Nanowire FET Based Neural Element for Robotic Tactile Sensing Skin

Abstract

This paper presents novel Neural Nanowire Field Effect Transistors (υ-NWFETs) based hardware-implementable neural network (HNN) approach for tactile data processing in electronic skin (e-skin). The viability of Si nanowires (NWs) as the active material for υ-NWFETs in HNN is explored through modeling and demonstrated by fabricating the first device. Using υ-NWFETs to realize HNNs is an interesting approach as by printing NWs on large area flexible substrates it will be possible to develop a bendable tactile skin with distributed neural elements (for local data processing, as in biological skin) in the backplane. The modeling and simulation of υ-NWFET based devices show that the overlapping areas between individual gates and the floating gate determines the initial synaptic weights of the neural network - thus validating the working of υ-NWFETs as the building block for HNN. The simulation has been further extended to υ-NWFET based circuits and neuronal computation system and this has been validated by interfacing it with a transparent tactile skin prototype (comprising of 6 × 6 ITO based capacitive tactile sensors array) integrated on the palm of a 3D printed robotic hand. In this regard, a tactile data coding system is presented to detect touch gesture and the direction of touch. Following these simulation studies, a four-gated υ-NWFET is fabricated with Pt/Ti metal stack for gates, source and drain, Ni floating gate, and Al2O3 high-k dielectric layer. The current-voltage characteristics of fabricated υ-NWFET devices confirm the dependence of turn-off voltages on the (synaptic) weight of each gate. The presented υ-NWFET approach is promising for a neuro-robotic tactile sensory system with distributed computing as well as numerous futuristic applications such as prosthetics, and electroceuticals.

Tactile innervation densities across the whole body

“…Despite its importance for manipulation (3), movement (4), our sense of body ownership (5), and affection (6), we know little about the number and distribution of cutaneous fibers innervating different skin regions across the body. Estimates of tactile fiber innervation in the current literature are few, often incomplete and inconsistent, and range from a total innervation of around 45,000 fibers (7) into the millions (8). Most textbooks do not even venture a guess (9)(10)(11)(12).…”

Transforming the short-term sensing stimuli to long-term e-skin memory

“…With such integration strategy, the eskin is able to not only detect the short term stimuli from external environment, but transform it to a long term information storage without power supply as well. We believe this work can enrich the study of e-skin and can be explored in the future for more potential applications in bionics [6,7].…”

Propagation of amorphous oxide nanowires via the VLS mechanism: growth kinetics

“…Inorganic nanowires (NWs) with diameters < 100 nm are widely studied as they hold great potential for nanoelectronics, 1,2 sensors, 3,4 exible electronics, 5-7 energy generation, 8 energy storage, 9,10 etc., owing to their interesting physical and chemical properties. [11][12][13][14][15][16] For example, the rapid change in the resistance of ZnO NWs with exposure to UV light makes them ideal for wearable dosimeters.…”