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We present iSoft, a single volume soft sensor capable of sensing real-time continuous contact and unidirectional stretching. We propose a low-cost and an easy way to fabricate such piezoresistive elastomer-based soft sensors for instant interactions. We employ an electrical impedance tomography (EIT) technique to estimate changes of resistance distribution on the sensor caused by fingertip contact. To compensate for the rebound elasticity of the elastomer and achieve real-time continuous contact sensing, we apply a dynamic baseline update for EIT. The baseline updates are triggered by fingertip contact and movement detections. Further, we support unidirectional stretching sensing using a model-based approach which works separately with continuous contact sensing. We also provide a software toolkit for users to design and deploy personalized interfaces with customized sensors. Through a series of experiments and evaluations, we validate the performance of contact and stretching sensing. Through example applications, we show the variety of examples enabled by iSoft.
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This content will become publicly available on May 5, 2026
A Direct Solution to the Self-Sensing Inverse Problem Via the Primal-Dual Interior Point Method
Abstract Materials that are self-sensing via the piezoresistive effect have been widely explored for embedded sensing in aerospace structural composites, pressure sensing in touch pads, diagnostics in biomedical implant technology, and many other applications. In this approach, changes in electrical transport of the material are used as an indicator of stress/strain, pressure, or damage. However, engineers and other users of self-sensing materials are typically not directly interested in the electrical state of the material. Rather, they want to know the underlying mechanical state of the material that gives rise to an observed electrical change. Recovering material condition from electrical observations is referred to as the self-sensing inverse problem (SSIP). Prior work by the author has shown that the SSIP can be solved using an electrical impedance tomography (EIT)-generated conductivity map as an input, but this is undesirable because it requires solving a second inverse problem (i.e., the SSIP) on top of the EIT inverse problem. To that end, a direct formulation for the SSIP is herein presented. In this approach, voltage-current data is directly inverted to find the displacement field without using EIT as an intermediate step. Additionally, the direct SSIP is solved within the primal-dual interior point (PDIPM) framework such that an ℓ1-norm can be used on the regularization term, which promotes sparsity in the solution space. This approach is applied to a representative piezoresistive nanocomposite using the Laplace matrix as regularization to promote a spatially smooth solution. From the displacement field, strains and stresses are calculated and compared to a commercial finite element solution with good accuracy.
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- Award ID(s):
- 2239039
- PAR ID:
- 10616946
- Publisher / Repository:
- American Society of Mechanical Engineers
- Date Published:
- ISBN:
- 978-0-7918-8875-9
- Format(s):
- Medium: X
- Location:
- Houston, Texas, USA
- Sponsoring Org:
- National Science Foundation
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