Spontaneous Self-Folding in Confined Ultrathin Polymer Gels

The formation of high-aspect folded structures with uniform feature sizes in responsive gel films are described. The folding patterns observed here in ultrathin films (20-100 nm) are strikingly different compared to the smooth sinusoidal buckling and cusp-shaped singularities observed earlier in relatively thick (a few tens of micrometers to a few millimeters) aid stiffer films.