Department of Bioengineering FAILURE ENERGY: COMPARING SUTURE PERFORMANCE UNDER UNIAXIAL TENSION GROUP 101B1 Alison Agres – Background & Objective Ted Gomez – Proposed Methods & Protocol Terry Li – Proposed Deliverables/Findings Akriti Saxena – Potential Pitfalls Tom Werner – Equipment/Materials & Budget Justification

Department of Bioengineering Background: Motivation – to create an experiment for the BE 210 curriculum that combines multiple laboratory skills learned during the semester and improves upon two previous lab experiments while remaining low-cost. Basis – The abruptness and irregularity of failure patterns in Experiment 3 (tensile testing) made consistent determination of failure time difficult. The availability of only static loads for Experiment 5 left open the possibility of investigating suture effectiveness under conditions of dynamic load. Proposed Solution – By recording real-time video of tensile tests, students can test suture methods under conditions of increasing load while observing clear image of the sample at the exact time of each force and displacement value. Objective: To compare failure (when material tears or suture begins unraveling) energies of two suture techniques or of suture and no-suture. Alison Agres

Department of Bioengineering Methods & Protocol: Samples – rectangular fabric materials with slit cut along center to serve as a wound surrogate (see diagram). ½ of samples will be sutured using any method. ½ of samples can have another suture method or no suture. Ted Gomez Trials – students will perform tensile test on sutured and non-sutured samples with Instron while capturing video of trial. Students should perform at least 10 total trials within 6 hours with given materials. Instron and video camera should both be calibrated and have same sample rate. Data Analysis – Using force-displacement graphs from Instron 4444, students should calculate and compare average failure energy for the two sample groups. These two groups depend on whether students chose to compare sutured to non-suture or to compare two different suture methods. A t-test should be used to compare the two groups. Students should use video data to accurately determine time of failure and to observe nature of the material and suture at and around time of failure. Dir. of tension Sample Diagram 3 cm Dir. of tension 3 cm

Department of Bioengineering Proposed Deliverables/Findings: Raw Data: video files of tensile tests obtained from camera, load and displacement data from Instron, observable failure patterns Separation displacements in pixels obtained from analysis of video frames Real separation displacements obtained from ruler calibration Displacement rates, load and displacement at failure Terry Li Final Results: plot of force vs. displacement for each sample, failure energy obtained from integration

Department of Bioengineering Potential Pitfalls: Akriti Saxena Failure of the material could occur before suture failure Possible Solution – choose material-suture combination such that suture is more likely to fail before material does Sutures can rip through material instead of breaking or untying Possible Solution – increase distance between holes made in material Suture separates at an angle: data may not reflect suture performance Possible Solution – use video images to find an average displacement value that will account for the uneven failure pattern Deformation of the material itself Possible Solution – material must be stiff and more compliant than suture, however deformation of material should be taken into account since tissue- suture interaction is as important as suture behavior alone Camera movement during recording – bad reference point for displacement Possible Solution – camera must remain still during recording with rigid body point of reference in field of vision for all trials

Department of Bioengineering Equipment/Materials & Budget Justification: Thomas Werner Equipment: Instron Model 4444 benchtop materials testing machine with weight set Camera stand and ruler PC with LabView and imaging software Justification: Instron Model 4444 and weights needed to properly load samples; ruler for image calibration, PC for data acquisition Supplies: Various fabric materials, string (suture) and sewing needle Marker pens, scalpel and scissors Justification: fabric needed to serve as wound surrogate; string and sewing needle for suturing; rest needed for cutting samples Newly purchased Equipment: BioVid (110/NTSC) Laboratory Video Camera ($852; 8mm lens) Supplier: LW Scientific (Product Code: LWS0012) Justification: high-resolution video camera needed to make precise separation displacement measurements