Spontaneous Periodic Delamination of Thin Films To Form Crack-Free Metal and Silicon Ribbons with High Stretchability

Design of electronic materials with high stretchability is of great importance for realizing soft and conformal electronics. One strategy of realizing stretchable metals and semiconductors is to exploit the buckling of materials bonded to elastomers. However, the level of stretchability is often limited by the cracking and fragmentation of the materials that occurs when constrained buckling occurs while bonded to the substrate. Here, we exploit a failure mechanism, spontaneous buckling driven periodic delamination, to achieve high stretchability in metal and silicon films that are deposited on prestrained elastomer substrates. We find that both globally periodic buckle-delaminated pattern and ordered cracking patterns over large areas are observed in the spontaneously buckle-delaminated thin films. The geometry of periodic delaminated buckles and cracking periodicity can be predicted by theoretical models. By patterning the films into ribbons with widths smaller than the predicted cracking periodicity, we demonstrate the design of crack-free and spontaneous delaminated ribbons on highly prestrained elastomer substrates, which provides a high stretchability of about 120% and 400% in Si and Au ribbons, respectively. We find that the high stretchability is mainly attributed to the largely relaxed strain in the ribbons via spontaneous buckling-driven delamination, as made evident by the small maximum tensile strain in both ribbons, which is measured to be over 100 times smaller than that of the substrate prestrain.

设计具有高拉伸性的电子材料对于实现柔软且共形的电子器件至关重要。实现可拉伸金属和半导体的一种策略是利用与弹性体结合的材料的屈曲。然而，拉伸性程度往往受到材料在与基底结合时发生约束屈曲所产生的开裂和破碎的限制。在此，我们利用一种失效机制，即自发屈曲驱动的周期性分层，在预应变弹性体基底上沉积的金属和硅薄膜中实现高拉伸性。我们发现，在自发屈曲 - 分层的薄膜中，在大面积上既能观察到全局周期性的屈曲 - 分层图案，也能观察到有序的开裂图案。周期性分层屈曲的几何形状和开裂周期可以通过理论模型进行预测。通过将薄膜图案化为宽度小于预测开裂周期的条带，我们展示了在高度预应变的弹性体基底上无裂纹且自发分层条带的设计，这使得硅条带和金条带分别具有约120%和400%的高拉伸性。我们发现高拉伸性主要归因于通过自发屈曲驱动的分层使条带中的应变大幅松弛，这从两条带中的最大拉伸应变很小可以明显看出，其测量值比基底预应变小100倍以上。