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The emerging billions of Internet of Things will need to connect billions of devices deployed in the physical world (the so-called “edge” of IoT) to the cloud, bringing real-world data and analytics to operations. …a challenge with current solutions. Much of the Internet of Things (IoT) is mobile, and sensors play a key role in delivering status information for these connected devices. Sensors ideally need to be small, smart, zero-power and cost-effective. They range from tiny microelectromechanical-systems (MEMS) accelerometers to high-resolution cameras to time-of-flight (ToF) 3D imaging (see “Time-Of-Flight 3D Coming To A Device Near You”). These devices are common fare on smartphones and tablets. MEMS devices are designed to work in concert to sense and report on the physical properties of their immediate or local environment, or, when signaled to do so, to perform some kind of controlled physical interaction or actuation with their immediate or local environment.
Mechanical-Systems (MEMS) is the integration of mechanical elements (levers, springs, deformable membranes, vibrating structures, etc.), sensors, actuators, and electronics (resistors, capacitors, inductors, etc.) on a common silicon substrate through microfabrication technology. MEMS devices are today considered as one among the most promising technologies of this century, capable to revolutionize the industrial world and the commercial product market. Micro-Electro- MEMS can be considered as “intelligent” systems which combine mechanical and electronic functions in extremely reduced dimension. The dimension of a MEMS device is in the order of the microns and it is manufactured directly on a silicon wafer.
The advanced device and process concepts thrust enables the integration and co-location of actuators, sensors, electronics, and power supplies to merge the functions of compute, communicate and power together with sense, actuate and control to change completely the way people and machines interact with the physical world. Some well-known examples of MEMS-enabled functionality in everyday life are airbag deployment in automobiles; motion and orientation detection in smartphones; and blood pressure measurement in IV lines and catheters.
Using an ever-expanding set of fabrication processes and materials, MEMS will provide the advantages of small size, low-power, low-mass, low-cost and high-functionality to integrated electromechanical systems both on the micro as well as on the macro scales. Further, demands for increased performance, reliability, robustness, lifetime, maintainability and capability of military equipment of all kinds can be met by the integration of MEMS into macro devices and systems.
Analyst firm Yole Développement expects the global market for MEMS and sensors to double in the next five years, reaching $100B by 2023, spurred by growth of autonomous mobility products such as Internet of Things (IoT) devices, autonomous cars, fitness and healthcare wearables, and agricultural sensors.
MEMS Applications
The list of amazing new products incorporating MEMS and sensor devices is growing rapidly. Applications are wide and varied—from beds that monitor heart rates and breathing, to agricultural devices that measure sunlight, soil pH, and moisture content, to products aimed at enhancing athletic performance. The list goes on and on, growing daily with nearly limitless potential.
Some of device concepts include: the integration of micro devices with communication, control, computation and power components, miniature electromechanical signal processing elements (tuning elements, antennas, filters, mixers), miniature optoelectromechanical devices (cross-bar switches, fiber-optic interconnects and aligners, deformable gratings, and tunable interferometers), force/motion balanced accelerometers and pressure sensors, atomic-resolution data storage, electromechanical signal processing, process control (HV AC equipment, mass flow controllers), simultaneous, multi-parameter sensing with monolithic sensor clusters, and biochemical identification and manipulation
Advancements in MEMS technology such as sensor fusion led to high usage in various industrial verticals such as automotive, healthcare, aviation and consumer electronics. In the automotive sector, where more and more sensors are being integrated into both conventional and self-driving vehicles, demand for MEMS-based technology is also high. Micro Electro-Mechanical Systems (MEMS) accelerometer devices have became commercial products for large-volume and large-scale applications such as: airbag crash sensing, inertial measurement and navigation, vibration monitoring of machines and structures, and also for earthquake monitoring. In automotive industry, this technology is widely implemented in the airbag systems pertaining to rising passenger safety concerns coupled with favourable government regulations further contributing to the smart sensors market growth.
