Aerosol jet printed capacitive strain gauge for soft structural materials

Abstract

Soft structural textiles, or softgoods, are used within the space industry for inflatable habitats, parachutes and decelerator systems. Evaluating the safety and structural integrity of these systems occurs through structural health monitoring systems (SHM), which integrate non-invasive/non-destructive testing methods to detect, diagnose, and locate damage. Strain/load monitoring of these systems is limited while utilizing traditional strain gauges as these gauges are typically stiff, operate at low temperatures, and fail when subjected to high strain that is a result of high loading classifying them as unsuitable for SHM of soft structural textiles. For this work, a capacitance based strain gauge (CSG) was fabricated via aerosol jet printing (AJP) using silver nanoparticle ink on a flexible polymer substrate. Printed strain gauges were then compared to a commercially available high elongation resistance-based strain gauge (HE-RSG) for their ability to monitor strained Kevlar straps having a 26.7 kN (6 klbf) load. Dynamic, static and cyclic loads were used to characterize both types of strain monitoring devices. Printed CSGs demonstrated superior performance for high elongation strain measurements when compared to commonly used HE-RSGs, and were observed to operate with a gauge factor of 5.2 when the electrode arrangement was perpendicular to the direction of strain.

A sensitive and flexible interdigitated capacitive strain gauge based on carbon nanofiber/PANI/silicone rubber nanocomposite for body motion monitoring

“…In recent years, strain gauges manufactured of stretchable nanocomposites have attracted pervasive attention due to their adjustable properties, which are required in a different variety of applications in soft robotics, human health monitoring, body motion detection, structural health monitoring, electronic skin, and artificial intelligence [1][2][3][4][5][6][7]. For these types of applications, these sensors must be lightweight, highly conformable, soft, and mechanically durable for long-term use [8], which we can achieve these characteristics by flexible nanocomposites.…”

“…The following relation for interdigitated capacitive strain gauges has been derived from other work [6,39,42]. According to figure 1, the initial capacitance C 0 of the interdigitated capacitive strain gauge is expressed by:…”

Additive Manufacturing of Miniaturized Peak Temperature Monitors for In-Pile Applications

“…Activemonitoring techniques, such as thermocouples, provide real-time data and are typically expensive because they require the implementation of instrumentation leads. On the other hand, passive-monitoring techniques are typically used in static irradiation capsules, and can provide an insight toward peak temperatures [13]. For those instances where irradiation tests are seeking a less-expensive measurement method and/or the experiment requires instrumentation without leads such as static capsule experiments, passive techniques are the preferred method for temperature monitoring [10].…”

“…The incorporation of these AM techniques in the design of in-pile instrumentation enables the development of advanced sensors for MTRs with features as small as 10 µm, which is advantageous for device miniaturization, especially when considering that traditional melt-wire capsules typically require a wire length of approximately 2 mm [16,17]. Currently, novel technologies such as AJP are being explored for the development of unique sensors that are otherwise unobtainable with conventional fabrication processes [13,[18][19][20][21].…”

Characterization of low-cost inkjet printed-photonic cured strain gauges for remote sensing and structural monitoring applications

“…Strain gauges are electromechanical sensing devices created from thin conductive lines on top of a rigid or flexible substrate, which are then attached to the measurement region [1,2]. The resistance, capacitance, impedance or piezoelectric characteristics of such devices change when the measurement region is subject to any source of deformation [3,4].…”