Artificial microtubules for rapid and collective transport of magnetic microcargoes

Abstract

Directed transport of microcargoes is essential for living organisms as well as for applications in microrobotics, nanotechnology and biomedicine. Existing delivery technologies often suffer from low speeds, limited navigation control and dispersal by cardiovascular flows. In cell biology, these issues are largely overcome by cytoskeletal motors that carry vesicles along microtubule highways. Thus inspired, here we developed an artificial microtubule (AMT), a structured microfibre with embedded micromagnets that serve as stepping stones to guide particles rapidly through flow networks. Compared with established techniques, the microcargo travels an order of magnitude faster using the same driving frequency, and dispersal is mitigated by a strong dynamic anchoring effect. Even against strong fluid flows, the large local magnetic-field gradients enable both anchoring and guided propulsion. Finally, we show that AMTs can facilitate the self-assembly of microparticles into active-matter clusters, which then enhance their walking speed by bridging over stepping stones collectively. Hence, we demonstrate a unique strategy for robust delivery inside microvascular networks and for minimally invasive interventions, with non-equilibrium effects that could be equally relevant for enhancing biological transport processes. Targeted drug delivery is an exciting application of nanorobotics, but directing particles in the blood stream to the right location and in sufficient number is challenging. Gu and colleagues have developed a microtubule scaffold with embedded micromagnets that allows cargo, such as drug particles, to be transported in microvascular networks with precision and speed.