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Piezoresistive soft composite materials exhibit a change in resistance when undergoing deformation. This combined with their optical, thermal, and mechanical properties makes these composites good candidates for force sensors. Tactile force sensors have long been studied for applications in healthcare, robot–human interactions, and displacement monitoring. The main goal in this work is to characterize a soft piezoresistive layer in both tension and compression to enable a model system for a piezoresistive tactile force sensor and a characterization platform. However, the mechanisms by which these composites exhibit piezoresistivity are complex and must be characterized before use not only in bulk but at the exact locations where contact is expected. In this paper, a cantilevered beam is proposed as a base-mounted force-sensing mechanism. This mechanism allows for characterization of the composites at multiple locations across the sample using a two-probe technique. Multiwalled carbon nanotubes (MWCNTs) are mixed by weight with a soft polyurethane in 15, 16, and 17 wt. % concentrations. Because the elastic modulus of the piezoresistive layer is not known, indentation tests using Hertz theory and numerical calculations are used to simulate the effective elastic modulus and average strain. These results are then compared with the experimental stress results. In general, these tests show a greater sensitivity in tension than in compression. However, the difference lessens as the concentration increases. A linear fit is applied to the ΔR/R versus strain graphs to calculate the gauge factors. Each sensor exhibits a positive and negative gauge factor over two different ranges. ΔR/R versus strain graphs for tension and compression show gauge factors between −19 and 24 with the range decreasing with increasing MWCNT percentage.

Flexible piezoresistive films, such as, carbon black/polydimethylsiloxane (C‐PDMS) composites, are often used as skin analogs and integrated into complex array sensors for tactile sensing. The uniformity of the sensor characteristics heavily depends on the homogeneity of the composite. Therefore, the ability to locally characterize a film that will be integrated into a complex force sensor could be critical. Here, a method to characterize the local sensitivity of flexible piezoresistive films is presented. Using a conductive sphere, which was chosen over a flat probe to eliminate misalignment issues, the surface of a thin film composite is indented to characterize the change in resistivity in terms of average strain. Experiments were performed with 15 and 18 wt% carbon black C‐PDMS films of varying thickness. The contact radius of the probe with the piezoresistive film was estimated using the Johnson‐Roberts‐Kendall contact theory. Theoretical contact area estimates were found to agree with contact radius measurements carried out using optically transparent PDMS films observed through an optical microscope. Results show that C‐PDMS with 15 wt% carbon black exhibit a higher rate if change of resistivity and gauge factor than films of same thickness with 18 wt% carbon black. On the other hand, thicker films exhibit higher gauge factors for the two tested carbon black contents. Tests carried out at multiple locations yielded consistent sensitivity values, making these types of composites suitable for array type force sensors.

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