Faculty Sponsor's Department:
Lubricious interfaces are ubiquitous in biology and are often on the order of micrometers or less in thickness. One example is the tear film in the eye, which protects the sensitive, highly innervated cornea. Biomedical implants in contact with the eye, including contact lenses, must be designed to interface with the natural lubrication mechanisms of the ocular environment to prevent irritation or inflammatory responses. Hydrogels, common contact lens materials, consist of highly hydrophilic crosslinked polymer chains and thus absorb large amounts of water, which imparts high lubricity, or very low friction, to their surfaces. In some cases, hydrogels can be extremely slippery, with friction coefficients on the order of 10-3 measured between contacting swollen gels. Despite their widespread use, the mechanical properties of thin hydrogel films remain poorly understood. In this work, a casting method for creating thin hydrogel films was used to study their mechanical properties. Gel thickness was measured using confocal microscopy, and adhesion between a glass probe and a hydrogel film was measured using a Surface Forces Apparatus. The results suggest that the contact mechanics, including adhesion, of thin hydrogel films to rigid glass surfaces depend on hydrogel water content as well as indentation depth. This work and further investigation of other properties of thin hydrogel films, such as friction, are of great interest to better understand and control these materials for use in biomedicine.