Study of blended agar and gelatin gel phantoms for elastography by application of statistical mechanics and thermodynamics to dynamic stress-strain, x-ray, and NMR data

In the field of biomedical research there is a need for tissue mimicking materials. In ultrasonic elastography, a new engineering discipline for producing strain images of soft tissues, there is a need for gel phantoms which mimic both the mechanical and the ultrasonic characteristics of soft tissues. Blended gels of gelatin and agar are one such type of gel phantom, with the agar serving the dual role of a strengthening and ultrasonic scattering material. An experimental and theoretical investigation of these blended gels was conducted. By percent with respect to the total weight, arrays of gels were made with the concentration of gelatin ranging from 6.00% to 10.00%, and the agar concentration varying from 0.00% to 1.33%. Dynamic stress strain curves were obtained. Gels doped with agar displayed a first-order phase transition. Pure gelatin gels did not undergo a phase transition. A theoretical investigation involving the theories of polymer statistical mechanics, blending, network formation, crystallization, entanglements, and network imperfections was conducted. A molecular hypotheses, inspired by the van der Waals theory of gas and the Mooney-Rivlin theory of rubberlike materials, was proposed to explain the first-order phase transition in terms of the known molecular properties of agar and gelatin. The essential feature of the hypothesis proposes hydrogen bond evaporation under strain loading and hydrogen bond condensation under strain unloading. X-ray and NMR studies were conducted on gels doped with agar to support the hypothetical model.