An Opening in the Abdomen An Opening in the Market: Hernia Tensiometer GROUP 2: Martha Ingram Megan Johnston Chelsea Samson

Timeline - Done Met with advisors Researched hernia surgery and device requirements Innovation Workbench Literature research on current technologies

Timeline - Current Finalize materials list Determine force sensor type and design circuit Finalize mechanical system

Timeline – Future Order materials – Next week First prototype made with acrylic Test on porcine model – 4 th week of Feb Modify design – early March Rebuild with surgical steel Test new design – Late March Report and Poster – April

Force Sensors Flexible Stretch Sensor –Changes resistance when stretched –Both ends must be wired –Requires cords for our estimated load –All cords must be insulated

Force Sensors Flexiforce –0-25lb (0-100N) –Conductance (1/R) linear with load –Both terminal at one end –Requires compression force –We have Starter Kit

Modified Mechanics Flexiforce measures compression Convert tensile force to compression force System pulls against itself

Force Sensors Strain Gage –Interlocking links –Strain gage mounted to a small piece of metal –Defected when tension applied to links –Requires Wheatstone circuit

Circuit Design Design proposed by Flexiforce –Converts change in resistance to change in voltage Voltage will be converted to Force

Calibration Initial calibration –Known weights applied –Measure voltage output –Create calibration curve to convert to force –Simple in Labview, more difficult in self- contained circuit Tare –Zero out capacitor to indicate zero force Normal testing –Provide surgeons with weights to test every 5-10 uses to confirm accurate results

Current Issues Federal Constraints --having minimal contact points with the body allows for easier acceptance through IRB

Physical Limitations ---with an 18cm hernia diameter, the device has to be small (~9cm, or 3.5 inches, long & 2-3 cm high) --small volume for both a movable arm and required circuitry Current Issues

Mechanical Difficulties -- Need for a small internal power supply --Device for keeping tissue stationary: handles get in the way --How do we hold the moving arm in desired position while taking desired tension reading? --Lesser experience/courses in utilizing magnets or advanced techniques in electronics adds some limitations to feasible solutions for our time period. Current Issues

System environment Hernia-Tensiometer Interface The system (tensiometer) needs to be self-contained, having minimal points of contact with the environment (patient)

Potential Solutions Federal Considerations Design the system so that the clamping arm may also support the console above the patient (not on the patient) Use stainless steel and other surgical materials that can be sterilized Experience/Time Limitations Seek advice from Mechanical Engineering & Electrical Engineering departments on creative internal power supply sources that are currently available Physical & Mechanical Limitations Perhaps use test-tube holders or similar alternative holding devices in place of surgical clamps Position circuit near top of the console, and arrange force sensors near the moving arms at the base of the console

References Multianvil%20Page/TheCube.html t/p/id/ force-sensors /stretch-sensor.html