Pneumatic Delivery of Untethered Micro-Surgical Tools
Choi, Andrew Young-Joon
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Colorectal cancer is an extremely prevalent disease within the US with high morbidity rates, which can be significantly reduced with early detection and early treatment. However, many patients are hesitant to get regular colorectal cancer screenings, and random biopsy sampling may miss small cancerous lesions. To address this issue, medical technology has improved to make procedures less invasive and yield better results with less pain and discomfort. Surgical innovations such as natural orifice translumenal endoscopic surgery (NOTES), uses natural orifices instead of incisions to gain access inside the body for surgery. Capsular endoscopes offer an ingestible alternative to colonoscopies. Untethered, thermally actuated microgrippers, which are smaller than a millimeter in diameter, have performed successful in vivo biopsies of hard to reach areas such as the bile duct, and have the potential to mass sample the gastrointestinal tract for cancer screening while minimizing tissue damage. However, it was observed that many microgrippers had difficulty attaching to gastrointestinal tissue. I have performed experiments to determine success rates of microgrippers in a random biopsy environment, assessed appropriate pressure ranges to deliver microgrippers to preserve microgripper quality during pneumatic transport, and tested pneumatically delivered microgrippers on porcine gastrointestinal tissue with good results. A pressure of 10 psi resulted in 75.51 ± 5.56% gripper viability, which we determined to be the maximum pressure for this setup due to excessive microgripper breakage beyond that pressure. Microgrippers fired onto gastrointestinal tissue in an aqueous environment with a pressure of 8 psi attached at a rate of 65.03 ± 6.87% after an external flow of 19 mL/min versus 20.44 ± 1.95% at 0 psi after flow, showing over a 3-fold increase in gripping attachment with pneumatic delivery. In all experiments, microgrippers which were fired onto tissue with an input pressure performed better than without pressure. Pneumatic delivery also showed significant improvements in vertically oriented tissue adhesion compared to previous methods of deployment. My results suggest that the introduction of pneumatics to accelerate the microgrippers to the target at higher speeds has a strong positive impact on microgripper attachment rates.