15:30-16:15

Stability and Reversibility Control of Micropillar Assembly by Surface Chemistry: Expanding Application of Intramolecular Interactions at Solid/Liquid Interface

Modification of surface chemistry by monolayers have been applied to many applications including our study for development of chiral sensor. In the presentation, the content of paper published in JACS in 2011, which abstract is attached below will be mainly introduced as a new type of applications. For many natural and synthetic self-assembled materials, adaptive behavior is central to their function, yet the design of such systems has mainly focused on the static form rather than the dynamic potential of the final structure. Here we show that, following the initial evaporation-induced assembly of micropillars determined by the balance between capillarity and elasticity, the stability and reversibility of the produced clusters are highly sensitive to the adhesion between the pillars, as determined by their surface chemistry and further regulated by added solvents. When the native surface of the epoxy pillars is masked by a thin gold layer and modified with monolayers terminated with various chemical functional groups, the resulting effect is a graded influence on the stability of cluster formation, ranging from fully disassembled clusters to an entire array of stable clusters. The observed assembly stabilization effect parallels the order of the strengths of the chemical bonds expected to form by the respective monolayer end groups: NH₂ ≈ OH < COOH < SH. For each functional group, the stability of the clusters can be further modified by varying the carbon chain length of the monolayer molecules and by introducing solvents into the clustered samples, allowing even finer tuning as well as temporal control of disassembly. Using these features together with microcontact printing, we demonstrate straightforward patterning of the microstructured surfaces with clusters that can be erased and regenerated at will by the addition of appropriate solvents. Subtle modifications to surface and solvent chemistry provide a simple way to tune the balance between adhesion and elasticity in real time, enabling structures to be designed for dynamic, responsive behavior.

Speaker

Prof. Mariko Matsunaga, Department of Electrical, Electronic and Communication Engineering, Chuo University, Japan

Chair

Dr. Yusuke Yamauchi, MANA Independent Scientist, MANA, NIMS