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

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.

Experimental validation of textured sensing skin for fatigue crack monitoring

“…Based on results from prior work evaluating the performance of various non-auxetic 19 and auxetic 20 textures, four candidate corrugated patterns are selected: a symmetric diagonal grid, a diagrid, a reinforced diagrid, and a non-symmetric re-entrant hexagonal honeycomb pattern. The diagonal grid (Figure 2(a)) is selected because of its fabrication simplicity.…”

“…The re-entrant hexagonal honeycomb pattern (Figure 2(d)) is an auxetic pattern, selected because it exhibited best performance among other auxetic patterns in. 20 Each corrugated pattern forms the top-surface texture of the sensing film with a sensing area of 63.5 mm by 63.5 mm (2.5 in by 2.5 in). The untextured pattern (flat pattern) used in prior work 9 is also considered in the evaluation for benchmarking purposes.…”

“…Recent discoveries on the SEC showed that texturing the dielectric layer through various corrugated surface patters yielded significant improvement in signal linearity stability, and resolution, attributable to a higher gauge factor resulting from lowering the sensor's transverse Poisson's ratio, and to higher mechanical stability from augmenting the in-plane stiffnesses. 19 This study was conducted experimentally on free-standing SEC specimens, and extended numerically to auxetic patterns in, 20 where these auxetic patterns exhibited better performance compared to the non-auxetic patterns evaluated in. 19 In this paper, the use of textured SECs for detecting and quantifying fatigue cracks in steel specimens is studied.…”

“…Its fabrication process is discussed in details by Laflamme et al 21 Briefly, its dielectric is formed by drop-casting a styrene-ethylene/butylene-styrene (SEBS)-titania solution, and the electrodes consist of a painted SEBS-carbon black solution. A textured SEC is fabricated by drop-casting the dielectric into a steel mold, 20 and painting the conductive paint onto the dried surfaces. Figure 1(a) shows the picture of an SEC with a re-entrant hexagonal honeycomb pattern.…”

Bio-inspired metasurface skin to enhance the performance of blue energy harvesting

“…Metamaterials are used to augment materials with additional functionalities including energy absorption, sensitivity, stretchability, and negative Poisson's ratio (NPR) [16]. Recently, auxetic metamaterials with NPR have been employed as conversion media in lieu of natural materials for developing high-performance PEH [17] and sensors [18]. In one of the initial works on metamaterial-inspired PEH, Farhangdoust et al [17] have analytically and numerically demonstrated that the harvested power output of a kirigami auxetic type of PEH could be 19.2 times greater than the power output produced by an equivalent conventional PEH.…”