Magnetothermal pneumatic robot with reversible inflation and contraction for separable microneedle delivery

Effective transgastric drug delivery is hindered by the gastric mucosal barrier. To address this challenge, this study introduces a remotely controllable magnetothermal pneumatic microneedle robot. The system consists of a phase-change actuator, made from a bilayer Fe₃O₄/Ecoflex magnetic film encapsulating a low-boiling-point liquid, and separable gelatin methacryloyl microneedles embedded with engineered internal microbubbles. When exposed to an alternating magnetic field (AMF), the embedded Fe₃O₄ nanoparticles generate heat, vaporizing the internal liquid and inducing rapid inflation. This process generates a highly tunable output force that linearly correlates with the inflation ratio, enabling precise microneedle penetration into tissue. Notably, this expansion process is reversible, and combined with the low-shear characteristics of the bubble-embedded microneedles, the contraction process of the magnetothermal pneumatic robot upon switching off the AMF directly achieves microneedle detachment. Under the actuation of the magnetothermal pneumatic robot, the optimized bubble-embedded microneedles exhibit sufficient mechanical strength, achieving a penetration efficiency of up to 90% in ex vivo porcine stomachs, along with a favorable post-penetration detachment efficiency of approximately 70%. In summary, this magneto-thermal platform offers a safe, precise, and minimally invasive strategy to overcome the gastric mucosal barrier, demonstrating great potential for local oral drug delivery.