The healthcare sector, where a growing number of handheld medical devices are being used to diagnose and monitor patients, is also helping to drive growth in the MEMS market. Rising adoption of wearable technology such as smart watches and wrist bands is expected to surge the demand for MEMS technology in the smart sensor market.
On the gaming front, for example, AdHawk Microsystems recently developed a tiny chip with low cost, and minimal power consumption, that is expected to “revolutionize the next generation of VR/AR headsets. Currently, bulky camera-based sensors make AR/VR products heavy and oversized, the publication reports, while AdHawk’s eye-tracking sensors are created from MEMS. “Previous eye-tracking systems have had to rely on cameras tethered to a computer. In contrast, the AdHawk system is embedded in AR/VR headsets or glasses and captures thousands of data points per second.”
Defense and Aerospace applications
Miniaturised MEMS sensors have become popular for military applications. These sensors could be deployed in airports, military camps, public buildings and other strategic locations. For example, MEMS pressure sensors are used in aircraft, jets, helicopters and various harsh environments; chemical sensors are used to provide accurate and timely information to the soldiers regarding noxious battlefield chemicals; friend-or-foe-identification devices enable soldiers to more easily distinguish their own forces from the enemy’s.
The use of MEMS technology in aerospace is used in a wide variety of applications. Few of them to include are
- An active control of thin boundary layer flows with the potential to reduce drag, to eliminate conventional flight control surfaces, enhance aerodynamic performance of turbines, compressors, and low-observable intakes, provide lift-on-demand.
- Compared to conventional systems, complete navigation and inertial units on a single chip, which provide main benefits in terms of weight, size and cost over conventional systems.
- Arming and fuzing/safety systems for torpedo applications
- Applications in harsh environments
- Applications for storage environments monitoring, autonomous inventory and for service life predictions
- Spacecraft applications of micro machined systems. Extensive tests have been performed by the researchers and determined that space vacuum produces an ideal environment for some applications using MEMS devices.
Chemical attack warning sensor
The MEMS chemical sensors are currently being developed for the semiconductor wafer industry. It may also be possible to develop chemical sensors for the soldier, which inform him of the presence of noxious chemicals. Micro-chemical sensors are also being addressed by numerous other researchers. The size and cost are the major benefits that MEMS bring to this application. Currently, the chemical sensors carried by man are expensive and bulky, built of distinct components. The MEMS technology would allow the systems to be mini-sized, throwaway modules, customized to the threat. The MEMS device used in military applications should be able to precisely detect chemical agents below the thresholds, at which those agents become harmful to the soldier. It should also meet all the usual military requirements of long shelf life, ease of use, ruggedness, etc.
Identification Friend or Foe (IFF)
To signal a vehicle’s presence, most of discrimination aids use active beacons, reflective tapes, or transponders. Such systems, especially in fluid battlefields with intermingled forces, are extremely susceptible to interception. A concept for an IFF system was developed by a senior researcher based on macro-sized corner cubes mounted on the surface of a vehicle. The main benefits that MEMS provide to this application are – proliferation across the vehicle by reducing dust, mud problems and laser pointing errors. It does not require the system to be connected through armor to vehicle data/power buses. It has a low power drain because of minute actuator excursions, and has a fast response because of resulting high frequency of actuating elements and small size.
Active Surfaces
Originally developed by Defense Advanced Research Projects Agency (DARPA), a special application of active surface technology is possible with the X-wing experimental aircraft. The key aspects provided by MEMS in all active surface applications are performance, size and self-contained operations.
Distributed battlefield Sensor Net (DBSN)
Vast sums have been invested by modern armies in fielding and developing systems to locate the enemy. There would be difficulties in detecting a number of important targets. However, MEMS could possibly help greatly in such task. A possible solution for this would be the distributed battlefield sensor net (DBSN). The basic idea behind this is to deploy a large number of disposable and cheap sensor systems over critical areas.
Microrobotic Electronic disabling systems (MEDS)
The MEDS would be present in the general target vicinity in a manner similar to DBSN. Rather than indiscriminate coverage of an area, timely and accurate placement of the MEDS devices appears to be important for payload, cost and time reasons.
