Surface Function Transformation Through Deformation of 3D Structure using Soft Materials

Recently, the study of surface morphology alterations has been extensively studied due to their ability to control material properties by changing surface morphology. As for materials, hydrogels are gaining attention due to structural changes through water penetration into the hydrogel network in a wet environment. And as for technology, there are various processes to fabricate three-dimensional (3D) structures but issues of low throughput or low resolution remain. Therefore, we propose a novel approach that 2D structures, made of conventional lithography, transform into complicated 3D structures using hydrogels. By swelling hydrogels under constrained conditions, we achieved the desired shape transformations. We replicated the swollen pattern because of its moisture transport behavior. To optimize material for replication, we investigated about affinity for water of prepolymer and indentified that the lower the affinity for water compared to hydrogels the better the swollen pattern retained its shape. In this way, we manufactured molds for buckling and inversely tapered structures and noted that replication from complicated 3D shapes was possible due to the softness of swollen hydrogel. In this method, buckling structures made of polydimethylsiloxane (PDMS) can be utilized as protective films due to their ability to disperse forces laterally. Also, the inverse tapered patterns made of perfluoropolyether (PFPE) exhibit oleophobic surfaces, enabling self-cleaning properties for oil. We also identified that as swelling ratio increased, dispersion capability in buckling film and oleophobicity in inversely tapered film were improved. Therefore, this research demonstrated the potential of utilizing surface shape modifications to achieve various properties using desired materials. It is expected that function transformation can be a platform to create unprecedented functions arising from unique shapes morphed from conventional straight shapes.