MEMS pressure sensor solves new pain points of human-machine interface

[Introduction]In May 2021, Qorvo announced the acquisition of NextInput, the first acquisition of its sensor fusion product line. Qorvo has high hopes for NextInput’s innovation in improving the human-machine interaction (HMI) market. At the same time, it also means that in addition to RF MEMS, Qorvo also has the technical accumulation of MEMS pressure sensors.

MEMS pressure sensor solves new pain points of human-machine interface

NextInput founder and CEO Ali Foughi said at the time of the acquisition: “We continue our mission to innovate and revolutionize the touch experience with outstanding sensing solutions. Qorvo’s broad portfolio of complementary technologies and world-class supply chain capabilities Allows us to rapidly expand our business. After merging a global leader in semiconductor solutions, we hope to continue our success in the HMI (human machine interface) market.”

So what has Qorvo done with pressure sensors a year later? Recently, we interviewed Qorvo engineer Will Wang, and asked him to introduce the current status and prospects of pressure sensors in the HMI field, covering mobile phones, wearables, and automobiles.

How big is the imagination space for pressure?

Will said that MEMS pressure sensors are a completely new way of interaction to complement traditional touch. Intuitively, “touching” is an action, and “pressing” is also an action. When your finger clicks on an APP on the phone screen, the brain will get the expectation of “opening”. At the same time, when you press an item, the brain will expect different results according to the different pressure on the surface, and this is pressure. The purpose of the sensor is to accurately determine the force exerted on the object and make the device complete the prediction of the brain.

Combining a pressure sensor with a capacitive sensor increases the Z-axis (vertical) data interaction compared to a two-dimensional capacitive sensing solution with only XY axes, thus opening up more possibilities for HMI applications. In addition, because the data volume of Z-axis pressure is more abundant, not only a simple on/off operation can be realized, but more information can be transmitted through different pressure values.

At the same time, another way is to arrange multiple pressure sensors and cooperate with the corresponding algorithm, the three-dimensional identification of XYZ can be realized only by the pressure sensor. This technology can theoretically be adapted to a variety of environmental challenges including metal, thick gloves, and operating with water.

In theory, any mechanical button or capacitive touch switch scene can be replaced by a pressure sensor, which has many advantages such as no punching, no accidental touch, and enhanced waterproofness.

However, Qorvo’s ambition in HMI is not just a “replacement of buttons”, but has a broader imagination.

MEMS pressure sensor solves new pain points of human-machine interface

Multiple pressure sensor technologies for different applications

Pressure Sensitivity Enhances the Operating Experience of Gaming Phones

If the pressure sensor wants to replace capacitive or other sensors, the most important thing is to find the application pain point. The pressure sensor first appeared on the iPhone6s and implemented the 3D Touch function (Peek and Pop), but this function lacked enough killer usage scenarios, so it has not been widely favored by users and developers, and Apple decided to use it in a few years. 3D Touch was replaced by Haptic Touch, which implements similar functions in software, thus saving cost and power consumption. The Android ecosystem is the same.

However, with the segmentation of the mobile phone market, including the emergence of new formats such as gaming phones and folding screens, Qorvo has seen new opportunities and successfully introduced products including Black Shark, Meizu, and iQoo. For example, in the Black Shark, by combining the pressure sensor and the special setting software of the Black Shark, the dual-zone screen pressure-sensitive touch operation is realized, adding more differentiation to the game. For example, in MOBA games, you can instantly add blood and change clothes through the pressure-sensitive function when moving and attacking. In FPS games, you can press and shoot when moving and aiming, and you can instantly lie down when you press while shooting. In racing games, you can fully The range of the screen flexibly controls the accelerator and braking force. A series of examples can show that the pressure sensor facilitates the operation and enhances the hitting experience of the game. In addition to games, the pressure sensor has also been extended by Black Shark to pressure-sensitive navigation in system applications. Users can press the screen anywhere to drop out of the operation navigation, turning the phone into a one-handed operation artifact.

Will added: “Pressure sensitivity allows for more accurate operations without false triggering, a demand that will grow with the advent of full-screen, foldable, gaming phones, and more.”

According to reports, there are currently two solutions for the realization of pressure sensitivity. One is in the form of a module, which uses MCU to process pressure-sensitive signals. This kind of module is composed of multiple FPCs, so the middle frame of the mobile phone must have multiple large holes, and there are some drawbacks in the durability and yield of the FPC.

Qorvo’s solution is to use a single chip that integrates sensors and analog front ends to communicate directly with the CPU without the need for an MCU. The opening is small, which has relatively little impact on robustness and heat dissipation, and is easier to install.

According to Will, Qorvo’s current solution requires only two chips to detect two-finger pressure on the upper and lower screens.

