Small-scale robots hold great potential for targeted cargo delivery in minimally-inv asive medicine. However, current robots often face challenges to locomote efficiently on slip pery biological tissue surfaces, especially when loaded with heavy cargos. Here, we report a magnetic millirobot that can walk on rough and slippery biological tissues by anchoring itself on the soft tissue surface alternatingly with two feet and reciprocally rotating the body to mov e forward. We experimentally studied the locomotion, validated it with numerical simulations and optimized the actuation parameters to fit various terrains and loading conditions. Further more, we developed a permanent magnet set-up to enable wireless actuation within a huma n-scale volume which allows precise control of the millirobot to follow complex trajectories, cl imb vertical walls, and carry cargo up to four times of its own weight. Upon reaching the targ et location, it performs a deployment sequence to release the liquid drug into tissues. The ro bust gait of our millirobot on rough biological terrains, combined with its heavy load capacity, make it a versatile and effective miniaturized vehicle for targeted cargo delivery.

翻译：小型机器人在微创医学的靶向药物递送方面具有巨大潜力。然而，现有机器人在光滑生物组织表面高效运动时面临挑战，尤其是承载重物时。本文报道了一种磁性毫米机器人，它通过交替用两只脚锚定在柔软组织表面并往复旋转身体以向前移动，从而能够在粗糙且光滑的生物组织上行走。我们实验研究了其运动特性，通过数值模拟验证了结果，并优化了驱动参数以适应不同地形和负载条件。此外，我们开发了一套永磁体装置，可在人体尺度的体积内实现无线驱动，从而精确控制毫米机器人遵循复杂轨迹、攀爬垂直墙壁，并携带多达自身重量四倍的货物。到达目标位置后，它会执行部署序列，将液体药物释放到组织中。该毫米机器人在粗糙生物地形上的稳健步态，结合其强大的负载能力，使其成为一种多功能且有效的小型化靶向药物递送载体。