Characterization of mass and swelling of hydrogel microstructures using MEMS resonant mass sensor arrays.

The use of hydrogels for biomedical engineering, and for the development of biologically inspired cellular systems at the microscale, is advancing at a rapid pace. Microelectromechanical system (MEMS) resonant mass sensors enable the mass measurement of a range of materials. The integration of hydrogels onto MEMS resonant mass sensors is demonstrated, and these sensors are used to characterize the hydrogel mass and swelling characteristics. The mass values obtained from resonant frequency measurements of poly(ethylene glycol)diacrylate (PEGDA) microstructures match well with the values independently verified through volume measurements. The sensors are also used to measure the influence of fluids of similar and greater density on the mass measurements of microstructures. The data show a size-dependent increase in gel mass when fluid density is increased. Lastly, volume comparisons of bulk hydrogels with a range polymer concentration (5% to 100% (v/v)) show a non-linear swelling trend.