Artificially innervated self-healing foams as synthetic piezo-impedance sensor skins

Hongchen Guo,Zi Wei Lim,Yu Jun Tan,Benjamin C K Tee,Glenys Jocelin Susanto,Le Yang,Hian Hian See,Zijie Yang,Ge Chen,Zifeng Wang

doi:10.1038/s41467-020-19531-0

Abstract

Human skin is a self-healing mechanosensory system that detects various mechanical contact forces efficiently through three-dimensional innervations. Here, we propose a biomimetic artificially innervated foam by embedding three-dimensional electrodes within a new low-modulus self-healing foam material. The foam material is synthesized from a one-step self-foaming process. By tuning the concentration of conductive metal particles in the foam at near-percolation, we demonstrate that it can operate as a piezo-impedance sensor in both piezoresistive and piezocapacitive sensing modes without the need for an encapsulation layer. The sensor is sensitive to an object’s contact force directions as well as to human proximity. Moreover, the foam material self-heals autonomously with immediate function restoration despite mechanical damage. It further recovers from mechanical bifurcations with gentle heating (70 °C). We anticipate that this material will be useful as damage robust human-machine interfaces.

Highlights

Human skin is a self-healing mechanosensory system that detects various mechanical contact forces efficiently through three-dimensional innervations
When a normal or shear-force is applied, the foam material will be compressed, which deforms in shape to the relative electrodes
The 3D electrodes hold the foam material in place, even if the sensing material is delaminated from the printed circuit board (PCB) due to wear-and-tear (Supplementary Fig. 1)

Summary

Introduction

Human skin is a self-healing mechanosensory system that detects various mechanical contact forces efficiently through three-dimensional innervations. 1234567890():,; Human skin has remarkable self-healing abilities while being innervated by a wide variety of sensory neuron subtypes known as mechanoreceptors[1,2] These mechanoreceptors buried beneath the skin extending into the epidermis convey the tactile stimuli to the nerves and enable us to use the sense of touch to manipulate objects, perform social communication, and react to unstructured external environments[1,2]. Inspired by the architecture of the human somatosensory innervations, we propose a new structure that uses threedimensional (3D) metal wire electrodes as “nerves” embedded within a low-modulus yet elastic self-healing foam we termed artificially innervated foam (AiFoam) (Fig. 1). Compared with other foam-based sensors (Table 2), our synthesized self-healing foam material has a low-modulus of 600 kPa and is relatively elastic to provide a restoring force for contact forces sensing. The AiFoam e-skin can detect both tactile contact and proximity of the human touch

Methods

Results

Conclusion