Microvalves play a crucial role in many industries, from aerospace to biomedical engineering, controlling the flow of liquids and gases in compact dimensions. There are various options available when it comes to microvalves, and it can be difficult to choose the best one for your application.
In this article we shortly compare two common microvalve technologies: shape memory alloy (SMA) microvalves and solenoid valves.
First, we briefly explain the basis of the two technologies and their main advantages. Then we summarize the key differences, present the valve technology function schematics and compare some of the microvalve types available on the market.
SMA mircovalves are notable for utilizing shape memory alloys (SMA), typically Nickel-Titanium (NiTi) alloys, known for their ability to return to a pre-defined shape after deformation. This property is harnessed in valve design by using actuators that respond to temperature changes. When heated past a certain transition temperature, the SMA material changes its phase and consequently its shape, actuating the valve without the need for external mechanical input.
There are two main forms of SMA actuators used in microvalves: One is a wire with a round cross section, explained in this video by Dolphin Fluidics. While the other is a flat-foil where a slim sheet of alloy is used for actuation, see memetis microvalve example here.
Smooth and Silent Switching: The inherent properties of SMAs allow for pulsation-free and step-less gas and liquid actuation that can be proportionally controlled, without any noise made when changing states.
Compactness and Light-Weight: SMA microvalves are significantly smaller and lighter than many mechanical alternatives, making them ideal for applications where size and weight are critical.
Energy Efficiency: SMA microvalves require less energy for switching, as only a very small actuator needs to be heated to open and close the valves. This means less heat production and lower operational costs over time.
Solenoid valves are electromechanical devices that control the fluid flow by using a tubular electromagnet called a solenoid. When electrical current is passed through the solenoid coil, a uniform magnetic field is generated. It is the strongest in the middle of the coil, which is where the plunger for opening and closing the valve is installed. Once the valve is powered, it takes just a few milliseconds to switch. This is very good in certain applications, while in others it can cause issues because of the water hammer effect that creates back pressure in the fluid system above the valve.
Solenoid valves are versatile and can be found in everything from household appliances to industrial machinery. The miniature solenoid valves are usually named with a millimetre size, e.g. 5 mm, 8 mm, 10 mm, that relates to the smallest dimension (width or diameter) of the valve housing.
Fast Switching: These valves can open and close very quickly, making them suitable for applications that require rapid cycling.
Versatility: Available in various sizes and designs, solenoid microvalves can handle a wide range of fluids and pressures.
Established Technology: Solenoid valves have been on the market for significantly longer than SMA microvalves, impacting their current use, availability and the high extent of integration into various industries.
| Shape Memory Alloy Microvalves | Solenoid Microvalves |
| Innovative technology | Established technology |
| Thermomechanical principle | Electromechanical principle |
| Step-less switching | Fast switching |
| Low power consumption | Higher power consumption |
| Compact size that can be further minimized | Miniaturization limited by solenoid actuator size |
| Low heat production | Production of heat and magnetic stray fields |
| Few producers | Many producers |
Valve function schematics:
To provide an insight into the numerical specifications that set the SMA and solenoid microvalves apart, we have roughly compared four typical miniature 2/2-way valves that are media separated.
The comparison includes two types of SMA microvalves, one of which is the memetis normally-closed valve, and two common types of solenoid microvalves with 6 mm and 8 mm diameter.
Among the other miniature valves on the market, memetis offers the smallest solution with the fastest SMA-valve switching time. Choosing memetis SMA microvalves allows device designers to create exceptionally small solutions where smooth valve switching is crucial, with the additional benefits of reducing energy consumption without adding any additional noise to the fluid control system.
Both shape memory alloy (SMA) microvalves and solenoid miniature valves offer distinct advantages that make them suitable for different applications. The choice between the two will largely depend on factors such as the required actuation speed, power availability, application specifics (sound, proportional control need), and space constraints. The fundamental differences and operational characteristics of the two microvalve types described in this article give engineers and designers crucial insights to evaluate the most appropriate technology for their application requirements.
Last edited Dec 10, 2024
memetis Innovation - more about the shape memory effect
Stepless Actuation (coming soon) - how the SMA technology provides proportional, pulsation-free movement