MEMS Directional Acoustic Sensors for Underwater Operation
The bearing of underwater sound sources is typically obtained using a linear array of omnidirectional hydrophones spaced proportionally to the wavelength of the source to be located. These arrays require time delay, amplitude difference, or phase-weighting algorithms to determine the direction of the detected sound. These sensors have evolved over the years, from relatively heavy and complex systems that required significant space onboard ships to thin light linear arrays easily handled by relatively small autonomous platforms.
An alternative approach is the use of vector sensors, which are designed to acquire vector quantities associated with the sound field. The most common method to determine the direction of sound is the measurement of pressure gradient or particle velocity due to the volumetric motion of the medium. These variables carry the directional information of the acoustic energy propagation, which helps to identify the direction of the source. Multiple other techniques have been studied and combined to produce a directional response from underwater acoustic sensors. These include a combination of omnidirectional hydrophones to measure the pressure and an accelerometer to acquire particle velocity . Commercially available vector sensors use different techniques. For example, the Microflown vector sensor measures the particle velocity by means of the temperature difference between two parallel platinum hot-wire resistors. The Wilcoxon vector sensor uses three lead magnesium niobate-lead titanate (PMN-PT) crystal-based axial accelerometers and a lead zirconate titanate (PZT) omnidirectional hydrophone to extract directionality.
More recently, there have been efforts to develop bio-inspired hydrophones using micromechanical structures. One of the biological systems mimicked is the lateral line tube organ of a fish. The sensor uses a pair of long cantilever beams with piezoresistors, which deform depending on the direction and pressure of the incident wave, inducing a resistance variation of the beams. A bionic vector sensor was also explored using a solitary vertical cylinder that rests in the center of two crossed beams fabricated using microelectromechanical systems (MEMS) technology. Acoustic waves incident to the solitary vertical cylinder create compressive and tensile stresses in the structure. These stresses are transduced to a voltage by the piezoresistive effect of resonant tunneling diodes.
Researchers from Naval Postgraduate School, Monterey, CA, are developing bio-inspired MEMS directional sound sensors that operate in air based on the hearing system of the Ormia Ochracea parasitic fly. The main advantage of this system is the ability to determine the direction of a sound with a size much smaller than the wavelength of sound it detects. A typical sensor consists of two wings that are coupled by a bridge and attached to a substrate using two torsional legs. Sensors are built using MEMS technology on a silicon-on-insulator (SOI) substrate with integrated comb finger capacitors attached to the outer edge of the wings for electronic readout of the wings’ vibration under sound excitation .
Future Trends
Eric Mounier, a featured speaker at SEMI-MSIG European MEMS & Sensors Summit, has identified three distinct eras in MEMS’ evolution:
- The “detection era” in the very first years, when we used simple sensors to detect a shock.
- The “measuring era” when sensors could not only sense and detect but also measure (e.g., a rotation).
- The “global-perception awareness era” when we increasingly use sensors to map the environment. We conduct 3D imaging with Lidar for autonomous vehicles. We monitor air quality using environmental sensors. We recognize gestures using accelerometers and/or ultrasonics. We implement biometry with fingerprint and facial recognition sensors. This is possible thanks to sensor fusion of multiple parameters, together with artificial intelligence.
Numerous technological breakthroughs are responsible for this steady stream of advancements: new sensor design, new processes and materials, new integration approaches, new packaging, sensor fusion, and new detection principles. MEMS and sensors are entering a new and exciting phase of evolution as they transcend human perception, progressing toward ultrasonic, infrared and hyperspectral sensing.
The future is the point when sensors can mimic or augment most of our perception: vision, hearing, touch, smell and even emotion/empathy as well as some aesthetic senses. “The era of global awareness sensing is upon us. We can either view global awareness as an extension of human sensing capabilities (e.g., adding infrared imaging to visible) or as beyond-human sensing capabilities (e.g., machines with superior environmental perception, such as Lidar in a robotic vehicle),” writes Eric.
