The world is being sensorised, which means one thing—more MEMS sensors. The trend is most prominent in consumer applications, worth 62% of the market, but these tiny sensors are now prevalent in every sector: from industry to space to medicine. In 2020, the MEMS market was worth around US$12.1 billion, which is expected to increase to approximately US$18.2 billion by 2026. MEMS sensors are big business as they are quite literally everywhere—from our phones to outer space. Here are five fascinating examples of high-tech MEMS technology.
But first, what is MEMS technology?
Micro-Electro-Mechanical Systems (MEMS) technology uses processes that employ semiconductors to make tiny mechanical and electro-mechanical components (ranging in size from less than a micrometre to several millimetres). A massive amount of technology is made using MEMS sensors—from simple structures with no moving parts to intricate electromechanical systems with many moving parts.
Tech using MEMS devices can be much smaller, costs less, and consumes less power than older tech fulfilling the same function. Also, any device made using the sensors will be highly accurate.
1. Altitude and Heading Reference Systems
Aircraft instruments, including compass, altitude, and turn coordinators, traditionally used large, mechanical gyros driven either electrically or by vacuum pressure through a pump on the engine. Modern aircraft, however, use MEMS sensors in their systems.
The Altitude and Heading Reference System (AHRS) uses these sensors to detect the aircraft's acceleration and aircraft movement. AHRS are multi-axis sensors that provide an aircraft's heading, attitude, and yaw information. They work with Flight Control Systems, which control an aircraft's direction in flight and change speed. AHRS is made up of accelerometers, gyroscopes, and magnetometers on all three axes. Some AHRS also use GPS receivers to improve the long-term stability of the gyroscopes.
The AHRS provides flight instruments, head-up displays, autopilots, and moving map navigation systems with the data they need to function correctly. Solid-state MEMS sensors and Kalman filter algorithms designed to mitigate high drift rates combine to give aircraft high-performing and low-cost AHRS.
2. Kidney transplants
Unfortunately, the supply of kidneys for donation is not meeting the demand. In the US, Americans needing 35,000 kidney replacements must be given dialysis at the cost of $25 billion per year. Only 15,000 kidney transplants are carried out in the United States, while 58,000 people sit on the waiting list. So medical researchers have been planning to create an artificial kidney. The technology needed to do so is still being developed but uses MEMS technology.
Biomedical engineers are still determining whether the artificial kidney should be organic, an inorganic structure, or a biological hybrid. They are employing semiconductor processes with MEMS techniques that allow them to make a 3D prototype structure that could be a micro- or nano-filter to meet the kidney's capacity needs.
Currently, the technology is focusing on creating an artificial kidney that would work outside the body; however, the long-term goal is to implant it inside the body. The project is challenging as the kidney filters 180 litres per day of blood, so the solution must involve MEMS development using microfluidic devices.
3. Space travel and checking the weather on Mars
As space exploration becomes more commonplace, the focus will shift from a few costly missions to more frequent endeavours, requiring reduced costs. The cost of travelling to space is directly related to the weight of everything that needs to be transported to space—launching even to low earth orbit costs around $10k per kilogram. Therefore, heavy equipment such as communication and navigation platforms and scientific payloads will need to be replaced.
Fortunately, devices using MEMS technology are well placed to substitute older, heavier tech. Three areas can be made lighter by replacing them with MEMS tech: heavy gyroscopes, subsystems such as inertial measurement units, and highly integrated real-time tracking satellites. Making components lighter will enable detailed investigations of the space environment and planetary surfaces—Mars, for example.
One focus of Martian explanations is the planet's meteorological parameters, including humidity, wind, pressure, and temperature. Scientists must be able to create tech that can land on Mars and then be used to measure these parameters; therefore, they have designed a micro weather station that uses MEMS-fabricated components, including the microhygrometer that measures humidity—difficult to do on the Red Planet's cold, dry surface. MEMS technology helps the microhygrometer be sensitive and accurate enough even at low humidity, meaning it is perfect for Mars exploration.
4. Drones
Drones were first seen as a bit of fun, but the technology has radically improved over the past few years. Their flying capabilities have improved, and they have become safer, more stable, and easier to control, meaning they are being used much more frequently in various situations. And MEMS sensors have been crucial to the improvement in drones' performance.
Inertial MEMS sensors help drones remain stable whilst in flight and allow the user to control them carefully. However, for a drone to be more than just a toy—to turn it into a precise tool—several issues must be addressed, including calibrating the motors, fine-tuning system dynamics, and addressing changing operating conditions.
And the answer lies in more MEMS sensors working with sophisticated software, which together improve the drone’s flight performance. They make the Inertial Measurement Unit more precise and allow the barometric pressure sensor, geomagnetic sensor, Application Specific Sensor Node, and sensor data fusion to make the devices more sophisticated.
The smaller drones can be made the better, so using MEMS technology is advantageous for keeping weight down. The sensors also make the devices more precise by allowing them to handle variable and demanding environmental and operational conditions, including temperature changes and vibrations.
5. Biometric gaming
Gaming used to be 2D, but MEMS sensors are making it more realistic by allowing gamers to contribute with their biometric information. MEMS sensors are found in audio earbuds, headsets, armbands, and wrist devices that gamers can wear to measure biometric parameters. (People exercising also tend to wear the same peripherals to track and measure their fitness metrics.)
The sensors in these peripherals can measure, for example, a gamer’s heart rate, which could then be used as a control measure in a game. Or they could be used to measure the user’s capacity to hold their breath—if they were competing in an online underwater swimming challenge.
Games can use biometric data from active signal characterisation: segmenting raw signal data from biometric sensors into biological, motion, and environmental signals and noise. This technology can significantly affect the gaming experience whilst also gathering meaningful health data about the person playing the game—meaning there is a positive healthcare benefit and increased enjoyment.
Biometric gaming is also being used by physical therapists and in rehabilitation to measure and accurately control patients’ recovery.
Conclusion
MEMS sensors are sometimes only associated with cell phones, but any high-tech device needing its movement to be measured exceptionally precisely can benefit from MEMS technology. Original equipment manufacturers can integrate sensors that measure and control positioning into any device, even those that work on Mars.
