Temperature-Regulated Bidirectional Capillary Force Self-Assembly of Femtosecond Laser Printed Micropillars for Switchable Chiral Microstructures.

Bottom-up self-assembly is regarded as an alternative way to manufacture series of microstructures in many fields, especially chiral microstructures, which attract tremendous attention because of their optical micromanipulations and chiroptical spectroscopies. However, most of the self-assembled microstructures cannot be tuned after processing, which largely hinders their broad applications. Here, we demonstrate a promising manufacturing strategy for switchable microstructures by combining the flexibility of femtosecond laser printing induced capillary force self-assembly and the temperature-responsive characteristics of smart hydrogels. Through designing asymmetric cross-link density, the printed microarchitectures can be deformed in the opposite direction and assembled into switchable ordered microstructures driven by capillary forces under different temperatures. Finally, the assembled chiral microstructures with switchable opposite handedness are realized, which shows tunable vortical dichroism. The proposed strategy holds potential applications in the fields of chiral photonics, chiral sensing, and so on.

Femtosecond Laser Regulated Ultrafast Growth of Mushroom-Like Architecture for Oil Repellency and Manipulation.

Natural organisms can create various microstructures via a spontaneous growth mode. In contrast, artificial protruding microstructures are constructed by subtractive methods that waste materials and time or by additive methods that require additional materials. Here, we report a facile and straightforward strategy for a laser-induced self-growing mushroom-like microstructure on a flat surface. By simply controlling the localized femtosecond laser heating and ablation on the poly(ethylene terephthalate) tape/heat-shrinkable polystyrene bilayer surface, it is discovered that a mushroom-like architecture can spontaneously and rapidly grow out from the original surface within 0.36 s. The dimension of the re-entrant micropillar array (cap diameter, pillar spacing, and height) can be accurately controlled through the intentional control of laser scanning. Followed by a fluorination and spray coating, the obtained surface can realize the repellency and manipulation of oil droplets. This work provides new opportunities in the fields of microfabrication, microfluidics, microreactor engineering, and wearable antifouling electronics.