Research On Key Technologies And Experiments Of A Conoic Microrobot

Under the supports of the National Natural Science Foundation ofChina, the National High Technology Research and Development Programof China (863Program), the Advanced Study of Manned Space Project andthe Program of Shanghai Science and Technology Commision, the keytechnologies and experiments of a colonic microrobot were researched withthe purpose of exploring a new way for colonic diagnosis and therapy withminimal invasion or non invasion. The colonic minimal invasive diagnosiand therapy make four basic functions to the colonic microrbot. The basicfunctions are locomotion, power, treat and manipulation respectivelycorresponding to locomotion technology research, wireless power supplytechnology research, diagnosis&therapy technology research andcommunication&control technology research.The research on locomotion technology of the colonic microrobotstarted from the characteristics of the colonic tract, and detailedly analysedthe basic form and biomechanical characteristics of the colonic environment. Based on comprehensive analyses, the inchworm like locomotion and themotor actuator were proposed for the active locomotion of the colonicmicrorobot. The inchworm like locomotion mechanism was composed ofradial clamping mechanisms at the two ends and axial telescopic mechanismin the middle section. The clamping mechanism was used to realize themaximum clamping diameter of60mm and the maximum clamping force of1.7N. Moreover, the telescopic mechanism was used to realize themaximum axial stroke of45mm and the maximum axial force of4.5N.These mechanisms could keep the locomotion state without extra powercomsumption. The colonic tract, with complicated surface morphology andviscelastic characteristiss, would reduce the locomotion contact efficiency.In order to effectively control the contact friction on the colonic surface, acontact device was designed and fabricated, based on the intestinal fricitionmodel, experiments and analyses. In addition, the colonic microrobot wasimplemented with kinematic analysis, dynamic analysis, critical stepanalysis and locomotion efficiency analysis in order to clearly acquise itslocomotion performance, which could improve the development of thelocomotion technology of the colonic microrobot.The research on wireless power supply technology of the colonicmicrorobot, based on the electromagnetic induction principle, foused on thewireless way to realize the continuous high power supply. Helmholtz coil was used to stimulate a uniform resonant magnetic field to improve positionstability;3D receiving coils improved the attitude stability; the frequencystability was improved by matching compensation capacitor and adjustableinductance for the Helmholtz coil. The efficiency researche of the wirelessspower supply relate to some influences caused by transmission system, coilscoupling and receiving system. A wireless power supply system wasdesigned and fabricated,which, with14.7W input, could provide theminimum378mW and the maximum705mW for the colonic microrobot.The diagnosis&therapy technology research of the colonic microrobotincludes wireless image diagnosis and hyperthermia. Considering therequirements of colonoscopy, the wireless image diagnosis based onwireless capsule endoscope proposed a double imge acquisition system,which can realize the continuous image acquisition at30fps for320×240pixels. The research on hyperthermia, based on the development of tumorhyperthermia, proposed a colonic heating coil, and exploited an optimalheating coil by testing the surface temperature of the experimental coils. Inorder to realize the precise temperature control, the heating coil wasequeiped with a temperature detection circuit. Therefore, the surfacetemperature of the heating coil could be maintained in the tumorhyperthermia region of41~45℃with a precise temperature control. The research on communication&control technology of the colonicmicrorobot, based on wireless communication, helped the doctor to monitorthe colonic microrobot in time. A half duplex communication between thein vivo and the in vitro was established under the use of two Si4420transceiver chips and combined with the specific communication program.In order to improve multitasking and multiperipheral management, a doublehard core was build up with two micro controllers. There was a four prioritysoft core in each hard core. The design of hardware and software make thecolonic robot have the abilities of collaboration operating andsynchronization control.The combination of the key technologies and MEMS developed aprototype of the colonic microrobot. The prototype has the diameter of17mm, the contracted axial length of128mm, the maximum axial stroke of44mm and the maximum clamping diameter of60mm. Consideringbiocompatibility of the colonic tract, the prototype's shell was made ofmedical polypropylene material and fabricated with CNC. A bellows madeof food medicine silicone ruber was used as the sealing connection betweenthe two cavities of the prototype. In order to reduce the weight, the frame ofthe prototype was made of light aviation aluminum and fabricated with highaccuracy wire cutting machine. The total weight of the prototype was only53.5g. Some experiments were carried out to evaluate the key technologies ofthe colonic microrobot. The prototype of the colonic microrobot had theconcise and efficient locomotion gait. The actual output force of theclamping mechanism was1.5N, and the one of the telescopic mechanismwas4.2N. They were closed to their theory values, and the locomotionprocess was according to the locomotion requirements in the colonic tract.The customized contact device not only increased the friction coefficient65%, but also made the active contact with the colonic tract safer. Thewireless image system could provide the continuous and clear images for thevisual diagnosis. The prototype could move in the rigid or flexible tubeswith different oblique angles. With the decrease of the tube rigid and theincrease of the oblique angle, the locomotion speed of the prototype wasreduced, but its locomotion processes was still stable and continuous. Theprototype had the complicated locomotion characteristics in the in vitrocolonic tract, which was caused by colonic morphology and viscoelastictissue. In the wireless power supply system, the receiving coils couldproduce the heat to improve the environment temperature; in addition, theresonant magnetic field actuated by the transmission coil could affectspecific absorption rate and the current density of the human body. However,the temperate tests and the analyses of human digital model confirmed thatthat the wireless power supply system was relatively safe for the human body. It was worth nothing that some experiments were first carried out inthe living environment. Obviously, the key technologies have the goodactual application value in clinic, and will provid some valuable referencesfor the development of the colonic microrobot.