RESEARCH

1. Light-stimuli responsive liquid crystalline polymers

Polymer-based soft materials that are free of rigid joints can achieve locomotion with a high degree of freedom. We investigate the photomotility of soft actuators and soft robots with programmable light-responsive liquid crystalline polymers (LCPs). LCPs with anisotropic molecular orientation and controlled geometry can demonstrate rolling, steering, and even jumping motions by photo-triggered actuation. By introducing conductive materials to LCPs, we also explore shape-reconfigurable electronics that can transform their 2D shape into 3D structure. Having on-demand and contactless shape-programmability, LCPs can be promising materials for stretchable devices and untethered soft robotic systems.

2. Magnetically responsive polymer composites

Soft robots: Magnetic fields facilitate battery-free remote control of soft robots. We investigate the magnetically-responsive soft robots. Diverse 3D anisotropic magnetic robots are capable of versatile locomotion such as uphill climbing and agile swimming both underwater and above water. Additionally, the autonomous coordination of the magnetic robots facilitated various robotic tasks, including cargo transportation and microfluidic vortex regulation.

Micropillar arrays: Our research interests include 3D micro-structured surfaces for wetting, adhesion, antireflection, printing, and other diverse applications. Magneto-responsive micropillar arrays provide various reconfigurable surfaces by bringing about instantaneous responses from multiple objects via contactless control. We demonstrate reversible multimodal magneto-actuation and stepwise collective magnetic self-assembly of micropillars capable of shape-fixation by controlling wetting behaviors. Recently, our team achieved on-demand chirality selection of nature-inspired arrays as well as guided worm locomotion using magnetically reconfigurable 3D microtopography.

1. Petroleum-derived materials 

Elemental sulfur (S) is a by-product which is generated to a vast surplus of 7 million tons per year in the petroleum refining processes. We can easily synthesize the stable and solid-state sulfur-rich polymer having a sulfur backbone by inverse-vulcanization. The sulfur-rich polymer has unique properties that can be applied to infrared (IR) optics and green energy harvesting. Compared to carbon-based polymers, sulfur-rich polymers show intrinsically high refractive index and transmission of IR region, allowing them to have applications in IR lenses and polarizers. Furthermore, the high electron affinity of elemental sulfur (−200 kJ/mol) enables the sulfur-rich polymer to generate surface charge density facilitating its application in triboelectric nanogenerator (TENG). The sulfur-rich polymer can also be applied in the field including battery and mercury filtration.

2. Bio-derived materials (cellulose, lignin)

The fabrication of polymer composites has been a prevailing research interest with its straightforward methods, but the fundamental understanding of the properties of polymer composites remains a puzzling and challenging area. Our aim is to fabricate polymer composites with enhanced thermomechanical properties using natural-derived filler materials and to clarify the processing-structure-property relationships. Designed to maximize favorable interactions among the components and following optimization efforts, plain melt mixing strategies can effectively blend conventional polymers with excess wood waste materials, such as cellulose and lignin.