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Chien-Chung Shih1 Mercedes Wu1 Shen-Ning Hsu1 Chao-Wei Huang1 Li-Che Hsu1 Jeun-Yan Lam1 Wen-Chang Chen1

1, NTU, Taipei, , Taiwan

In order to address the issue of ever-growing and non-recyclable electronic wastes in recent years, natural green materials including silks, polysaccharides, and cellulose papers have been employed as the substrate for modern electronics. However, none of these substrates possess sufficiently robust mechanical properties, such as accommodating large deformation under strain, to serve as a suitable substrate for next-generation stretchable-electronics devices. Here we have demonstrated a hygroscopic hydrogel that are air-stable, recyclable and stretchable. They were prepared by a simple polymer blend, which consisted of two hydrophilic polymers, PVA and PMAA. EG is used as a hygroscopic solvent and crosslinker. In contrast with conventional hydrogels, this hydrogel does not need to be rehydrated by aqueous water to maintain its high stretchability; they can absorb water molecules from the ambient environment as plasticizers to increase chain mobility and make the network softer. The hydrogel exhibited high mechanical performance with a Young’s modulus of 7.5kPa, linear region of 40%, and elongation of over 550% at break. Most importantly, the hydrogels could be hydrolyzed by water and re-casted many times. We further built on the unique advantages of the hydrogel to demonstrate a stretchable memory device that used deoxyribonucleic acid (DNA) as the memory layer on top of the hydrogel substrate. The device exhibited a write-once-read-many-times (WORM) type behavior with a memory ratio of 104, retention time over 105 s, and mechanical durability over 30% strain. To the best of our knowledge, this is the first report of a resistive memory successfully integrated with a stretchable and recyclable substrate.

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