Is it really possible to never recharge? Xiaomi’s new patent for wearable devices exposed

Amid the overall decline in the consumer market, the growth of the wearable device market will inevitably slow down this year. However, thanks to the continuous iteration of related products, including smart watches, TWS headsets and other products, the wearable market is maturing, and many institutions predict that the wearable market will resume growth in 2023.

In terms of technological innovation in wearable devices, major manufacturers are also continuing to make corresponding arrangements for subsequent market demand. Recently, a new patent from Beijing Xiaomi Mobile Software Co., Ltd. on "an integrated wearable device" was granted an invention patent and the abstract was published, showing a new form of wearable device.

As shown in the picture above, this all-in-one wearable device is a product that combines glasses and Bluetooth headsets. It looks ordinary and is no different from other "smart glasses" on the market. But there is a lot going on inside the glasses. The patent summary shows that inside the glasses frame, there are built-in piezoelectric materials and rechargeable battery charging components. Through the principle of piezoelectric materials being pressed to generate electricity, the built-in ball bearings are used when the human body moves. The mechanical energy of rolling is converted into electrical energy, which charges a battery built into the frame.

At the same time, the frame battery is connected to the Bluetooth headset through a wire to continuously provide power. In daily use, it can achieve uninterrupted battery life of the Bluetooth headset, reduce the frequency of users charging the Bluetooth headset, and improve the user experience.

However, the detailed documents of the patent have not yet been made public on the national patent search website. Generally speaking, they will not be made public until a few months after the patent is granted. But we can guess the technology used in this wearable device based on the description in the abstract.

From an innovation point of view, the main difference between the integrated wearable device described by Xiaomi in the patent and the existing products on the market is its self-generating function. One of the pain points of wearable devices in the past is that despite continuous efforts towards low power consumption, regular charging is still a relatively cumbersome method for users.

Using piezoelectric materials to generate electricity during the use of wearable devices is a good idea for low-power products such as wearable devices. Just like a self-winding mechanical watch, after getting rid of regular recharge, it will undoubtedly increase consumers' acceptance of wearable devices to a new level.

However, whether the power generation efficiency of piezoelectric materials can meet the needs of wearable devices has been questioned by many in the past. In many studies, the actual conversion efficiency of wearable energy harvesters made of piezoelectric materials is still not ideal. The main problem is that on the one hand, the frequency of human activities is low, which has a great impact on the ability to sustain power supply. On the other hand, The energy conversion efficiency of the material itself is low, and there is still a long way to go before practical application. What’s interesting about

wearable applications of piezoelectric materials

is that based on piezoelectric materials, there have been a lot of innovative research on wearable devices in academia this year.

In March this year, Professor Yoel Fink's team at MIT tried to use piezoelectric fibers to weave fabrics that can be used as sensitive audible microphones while retaining the traditional qualities of the fabrics and even supporting machine washing. The fabric medium consists of high Young's modulus textile yarns in cotton warp and weft yarns, which convert weak pressure waves at audible frequencies of 107 atmospheres into low-order mechanical vibration modes. Woven into the fabric are heat-stretched composite piezoelectric fibers that bond with the fabric and convert mechanical vibrations into electrical signals.

In applications, clothes made of this fabric can detect sounds with performance comparable to commercial microphones and can emit sounds. In medical applications, it can also be used as a wearable device for heartbeat monitoring.

In November, Professor Xie Jin of Zhejiang University, Professor Fu Yongqing of Northumbria University in the UK and others developed a wireless system based on flexible piezoelectric acoustics, which has multiple functions such as sensing, communication and positioning. Under high-frequency stimulation (≈13MHz), the system can generate Lamb waves for respiratory monitoring. Under low-frequency stimulation (≈20kHz), the device can function as a vibrating membrane for communication and positioning applications. The indoor communication distance of this system is 2.8 m at 200 bps and 4.2 m at 25 bps. Combined with sensing capabilities, the system can simultaneously achieve real-time respiratory monitoring and wireless communication.

In practical applications, this intelligent wireless sensing system based on flexible acoustic wave devices has the characteristics of low power consumption and flexibility, and can be used in fields such as smart homes, wearable devices, medical health monitoring, and multi-robot coordination in the future.

Another solution for self-powering of wearable devices - TENG.

In the research on self-powering of wearable devices, the research group of Professor Nie Shuangxi, led by Academician Wang Shuangfei of Guangxi University, recently reported a new type of visual tactile sensor that does not require external connections. Self-powered tactile feedback from the power supply. They designed a high-output triboelectric nanogenerator called X-TENG. Through the structural design of triboelectric materials and devices, the transferred charge of the TENG was enhanced to 746 nC, which can easily drive a light source to produce a brightness of 9.8 cd m -2 optical signal.

So what's the use? In the demonstrated application, this sensor can be used on the glove to visually sense the grasping state of the palm and provide force feedback without external power supply. For example, when the hand holds an object, X-TENG can generate The energy that powers LEDs, etc., feeds back the status of the current hand and the strength of the grip. It can also monitor movement intensity while generating electricity, which may have great application prospects in future human-computer interaction applications of wearable devices such as AR/VR.

In addition, a team from Northwestern Polytechnical University in China also reported a self-generated wearable sensor at the beginning of this year, which is a tactile hydrogel sensor (THS) based on a micro-pyramid pattern double-network ionic organic hydrogel. It also detects subtle pressure changes by measuring changes in triboelectric output signals and achieves self-power supply. Compared with other similar sensors, THS has the advantages of approximately 85% high transparency, high sensitivity, high flexibility, and high power density electrical output (peak value 20 µW/cm2), making this technology more suitable for wearable electronics. application.