New materials and advances in making electronic skin for interactive robots

Flexible electronics has huge potential to bring revolution in robotics and prosthetics as well as to bring about the next big evolution in electronics industry. In robotics and related applications, it is expected to revolutionise the way with which machines interact with humans, real-world objects and the environment. For example, the conformable electronic or tactile skin on robot’s body, enabled by advances in flexible electronics, will allow safe robotic interaction during physical contact of robot with various objects. Developing a conformable, bendable and stretchable electronic system requires distributing electronics over large non-planar surfaces and movable components. The current research focus in this direction is marked by the use of novel materials or by the smart engineering of the traditional materials to develop new sensors, electronics on substrates that can be wrapped around curved surfaces. Attempts are being made to achieve flexibility/stretchability in e-skin while retaining a reliable operation. This review provides insight into various materials that have been used in the development of flexible electronics primarily for e-skin applications

Glycine–Chitosan-Based Flexible Biodegradable Piezoelectric Pressure Sensor

This paper presents flexible pressure sensors based on free-standing and biodegradable glycine-chitosan piezoelectric films. Fabricated by self-assembly of biological molecules of glycine within a water-based chitosan solution, the piezoelectric films consist of stable spherulite structure of β-glycine (size varying from few millimetres to centimetre) embedded in amorphous chitosan polymer. The polymorphic phase of glycine crystals in chitosan, evaluated by X-ray diffraction, confirms the formation of pure ferroelectric phase of glycine (β-phase). Our results show that a simple solvent casting method can be used to prepare a biodegradable β-glycine/chitosan based piezoelectric film with sensitivity (~ 2.82 ± 0.2 mV kPa−1) comparable to those of non-degradable commercial piezoelectric materials. The measured capacitance of the β-glycine/chitosan film is in the range of 0.26 nF to 0.12 nF at a frequency range of 100 Hz and 1 MHz and its dielectric constant and the loss factor are 7.7 and 0.18 respectively in high impedance range under ambient conditions. The results suggest that glycine-chitosan composite is a promising new bio-based piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics

VLS growth mechanism of Si-nanowires for flexible electronics

Nanowires (NWs) are promising building blocks for flexible electronics and sensors and a number of approaches have been used to develop them. Among these, the vapor-liquid-solid (VLS) mechanism has been most appealing as it provides the electronic quality NWs at low fabrication cost. For these reasons, this method plays an important role in many applications including NWs based flexible electronics. The performance of NWs based electronics and sensors depend on their quality and the underlying growth mechanism, which thus far has not attracted much attention. In this paper, we present the physical chemistry model that explains the atomistic aspects of the growth mechanism of silicon nanowires. The mechanistic equations have been derived for various steps involved in a standard VLS growth process. The supersaturation under the steady state conditions has been calculated and utilized to estimate the growth rate of Si-NWs under different temperature conditions. The estimated values are found to be consistent with the reported measured values. The results from our study indicate that the Si-NW growth rate is directly related to the temperature. High-temperatures (~900°C) lead to longer Si-NWs (tens of microns length). This knowledge about growth conditions for Si-NW will enable better control of Si-NW dimensions and hence will have significant positive impact on using Si-NW in flexible electronics - especially the contact printing of NWs based electronic layers on flexible substrates