Tag Archives: MEMS

Coin-Sized MEMS Rocket Thruster

Thrusters, in addition to engine and control systems, typically require hydrazine rocket fuel, which they must store in tanks, making the entire setup physically rather large. Recent innovations are under development, and they use ion and electric propulsion systems. Although the newer thrusters are physically smaller, they are still too large for Nano and Pico satellites, which weigh between 1 and 10 kg, and between 0.1 and 1 kg respectively.

These small satellites require miniature satellite thrusters. These are rocket engines with combustion chambers of 1 mm size. They use only electricity and ice to create thrust. Manufacturing such tiny coin-sized thrusters requires MEMS fabrication techniques.

Miniaturization of electronics is leading to increased accessibility of orbital launch capacity. In addition, small satellites are experiencing fast growth. But, along with electronics, many other things need to shrink too.

For small satellites, thrusters and other equipment for stabilization must also proportionally shrink in size. Although satellites for special purposes are getting smaller, some key components, especially thrusters, have not kept pace with the downsizing.

Enter The Imperial College of London, where a team has designed a new micro thruster especially meant for Nano and Pico satellite applications. The ESA or European Space Agency, who tested the new thrusters, has dubbed them as ICE-Cubes or Iridium Catalyzed Electrolysis CubeSat Thrusters. ICE-Cube thrusters use the process of electrolysis to separate oxygen and hydrogen from water.

The thruster then recombines the two gasses in a combustion chamber less than 1 mm long. The miniature size of the chamber requires a MEMS fabrication process to create it. In laboratory tests, the thruster delivered 1.25 millinewtons of thrust, and it could sustain it for an impulse of 185 seconds.

Although a fast-growing category of space vehicles, Nano satellites are a relatively new breed. While 2012 saw only 25 launches, a decade later, there were 334 launches in 2022. By 2023, that number has nearly doubled.

Being tiny, Nano satellites have little room to spare. That means, conventional tankage carrying corrosive and toxic propellants, such as hydrazine, is no longer practical. While there are forms of propulsion available on a smaller scale, and they typically use compressed air, ions, or steam, these are neither energy-efficient nor do they offer sufficient lifetime. The highest energy efficiency comes from using oxygen and hydrogen in a combustion system.

Nano satellites typically store their propellant as water-ice, because it is safer and less expensive as compared to holding it in liquid or gaseous form. The electrolysis process requires only 20 Watts, which storage batteries or solar cells can easily produce. Therefore, the satellites typically convert solar energy into thrust using ice.

The Imperial Plasma Propulsion Laboratory of the college fabricates the above devices in-house, using their own MEMS process. They create the shape of the device with a reactive ion etching technique using a refractory metal. Then they sputter-deposit an indium layer, which acts like an ignition catalyst, while simultaneously creating a protective oxidation layer for the walls of the device.

The college laboratory has developed two types of micro thrusters—the ICE-200 producing a design thrust of 1-2 N, and the ICE-Cube, generating a thrust of 5 mN.

MEMS Replacing Quartz?

The automotive market is transforming very fast. We have next-generation technologies already—semi-autonomous cars, ADAS or advanced driver assistance systems, and an array of electric vehicle options—smart mirrors, backup cameras, voice recognition, smartphone integration, telematics, keyless entry, and start. Some of the latest models feature lane-keep assist technology, automated parallel parking, and many other self-driving capabilities as these vehicles move steadily toward fully autonomous driving.

All the above has required a redefinition of the automotive design, including infotainment, convenience, and safety features, as the users of smart and connected cars expect. With automotive being the fastest-growing market segment in the semiconductor field, the key drivers for this growth come from electronic components for ADAS and other EV applications. Consider that an average car has about 1,500 semiconductors to control everything from the drivetrain to the safety systems.

However, apart from sensing, processing, and communication chips, there is another critical technology contributing to the reliable, safe operation of autonomous systems, and that is precision timing.

Most car owners understand automotive timing as the timing that belts, camshafts, or ignition systems keep for the engine to run efficiently and smoothly. For automotive systems developers, however, timing means devices providing the clock for buffers, oscillators, and resonators. In the vehicle, each timing device has a different but essential clocking function that ensures stable, accurate, and reliable frequency control for digital components. This precision timing is especially important for modern complex automotive systems like the ADAS that generate, process, and transmit huge volumes of data.

As a result, modern cars may use up to 70 timing devices to keep the automotive system operating smoothly. As vehicles get smarter with each new model, the number of timing devices is also growing. The automotive design has a wide array of digital systems that require precise, reliable timing references from clock generators and oscillators. They provide the essential timing functions for networks, infotainment, and other subsystems within the vehicle and electronic control system units like ADAS.

