Photoredox induced molecular aggregation/phase separation enables general material and 3D microprinting

Abstract

Phase transitions are ubiquitously observed in materials as well as living matter, where molecular interaction dictates the formation of phases and their properties. The ability to control such interactions would enable on-demand phase transitions and materials with novel responsive properties. While canonical molecular forces are commonly behind this control, dissipative chemical reactions may induce effective interaction and phase transitions, which have rarely been studied. In this thesis, we showed that the photoredox reaction causes substantial apparent attraction between reacting molecules without net chemical reaction, which leads to Avrami-like aggregation and phase transitions. More importantly, the photoredox reaction solution may act as a non-equilibrium bath, allowing any immersed inert colloids and solute molecules to partially inherit the active behavior of the bath, thereby inducing a similar attraction potential and leading to light-induced aggregation and phase separation. With this universality, the photoredox ink can be formulated for 3D direct laser writing (DLW), allowing general materials to be printed with 200 nm resolution. We demonstrated that protein, DNA, enzyme microstructures, and operational nanoscale organic electronic components, such as conductive nanowires and field-effect transistors (FET), can be directly printed from photoredox ink. By integrating conductive wires and FET, an electronic inverter with 3D microstructure was printed and successfully inverted the input signal at 1 Hz. This photo-induced phase separation assisted DLW strategy should provide a new approach to print integrated microcircuits with 3D structures.