pH-driven artificial hybrid architectures as model systems for directed movement and transport

• Applicant: Dr. Friedrich Stricker
• Subject Area: Solid State and Surface Chemistry, Material Synthesis
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 520766332

Biological systems rely on the complex interplay of stimuli to fuel and control the functions of living organisms. Material science often aims to understand and mimic these functions, ultimately to develop materials which can adapt to and control their environment. One such function is the translation of chemical stimuli into physical motion, as carried out by motor proteins in biological organisms. Motor proteins are responsible for the transport of proteins and molecules in cells as well as the macroscopic motion of muscles. Developing a biomimetic material for motor proteins would be highly useful for soft robotics and for controlling the flow and transport of molecules in enclosed systems. I propose to mimic the directed movement of a biological muscle by applying a stimulus-controlled binding/unbinding process to a system of stiff nanopillars actuated by a shape change of a hydrogel. This hydrogel-actuated integrated responsive system (HAIRS) has been established by Prof. Aizenberg and coworkers and uses stimulus-induced swelling of hydrogels to bend embedded stiff nanopillars. Upon the influx or efflux of water, the hydrogel changes size and actuates the bending of embedded nanopillars. This bending motion could be translated into movement of secondary particles or surfaces by binding and unbinding to the nanopillar structures at precise times: binding before actuation, unbinding after actuation, and relaxing before subsequent binding. The amount of swelling and deswelling of the hydrogel—and therefore the magnitude and direction of the nanopillar actuation—can be controlled through stimuli (e.g., pH or light) responsive functional groups. Additionally, I will use pH-responsive covalent bonds to induce repeated actuation and binding/unbinding behavior on the correct timescales with the same stimuli. Furthermore, the use of light as an orthogonal stimulus will allow not only the transport but also the direction of the secondary particle or surface. Owing to the directionality of transport, this system will generate highly concentrated areas of particles akin to the transport of chemical fuel or proteins in living systems. To demonstrate the capabilities of this system I propose to enable the secondary particles to catalyze a reaction, resulting in measurable compartmentalization of activity. Furthermore, a chemical pH oscillator could be used to fuel autonomous actuation and lead to an out-of-equilibrium system, laying the groundwork for potential fuel-driven compartmentalization. By taking a biomimetic approach to the intracellular transport of motor proteins, this proof-of-principle will pave the way for applications that require the localization of multiple reactions inside the same system, while also mimicking biological muscle.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professorin Dr. Joanna Aizenberg