The enhanced perception will also allow robots to help us in our daily lives (through smart transportation, better medical care, contextually aware environments and more). We need to couple smart sensors’ development with AI to further enhance our experiences with the people, places and things in our lives.
The rising applications of MEMS and sensors into vast array of connected devices, is also raising cyber security risks. MITRE cybersecurity expert Cynthia Wright opened MSEC 2018 with a keynote on cybersecurity, “From the destruction of critical infrastructure, cyberattacks on life-critical medical devices such as insulin pumps and heart monitors, and intrusions on autonomous vehicle safety systems, MEMS and sensors suppliers have a responsibility to help improve cybersecurity of connected devices,” she added. Allaying the potential fears of a roomful of suppliers envisioning complete redesigns of their products, Wright said that not every device requires the same level of security, and suppliers can make a difference with even “minor tweaks.”
Future marrying AI with MEMS
In order to achieve the edge computing that people talk about in a host of applications including 5G networks and the Internet of Things (IoT), you need to pack a lot of processing power into comparatively small devices. Researchers at the Université de Sherbrooke in Québec, Canada, have managed to equip a microelectromechanical system (MEMS) device with a form of artificial intelligence, marking the first time that any type of AI has been included in a MEMS device. The result is a kind of neuromorphic computing that operates like the human brain but in a microscale device. The combination makes it possible to process data on the device itself, thus improving the prospects for edge computing.
The AI method the researchers demonstrated in their research, which is described in the Journal of Applied Physics, is something called “reservoir computing.” Reservoir computing is most often used on inputs that depend on time (as opposed to inputs such as images, which are static). So reservoir computing uses a dynamical system driven by the time-dependent input. The dynamical system is chosen to be relatively complex, so its response to the input can be fairly different from the input itself.
The special trick used by reservoir computing is to combine all the dimensions linearly to get an output that corresponds to what we want the computer to give as an answer for a given input,” said Sylvestre. “That’s what we call ‘training’ the reservoir computing. The linear combination is very simple to compute, unlike other approaches to AI, where one would attempt to modify the inner working of the dynamical system to get the desired output.”
In most reservoir computing systems, the dynamical system is the software. In this work, the dynamical system is the MEMS device itself. To achieve this dynamical system, the device uses the nonlinear dynamics of how a very thin silicon beam oscillates in space. These oscillations create a kind of neural network that transforms the input signal into the higher dimensional space required for neural network computing.
Sylvestre explained that it’s hard to modify the inner workings of a MEMS device, but it’s not necessary in reservoir computing, which is why they used this approach to do AI in MEMS. “Our work shows that it’s possible to use the nonlinear resources in MEMS to do AI,” said Sylvestre. “It’s a novel way to build ‘artificially smart’ devices that can be really small and efficient.”
A possible application for this AI-equipped MEMS could be an accelerometer MEMS in which all the data the device is collecting is processed within the device without the need for sending that data back to a computer, according to Sylvestre. While the researchers have not yet focused on how they would power these MEMS, it’s assumed that the devices’ miserly power use would allow them to run on only energy harvesters without the need for batteries. With that in mind, the researchers are looking to apply their AI MEMS approach to applications in sensing and robot control.
Market Growth
MEMS market will experience a 17.5% growth in value between 2018 and 2023, to reach US$ 31 billion at the end of the period. The Micro-Electro-Mechanical Systems (MEMS) market is anticipated to witness a CAGR of 6.34% over the forecast period (2020-2025). The increasing popularity of IoT in semiconductors, increasing demand for smart consumer electronics and wearable devices, and growing adoption of automation in industries and homes are some of the significant factors influencing the growth of MEMS market while the highly complex manufacturing process and demanding cycle time, and lack of standardized fabrication process for MEMS is expected to hinder the growth of market.
