A magnetic balloon fiberbot for catheter-free angioplasty in small arteries

Blockages in cerebral arteries restrict blood flow to the brain, leading to several life-threatening conditions such as stroke. The standard treatment, known as catheter-assisted balloon angioplasty, involves threading a mechanical guidewire and catheter-mounted balloon to the blockage, where the balloon is inflated to reopen the blocked artery. However, this approach struggles with the limited navigation capability of pre-shaped guidewires and catheters, especially in tortuous and small arteries with diameters ≤ 2 mm. Emerging miniature robots offer a potential alternative for catheter-free angioplasty via wirelessly actuated expansion. Still, they typically require high-power electromagnetic coils and short actuation distances, limiting their practicality for small-vessel interventions. In this work, we introduce a magnetic balloon fiberbot (MBF) that synthesizes advanced materials, electromagnetic resonance strategies, and minimally invasive magnetic actuation. The MBF incorporates a magnetically deflectable tip for navigating complex vasculature, along with a phase-change balloon integrated into a nitinol‑cored PDMS fiber. Under low‑power microwave heating (50 W at 15 cm), the balloon expands safely within 42-50 °C. This efficient heating stems from a carbon‑nanotube coating that absorbs energy effectively, combined with the electromagnetic resonance of the optimized nitinol core. The nitinol core thus acts as both a structural backbone and a microwave‑coupling element. We validate MBF performance in vitro using a 3D cerebrovascular phantom and ex vivo in porcine placenta models. With reduced power demands, long-range actuation, and favorable biocompatibility, the MBF represents a promising catheter-free strategy for minimally invasive treatment of blockages in small arteries.