Building on-chip cytoskeletal circuits via branched microtubule networks

Controllable platforms to engineer robust cytoskeletal scaffolds have the potential to create novel on-chip nanotechnologies. Inspired by axons, we combined the branching microtubule (MT) nucleation pathway with microfabrication to develop “cytoskeletal circuits”. This active matter platform allows control over the adaptive self-organization of uniformly polarized MT arrays via geometric features of microstructures designed within a microfluidic confinement. We build and characterize basic elements, including turns and divisions, as well as complex regulatory elements, such as biased division and MT diodes, to construct various MT architectures on a chip. Our platform could be used in diverse applications, ranging from efficient on-chip molecular transport to mechanical nano-actuators. Further, cytoskeletal circuits can serve as a tool to study how the physical environment contributes to MT architecture in living cells. Significance Microtubules have essential functions within the cell, including providing a robust railroad for motor-driven cargo transport. The unique properties of microtubules have stimulated attempts to harness these characteristics for targeted delivery of molecular complexes, novel material design, and developing nanotechnologies with precision comparable to living organisms. However, Previous efforts mainly focused on microtubules with fixed length and layout and no controlled MT generation, setting a limit on designing MT architecture. In this study, we integrated nanofabrication with microtubule branching reactions borrowed directly from the cell’s toolkit to construct cytoskeletal circuits and generate microtubule architectures from scratch. That is, our system enables control over microtubule growth and autocatalytic nucleation on a microfluidic chip with micro/nanostructures patterned within.