Towards Electricity-free Pneumatic Miniature Rotation Actuator for Optical Coherence Tomography Endoscopy

Miniature rotation actuators have been extensively developed and utilized in optical coherence tomography (OCT) endoscopy, enabling distortion-free OCT imaging in complex and tortuous environments. However, the use of electrical-driven rotation actuators raises safety concerns. Although magnetic-driven rotation actuators have been reported in OCT endoscopy, their use can potentially interfere with other medical devices in clinical settings. Here, we propose a pneumatic miniature rotation actuator that eliminates the electricity and magnetism concerns in circumferential imaging for OCT endoscopy. The rotor of the actuator is designed as a windmill, enabling it to convert air energy into rotation energy. In addition, to maintain the stable rotation, both a sliding bearing with two supporting points and a glass spindle with a half-ball end surface are developed. The rotation speed of our pneumatic actuator can be controlled from 66 to 97 revolutions per second by adjusting the airflow rate from 3.25 to 4.00 liters per minute. By OCT imaging of the human fingers, we demonstrate the feasibility of the pneumatic actuator in electricity-free distal scanning OCT endoscopy. Our pneumatic rotation actuator has wide-ranging potential in various fiber-imaging modalities, including not only OCT but also ultrasound imaging that requires similar rotation capabilities.