Fig. 4: Stretch-induced self-growth and reversible tuning of bent micropillars.

a Schematics and simulations illustrating the fabrication and reversible tuning of bent micropillars. H₂ and H₃ represent the laser scribing depths corresponding to circular and semicircular paths, respectively. b Simulated radial stress distributions of the bent micropillars fabricated with varying H₃. Bending angle (α) and micropillar length (L) are defined in the illustration. c Comparison of the stresses at the left and right roots of the bent micropillars shown in (b). d Laser confocal image of the bent micropillars fabricated with increasing H₃ at stretching ratio of 1.67. e Corresponding cross-sectional profiles of bent micropillars in (d). f Laser confocal image of microstructures in (d) after full release of the membrane. g Cross-sectional profiles of microstructures in (f). h Simulated height profiles of bent micropillars with the increasing H₃. i Experimental and simulation results of bending angle (α) and length (L) of micropillars as a function of H₃. The variation in the bending angle (j) and length (k) of the micropillars fabricated with increasing H₃ during release. The variation in the bending angle (l) and length (m) of the micropillars fabricated with increasing H₃ during ten cycles of release and re-stretching. Error bars represent the standard deviation of three independent measurements.