Design Of Liquid Sensing Material Based On CNF And Its Flexible Strain Sensor

Flexible electronic devices have become a research hotspot due to their potential applications in new human health monitoring and medical diagnosis systems.Nowadays,portable,lightweight and high-performance flexible strain sensors have attracted more attention in the field of wearable electronics.Cellulose nanofiber(CNF)is a natural green material with biodegradable,high specific surface area,high electrical inertness and excellent mechanical properties.In this paper,a variety of liquid sensing materials are designed by means of ultrasonic dispersion based on CNF and the excellent conductivity of carbon materials and inorganic salts ions.Flexible strain sensors and stretchable electrodes with different response characteristics are constructed by the split template method and the precursor filling-curing process,which showed great application potential in wearable electronic devices and human physiological signal monitoring.The main research works are as follows:A flexible strain sensor based on GCB/CNF liquid sensing material was designed and constructed.Due to the "micro-contact effect" of GCB conductive phase in the CNF insulating framework,the device resistance increases regularly with the increase of strain,showing the negative piezoconductive characteristic,and the response to tensile strain is highly linear and sensitive.The analysis of the sensing mechanism of the flexible strain sensor lays a theoretical foundation for the subsequent research work.A flexible strain sensor based on Na Cl/CNF liquid sensing material was designed and constructed.Because of the "shutter effect" caused by the flipping of the CNF layer,the transport channel of ions increases,and the resistance of the device decreases regularly with the increase of strain,showing unique positive piezoconductive characteristic.The analysis of the sensing mechanism shows that the positive pressure conductivity characteristic is independent of ion type and tensile direction,and is expected to be generalized to solid-state sensing systems.This new sensing mechanism in liquid systems provides ideas for the subsequent development of flexible stretchable electrodes.A flexible stretchable electrode based on GCB/Na Cl/CNF ternary liquid conductive material was designed and constructed to study the synergistic effect of two different response characteristics in the ternary system.Due to the self-compensation effect of positive and negative pressure conductivity,the sensitivity of GCB/Na Cl/CNF electrode to strain is extremely low,showing stable electrical performance.Moreover,the sensitivity of the electrode to strain can be further reduced by properly adjusting the component ratio of the liquid conductive material.This low-cost flexible stretchable electrode based on the liquid system provides a new possibility to improve the high-performance flexible electronic system in the future.