Tailoring Ionic Conductivity of Chitosan Films Through Controlled Lactic Acid Incorporation

Chitosan, a biodegradable and biocompatible biopolymer, is widely utilized due to its excellent film-forming capability and versatile applicability in various industries, including food packaging, pharmaceuticals, agriculture, and bioelectronics. This study investigates the influence of lactic acid concentration (2 wt%, 4 wt%, and 6 wt%) on the structural, thermal, and electrochemical properties of chitosan films. Films were prepared by dissolving chitosan in lactic acid solutions and casting them via solvent casting. Structural properties were characterized using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), thermal stability was analyzed by thermogravimetric analysis (TGA), and electrochemical properties were examined through ionic conductivity and capacitance measurements. The results reveal that increasing lactic acid concentration enhances ionic conductivity and areal capacitance of the chitosan films. At the highest lactic acid content (6 wt%), the films exhibited an ionic conductivity of 2.6 × 10⁻⁴ S/cm and an areal capacitance of 7.14 µF/cm² at 100 Hz. The results demonstrate the high potential of chitosan films for use in flexible energy storage systems, capacitive sensors and implantable bioelectronic devices.