Research On Key Technology And Experiments Of Bionic Artificial Anal Sphincter System

Fecal incontinence(FI)is defined as recurring episodes of involuntary loss of feces.It is a common clinical disease.For curing the severe FI,researchers proposed lots of methods and one of the most popular treatment means was artificial anal sphincter system(AASS).However,the shortcomings,such as difficult surgery,high risks and no sensory perception,limit the clinical application of artificial anal sphincter system.Under the supports of the National Natural Science Foundation of China(N0.61673271,NO.81601631)and the Science and Technology Commission of Shanghai Municipality(NO.14441902800,NO.15441903100),this paper conducts the intensive research on key technology and experiments of bionic artificial anal sphincter system.The specific works of this paper can be divided as following parts.1.Based on the bionic and abstract of puborectalis muscle,four generations actuator of PM-AASS were developed in this paper.The actuator was mainly composed of the structure of rings and actuating device.The structure of rings was composed of three parts.The supper-ring and bottom-ring supported and fixed the whole structure,while the middle-ring enhanced the function of defecation.The movement of middle-ring was driven by the motor and passed by the reduction gearbox.The actuator was made of biocompatible material.The design of O-ring grooves and sensor wire holes enhanced the waterproof performance of the whole system.Through the abstraction and modeling of the inherent structure and swinging trajectory of the swinging arm,the design equations of the middle-ring were deduced.The swinging arm was manufactured by 3D printing technology,while under the guidance of the above equations.In this way,middle-ring would reduce the damage to intestine and its surrounding tissue.Intestinal flexible pressure sensors were embedded in the rings to realize the sensory perception.It could collect the surface area pressure of intestine to avoid misjudgment caused by local extreme pressure.Through the improvement of packaging structure,process and production materials,the success rate of sensor production was risen by 60%.The results of calibration and stability experiments showed that the linearity of the sensor was better than 0.998.Moreover,the error between the actual measured data and the fitted line is less than ± 0.3%.2.This paper improved the function module of hardware circuit and software program of PM-AASS to strengthen the stability and reliability of the control system.In order to achieve the miniaturization of implanted hardware,it was necessary to balance the packaging and function of the components.Besides,the signal and power traces of printed circuit board should be optimized.The original sub-functional modules of the control system included power management,wireless communication,sensing,motor drive and current detection.Through the addition of chips,components and corresponding program,this paper achieved the function of low-power processing,temperature control and triple protection mechanism,which realized by pressure detection,position detection and current flow detection.The stability of this system was verified by long-term load test.The power consumption of the system was 48.8mAh/d,which was dropped by 91.5%,compared to previous design.The usual 600 mAh rechargeable lithium battery could supply for this system for about 12 days without charged.3.In this paper,biocompatible materials were used for the packaging of the whole system.The integration of the whole system was helpful for compacting the size of this system.Furthermore,it was conducive to in-vitro experiments and in-vivo experiments.In-vitro experiments included percutaneous energy supply experiment,in vitro-clamping experiment and in vitro-water experiment.Through the analyzing of experimental data,the safe charging distance of the system was set at 23 cm.In addition,difference of the sensitive area of radial and axial sensors was demonstrated.Besides,the water-proofing of the whole system and the effectivity of defecation of the PM-AASSS actuator were proved.Animal experiments were performed twice.PM-AASS ? beagle experiment verified the feasibility of the function of intelligent defecation.The biocompatibility of the system was preliminarily verified by pathology analysis in PM-AASS ? animal experiments.