3D printing of self-assembled dipeptides

Abstract

Molecular self-assembly is an autonomous nature-driven manufacturing process that transforms individual molecules into condensed micro-and nanoarchitectures, providing various bottom-up routes to prepare functional materials. Self-assembled peptides are the example deeply involved in biological phenomena in our lives. In addition to their fundamental interest, the self-assembled peptides have attracted attention from electronics, photonics, and energy technology due to their molecular crystal structures leading to unique physical- and chemical properties. Traditional routes to prepare the self-assembled structures rely on solution-mediated precipitation. However, the resulting structures continue to suffer from their stochastic and incoherent nature, restricting the practicality of the fabrication of integrated circuits. A new scheme that can improve a degree of control over the shape and position of peptide nanostructures is in great demand. This thesis introduces the 3D printing technique that is capable of tackling the challenging issue. The key idea of this thesis is to combine nature-driven molecular self-assembly and technology-driven 3D printing, by thorough investigations of the peptide thermodynamics in the manufacturing process. First, we have demonstrated freeform, crystalline diphenylalanine (FF) peptide structures by combining meniscus-guided 3D printing with molecular self-assembly. These features result from two steps: layer-by-layer fabrication of FF under solvent evaporation and subsequent mild thermal activation. Our 3D printing approach has achieved a high spatial resolution of 2 µm laterally and 200 nm vertically. Successful demonstration of the uniform piezoelectricity (> 7.23 pm/V) in the 3D FF microarchitectures has proved the practicality of our approach for realizing bioelectronic devices. Furthermore, we have developed an in-situ protocol to spatially control the crystallinity in high-resolution FF 3D printing. The reprecipitation of FF (i.e., crystallization) during the 3D printing process is controlled by binary solvent (water/HFIP) composition dynamically changed with humidity. As a proof-of-concept, it has been demonstrated that a 3D-printed FF microarchitecture with spatially programmed crystallinity can carry a 3D digital optical anisotropy pattern for polarization-encoded anticounterfeiting labels. We expect the works presented in this thesis to open up the possibility to design and manufacture functional peptide integrated circuits (ICs) in a minimalist, cost-effective manner, without design restrictions. (343 words)