Glycine–Chitosan-Based Flexible Biodegradable Piezoelectric Pressure Sensor

This paper presents flexible pressure sensors based on free-standing and biodegradable glycine-chitosan piezoelectric films. Fabricated by self-assembly of biological molecules of glycine within a water-based chitosan solution, the piezoelectric films consist of stable spherulite structure of β-glycine (size varying from few millimetres to centimetre) embedded in amorphous chitosan polymer. The polymorphic phase of glycine crystals in chitosan, evaluated by X-ray diffraction, confirms the formation of pure ferroelectric phase of glycine (β-phase). Our results show that a simple solvent casting method can be used to prepare a biodegradable β-glycine/chitosan based piezoelectric film with sensitivity (~ 2.82 ± 0.2 mV kPa−1) comparable to those of non-degradable commercial piezoelectric materials. The measured capacitance of the β-glycine/chitosan film is in the range of 0.26 nF to 0.12 nF at a frequency range of 100 Hz and 1 MHz and its dielectric constant and the loss factor are 7.7 and 0.18 respectively in high impedance range under ambient conditions. The results suggest that glycine-chitosan composite is a promising new bio-based piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics.