Demonstrates control in nonliving biomolecular systems, suggesting potential for synthetic biology applications.
Living cells convert environmental and internal information into physical and biochemical action. This dissertation focuses on two layers of cell-like control that can be rebuilt in nonliving biomolecular systems: active physical machinery, where cytoskeletal architecture turns molecular force generation into mechanics and transport, and molecular sense-and-response, where compartment architecture turns environmental cues into biochemical output. The common problem is control. Active cytoskeletal materials remodel while generating force, so force transmission must remain predictable in a scaffold that also acts as a machine. Synthetic compartments face a related boundary problem: a compartment must preserve internal state while admitting inputs, sustaining production, and releasing functional output. Study 1 asks how nanoscale motor forces become network-scale mechanical work. We use PRC1-mediated microtubule crosslinking to tune architecture in kinesin-driven active materials and show that connectivity alone does not guarantee mechanical output. Low-connectivity networks dissipate motor activity locally. Connected but mechanically floppy networks reorganize collectively but fail to sustain long-range force propagation or perform substantial work. Mechanically persistent networks support coherent contraction and extractable work. Velocity correlations reveal a transition from local motion to collective organization, while work measurements and a semiflexible-network model separate connectivity from rigidity. The result is a force-to-work rule for active matter: motors generate force, but crosslinkers determine whether force dissipates locally or becomes coherent, extractable mechanical work. Study 2 asks how spatial patterning can make active matter predictable enough for task execution despite nonlinear dynamics. Motor--microtubule active fluids generate autonomous motion, but useful engineering requires flow fields specifying where material moves, which objects separate, and how fluids mix. We use light to pattern contracting motor--filament networks and use predictive modeling to compose hydrodynamic outputs into micrometre-scale flow fields. Programmed flows move and separate cell clusters, impose extensional deformation on polymers and giant vesicles, and mix fluids at low Reynolds number. The result is a force-to-flow rule: optical geometry converts internally generated active forces into predictable transport functions. Study 3 builds an acellular sense-and-response system. A giant unilamellar vesicle, or GUV, supplies a cell-sized lipid boundary for preserving internal biochemical state. Cell-free transcription--translation, or TX-TL, supplies a nonliving biochemical engine for reading DNA and synthesizing proteins outside a cell. We engineer input-output separation across the compartment boundary: small-molecule access admits lactate and nutrients, lactate sensing switches internal productive state, TX-TL synthesizes a bispecific T-cell engager and a genetically encoded membrane gate, and controlled release exports macromolecular output. Lactate-conditioned GUVs recruit T cells to kill CD19-positive target cells. Study 3 brings selective input, productive internal state, controlled output, and target-cell killing into one nonliving compartment. Across the three studies, we rebuild cellular functions outside living cells. Molecular architecture controls force-to-work conversion, optical patterning controls force-to-flow conversion, and compartment architecture controls cue-to-output conversion. In each case, nonliving biomolecular matter uses molecular, spatial, or compartmental structure to link input with output.
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Shichen Liu (2026) studied this question.
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