Lubricous Hydrogel Surface Coatings on Polydimethylsiloxane (PDMS)

A surface-attached hydrogel made from an entangled network of poly(acrylamide–acrylic acid) random copolymer chains has been chemically bonded to the surface of polydimethylsiloxane (PDMS) and demonstrated ultralow friction in aqueous environments. The hydrogel polymer, preformed in solution, possesses a high molecular weight and exists as an entangled network under the solution concentrations employed. Surface attachment is accomplished through chemical modification of the PDMS surface followed by subsequent reaction with acrylic acid moieties along the polymer backbone. The friction coefficients of untreated and hydrogel-modified PDMS surfaces were measured via microtribometry, employing both a glass probe and a novel bioprobe made from the anterior surface of a rat thoracic aorta. The unique approach to hydrogel synthesis and its attachment to PDMS succeeds in producing a robust, highly solvated polymer network of sufficient water content to enable friction coefficients as low as µ = 0.003.