Polyacrylamide hydrogel friction controlled by time-dependent surface energy due to poroelastic relaxation
This thesis explores the control of friction by varying contact area, contact time, and sliding speed of polyacrylamide hydrogel. With a comprehensive understanding of the phenomenon, hydrogels could be designed with targeted friction behavior, and be used to design surfaces for tissue engineering and drug delivery. Polyacrylamide gels were tested to quantify how the coefficient of friction changes under different conditions. Unlike common single-phase materials, hydrogels store water within a hydrophilic polymer matrix, in which the fluid can flow under applied pressure. It is known that this mass transfer contributes to lubrication, though there is not yet a direct connection. We find that mass transfer results in a local concentration of polymer, adhering and increasing the energy needed to move contacting surfaces. The final result is a coefficient of friction which depends on sliding speed, diffusivity, elastic modulus, applied load, and surface energy.
hydrogel, tribology, poroelasticity, adhesion
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign