No abstract

Microcoils are used in various mechanical devices. However, existing methods for producing microcoils from polymers often require expensive equipment. In this study, microcoils were prepared using a cost-effective and simple method. The material used was silicone, which is a biocompatible polymeric material. Silicone was solidified inside glass capillaries to form thin, straight strings with a diameter of 140 μm. The string was then transformed to a coil shape by oxidation using UV–ozone treatment while it was prestretched and pretwisted. The resilience force from the prestretching and pretwisting forces caused the string to bend and twist, respectively. As a result of the combination of these deformation modes, a coil was formed. As an application of the coils, an actuator was prepared, which repeatedly transforms between straight and coiled shapes. The actuation was caused by the swelling/deswelling of silicone with hexane. A large strain of 54% was obtained.

One‐dimensional micromaterials are potentially applicable in various technologies, including sensor fabrications. Variations in the sensing performance of such materials can be ameliorated by their regular arrangement. For example, the materials can be aligned unidirectionally. However, controlling both their orientation and spacing remains challenging. In this study, small evenly spaced droplets were aligned on a surface and the solvent in the droplets was then evaporated in air to obtain evenly spaced, aligned needle‐like crystals of the solute. The droplets were confined to the concave portions of regular wrinkles formed due to buckling instability on a polydimethylsiloxane (PDMS) rubber surface. However, crystallization in small droplets with diameters of less than 100 μm was difficult to achieve because the probability of nucleus formation in each droplet was very low. To address this drawback, nuclei were added to the droplets externally, obtaining well‐aligned needle‐like crystals of 9,10‐dibromoanthracene (DBA), an organic semiconductor. The advantages of this method include its simplicity, cost efficiency, and applicability to fragile materials, because the application of mechanical force to the needle‐like crystals is not required.