Rheological and recovery properties of poly(ethylene glycol) diacrylate hydrogels and human adipose tissue

The viscosity and elastic and viscous moduli of poly(ethylene glycol) diacrylate (PEGDA) hydrogels and human abdominal adipose tissue are measured as a function of shear rate and frequency. Results indicate that both materials exhibit shear thinning and are viscoelastic in nature. Rheological tests suggest that the hydrogels become firmer as strain and frequency increase. Adipose tissue, however, begins to fail at higher strains and frequencies. This behavior is confirmed by measuring the complex modulus of both materials as a function of strain. Recovery properties are also measured for each material as a function of deformation. Although PEGDA hydrogels are able to recover up to 78% of their original height after 15% deformation, adipose tissue is not able to recover over the range of deformations tested. The frequencies and strains over which the tests are conducted are those physiologically experienced by the human body. The hydrogels are able to withstand this range of forces and, hence, are appropriate for use as a soft tissue filler material. In addition, the hydrogels swell 38.1% +/- 0.9% independent of surface area. The complex modulus of hydrogels of varying polymer concentrations is also measured as a function of strain to determine the effects of changing polymer content. These results indicate that as polymer content increases, the hydrogels become firmer due to the higher number of polymer chains and behave more elastically.