Inductance-Based Soft and Flexible Pressure Sensors using Various Compositions of Iron Particles

This paper presents inductance-based soft and flexible pressure sensors comprising of a spiral coil made with LIGA process and ferromagnetic elastomer made with different ratios of ecoflex to iron powder (1:1, 2:1, 3:1, 5:1, 1:2, 1:3, 1:5). Seven different sensors were fabricated, and their detailed performance investigated and compared. The results show that increasing the weight percentage of iron particles in ecoflex improved the linearity, response and recovery time and has significant effect on the sensitivity of the resulting sensor. The ratio 1:5, which has the highest iron particle by weight, showed the best performance with sensitivity of ~0.07kPa
^-1
over a pressure range of 2 - 13.5kPa and a response time of ~90ms. In contrast, 5:1 (which had the least iron particle by weight) had the least sensitivity (~ -0.016kPa
^-1
) with a behavior almost similar to bare ecoflex. The presented soft sensors find application in tactile interface for assistive communication devices and for dual tactile sensing and actuation in robotics.