With the accelerating pace of automotive innovation, one critical component has remained constant for the past 70 years—the quartz-base timing devices, or the quartz crystal oscillator. But in the automotive environment, quartz crystals face fundamental limitations like fragility due to their susceptibility to environmental and mechanical stresses. Quartz timing devices are now becoming a bottleneck for safety and reliability because of their inherent drawbacks.

MEMS timing components, on the other hand, can easily meet the rigors of AEC-Q100 automotive qualification requirements. MEMS is a well-established technology, widely useful in many fields, including automotive systems. Here, they serve as gyroscopes, accelerometers, and a wide variety of sensor types.

The industry qualification of AEC-Q100 for MEMS devices offers the assurance that these timing components will provide the robustness, reliability, ad performance as the automotive electronic systems demand.

Stringent testing has proven the greater reliability of the silicon-based MEMS technology overclocking applications of quartz crystals. Being much smaller than quartz crystals, MEMS resonators are ideal for space-sensitive automotive applications like radar/LIDAR, smart mirrors, and camera module sensors. Their low mass and smaller size make MEMS timing devices far more resilient to mechanical shock and vibration.

New MEMS Switches Accelerate Testing

If you are using processor ICs from Advanced Digital, testing them may be costly and logistically challenging. This is because testing these ICs requires isolated DC parametric test equipment, including high-speed digital ATE or automatic testing equipment to assuring the quality. New MEMS switch technology from ADI, working at 34 GHz, offers both DC and high-speed digital testing, despite having a small form factor in the form of a 5x4x0.9 mm LGA package. They reduce the test costs and simplify the logistics necessary for testing RF/digital SoCs or systems on chips.

There are many high-speed chips on the market. These include high-density inter-chip communications for advanced processors. Such advanced processors are the norm for 5G modems, computer graphics systems, and other central processing units. Therefore, ATE designers constantly face the increase in demand and complexity for throughput while assuring quality. For instance, the greatest challenge comes from the increasing number of transmitter/receiver channels, and these require both DC parametric and high-speed digital testing. Not only does this increase the testing time, but it also increases the complexity of the load board, while reducing the test throughput. In turn, this drives up operational expenses, while reducing the productivity of modern ATE environments.

One way of solving such ATE challenges requires a switch that not only operates at DC conditions but also at high frequencies. The new MEMS switch ADGM1001 from ADI, while passing true 0 Hz DC signals, can also operate equally effectively at high-speed signals up to 64 Gbps. Therefore, testing with these new switches requires only one insertion for an efficient single test platform. It is possible to configure the test platform for both DC parameter testing and standards for high-speed digital communications.

High-volume manufacturing requiring HSIO or high-speed input-output testing is often a challenge. Testing strategies typically employ a high-speed test architecture as a common approach for validating HSIO interfaces. Such test equipment typically incorporates two test paths in one configuration—one for DC tests, and the other for high-speed tests.

Testers employ a few methods for performing tests at both DC and high speed on HSIOs or digital SoCs. They may use relays, MEMS switches, or different load boards—one for DC testing, and the other for high-speed testing, but this requires two insertions.

Use of relays for DC and high-speed testing can be challenging. This is primarily due to relays being unable to operate beyond 8 GHz. Therefore, users must compromise on test coverage and signal speed. Moreover, relays take up large areas on PCBs on account of their larger size, and this makes the load boards rather large. Another concern with relays is their limited life and reliability. Relays typically only last for about 10 million cycles, thereby limiting the lifetime and system uptime of the load board.

With its superior density and small form factor, the 34 GHz MEMS switch from ADI offers both DC testing and high-speed digital testing capabilities, overcoming the above challenges.

MEMS Microphones for Laptops

In the recent pandemic, people took to virtual meetings using their computers and laptops. However, most often, the substandard quality of the audio led to an unsatisfactory experience. That’s because people’s expectation of consumer devices has increased significantly. They want to make high-quality calls from wherever they may be. They could be on the street, in an open office, or in a crowd.

People expect their devices to have ANC or active noise cancellation, transparent hearing, and voice control. However, these require more sophisticated and better microphones.

For instance, people engaged in video conferencing, want their experience to be as close as possible to a real, face-to-face meeting. Now this depends, to a great extent, on the audio quality, and people expect high-quality audio without having to put on additional devices, such as headphones.

Achieving good quality audio requires the application to use a combination of high-quality hardware and software. It is necessary to have algorithms that provide good noise reduction, reverberation reduction, enhanced beamforming, and good direction of arrival detection. These are essential for high-fidelity transmission and audio recording in a wide variety of conditions and situations. However, the quality of the entire chain is dependent on the primary sensor, the microphone.

Most good-quality microphones that have been around for a long time tend to be large and expensive, and primarily confined to audio recording studios. However, consumer equipment typically requires microphones that are mass-produced with tight manufacturing tolerances, and physically small. MEMS microphones suit these requirements very well.

