Bioinspired navigation in shape morphing micromachines for autonomous targeted drug delivery

Soft micromachines made out of stimuli-responsive hydrogels have the potential to emulate the navigation strategy of leukocytes to implement autonomous targeted drug delivery. Leukocytes navigate in their natural environment with a variety of strategies in response to chemical gradients. They can detect gradients and redirect their movement towards the gradient source, or adjust their speed while moving up-gradient through cell body morphing known as cell polarization. In this work, we use thermo-responsive hydrogels to engineer self-folding micromachiness that can sense near infrared (NIR) light gradients and react in a morphing manner to adjust their speed. We load drug molecules into the unfolded micromachines and encapsulate the drug by folding the micromachines at body temperature. A location of interest is targeted with an NIR light, and a rotating magnetic field is applied to navigate the microrobots to explore the region. Results from in vitro experiments demonstrate that the robots speed up while moving up-gradient, automatically stop at the location of interest, and start to release the encapsulated drug molecules by unfolding their shape. The autonomous navigation is achieved without any external imaging feedback by coordinating the sensory input and shape morphing output of the microrobots through the single degree of freedom (DOF) shape control.