Neuromorphic high-density tactile sensor readout for electronic skins (e-skins)

To mimic the rich tactile information captured by human hands and fingertips during object manipulation in electronic skin (e-skin) applications such as for prosthetics and robotics, it is necessary to achieve tactile sensing and processing with at least the same energy efficiency and taxel density. The research aims for this goal by integrating a dense tactile sensor array on a custom readout chip, allowing for dense and power-efficient readout with local processing capabilities. The sensor-to-readout chip integration supports dense per-taxel connections, enabling true per-taxel sparse-sampling conversion (i.e., spikes) for further local signal processing. Two versions of the taxel readout design have been developed.
The first design is an e-skin taxel readout chip in 0.18μm CMOS technology has been realized that achieves the highest reported spatial resolution of 200μm, comparable to human fingertips. PVDF-based piezoelectric sensors are integrated on the chip, enabling a per-taxel signal conditioning frontend and spiking readout combined with local embedded neuromorphic first-order processing through complex receptive fields (CRFs). Experimental results show that Spiking Neural Network (SNN)-based offline classification of the chip’s spatiotemporal spiking output for input tactile stimuli such as texture and flutter frequency achieves excellent accuracies up to 97.1% and 99.2%, respectively.
The second design is an e-skin taxel readout chip in a-IGZO thin-film transistor (TFT) technology. It has lower spatial resolution, but has been designed to enable slip detection during grasping.