Flexible electronics has been remarked as suitable tool for next-generation electronics such as wearable devices. Printed electronics is the technology which is adequate for manufacturing flexible electronics devices. For the commercialization of devices, guaranteeing the electrical performance under various environmental conditions such as temperature and humidity is very important. However, there has been a few researches of environmental test for flexible printed electronic devices. Moreover, the flexible electronics devices generally undergoes deformation. Therefore, as an example flexible electronics devices, effect of temperature and humidity on flexible printed electrodes under static deformation is studied.
The temperature factors are set to 3-levels(5, 27.5, 50℃), and the humidity factors are set to 2-levels(40, 80%), which are controlled by temperature and humidity chamber. The mechanical deformation including bending and twisting is loaded by in-house test apparatus; and magnitude of deformation is set to 2-level. The printed electrodes are made by screen printing method with nano-silver conductive inks on PET film as test samples. These test samples are exposed to environmental conditions, and their resistance are measured at real time. The measured resistances obtained from experiments are transformed to resistance change rates in order to compare the results with the different initial resistances.
In the experiments, the effects of environmental conditions on the resistance change are as follows: Increasing temperature increases the resistance change rate; increasing humidity also increases the resistance change rate. Effect of mechanical deformation on resistance change depends on type of deformation and shows the largest value from twisting, bending, to no-deformation. Magnitude of deformation does not affect resistance change rate. Effect of line width of electrode on resistance change rate depends on type of deformation. In the case of no-deformation and bending, line width of electrode does not affect resistance change seriously. However, in twisting deformation, the thicker line width shows larger resistance change rate than those of other cases. In this study, it is concluded that the environment in which mechanical deformation together with temperature and humidity has the greater influence on the resistance of the flexible printed electrodes.