For a microphone to be qualitatively described as good, it must possess some performance characteristics. The first among them is the SNR or signal-to-noise ratio. SNR of a microphone is the difference in its output between a standard reference signal input and the microphone’s self-noise. All elements of a microphone contribute to its self-noise. This includes the MEMS sensor, package, ASIC, and the sound ports.

SNR is important when the microphone is detecting sounds or voices that are at a distance from it. This is because the input signal decreases with distance, as sound level halves at twice the distance. Further, signal losses can come from the system design, room conditions, and sound channel. A good microphone with a large SNR can capture sound even at large distances. This helps with capturing input signals for algorithms, voice commands, and recording.

The next important characteristic of a good microphone is its THD or total harmonic distortion. This refers to the presence of harmonics in the microphone’s output that are not present in the input signal. The point where the THD reaches 10% is important as this represents AOP or acoustic overload point. At this point, the output from the microphone contains clipping and other noises, because the signal is too loud for the microphone.

The latest MEMS technology allows building of studio-level microphones for consumer devices like laptops. This has been aptly demonstrated by Infineon using their XENSIV IM69D127 and IM73A135 MEMS microphones that are allowing OEMs to build laptops with the next level of audio quality.


A solid-state Lidar chip works by emitting laser light from an optical antenna. A tiny switch turns the antenna on and off. The light reflects off the sample and the same antenna captures it. For 3D imaging, the Lidar chip has an array of such antennae. The switches sequentially turn them on in the array.

An array of MEMS switches for high-resolution solid-state Lidar can reduce its cost significantly. This allows the solid-state Lidar to match other inexpensive chip-based radar and camera systems. This removes the major barrier to the adoption of Lidar for autonomous vehicles.

At present, autonomous highway driving and collision avoidance systems use inexpensive chip-based radar and cameras as their mainstream building blocks. At the same time, Lidar navigation systems, being mechanical devices and unwieldy, are also expensive, costing thousands of dollars.

However, researchers at the University of California, Berkeley, are working on a new type of high-resolution Lidar chip and this may be the game-changer. The new Lidar uses an FPSA or Focal Plane Switch Array. This is a matrix of micron-scale antennas made of semiconductors. Just like the sensors in digital cameras do, these antennas also gather light. While smartphone cameras have impressive resolutions of millions of pixels, FPSA on the new Lidar has a resolution of only 16,384 pixels. However, this is substantially larger than the 512 pixels that the current FPSA has.

Another advantage of the new FPSA is its design is scalable. Using the same CMOS or Complementary Metal-Oxide Semiconductor technology that produces computer processors, it is possible to reach megapixel sizes easily. According to the researchers, this can lead to a new generation of 3D sensors that are not only immensely powerful but also low-cost. Such powerful 3D sensors will be of great use in smartphones, robots, drones, and autonomous cars.

Surprisingly, the new Lidar system works the same way as mechanical Lidar systems do.  Mechanical Lidars also use lasers for visualizing objects situated several hundreds of yards away, even when they are in the dark. They also generate high-resolution 3D maps for the artificial intelligence in a vehicle for distinguishing between obstacles like pedestrians, bicycles, and other vehicles. But for over a decade, researchers have tried to put these capabilities on a chip, without success, up until now.

The idea is to illuminate a large area. However, the larger the area illuminated, the weaker is the light intensity. This does not allow reaching a reasonable distance. Therefore, researchers had to make a trade-off for maintaining the light intensity. They had to reduce the area that their laser light was illuminating.

The new Lidar has an FPSA matrix consisting of tiny optical transmitters. Each transmitter has a MEMS switch that can rapidly turn on and off. This allows time for the waveguides to move from one position to another while allowing channeling the entire laser power through a single antenna at any time.

Routing light in communications networks commonly uses MEMS switches. The researchers have used this technology for the first time for Lidar. Compared to the thermo-optic switches that the mechanical Lidar uses, the MEMs switches have the advantage of being much smaller, consuming far less power, operating faster, and performing with significantly lower light losses.

Motion Tracking through the MC3672

This year, the MSEC or MEMS & Sensors Executive Congress had mCube exhibiting their incredibly small and low-power MC3672, an inertial sensor product. This is a three-axis accelerometer, and its size is only 1.1 x 1.3 mm. This tiny WLCSP packaged device is a low parasitic unit, with enormous possibilities of unobtrusive use as low power motion tracking in wearable design, and in a completely new set of applications in future.

Recently, mCube acquired Xsens and they were able to couple a sensor fusion software to their tiny accelerometer. This gave them the ability to sense body motion and capture solutions for health, entertainment, and fitness. The combination also allows them to control and stabilize inertial measurement units in industrial applications.

