Health monitoring function has gradually become one of the important reasons for the use of mental wear. The mental wearable device needs to be recharged, which will affect the integrity of monitoring a fixed number of health.
Recently, researchers at the University of Massachusetts Amherst have set up a new solution called ShaZam that can be used without wearable equipment.
The principle of ShaZam involves in vivo energy transfer (Intra-Body Power Transfer,IBPT) technology, which uses the human body as the medium of blood transfusion power to charge wearable devices wirelessly when interacting with everyday objects.
The research paper, entitled "ShaZam, a popular technique for measuring blood transfusion in the human body, using everyday items to charge mental wearable devices (ShaZam:Charge-Free Wearable Devices via Intra-Body Power Transfer from Everyday Objects)," was published in the proceedings of the International Computing Society (ACM) meeting on June 24.
Links to papers:
Https://dl.acm.org/doi/10.1145/3463505
01 let the electric energy flow in and out while ensuring the safety of the human body
Although the concept of IBPT was introduced in the 1990s, there is not much exploration on feasibility evaluation and practical anti-application. The main technical challenge associated with IBPT is to ensure the safety of the human body during the forward flow of electricity into the body and the reverse flow out of the body.
Inspired by the field of in vivo communication (IBC) (IBC is a technology that uses the human body as an electrical sleeve and uses communication devices for two-way automatic communication), two potential solutions to human body charging are used: one is to take the human body as the forward path and the quasi-static near-field capacitance coupling is used to establish the electrical coupling method of signal return circuit diameter, and the other is the electrical coupling method in which the visual human body is electrically conductive.
In the coupling method, both the frequency transmitter and receiver will have an electrode (called a skin electrode) to establish a capacitive coupling with the human body and a floating metal plate (called a grounding electrode) to erect a parasitic coupling between another grounding electrode in the air (covering two grounding electrodes).
In this configuration, the time-varying electric field around the human body can be approximated, which will induce the current to flow through the human tissue, thus transmitting the amount.
A schematic diagram of using the electrical conductivity of the human body
The ShaZam mental wearable device charging solution of the University of Massachusetts in the United States uses this electrical coupling mechanism, in which the forward circuit structure is through the ultra-dry copper material electrode to let the signal into the body tissue, and the return circuit rule is established by the inherent natural capacitance between a pair of floating metal electrodes and the surrounding environment.
When the researchers come into contact with three different devices-the external keyboard on the desktop, the keyboard on the laptop and the train steering wheel-these devices transmit electricity to arm-mounted mental devices through the human body.
The researchers used three kinds of daily equipment to carry out the experiment.
The charging method designed by the researchers can currently support ultra-low-power health trackers such as Fitbit Flex and Xiaomi bracelets, but not for expensive wearable devices such as the Apple Watch.
02ShaZam indicator, the device is different from other wireless charging
In fact, wireless charging is no longer a new technology, major machines and mental wear manufacturers are showing off their wireless charging technology, such as this year Xiaomi, OPPO released their own wireless charging technology.
Wireless charging refers to the near-ground power transmission and output technology which uses the functions of magnetic sensitivity, magnetic resonance and capacitive coupling to realize power supply to load.
There are two types of wireless power transmission methods: one is interchangeable switching and transmitting wireless lines, which wirelessly charge the frequency at the outlet of data transmission, and the other is a commission-based infrastructure. it is possible to create electromagnetically coupled wireless charging that allows a coupled electric or magnetic field to be established in pairs of devices (there are two slightly different charging methods: electromagnetic stress wireless charging and electromagnetic resonance wireless charging).
What radio frequency wireless charging equipment needs to use a dedicated transmitter / receiver for periodic power transmission, to collect energy from environmental wave sources (such as electricity or radio stations).
