Numerical Investigation of Auxetic Textured Soft Strain Gauge for Monitoring Animal Skin.

Han Liu,Colin Wiersema,Eric M Zellner,Sarah A Bentil,Jin Yan,Iris V Rivero,Matthias Kollosche,Simon Laflamme

doi:10.3390/s20154185

Abstract

Recent advances in hyperelastic materials and self-sensing sensor designs have enabled the creation of dense compliant sensor networks for the cost-effective monitoring of structures. The authors have proposed a sensing skin based on soft polymer composites by developing soft elastomeric capacitor (SEC) technology that transduces geometric variations into a measurable change in capacitance. A limitation of the technology is in its low gauge factor and lack of sensing directionality. In this paper, we propose a corrugated SEC through surface texture, which provides improvements in its performance by significantly decreasing its transverse Poisson’s ratio, and thus improving its sensing directionality and gauge factor. We investigate patterns inspired by auxetic structures for enhanced unidirectional strain monitoring. Numerical models are constructed and validated to evaluate the performance of textured SECs, and to study their performance at monitoring strain on animal skin. Results show that the auxetic patterns can yield a significant increase in the overall gauge factor and decrease the stress experienced by the animal skin, with the re-entrant hexagonal honeycomb pattern outperforming all of the other patterns.

Highlights

The study of the mechanical, physiological, and morphological structural responses of skin tissues is of great interest in biomedical fields such as tissue engineering and regenerative medicine [1], and can affect surgical outcomes including the amelioration of scar tissue
The current paper extends the previous study to auxetic patterns, known to yield a negative Poisson’s ratio [22,23]
This study investigates, for the first time, five auxetic patterns to form textured soft elastomeric capacitor (SEC) for tailoring the mechanic inhomogeneities to enhance sensing properties and how they might be described in terms of Poisson’s ratio

Summary

Introduction

The study of the mechanical, physiological, and morphological structural responses of skin tissues is of great interest in biomedical fields such as tissue engineering and regenerative medicine [1], and can affect surgical outcomes including the amelioration of scar tissue. The heterogeneous skin is comprised of collagen, elastin fibers, and ground substance in a proteolytic matrix [2], and the study of the mechanical, physiological, and morphological structural responses of skin tissues is of great interest. Different techniques such as optical coherence tomography (OPT) [3] and digital image correlation (DIC) [4] have been used for ex vivo studies of the skin’s deformation. A solution to quantify deformation is the use of external stretchable and wearable strain sensors Such technology has been demonstrated for human motion detection [7], health monitoring [8], and soft robotics [9]. This fabrication process, described in more detail in [13], is adapted to create textures by drop-casting the SEBS composite solution in grooved steel molds instead of over smooth glass surfaces

Methods

Results

Conclusion