Medical Engineering PhD Defense, Hong Han

Zoom link: https://caltech.zoom.us/j/2126735504

Medical microrobots offer a strategy for minimally invasive therapy through active transport and localized delivery. However, in vivo applications face challenges in sustaining propulsion, achieving real-time imaging, and precisely controlling therapeutic delivery. Here, we develop imaging-guided acoustic hydrogel microrobots integrating bubble-mediated propulsion, ultrasound imaging, and magnetic steering for targeted delivery of drugs and therapeutic gases.

Fabricated using two-photon polymerization, the microrobots incorporate magnetic nanoparticles and therapeutic agents within a hydrolytically degradable hydrogel matrix. An asymmetric dual-opening cavity and selective surface functionalization support multiday microbubble retention and acoustic propulsion in biological fluids. The trapped microbubble provides ultrasound contrast for imaging-guided navigation.

We further extend this platform to enable controlled therapeutic gas delivery and gas–sonodynamic therapy. The microbubble serves as a therapeutic gas reservoir, with distinct acoustic regimes enabling propulsion and triggered gas release. Incorporating a sonosensitizer and a nitric oxide donor enables coordinated generation of reactive oxygen and nitrogen species to enhance tumor cell killing.

Studies in orthotopic bladder cancer models demonstrate tumor suppression with minimal systemic toxicity. Together, these studies advance the development of bioresorbable acoustic microrobots for image-guided in vivo therapeutic delivery.

Advisor: Wei Gao