Surface textures for stretchable capacitive strain sensors

Abstract

The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this thesis. The Graduate College will ensure this thesis is globally accessible and will not permit alterations after a degree is conferred.

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

“…Briefly, the Poisson’s ratio of an untextured dielectric film was measured with two digital cameras (FASTCAM SA-Z and Photron) by subjecting a specimen to a 30% uniaxial strain applied at 80 μm/s. Note that 30% is the maximum strain level used in this study, consistent with experimental tests conducted on free-standing SECs in [ 21 ] and with levels expected for the application [ 6 ], and that a characterization of the electromechanical model at higher strain levels is left to future work. A 7 × 7 mm 2 region around the transverse centerline was defined as the region of interest (red rectangle in Figure 3 a) to extract the Poisson’s ratio.…”

“…DIC was used to calculate Poisson’s ratio of the thin film, described in a previous work [ 21 ]. Briefly, the Poisson’s ratio of an untextured dielectric film was measured with two digital cameras (FASTCAM SA-Z and Photron) by subjecting a specimen to a 30% uniaxial strain applied at 80 μm/s.…”

“…The employed numerical model of a free-standing SEC was validated in previous work on several non-auxetic texture patterns [ 21 ], and textured sensors were fabricated and tested on animal skin. Here, previous experimental results obtained from a diagrid-like pattern, constructed from intersecting diagonals and vertical reinforcements, are used to validate the numerical model of the SEC partially adhered onto skin.…”

“…Previous work has demonstrated that the Poisson’s ratio of the thin film was tunable by augmenting the sensor with a texture. In particular, a diagrid-like pattern was experimentally shown to enhance directionality and to improve the experimental gauge factor by 30% [ 21 ]. The current paper extends the previous study to auxetic patterns, known to yield a negative Poisson’s ratio [ 22 , 23 ].…”

“…While the study presented in this paper is numerical, textured SECs (see Figure 1 a) were studied experimentally in a previous work [ 21 ] to validate the numerical model, and their fabrication is therefore of interest. The SEC consists of a stretchable parallel plate capacitor, where a dielectric layer is sandwiched between two electrode layers.…”