Characterization and fabrication of a force sensor using a multi-pillar array and a thin-film piezoresistive layer

Date

2019-12

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Abstract

In the field of tactile sensing, deformable piezoresistive materials have become a popular option for real-time and highly sensitive measurements. Generally, piezoresistive materials consist of a conductive component doped into a flexible polymer matrix. Thus providing the ability to change the conductive pathways when subjected to stress. It is the objective of this dissertation to provide a means to characterize piezoresistive materials and to implement them into a force sensor using an asymmetric pillar design. Studies were conducted to characterize the material using a conductive hemispherical probe. These studies were designed to measure applied force, resistance of the layer, and displacement of piezoresistive layers of varying thickness. The study showed that with decreasing thickness, the resistivity would increase. It is hypothesized that this is due to confinement effects within the material. Simulations and brightfield microscopy were used to determine the contact area. In addition to the characterization of the C-PDMS thin-film, a force sensor using an asymmetric pillar affixed to a thin-film piezoresistive layer was developed to detect lateral forces. Results show that the pillar would respond when subjected to a transverse force. When the pillar created a compression in the layer, the resistance would increase, while the resistance would decrease when subjected to tension. Results also show that the device could differentiate and appropriately sense dynamic and steady-state conditions subjected to it. With this characterization and initial pillar design, future work would include decreasing the size of the device to the micro-scale.

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Keywords

Force sensor, Piezoresistivity, Composite characterization

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