Design and optimization of a miniature actuator using shape memory alloy (SMA) wires

Microfluidic systems have proven to be very beneficial in many fields such as chemical and biomedical sciences. The reduced sample volume, among many other advantages attracts researcher's attention to this technology. Consequently the need for a precise fluid handling and flow control is greater than before. Although many micropump systems have been invented over the last decade, there is still a need for a small, fast, quiet, and robust pump design. Because various applications have their own specific pumping requirements, the search for application driven novel micropump designs still continues. Shape memory alloys have been gaining more attention recently, for their idiosyncrasies, namely shape memory effect and pseudoelasticity. The ability of the shape memory alloy to recover high deformations makes them appealing for various applications. Here we use both of its hallmark behaviors, shape memory effect and pseudoelasticity, to design an electrically driven actuator. We kept a micropump development in mind during the design and characterization of this actuator. Consequently, the obstruction level of a conductive fluid filled channel was quantified using impedance measurements of control fluid and used as an indicator of the actuation amplitude and rate. The fabricated actuator successfully closed the fluid channel even under fluid pressures of up to 150 mmHg. This scalable design can be used in different applications such as micropump development, and microfluidic World to Chip interface.