Air-stable gelatin composite memory devices on a paper substrate

“Green’’ electronics represents an emerging area of research aimed at identifying natural materials that are applicable for environmentally safe and biodegradable devices. Iron (Fe) ions are used in gelatin matrixes (gelatin composites) prepared on commercially available flexible paper substrates through the solution method, thus, the “green” electronics were achieved. Although atomic force microscopy images show that fiber-based paper substrates result in rough Al/paper structure surfaces, the uniform interface between top Al electrodes and gelatin composites can be clearly observed in transmission electron microscopy images. This might be due to the gelatin composite acts as not only the resistive layer, but also the smoothing layer. Moreover, Fe ions play an important role in assisting redox reaction or filament formation. An Al/gelatin/Al/paper device has no resistive switching behavior. Meanwhile, devices with Fe ions on a paper substrate show reproducible resistive switching for 18 cycles, an ON/OFF ratio of over 10⁵, and an excellent current distribution (coefficient of variation<60%). The ON/OFF ratio of the device after bending 180 cycles can be maintained at 10⁴. The biodegradable gelatin materials have good ductility and potential in recyclable and green electronic applications.