PROSTHETICS
low-cost, which are attractive advantages with respect to state-of-the-art techniques conventionally used to define patterns on graphene. The transfer of graphene from growth substrate to a flexible substrate and its later patterning to obtain capacitive structures is carried out by using techniques that are fully compatible with flexible substrates while preserving initial properties of the material at a very low production cost. The validity of fabricated tactile skin was probed by integrating touch patches at fingers’ phalanges of a state-of-the-art bionic hand. The response of each graphene sensor was converted from capacitive variation to a voltage through a home-made readout interface circuitry also designed and implemented in a flexible polyimide substrate. Resulting sensors response to both static and dynamic stimuli were evaluated by performing tasks, ranging from simple touching to grabbing of soft objects such as eggs, soft-balls, etc. This real-time tactile feedback given by the touch sensors allows the robotic hand to perform the controlled manipulation of surrounding objects. In this regard, the pressure measured by each individual sensor located at different positions along fingers of the robotic hand, determine the motion of each finger actuator. In this scenario, once the desired pressure is configured in the controlloing software, each finger will move up to reach that pressure set point. The described architecture is meant to mimick human behaviour for grabbing objects, which accurately allows the robotic hand - with the integrated electronic skin - to grab objects of different shapes, textures, and densities in a controlled way.
Producing power
The fabricated electronic-skin and its combination with a solar cell is a huge step towards the development of a fully
), the solar cell used in this work would generate around 19.2 mW, which is more than the power needed to drive an electronic-skin module, i.e. an indivudual graphene touch sensor. Further advancements in terms of high- efficiency energy-harvesting, energy-storing, and tetherless implementation could lead to a full autonomy of the electronic-skin. This new concept is a step forward toward a new generation of energy-autonomous tactile skins by harvesting ambient light energy, allowing the charging of batteries, either to power actuators or to power-up integrated circuits (ICs) on large area electronic-skin, leading to self-powered robotics/prosthetic limbs with tactile sensitivity. This approach can be further exploited by integrating our flexible touch sensors on flexible and stretchable solar cells, enabling a new concept of stretchable, energy- autonomous robotics and prosthetic skin. Furthermore, electronic-skin response could be in the future transmitted thorough a wireless communication protocol to a control unit (internet-of-things) increasing the functionality of electronic-skin by making the device portable as well as energy-autonomous. CSJ
autonomous electronic-skin. Transparency of all the layers used in our touch sensors, including the protective layer atop the active area, the capacitive layer based on single layer graphene and the thin and flexible plastic substrate, permitted the integration of touch sensitive layer directly on top of a solar cell. Due to the intrinsic transparency of all layers existing in the sensor (maximum absorbance in the visible range of the whole structure was measured up to 3.25%), incident light is efficienlty transmitted through the whole structure, reaching the surface of the solar cell. The solar cell used in this work can produce a power of 160 Wcm−2. If the tactile skin presented here were to cover the glabrous skin of a human hand (average area around 120 cm2
About the author
Dr Ravinder Dahiya is Reader and EPSRC (Engineering and Physical Science Research Council) Fellow in the School of Engineering at University of Glasgow, UK. He is also the director of Electronics Systems and Design Centre (ESDC) at the University. Dr Dahiya is leader of the Bendable Electronics and Sensing Technologies (BEST) group, which conducts fundamental research on high-mobility materials based flexible electronics and electronic skin, and their application in robotics, prosthetics and wearable systems.
He has led many international projects including those funded by European Commission, EPSRC, The Royal Society, The Royal Academy of Engineering, and The Scottish Funding Council. He is distinguished lecturer of IEEE Sensors Council and was general chair of IEEE PRIME 2015.
Dr Dahiya holds prestigious EPSRC
Fellowship. In the past, he received Marie Curie Fellowship and Japanese Monbusho Fellowship.
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