Direct printed silver nanowire thin film patterns for flexible transparent heaters with temperature gradients

In this study, a convenient and facile direct printing method is developed to fabricate patterned silver nanowire (AgNW) thin films. An aqueous silver nanowire (AgNW) ink was first formulated and inkjet printed on flexible substrates with precisely controlled AgNW density per unit area. With a mesh grid structure, the printed heater showed high electrical conductivity and transparency up to 90%. From infrared thermography, a steady-state temperature up to 100 degrees C was observed uniformly over the printed mesh grid heater with only 4 volts of applied voltage. With precise control on local resistances via AgNW density variation, a gradient heater was designed and printed directly to provide a temperature gradient of up to 10 degrees C cm(-1). When printed on thin polyethylene terephthalate (PET) sheets, the printed heater can have a fast response time within 3 s due to the thermal insulating nature of PET. The printed heaters on PET also showed great mechanical stability and the resistances remained almost the same after 1000 bending cycles.