The usage of MEMS in electronics such as wearable devices, smartphones, laptops, tablets, digital cameras portable navigation devices & media players, and gaming consoles has been on the rise, over the past few years. Owing to such increasing usage, consumer electronics vertical has accounted for a significant share in 2019 and is expected to maintain the lead during the forecast period. For consumer, mobiles and smartphones still account for 90% of pressure sensor sales, and cost reduction is the priority vs. size reduction because size is already very small. Although there are no big “killer” applications expected in the future, new applications are emerging: smart homes, electronic cigarette, drones, and wearables.
The increasing demand for safety & security in the automobiles is one of the major factors, which is impacting the growth of the market positively. According to the World Health Organization (WHO), globally, more than 1.55 million people are killed in road accidents every year, and about 50 million people get injured. MEMS sensors can be used extensively for controlling the airbags in the event of a car accident in the automotive industry. Thus, these sensors play a critical role in improving the safety features of the vehicle and act as the catalyst for the growth of the market. Numerous pressure sensor applications also contribute to market expansion. In automotive, pressure sensors have the highest number of applications, with many advantages such resistance to toxic exhaust gas and harsh environments, higher accuracy, and the development of intelligent tires that deliver more information on tire status (especially for future autonomous cars). The growing concept of connected cars, electric vehicles, and China’s regulations regarding automotive safety are anticipated to drive the adoption of MEMS sensors, thereby driving the growth of the market during the forecast period.
MEMS applications are witnessing various opportunities in the industrial automation sector, due to the reliability, sensitivity, and cost-effective solutions provided by the MEMS technology. Pressure and inertial sensors, like accelerometers and gyroscopes, influenced the area of industrial automation. Applications of MEMS pressure sensors in the sector include condition monitoring of refrigerators, HVAC fan control, detection of a gradual increase in pressure, detection of leaks and pressure drops, and other industrial process control applications.
The industrial robots are increasing using MEMS-based accelerometers and gyroscopes to continuously measure the changes in the angular rate and direction, which can replace the expensive rotary sensors and encoders. Moreover, these sensors can detect excessive vibration in joints and actuators that can cause premature failures.
MEMS market segments including inertial, optical MEMS, microfluidics, and new micro components. Amongst the numerous existing MEMS devices, inkjet heads will grow, with the consumer market representing more than 70% of printhead market demand. However, the RF industry is still playing a key role in the MEMS industry development. Excluding RF, the MEMS market will grow at 9% over 2018 – 2023. With RF MEMS devices, CAGR reaches 17.5% during the same period. Driven by the complexities associated with the move to 5G and the higher number of bands it brings, there is an increasing demand for RF filters in 4G/5G, making RF MEMS (mainly BAW filters) the largest-growing MEMS segment.
Then after, are coming the MEMS microphones. “In the range of US$105 million in 2008, the MEMS microphone market was worth US$402 million in 2012 and reached the US$1 billion milestone in 2016”, asserts Guillaume Girardin, Director of the Photonics, Sensing and Display division at Yole. “Currently, almost 4.5 billion units are shipped annually. The main application is mobile phones, which comprise 85% of shipment volumes, in a consumer market that makes up 98% of the total shipment volume. Tablets and PCs/laptops take second and third place, with 5% and 3.2% of total shipment volumes, respectively.”
The uncooled IR imager market keeps growing due to a continuous price decrease over the last few years stemming from new technologies such as WLP and silicon lenses, as well as increasing acceptance from customers. In 2017, the biggest surprise was Broadcom becoming the #1 MEMS player. Established players like Robert Bosch, STMicroelectronics and HP also performed well. Other MEMS players posting significant growth are: FormFactor, benefiting from the semiconductor business’s excellent health; and ULIS, with uncooled IR imaging still growing annually into multiple applications including consumer – thermography, firefighting, night vision, smartphones, drones, and military.
Global Smart Sensor Market is anticipated to grow at a CAGR of over 17% to reach USD 80 billion by 2024. Advancements in consumer electronics coupled with favourable government initiatives is anticipated to drive the smart sensors industry growth over the forecast timeline.
