Abstract
Conventional metallic strain sensors are flexible, but they can sustain maximum strains of only ∼5%, so there is a need for sensors that can bear high strains for multifunctional applications. In this study, we report stretchable and flexible high-strain sensors that consist of entangled and randomly distributed multiwall carbon nanotubes or graphite flakes on a natural rubber substrate. Carbon nanotubes/graphite flakes were sandwiched in natural rubber to produce these high-strain sensors. Using field emission scanning electron microscopy, the morphology of the films for both the carbon nanotube and graphite sensors were assessed under different strain conditions (0% and 400% strain). As the strain was increased, the films fractured, resulting in an increase in the electrical resistance of the sensor; this change was reversible. Strains of up to 246% (graphite sensor) and 620% (carbon nanotube sensor) were measured; these values are respectively ∼50 and ∼120 times greater than those of conventional metallic strain sensors.
Highlights
Piezoresistive materials are materials in which the electrical resistance is a function of the internal strain [1]
This sandwiched, middle layer of multiwalled carbon nanotubes (MWCNTs) between the two natural rubber (NR) layers acted as a strain sensor
The resistance and relative change in resistance versus strain response curves are shown in Figure 3 for the MWCNT and graphite samples
Summary
Piezoresistive materials are materials in which the electrical resistance is a function of the internal strain [1]. There are a number of different types of polymer-based strain sensors [3] They are typically made using conductive fillers such as single-walled carbon nanotubes, multiwalled carbon nanotubes (MWCNTs), carbon black, graphite in a polymer matrix, or film composites [4,5,6]. Yamada et al introduced a different method for the fabrication of strain sensors using aligned carbon nanotubes These sensors could measure strains of up to 280%. (sensitivity 0.82–0.06); the authors reported that maximum strains of only ~5% were measurable using randomly aligned single wall carbon nanotubes [9]. Shin et al reported a maximum measurable strain of up to 300% with a sensitivity 0.34–1.07 using a MWCNT forest [10] We introduce a linearization method to linearize the exponential response curves
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