Microextensional Rheology for Small Volume or Expensive Biological Sample Analysis

One of the methods to study microstructure of complex fluids is rheology. In general, rheological analysis requires relatively large volume samples to analyze meaningful characteristics. Many biological materials, however, do not naturally occur or are prohibitively expensive to produce in these requisite large volumes. Vitreous humor samples are small volumes available per specimen, and certain protein solutions, such as Tau protein, are very expensive to purchase ($10,000 per ml). Therefore, a method to perform complex analysis on small-volume biological samples is crucial to the growing field of micro-extensional rheology. Using a commercial tensiometer to induce an extensional flow and a high speed camera to capture the evolution of the fluid structures, we developed a technique that is capable of measuring important characteristics of biological samples such as extensional relaxation time and extensional viscosity with volumes less than 100 microliters. To demonstrate the effectiveness of this technique, we analyzed the relaxation times and extensional viscosity of several biological samples and have shown promising results. In addition, we were able to capture rheological properties of dilute polymer solutions using this technique, while shear rheology tests did not yield such results.