Materials that can perform functions autonomously - either on a pre-progammed lifecycle or at some point via decision-making processes - require energy to run. Unlike automobiles that run on gasoline or electrical charge, chemical systems require fuels and fuel-processors to per-organize the temporally occurring events. We tackle this challenge for autonomous materials by connecting to systems chemistry concepts to install fuel-driven reaction networks that lead to autonomous transient states. The resulting non-equilibrium systems take inspiration from the transient steady states found in GTP-fueled microtubules and phosphorylation/dephosphorylation networks in nature.
Using fuel-driven and pH-feedback controlled networks we create material systems that feature self-regulation, autonomous dynamics and programmable lifetimes as first macroscale properties (Soft Matter, invited Emerging Area article, 2015).
We are both interested in the fundamental kinetics of the underlying chemical reaction networks and in an exploitation of self-assemblies with lifetimes for materials, such as in hydrogels, photonics, and time-programmed burst release applications.
Read also our Review article on Materials learning from life: concepts for active, adaptive and autonomous molecular systems in Chem. Soc. Rev. 2017, and our Feature Article on pH-Feedback Mechanisms for Autonomous Systems Design in Chem. Commun. 2022.
Autonomously Dynamic Materials with Lifecycles
Selected References:
1. J. Krehan, C.-R. Li, M. Masukawa, E. Amstad, A. Walther* “Homeostatic Artificial Cells Enable Self-Protection in Prototissue Spheroids” Chem, 102409 (2025).
2. X. Yao, J. A. Vishnu, C. Lupfer, D. Hoenders, O. Skarsetz, W. Chen, D. Dattler, A. Perrot, W. Wang, C. Gao, N. Giuseppone, F. Schmid, A. Walther “Scalable Approach to Molecular Motor‐Polymer Conjugates for Light‐Driven Artificial Muscles” Adv. Mater. 2403514 (2024).
3. G. Fusi, D. Del Giudice, O. Skarsetz, S. DiStefano, A. Walther “Autonomous Soft Robots Empowered by Chemical Reaction Networks“ Adv. Mater. 2209870 (2022).
4. X. Fan, A. Walther “pH Feedback Lifecycles Programmed by Enzymatic Logic Gates Using Common Foods as Fuels” Angew. Chem. Int. Ed. 60, 2 (2021).
5. L. Heinen, T. Heuser, A. Steinschulte, A. Walther “Antagonistic Enzymes in a Biocatalytic pH Feedback System Program Autonomous DNA Hydrogel Life Cycles” Nano Lett. 17, 4989 (2017).
6. T. Heuser, R. Merindol, S. Loescher, A. Klaus, A. Walther “Photonic devices out of equilibrium: transient memory, signal propagation and sensing” Adv. Mater. 29, 1521 (2017) (VIP paper).
6. T. Heuser, E. Weyandt, A. Walther “Biocatalytic Feedback-Driven Temporal Programming of Self-Regulating Non-Equilibrium Peptide Hydrogels” Angew. Chem. Int. Ed, 54, 13258 (2015).
Reviews:
1. Invited Feature Article: C. Sharma, I. Maity, A. Walther “pH Feedback Systems to Program Autonomous Self-Assembly and Material Lifecycles“ Chem. Commun. 59, 1125 (2022).
2. R. Merindol, A. Walther “Materials Learning from Life: Concepts for Active, Adaptive and Autonomous Molecular Systems” Chem. Soc. Rev. 46, 5588 (2017). Invited Review for the Chem. Soc. Rev. special issue on “Chemical systems Out of Equilibrium”.
2. Emerging area article: L. Heinen, A. Walther “Approaches to Program the Time Domain of Self-Assemblies“ Invited emerging area article for the 10th year Soft Matter issue, Soft Matter, 11, 7857 (2015).