Developing AFM Techniques for Testing PEG Hydrogels

Many instruments are used to find elastic properties of biological samples using methods such as tensile and bending tests, but using the atomic force microscope (AFM) is considered a non-destructive method because it can provide repeated local stiffness information without damaging the sample. It additionally allows the sample to be tested in an aqueous environment, which is optimal for soft materials such as hydrogels. The nanoindentation is performed via cantilever, measuring the deflection of the cantilever during the contact of the sample using a laser. Compared to hard samples, testing soft materials can present more challenges when working with the AFM, creating the need for a refined technique.[1] This study will explore ways to improve the accuracy and feasibility of testing hydrogels, which are significant in biomaterials research as they offer the ability to be altered mechanically and chemically to fit the needs of cells.[2] The technique for testing the hydrogels will be refined through a process moving from dry to wet samples, attempting to repeatedly and successfully obtain topography and elastic properties through high resolution topography scans and force curves. References: Radmacher, M., Tillamnn, R.W., Fritz, M., and Gaub, H.E. (1992), From molecules to cells: imaging soft samples with the atomic force microscope. Science. 257: 1900-1905 Flake, M. M., Nguyen, P. K., Scott, R. A., Vandiver, L. R., Willits, R. K., and Elbert, D. L. Poly(ethylene glycol) microparticles produced by precipitation polymerization in aqueous solution. Biomacromolecules 12 (844-850). 2011