THE DESIGN & CHARACTERIZATION OF A MINIATURE SHAPE MEMORY ALLOY VALVE FOR PASSIVE THERMAL MANAGEMENT

Photonics Integrated Circuits (PICs) are being deployed by the telecommunications industry as transceivers for fibre optic networks. The core component of a typical PIC is the laser-array and the power density of these devices (10² W/cm²) now demands novel thermal management architectures including developments such as near-source liquid cooling. In such a system, thermal control is required through feedback and for this a micro-valve could be developed from the NiTi Shape Memory Alloy (SMA). Thermally coupled to the laser-array this micro-valve would work passively to regulate the flow of coolant in a micro-channel. The objective of the work is to realize a passive SMA valve at the millimetre scale, and to characterise this valve in a mini-channel. A prototype valve was designed and fabricated from 127 μm thick stainless steel sheet and 0.4 mm NiTi actuator wire. Experiments were conducted to observe the actuation of the valve and measure its hydro-dynamic characteristics. The results demonstrate that the valve is capable of actuating passively in response to the temperature of the flow in the channel. The proposed design was capable of completing 80% of the total valve movement in under two seconds, highlighting the capabilities of SMA valves for dynamic passive control. The pressure drop was 20-100 Pa for a range of Reynolds numbers between 100 and 220. The pressure drop measurements were then used to calculate the loss coefficient for the valve (K). This body of work takes a significant step towards realizing a passive NiTi SMA micro-valve.