GOALI: Modeling, analysis and numerical simulations of gels in the biomedical industry

点击翻译按钮获取中文摘要

CaldererDMS-1009181 This GOALI project supports a collaboration betweeninvestigators at the University of Minnesota and at Medtronic,Inc. To improve the design of implantable medical devices, theinvestigator and her colleagues develop fundamental understandingof, and modeling tools for, polymer and solvent interactions thatresult in swelling of the polymer. Many implantable devicesconsist of plastic and metal components that are affixed to eachother by adhesives. When such a device is placed in the humanbody, the plastic parts, made from polymer, interact with thesurrounding fluid and swell, while the metal parts are notaffected by the fluid. The consequent swelling mismatch causes ahigh stress at the interface, which can lead to deformation ofthe components and, if interfacial shear stresses exceed criticalvalues guaranteed by the adhesive manufacturer, to interfacedelamination. Deformation and delamination can cause devices tofail. The ability to model the behavior of the components iscritical in the design of implantable medical devices, such asdefibrillators, pacemakers, and neurological devices. Thisproject addresses the questions: (1) How does polymer swelling proceed without polymer chainrelaxation? (Only elasticity is accounted for, and viscouseffects are neglected.) (2) How does swelling proceed when polymer chains relax withinthe same time frame? (3) How does swelling proceed if there is mechanical strainapplied to the sample? (4) How does swelling proceed if two samples made of the samepolymer but with different initial swelling are bonded together? Many polymers can absorb an amount of water equivalent toabout 1 percent of their own weights; hydrogel can absorb watermany times its own volume. Swelling of polymers occurs in manyapplications, particularly in implantable biomedical devices,made of metal and plastic polymer components, that typically areburied in wet tissue. Polymers can relax mechanical loading anddeformation over time due to viscoelastic properties. Swelling-induced stress or size changes can relax as well. Theactual stress and geometric changes in polymers are determined bythe combined relaxation and swelling process. Each of theseprocesses is related to water diffusion, polymer chain motion,and water-polymer interactions. Estimation of these processesand interactions is critical for understanding swelling-induceddeformation, delamination, and stability, key factors in thedesign and quality control of medical devices. Building on anexisting collaboration between Medtronic Inc and the Universityof Minnesota, the investigator and her colleagues developmathematical models, analysis, and computational andvisualization tools to improve fundamental understanding ofpolymer and solvent interactions; the tools can be used toidentify unsuitable polymers and so reduce the number oflaboratory experiments performed by polymer scientists atMedtronic by more than half. Students and postdocs are part ofthe project, which also includes seminars, workshops, andoutreach activities sponsored jointly with Medtronic.