Dual chamber shape memory alloy unplugging and mixing system coupled to a high pressure optical cell for biophysical studies

Abstract

High pressure optical measurements are useful for understanding structure and function of biological molecules. Commonly used high-pressure optical cells can only observe a single sample under elevated pressure. If researchers wish to observe the interaction between different biological samples, they must mix the samples at atmospheric pressure, place the mixture within the pressure chamber, and wait until the desired pressure is reached. In many cases, researchers want to observe the initial reaction between two separate biological samples; however, the sample mixing and the assembly of the high pressure optical cell coupled with a spectrometer at desired pressures can take several minutes or longer. Our current design uses a shape memory alloy (SMA) spring actuator to seal a dual chamber cuvette for separation of two different biological samples. Once the desired pressure is reached, power is applied to the system that activates the SMA to unplug and mix the two samples using a micro dc-motor. During the mixing efficiency tests, deionized water was placed in the top chamber of the cuvette and an aqueous solution of carboxyfluorescein (a fluorescent dye) placed in the bottom chamber. Based on this design, we were able to achieve a total unplugging and mixing time within a few seconds (at atmospheric pressure). Quicker mixing means researchers will have more reliable data for analyzing the initial reactions between two different biological samples. Future tests on this new actuator will be conducted at elevated pressures.