Elastomeric Micro‐Balloons for Remote Control of Cerebral Blood Flow and Real‐Time In vivo Imaging of Rodent Brain Response to Hypoperfusion

Current preclinical models of ischemic stroke in mice do not permit simultaneous and continuous in vivo brain imaging during the peri-stroke period, therefore missing critical pathophysiological events that could be pivotal for stroke management at early stages. Here, we report the fabrication of micro-balloons using yield-stress fluids, in which the monolithic elastomeric wall has selectively stiffened regions for controlled inflation and elasticity, depending on the target vessels. A multi-step bubble-casting process successfully creates an inner layer in a channel with a diameter of <300 µm, despite the yield stress defying surface-tension-induced instability. The micro-balloon can expand up to four times its initial diameter, enabling remote control of the blood flow in cerebral arteries in live mice. By allowing continuous control of the common carotid artery diameter across different states to induce stroke in a precise, reliable, and reversible manner, the micro-balloon recapitulates clinically relevant hemodynamics in a mouse model of global brain ischemia, as evidenced by real-time intravital microscopy and magnetic resonance imaging. The presented micro-balloons hold significant potential to improve the treatment of stroke patients through minimally invasive interventions and in vivo imaging of pathophysiological events during the peri-stroke phase.