Biocompatible collagen-nanofibrils: An approach for sustainable energy harvesting and battery-free humidity sensor applications.

In contrast with the conventional ceramic/oxide humidity sensors (HS), a self-powered piezoelectric biopolymer (SP-PB)-HS with reasonable sensitivity, reliability, non-toxic, and eco-friendly nature is highly desirable. A piezoelectric nanogenerator (PNG) driven biopolymer based HS provides a pathway towards a sustainable and greener environment in the field of smart sensors. For that, a piezoelectric collagen-nanofibrils (PCNF) biopolymer coated on to a cotton fabric has dual functionality (energy harvesting and sensor). Collagen PNG (CPNG) generates a maximum of 45 V/250 nA upon 5 N and can also work as a sensor to measure various percentages of relative humidity (% RH). HS shows a linear response with a good sensitivity (0.1287 μA/ % RH)in the range of 50-90 % RH. These results open a field of eco-friendly multifunctional nanomaterials towards the development of non-invasive, implantable smart bio-medical systems.