Like the spaced charging of Xiaomi, the spaced charging circuit will have phase interference antennas for spatial positioning of the equipment, detect the position of the equipment, and phase control antenna arrays, and direct the millimeter wave transmitting equipment through beamforming. The equipment end is equipped with a signal antenna, which broadcasts the equipment position signal in space, and the receiving antenna array converts the millimeter wave signal transmitted by charge into electric energy through the rectifier circuit.
In the research of electromagnetic coupling wireless charging technology, more research is focused on capacitance and inductance transmission mode, which produce electric field or magnetic field in a large room, allowing equipment to obtain success rate through field coupling. Although the antenna charging and discharging system is more energy-efficient, a lot of infrastructure needs to be modified, and it is certain that there is no place for the electric field or magnetic field to cover the required area.
Now there are many mental watches, this electromagnetic coupling wireless charging method, these devices will pass through the magnetic field of the wireless magnetic circuit to replace the wire, to achieve power transmission. When charging, both the charger and the charged device get the coil, and the coils of both must be aligned and at a very close distance (touch) to work properly.
The need for alignment coils, distance limits, and the number of charging devices limit the development of electromagnetically induced wireless charging. For example, according to Huawei's HUAWEI WATCH3 manual, to ensure that two aspects are operated correctly in order to charge smoothly and safely, one is to "place the watch on the charging base, so that the back of the watch is attached to the charging base, and adjust the fit until the charging instructions appear on the hand screen", and "when charging wirelessly, please use a special base and fix the coil to be aligned".
Electromagnetic resonance wireless charging technology has lower requirements on position and distance, which helps to solve the problems of charging position and charging quantity. For example, the spaced charging technology released by OPPO this year uses electromagnetic resonance to transfer energy, which can be charged even if the position of the coil at the transmitter and receiver does not match completely.
ShaZam mental wearable charging solution combines radio frequency wireless charging, electromagnetic stress and electromagnetic resonance wireless charging are based on the electromagnetic principle of electromagnetic charging, different in other people use different dielectrics. Dielectrics can be divided into free space, man-made infrastructure and human tissue. And pay more attention to its security through the needs of human tissue.
The electrical media used in the ShaZam scheme are different, so the design of each equipment and index is quite different from the common wireless charging method.
The working principle of the included IBPT strictly limits the emission work of the human tissue directly coupling the transmitter and receiver, thus minimizing the size of the small transmitter and the loss of the human body medium.
03 the impact of wireless charging requirements on other devices
The security of short-range wireless charging is the key consideration. Especially in the high audio frequency (HF) range, the incident time-varying electromagnetic wave (EMF) wave will produce displacement current (that is, the time variation of the electric field in space) through the human tissue, which may lead to thermal damage to the tissue, so it is necessary to limit the working frequency.
Another problem exposed by radio frequency wireless charging will have an impact on the electromagnetic stem of primary / passive medical implants and on devices that also use radio frequency.
In the interim regulations on Radio Administration of Wireless charging (Power Transmission) equipment (draft for soliciting opinions) issued by the Ministry of Industry and Information Technology in February this year, there are relevant provisions, which mentioned that in order to protect radio astronomical business and ensure the safe use of special radio audio for ships and aircraft, the use of wireless charging equipment within the protection distance of radio astronomical sites and in ships and aircraft is prohibited.
How to solve or reduce these effects is also a situation that needs to be considered for mental wearing wireless charging.
Conclusion: household demand changes in design.
From the technical level, it is realistic to charge mental wearers through the human body, but the safety test is relatively simple, the number of volunteers involved in the experiment is small, trivial and unrepresentative. The next stage of the development of using the human body for dielectric charging has been established by the manager.
For example, a smartwatch made by Jiaming is equipped with solar charging function, and MATRIX's PowerWatch uses human heat to charge electricity, which may be more inclined to outdoor mental watches, and manufacturers are also studying whether there are more mental settings to add charging methods.
This article is from the Wechat popular account "Zhidong" (ID:zhidxcom). Author: Yang Chang, Editor: Panken,36 post published by Jingquan.
