Surface Hydroxylated CaCu3Ti4O12 Wrapped Polyurethane Sponge for Highly Sensitive Pressure Sensing Application

Herein we investigate a concept to design and fabricate a calcium copper titanate (CaCu
₃
Ti
₄
O
₁₂
, CCTO) wrapped polyurethane (CCTO@PU) dielectric sponge-based flexible capacitive pressure sensor. An ultrasoft CCTO@PU dielectric sponge was prepared via dip-coating of PU into the solution of surface hydroxylated CCTO (CCTO-OH) in ethanol and (3-aminopropyl) triethoxysilane (APTES) as a silane coupling agent. CCTO-OH attributes excellent adhesion with -NH
₂
terminated PU, enhancing interfacial polarization leading to the high dielectric permittivity (167.05) and low loss tangent (0.71) at 30 wt% CCTO concentration. Moreover, a high value of initial capacitance achieved makes the sensor more robust to parasitic effects in the proximity, which is highly desirable for low-cost electronics. The CCTO@PU dielectric sponge at 30 wt% CCTO-OH exhibited excellent electromechanical properties with a low-modulus of 29.87 kPa and pressure sensitivity of 0.73 kPa
^-1
in the low-pressure regime. Finally, we successfully applied the sensor for the detection of various human-induced motions.