2D Printing of Piezoresistive Auxetic Silicone Sensor Structures

In this letter, we developed a piezoresistive auxetic sensor structure based on a silicone elastomer and carbon-based conductive thermoplastic elastomer fiber sensor (CTPE fiber). Liquid silicone has been used as the matrix material. In addition silicone has been mixed with silica filler to tailor the stiffness of an auxetic elastic structure that improved the sensor behavior of silicone-based CTPE fiber composites. The 2D auxetic structures with and without silica fillers have been successfully printed with the direct ink writing method. The piezoresistive fiber was integrated and the auxetic structure were embedded in the silicone matrix in a second step, via casting method. To detect the electrical signal behavior of the integrated fiber sensor, the hybrid manufactured auxetic fiber sensor composite was investigated using dynamic cycle testing between 0 and 20% strain. Using silicone with silica filler for the printing of the auxetic structure, the sensor behavior of the piezoresistive fiber elastomer composite was improved and a secondary peak of the sensor signal could be avoided at low strains. Unfortunately, a constant gauge factor between 0 and 20% strain could not be obtained by implementing the auxetic structure element inside the CTPE fiber composite. However, this structure can already be integrated into a watchband and used for gesture-controlled applications.