This paper presents a novel microactuator driven by shape memory alloy (SMA). First, the helical spring-shaped SMA is fabricated from SMA wire (Ti50%-Ni45%-Cu5%) with one way shape memory effect and 0.6 mm in diameter. Subsequently, a compliant tube-type microactuator driven by helical spring-shaped SMA is developed. The performances of the helical spring-shaped SMA and the compliant tube-type microactuator, such as the response time, the recovery force and the surface temperature in terms of the driving currents, are investigated. The driving circuit system comprising a pulse width modulation (PWM) control circuit is used to drive the actuator. Experiments demonstrate that control of the SMA actuator using PWM effectively reduces the energy consumption and ensures a short cooling time to guarantee a high response time in actuating cycles. Finite element software (COSMOSWorks) is applied for the analysis of the compliant tube-type actuator, which aim is to demonstrate the agreement between the theoretical analysis and experiment as well as to improve the performance of the actuators.
We demonstrate a digital microfluidic system with an on-chip detection capability that is based on a guided-mode resonance filter (GMRF). Versatile droplet manipulation was achieved through the electrowetting-on-dielectric (EWOD) technique. GMRF was fabricated through replica molding and soft lithography, and the EWOD chip was fabricated through a typical photolithography process. Droplets measuring 1.125 µL were used to demonstrate merging, mixing, and cutting, and to achieve twofold and Threefold dilutions, and were then transported to the GMRF region for concentration measurement. The bulk sensitivity of GMRF is approximately 90 nm RIU−1 [17494 nm/(g/L)], resulting in a minimum detectable concentration of 4.66 × 10−5 g/L for a sucrose solution.
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