A conductive polymer capacitive sensor for skin-contact piloerection monitoring

Abstract

We present a conductive polymer capacitive sensor for the direct and quantitative monitoring of piloerection. The piloerection is a representative symptom of sudden body temperature change and emotional touch, from which human status such as thermal comfort and emotion change can be monitored. The previous indirect piloerection monitoring methods based on image analysis cause unintentional physical stimulus, preventing from an accurate estimation of the human conditions. The previous skin attachable piezoresistive sensors, measuring skin deformation directly with the minimal physical stimulus, need complex fabrication process using thin (~300 nm) silicon substrates, and require temperature compensation for the piezoresistive detection. In this thesis, we propose a skin-contact conductive polymer capacitive sensor suitable for direct and quantitative piloerection monitoring with the minimal physical stimulus. The capacitive sensor made of conductive polymer enables the simple and inexpensive fabrication, and temperature insensitive piloerection measurement. The piloerection monitoring capacitive sensor contains a 3×3 spiral coplanar capacitor array of conductive polymer (PEDOT:PSS) sandwiched by the outer layers of silicone rubber (Ecoflex 0030). Each of the coplanar capacitors consists of two conductive polymer electrode spirals having an identical width of 30μm with the inter-spiral gap of 10μm, so that the capacitance between the spiral electrode pair is decreased due to the increase of inter-spiral gaps when piloerection is evoked on the skin. We fabricate the conductive polymer layer using vacuum-assisted capillary micromolding process, followed by silicone layer enclosure process; thus making the entire sensor’s bending stiffness (1.21×10-9 N·m) small enough to make conformal contact to the human skin. We characterize the performance of the fabricated sensor using artificial bumps and have obtained the sensitivity of -0.00252%/μm and nonlinearity of 25....