Introduction Real biological tissue is perishable and expensive, especially if the origin is human. Therefore, researchers prefer to develop techniques for imaging, testing, cutting, and so forth on less valuable, inorganic materials. Researchers at the University of Wisconsin have developed such materials, called “phantoms”, for evaluating and improving magnetic- resonance and ultrasound imaging systems.1-4 In order to function as a substitute, these materials had to be temporally stable and mechanically comparable to real tissue. In this work, we developed a technique for measuring the storage and loss modulus of such materials using dynamic indentation5-6 on an Agilent Nano Indenter G200.