Microbubble Sheath Empowered Pneumatic Artificial Muscles for Highly-Precise and Stable Needle Insertion

Soft pneumatic actuators and robotic systems offer significant advantages in biomedical applications and enable tasks beyond the capabilities of rigid systems, benefitting from their inherent deformability, compliance, and adaptability. However, their low stiffness often leads to severe vibrations during rapid actuation or under external disturbances, limiting control accuracy and motion stability. To overcome these challenges, we proposed a bubble sheath-based damping solution by introducing a closed-cell silicone foam into the valleys of bellow-type pneumatic artificial muscles, forming a composite cylindrical muscle (CCM). The CCM incorporates an inductance-based self-sensing mechanism capable of detecting length changes as small as 2 μm. The experimental results show that the CCM achieves significantly reduced overshoot and vibrations by 70% due to rapid actuation and impact loading. Closed-loop control of the CCM (47 mm long) via self-length sensing data achieves stable and precise movement across scales ranging from 10 mm to 10 μm. Moreover, CCM-driven needle insertion experiments highlight its potential for high-precision biomedical applications. This work provides an effective and versatile solution toward low-cost, yet stable and precise movement via pneumatic-driven artificial muscles.