Almost all are aware of MEMS motion sensors, as tablets, smartphones, and wearables use them popularly. Use of the MC3672 accelerometer will generate more applications for these devices in the future. This could include new areas such as in the medical world, related to prevention and diagnostics of illness. For instance, when visually inspecting the throat, stomach, or intestines of a patient, physicians often need to perform invasive and unpleasant procedures.

In future, patients would be able to swallow a camera-pill that can wirelessly beam images from the inside of the body to a display for the physician to view. Miniature motion sensing incorporated within the camera-pill could allow medical practitioners to navigate the pill effectively by actuating and controlling it. This would allow them to monitor its location and orientation in real-time as it passed through the body. Images captured by the camera would enable precise diagnosis and investigation of any problems.

According to Dr. Sanjay Bhandari, Senior VP of mCube, a plethora of new applications will come into life based on the granular, precise measurement of motion, orientation, tilt, and heading of the sensor. For instance, some applications will be able to capture motion data to communicate it to cloud software services, and ultimately sharing it with networked systems for monitoring and analysis.

Achieving most of the envisaged applications is only possible with motion-sensing systems that are extremely small and drain very little power from an arrangement of energy harvesting or a battery.

Along with the low power consumption and small system size, all components in the system must adhere to the design features. The sensor interface uses Silicon and CMOS-based circuits that filter, amplify, and fit the analog to digital processors to work its magic.

The monolithic, single-chip design by mCube integrates both the CMOS and the MEMS within a clever extension using a standard CMOS-base process. This is a reliable procedure for handling high volumes and produces excellent yields. Within the chip, mCube has interconnected the MEMS and the CMOS very efficiently.

In future, mCube plans to integrate BLE or Bluetooth Low Energy into the MCU in its SIP package—they want to realize IoMT-on-a-Chip. They have protected their technology by 100 approved patents.

The acquisition of Xsens brought to mCube the 3D technology to track motion in the sensor world—a high-precision module for sensing motion in 9 degrees of freedom.

Redefining MEMS with 3-D Interactive Projection

At the Mobile World Congress 2017, Bosch introduced a combo of a micro-scanner and projector, capable of turning any surface into a virtual user interface. Bosch is the world’s oldest and biggest manufacturer of micro-electro-mechanical systems (MEMS), and in its combo projector, it is using infrared for scanning and laser for projecting.

Currently, engineers are using MEMS devices for a variety of gadgets, especially where a human-machine interface (HMI) is necessary. These include in-car heads-up displays, infotainment, medical devices, robotics, industrial equipment, and on the factory floor. With the new microscanner BML050, Bosch Sensortech has extended its portfolio to include optical microsystems. This move also expands Bosch’s market from being only a component supplier to becoming a system supplier as well.

To sense where the user has placed his finger on the projected interactive display, the new Bosch BML050 uses a combination on two MEMS scanning mirrors. One of the mirrors tracks the X-direction, while the other scans the Y-direction. Sensing the finger also makes use of an infrared laser and an RGB laser.

The integrated module for infrared, red, green, and blue (IR-RGB) is only 6 mm high, and is capable of HD resolution. The two MEMS scanning mirrors are capable of both projecting images as well as collecting the reflected light, thereby determining accurately where the user’s finger is touching the projected image. According to Bosch, this technique is adaptable to 3-D scanning as well, where they can apply time-of-flight calculations using the reflected light from an object.

A major advantage over Digital Light Processors (DLPs), the Bosch laser-based MEMS scanner is always in focus, even when the projection surface is uneven. According to Stefan Finkbeiner, the chief executive officer of Bosch Sensortech, DLPs require thousands of mirrors that need focusing, and the entire outfit is expensive.

At present, the reference design of the Bosch BML050, although containing all the technicalities for use in almost any application, is much larger than the expected OEM circuit board. Finkbeiner informs that despite this, customers are already integrating the BML050 into their products, and they will be in the market by Christmas this year.

The BML050 has a two-mirror system, with one hinged in the X-direction and the other in the Y-direction. The mirror system projects from the module, which measures only 6 x 24 mm, and uses 30-lumen lasers. This arrangement allows Bosch to alter the size when using low-power lasers, or when using high-power lasers for instance, for industrial sized images. The reference design for the BML050 contains all required drivers and processors. This includes ASICs for driving the mirrors, processing the video, managing all colors, managing the system and laser power with two PMICs.

According to Finkbeiner, the two-MEMS mirror architecture is very simple to integrate. Therefore, for the future, Bosch is planning to use a sealed module design after further miniaturization. The design will then be suitable for use in tiny gadgets such as for IoTs and smartphones. Very soon, you may find virtual human-machine interfaces on everything from toys to industry equipment on the factory floor, robotics, medical devices, and infotainment such as in in-car heads-up displays.