Solution-Processed Resistive Pressure Sensors Based on Sandwich Structures Using Silver Nanowires and Conductive Polymer

Highly sensitive resistive pressure sensors are fabricated by a direct spray coating of silver nanowires (AgNWs) on uncured polydimethylsiloxane (PDMS) and an additional coating of a conductive polymer, poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). We have fabricated non-sandwiched sensors (AgNW and AgNW/polymer sensors) and sandwich-structured sensors (sandwiched AgNW and AgNW/polymer sensors) by pressure lamination. The former exhibits a resistance increase, whereas the latter shows a resistance decrease upon loading. It is demonstrated that the AgNW/polymer sensor with the lowest initial resistance is suitable for medium pressure regime applications. In the presence of the over-coated PEDOT:PSS layer, the protrusion of AgNWs from PDMS is suppressed substantially, rendering the sensors more stable and reducing hysteresis. We have found that the sandwich-structured AgNW/polymer sensor with the highest initial resistance features the highest sensitivity (2.59 kPa -1 ) and gauge factor (37.8) in the low pressure regime. It can also detect a subtle placement and removal of a weight as low as 3.4 mg, the corresponding pressure of which is about 5.4 Pa.