Soft Pneumatic Actuator for Rendering Anal Sphincter Tone

Abstract

Sphincter tone examination, as part of digital rectal examination (DRE), can provide essential information to support the early detection of colorectal cancer. Mastering DRE skills for junior doctors is always challenging due to the lack of real training cases. We developed a soft pneumatic active actuator,made of a compound of silicone rubber materials, to mimic human sphincter muscles and simulate various anal sphincter tones for the purpose of training. Different pumping actuation (syringe and bellows) and driving mechanisms (linear, stepper, and servo motor) were implemented and compared for their effect on the rendered tones. A further comparison was made with a previous prototype based on a cable-driven mechanism. Both quantitative and qualitative assessments were conducted to evaluate the performance of each mechanism. A differential pressure sensor was used to measure applied pressure on a catheter balloon placed inside the sphincter, comparing the readings with anorectal manometry data obtained from real patients. Qualitative feedback was gathered through a user study with 10 colorectal expert practitioners. Four questions were asked targeting reaction/response time, pressure level, pressure quality, and similarity to a real case. The results show the capacity and limitation of each mechanism, with the one based on a servo motor and a bellows being the most favourably rated.

Validation of a Tool-Based Visual Anorectal Examination Advanced Simulator for the Early Detection of Colorectal Cancer

“…Each of the chambers is driven by a bellows that is pressed by a servo motor to render one of four predefined anal pressures. Both servo motors are controlled using an Arduino module [ 20 , 21 ].…”

Soft robotics for physical simulators, artificial organs and implantable assistive devices

“…The described sphincter model replicates the pressure profiles of real patients, that were obtained from the anorectal manometry exam. Future developments of the pneumatic driving circuit will also allow the simulation of fast dynamics (129), such as the fast movements associated with the natural cough reflex.…”

Biomimetic Small Intestinal Peristalsis Simulator Using Circumferential Pneumatic Artificial Muscles (cirPAM)

“…The peristaltic motion is imposed on the lumen by a series of circumferential pneumatic artificial muscles (cirPAM), contracting and expanding under negative and positive pressure respectively while keeping the bowel wall thickness t nom constant. Whereas soft robotic contracting muscles typically need a more rigid shell to direct the deformations radially inwards, [22,23] these novel cirPAM actuators provide a completely soft contracting actuator with a minimal footprint. Peristalsis is invoked by embedding multiple of these cirPAMs into a soft wall structure, and applying a periodic pressure signal.…”