A flexible carbonized melamine foam/silicone/epoxy composite pressure sensor with temperature and voltage-adjusted piezoresistivity for ultrawide pressure detection

Abstract

Monitoring human or robot activities is critical for health care, artificial intelligence and manufacturing, etc., but the broad range of pressure stimuli generated by human or robot activities is beyond the detection limit of most wearable sensors reported. Herein, we propose a novel wearable pressure sensor with an ultrawide detection range by introducing temperature-stimulated epoxy into the porous carbonized melamine foam (CMS)/silicone system. Owing to the low glass transition temperature (30.1 °C) and temperature-dependent mechanical properties of the epoxy used, the CMS/silicone/epoxy composite shows a high compressive modulus of 1.44 MPa at 23 °C, while a significantly decreased modulus of 0.73 MPa and 0.58 MPa at 40 and 60 °C, respectively, which is helpful to modulate the sensitivity and detection range of the sensor made from the composite. To be specific, the decreased modulus dramatically enhances the lower detection limit from 100 to ∼5 kPa, while the high modulus endows the sensor with a high upper detection limit of 1500 kPa (up to 2.11 MPa). Applying a voltage also provides the sensor with an ultrawide detection range (∼1–1500 kPa) via the electrothermal effect. The broad detection range is confirmed by cyclic loadings at 0.1–5 Hz and durability tests. We show that the CMS/silicone/epoxy composite, which has an ultrawide detection range, is suitable for monitoring a variety of motions, such as human breathing, walking, finger movement and object manipulation, etc.