Nanostructured hafnium-doped strontium oxide film for homeotropic/homogeneous convertible liquid crystal alignment depending on the curing temperature

A hafnium strontium oxide(HfSrO)liquid crystal(LC)alignment film was efficiently created through brush coating,and its ability to change the LC alignment direction was confirmed.A brush was applied to HfSrO sol coated on an indium-tin oxide substrate,after which the coating was solidified at var-ious curing temperatures.It was confirmed that a directional micro/nanostructure was formed above 280°C due to the shear stresses caused by the movement of the brush hairs.Surface chemical changes were analyzed by using X-ray photoelectron spectroscopy and contact angle measurements.As the curing temperature increased,the prevalence of oxygen bonds increased and the contact angle decreased,thereby increasing the surface energy.The anisotropic boundary of the micro-grooves and the van der Waals forces due to an increase in surface energy changed the alignment direction of LC mole-cules from vertical to horizontal,as verified through polarized optical microscopy and pretilt angle measurements.Thus,the efficiency of the brush-coating method,which dramatically simplifies the LC alignment film process,was confirmed.The homeotropic/homogeneous LC alignment property of the HfSrO film produced through brush coating depending on the curing temperature provides an innovative approach for LC alignment.

Autonomous self-healing 3D micro-suction adhesives for multi-layered amphibious soft skin electronics

Autonomously self-healing, reversible, and soft adhesive microarchitecturesand structured electric elements could be important features in stable and versatilebioelectronic devices adhere to complex surfaces of the human body(rough, dry, wet, and vulnerable). In this study, we propose an autonomousself-healing multi-layered adhesive patch inspired by the octopus, which possessself-healing and robust adhesion properties in dry/underwater conditions.To implement autonomously self-healing octopus-inspired architectures, adynamic polymer reflow model based on structural and material design suggestscriteria for three-dimensional patterning self-healing elastomers. In addition,self-healing multi-layered microstructures with different moduli endowsefficient self-healing ability, human-friendly reversible bio-adhesion, and stablemechanical deformability. Through programmed molecular behavior ofmicrolevel hybrid multiscale architectures, the bioinspired adhesive patchexhibited robust adhesion against rough skin surface under both dry andunderwater conditions while enabling autonomous adhesion restoring performanceafter damaged (over 95% healing efficiency under both conditions for24 h at 30℃). Finally, we developed a self-healing skin-mountable adhesiveelectronics with repeated attachment and minimal skin irritation by laminatingthin gold electrodes on octopus-like structures. Based on the robust adhesionand intimate contact with skin, we successfully obtained reliable measurements during dynamic motion under dry, wet, and damagedconditions.