For pressure sensor applications designed without side buttons, Qorvo will provide sensor fusion solutions, including pressure sensors, infrared sensors, ultrasonic sensors, and single-chip solutions without buttons implemented by analog front ends, in which IR plays a positioning role, so that It is possible to simply implement pressure sensing with only one sensor, thereby simplifying the design and avoiding false touch operations.

Importantly, Qorvo can provide a complete hardware solution as well as software algorithms to clear design barriers and allow customers to focus on differentiating their applications with pressure sensors.

TWS fully reflects the differentiation of pressure

Although Apple did not choose a pressure sensor in later iPhones, it has fully embraced pressure sensors on the TWS. The main pain point of HMI in TWS application is the false touch of capacitive sensor, including hair, rain, sweat, grease, etc., which will cause false touch, thus affecting the experience. In addition, the actual experience is not as direct as the pressure sensor for the MEMS acceleration sensor to operate by tapping. It is understood that the pressure sensors currently used in TWS have been gradually introduced from the mid-to-high end to the mid-end market.

Will said that for TWS applications, Qorvo’s products are more suitable for this scenario due to their single-chip, small size, support for digital output, and simple modules. And with the increasing number of imported cases in the market, customers are becoming more and more confident.

Other wearable devices

In addition to TWS, including watches, bracelets and even AR/VR devices, all have broad development prospects for pressure sensors. Taking smart watches as an example, Google-Fitbit adopts Qorvo’s solution, which replaces the mechanical switches, knobs or sliders in the watch, which can make the watch more waterproof.

However, Will also mentioned that there are still many debates on whether to cancel the mechanical buttons for smart watches. For example, the aesthetic cognition of the watch, or functions such as heart rate measurement, cannot replace the mechanical buttons. But at least for capacitive touch solutions in wearable devices, the pressure sensor is fully capable, and supports underwater/wet environments, making it a better experience.

Experience improvement of productivity tools

Pressure sensors are also great for productivity tools. Take Apple as an example, its notebooks have always adopted Force Touch technology, which has been widely recognized by customers, and now this technology is being favored by more brands.

In addition, for tablet computers for productivity applications, as well as handwriting tablets, the pressure sensor can simulate functions such as “brushes” by virtue of its high-level and delicate Z-axis response.

Cars will be another flashpoint

Qorvo also expressed concern about the automotive market. As the only pressure sensor supplier that has passed the vehicle-level certification, its products have been widely used in models including Tesla, Geely, Chery, etc., and have passed the PPAP certification of three Tier1 suppliers including Valeo, Yanfeng and Joyson .

Its applications include doors, multi-function steering wheels, central control, etc. Among them, more than 10 pressure sensors are used in Tesla alone. Especially with the deepening of the concept of “putting wheels on mobile phones”, we see that the interior of the car cab, whether it is the instrument Panel, the main control panel, the central control panel and even the co-pilot screen, are developing in more and larger directions. Mechanical buttons and knobs are gradually being replaced by virtual keys on LCD screens. Under this change, the car cockpit has changed from being surrounded by mechanical buttons, knobs and indicator lights like the cockpit of an airplane in the last century, to a more friendly, flexible and more concise way of displaying screens everywhere, which gives the car HMI It has brought the demand far beyond the mobile phone market, and also allowed the pressure sensor to have more room for Display.

High quality is the foundation of the experience

Last, but not least, product reliability is the foundation of any user experience. Needless to say, it’s impossible to command the car with precise keystrokes on a speeding highway, and even an unnecessary touch error while gaming can be frustrating for players.

From the system level, the pressure sensor technology is naturally more direct and reliable than traditional button or even capacitance, resistance, ultrasonic and other technologies.

As far as the chip itself is concerned, Qorvo’s pressure sensor can last for 10 million to more than 100 million cycles, while the life of traditional keys is only 200,000 to 500,000 times. In addition, Qorvo has successfully shipped tens of millions of products, achieving zero field failure rate, which also proves the reliability of MEMS pressure sensors. Qorvo products are waterproof, dustproof, and iceproof, and can work in high and low temperature environments. Its vehicle-grade version is also AEC-Q100 certified.

Pressure Sensitivity and the Future of HMI

In today’s fast-paced world, people are looking for products and services to live and work that run smoothly, save time, and ultimately improve comfort and operability, which requires a more intuitive and natural human-machine interaction experience, and Not subject to all kinds of interference. In addition, considering the post-epidemic era, there will also be more demands for non-contact human-computer interaction. These all bring differentiated demand challenges to HMIs and sensors.

On the one hand, the growth of emerging technologies such as voice interaction, face recognition, and gesture recognition is changing the human-computer interaction experience. At the same time, the relatively traditional touch technology is also being improved with the provision of innovative pressure sensors such as Qorvo. Cope with the future.

As Will says: “Qorvo’s pressure sensors can also be applied to a variety of emerging technologies, such as sleep monitoring, robotics, home appliances, and more. For Qorvo, the limits of technology are only limited by the engineer’s imagination.”

Source: Electronic Engineering World

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