibility of Courtesy: The Journal of Physical Chemistry Letters, lithium ions and the electrolyte. Graphene when integrated with vanadium oxide electrode results in fabrication of thin, lightweight and flexible batteries. The cathode material V2O5 is grown on graphene paper by pulsed laser deposition (PLD – a well- known technique in fabricating thin films with its capacity to make high quality oxide ceramics with batteries, LG chem. Ltd demonstrated a new concept relatively fast deposition rates.) in a vacuum chamber of a cable type lithium ion battery for better battery at a base pressure less than 10-5 Torr. The target was architecture significantly superior to conventional prepared by cold pressing from a V2O5 power and batteries. It resulted in better mechanical flexibility that allowed maximum freedom in designing of a device as the battery could be placed anywhere and 2.1.2.1Inkjet printable ink based on graphene take up any shape. Its architecture consists of several electrode (anode) strands coiled to form a hollow Graphene is considered to be one of the most spiral core with a multi-helix structure, surrounded by ideal materials suitable for flexible electronics due to a modified polyethylene terephthalate nonwoven its remarkable properties. Its unique properties have separator membrane. The next layers are aluminium expanded its application in flexible electronics and wires and tubular outer electrode (cathode) and have helped researchers to come up with a new finally the cable battery is sealed by a shrunken advancement in it. A graphene based ink has been packaging insulator. The hollow electrode structure developed by scientists showing high conductivity favours both electronic and mechanical properties of and tolerance to bending. They used it to create inkjet the battery. The linear shape and Omni-directional print graphene patterns that could be used for flexibility of the cable battery has helped the cell Proceedings of Fifth IRAJ International Conference, 15th September 2013, Pune, India, ISBN: 978-93-82702-29-0 Recent Technological Advances In Flexible Electronics In an addition to this, a bendable inorganic thin film battery has been developed which enables the formation of high temperature annealed electrodes on polymer substrates. The lithium ion battery incorporating the new electrode was integrated with a flexible light emitting diode which demonstrated the feasibility of manufacturing an all in one flexible electronic system. A concern associated with this system is that the flexibility of the battery may mainly arise from the polydimethylsiloxane (PDMS) sheet wrapping and not from the cell components. Fig.3. Schematic structure and operational principle of
Courtesy: Journal of Industrial and Engineering Chemistry 12:
175–183
Also called ultracapacitors or double layer capacitor, they are much more effective regenerative energy storage devices than conventional chemical batteries. Unlike regular capacitors, supercapacitors do not have the conventional dielectric. They have a double layer construction with two carbon electrodes immersed in an organic electrolyte. Supercapacitors are very useful in short duration power boost applications. They are already being used to provide backup power for memory in cell phones and microcomputers. They are also being considered as a replacement for batteries in hybrid cars. These Fig.2. Cable type lithium ion battery
supercapacitors are able to discharge on acceleration Courtesy: Advanced materials, Volume 24, 5192-5197, October
and charge on braking of a vehicle. Hence, it has several advantages, such as high power density, fast charge and discharge mechanisms, long life cycle, no chemical actions and low impedance. It has These fuel cells convert chemical energy of limitations like low energy density and availability of the electrochemical reaction between hydrogen and power for a short duration only. Research is being oxygen into electrical energy. It basically consists of an anode, a cathode and an electrolyte membrane separating the anode and cathode. Hydrogen is delivered to the anode and is split into protons and electrons. The protons (H+ions) pass through the electrolyte and reach the cathode. Simultaneously, the electrons reach the cathode after passing through a load and a stream of oxygen is transmitted to the cathode. The oxygen reacts with the protons and electrons reaching the cathode to form water molecules. The formation of water results in a release of energy. The practical efficiency of such a system is approximately 40-60%. However PEMFCs are compact and, therefore, being considered for vehicles and other applications such as mobile phones. It is also being considered for a substitute to alkaline fuel cells in space shuttles. Fig.4. Double layer capacitor Courtesy: The Charge of the
Ultra-Capacitors, IEEE Spectrum, November 2007
Proceedings of Fifth IRAJ International Conference, 15th September 2013, Pune, India, ISBN: 978-93-82702-29-0 Recent Technological Advances In Flexible Electronics CONCLUSION
REFERENCES
Flexible electronics is at the forefront of [1] Lee, J. S. et al. (2006). Polymer electrolyte membranes for fuel cells,Journal of Industrial and Engineering Chemistry 12:
technological innovation. We have presented some of the latest devices in this field that are showing a lot of [2] J. G. Schindall, The Charge of the Ultra-Capacitors, IEEE promise. With each passing day, these devices are being improved with the use of nanotechnology. [3] Yo Han Kwon, Sang-Wook Woo, Hye-Ran Jung, HyungKyun Yu, Kitae Kim, Byung Hun Oh, SoonhoAhn, Sang-Young Cable-type Lithium-Ion Batteries, PEMFCs and Lee, Seung-Wan Song, Jaephil Cho, Heon-Cheol Shin, and Je Supercapacitors are currently being researched and Young Kim. Cable type flexible lithium ion battery based on developed. Along with Inkjet printers and Carbon hollow multi-helix electrodes, Advanced materials, Volume Nanotubes, these devices are already being put into [4] Sang-Young Lee, KeunHo Choi, Woo-Sung Choi, Yo Han practice. These advancements in technology not only Kwon, Hye-Ran Jung, Heon-Cheol Shin, Je Young Kim, challenge the existing conventional technology but Progress in flexible energy storage and conversion systems, indicate the prospect of completely substituting them with a focus on cable-type lithium-ion batteries, Energy and Environmental Science, Issue 8, 2013 [5] Mark Harsem, The Journal of Physical Chemistry Letters [6] HyeokjoGwon,aHyun-Suk Kim,‡aKye Ung Lee,aDong- HwaSeo,aYun Chang Park,bYun-Sung Lee,c Byung Tae Ahnaand KisukKang, sFlexible energy storage devices based on grapheme paper, Energy and Environmental, 2011, 4, 1277 Proceedings of Fifth IRAJ International Conference, 15th September 2013, Pune, India, ISBN: 978-93-82702-29-0

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