Chemo-Mechanical and Chemo-Structural pH-Feedback Mechanisms to Program Transient and Autonomous Self-Assembling Systems

• Applicant: Professor Dr. Andreas Walther
• Subject Area: Preparatory and Physical Chemistry of Polymers
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258922244

Building on the preceding funding phase, where we conceived pH-feedback systems with transient pH-states in homogeneous solution, and coupled them to a diverse range of pH-switchable self-assemblies to program them with self-regulating lifetimes in autonomous systems, this proposal targets the next steps in terms of active feedback mechanisms and in the design of autonomous, chemically fuelled, non-equilibrium soft matter and self-assembly systems. This proposal hence goes beyond chemical feedback in homogeneous solution and aims to develop and quantitatively understand generalizable, self-regulating, coupled chemo-X pH-feedback mechanisms:(i) chemo-mechanical pH-feedback systems are based on pH-modulating enzymes (with pH-dependent activity profile) as embedded in pH-responsive core-shell colloids with pH-dependent gating effects (substrat diffusion) to self-regulate the enzymatic activity. (ii) chemo-structural pH-feedback system are based on pH-modulating enzyme cascades as embedded in co-assembling core-shell colloids, featuring pH-dependent co-assembly behavior, and in which a formed co-assembly encodes its own destruction. This will give rise to new systems features, including (a) transient pH-profiles with controlled lag times and lifetimes, (b) pH-profiles that can be reactivated by providing truly dormant areas to the embedded enzymes, and (c) oscillating systems by controlled synchronization of hysteresis effects, reaction/diffusion timescales, and temporally controlled self-gating effects imposed by chemo-mechanical feedback as well as temporally orchestrated self-regulating chemo-structural feedback.These enabling concepts allow advancements toward autonomously dynamic material systems, spawning self-regulation and time-programmed memory functions. We aim to investigate this behavior for new types of self-erasing dipeptide hydrogels and showcase their use for fluidic guidance in microfluidic circuits. Particular aims are to find pathways towards an orthogonal programming of lag and life times in sol-gel-sol systems, and to exploit controlled lag times before gelation occurs to allow controlled distribution of precursors into branching channel networks to mimic blood flow blocking in complex vascular networks.

• DFG Programme: Research Grants