Wearable devices: conditional classification

How to understand that this is a wearable device?

In the previous article we analysed in detail the foreign and domestic definitions of the concept of a wearable device. Now we will try to summarize all the criteria to define a wearable device by emphasizing the foreign interpretation. After all, the conceptual model of this area was first developed abroad.

So, here are some features of wearables that we would like to highlight.

Mandatory Criteria

1.A wearable device can be:

• worn directly near the body (pendants with integrated electronics);
• tightly attached to the body surface (electronics integrated into fabrics; patches, etc.);
• implanted in the body (pacemakers);
• taken orally (the so-called “indigestible sensors”).

2.The device or system of devices has sensors that recognize and collect the wearer’s physiological information, biomechanics or information about the environment (smart watches, fitness trackers);

Or the products transmit information from the Internet performing some smartphone functions (smart glasses);

3.The collected information can be immediately analysed and transmitted for analysis to the central processor or to the cloud storage.

The central processor is not necessarily wearable. It may be stationary. Or it may be a smartphone, tablet computer and so on.

4.Biofeedback (BFB) is ensured: transmission of visual, auditory and other information which is an analysis of the received physiological data (pulse, pressure, etc.) to the wearer and/or other persons/institutions.

Or the transfer of other types of information is ensured, such as augmented reality, navigation using smart glasses or a voice assistant, etc.

5.Wearable devices are designed for permanent or extended wear comparable to the frequency of use of accessories or certain garments.

Optional Criteria

• The device performs the function of a piece of jewellery, an accessory. It can be integrated into clothes or special patches, tattoos.
• Some data can be transferred and stored in the cloud making many wearable devices part of the Internet of Things.
• Based on the analysed data, the device can perform health-saving functions, have a direct physical, chemical or other effect on the body, such as some types of pacemakers, insulin pumps or prostheses.
• Some devices have voice assistant functions or can be operated and configured manually.

But due to market trends, many people have a simplistic understanding of what wearables are. Because of this, the idea of wearable devices as accessories is widespread in everyday life as if this is their essential criterion.

Classification of Wearable Devices

In the article A Survey of Wearable Devices and Challenges, the authors divide wearable devices (which do not require medical intervention) into three categories:

• Accessories
• Textiles with integrated electronics (E-Textiles)
• Skin patches with integrated electronics (E-patches)

   

  

  Fig. 3: Conditional classification of wearable devices which do not require medical intervention. Source: Seneviratne S. et al. A Survey of Wearable Devices and Challenges // IEEE Communications Surveys & Tutorials. 2017. Vol. 19(4)

I. Accessories

Accessories are not the main garments but decorate them. In today’s market, wearable devices in the form of accessories are the most popular category of wearable devices. Such devices include smart watches, fitness bands, smart glasses, VR devices, chest straps, various fastenings for clothing, smart rings, smart headsets in the form of ear rings, etc. (VR devices can hardly be included in this list because they are not designed to be worn for a period of time comparable to the wearing of jewellery or clothing)

Smart accessories can perform a variety of functions. In addition to the fact that they track some physiological parameters (pulse, pressure, stress level, etc.) and human biomechanics (number of steps, movements), they can perform some smartphone functions (use of the NFC module, contactless payment, mobile communication, alarm clock, navigation, etc.), as well as complement it (smart watches, smart glasses).

Smart glasses and virtual reality helmets can act as smartphone headsets. Different versions of glasses allow manipulation of virtual 3D objects, performance of navigator functions, notification of calls and messages, not to mention their use in the video game industry. Some models of smart glasses collect the wearer’s biological data and analyse them, thereby implementing biofeedback (BFB).

Fig. 5: Smart ring. Source: https://tehnobzor.ru/gadzhety/obzor-smart-koltsa-oura-ring/

Fig. 6: Smart glasses. Source: https://rg.ru/2019/12/04/na-smenu-smartfonam-mogut-prijti-umnye-ochki.html

II. Garments with integrated electronics

Smart garments are mainly used to monitor physiological signals and human biomechanics to apply the received information in sports and medicine. They are the most common garments with integrated electronics. They can be running shorts, shoe insoles or a bra. Such garments are sometimes used in fashion. One example is “a synapse dress” which displays the wearer’s emotions using light signals.

III. Skin patches with integrated electronics

Smart patches are patches with miniature sensors and electrical circuits which can be glued to the skin or applied to it as a temporary tattoo. Most of them are designed to monitor physiological parameters and human biomechanics. And some of them are used for sensory/tactile stimulations. For example, there is an adhesive strip which generates electrical impulses that stimulate the nerves in the neck and head to regulate the release of adrenaline to the brain. Another example is a start-up dedicated to the development of an electronic patch, which uses vibrations to notify the wearer of his/her posture. Another use of smart patches is the delivery of drugs, such as insulin via an adhesive pump.

Interesting ways have been found to use smart tattoos. They can be used for contactless payments. They can track the amount of UV received or transmit physiological data (ECG, EMG, strain gauge data, temperature, etc.) to a compatible device, such as a smartphone.

We would like to add to the abovementioned a few types of wearable devices which the authors of the study did not describe. These categories require medical intervention: smart injection systems, implantable devices and smart sensors/drugs taken orally.

Fig. 8: Smart patch. Source: https://www.vesti.ru/hitech/article/2572452

Fig. 9: Tattoo with electrodes. Source: https://discover24.ru/2017/03/umnye-tatuirovki-s-elektrodami-nachalo-puti-k-kibernetizacii-cheloveka-ili-prosto-modno/

IV. Injection systems

This category includes various insulin pumps and wearable injectors. The injection system analyses when and in what quantities it is necessary to administer the drug into the body. The main block with the drug is usually attached to the belt and connected to the injection site using a catheter. A sensor to monitor, for example, glucose is attached to the body separately from the injection system and transmits information to the main module via wireless communication.

V. Implantable devices and prostheses

Some types of pacemakers, cardioverter-defibrillators, an auxiliary blood circulation apparatus and an artificial kidney can be distinguished among the implantable devices.

For example, among smart wearable devices there is a smart prosthetic hand with the integrated GoPro system.

 Some brave individuals implant RFID/NFC chips in their palms, which can also be called wearable technology, although at a bit of a stretch because this device does not process data.

Fig. 11: Artificial ventricle WCAD (wearable circulatory assist device). Source: https://zdrav.fom.ru/post/a-vmesto-serdtsa-plamennyy-motor

Fig. 12: Wearable artificial kidney. Source: https://zelenograd24.ru/pressroom/society/detail/261352/

VI. Orally administered smart devices

Many companies are now developing “indigestible sensors”— capsules which are swallowed by the user and stay inside the body for as long as necessary. Some devices remain in the dige

stive system, others enter the bloodstream. Sensors can determine various parameters: the hormone level, the presen

ce of bacteria, viruses, toxins, markers of various diseases, including tumour markers. The device can diagnose diseases or dangerous conditions of the body, as well as measure the blood alcohol level and prevent the user from driving if the values are above acceptable levels.

Capsules can administer the right drugs in the body according to a premeditated algorithm or on a doctor’s command via a wireless connection. Some models can track whether a patient has taken drugs or not.

Another possible area of use for such capsules is diagnostic testing. So a gastroscopy or colonoscopy is performed with their help.

The operation of some of these devices is based on the principle of “lemon batteries”. We are talking about two electrodes — for example, a nail and copper — which are inserted into the lemon from different ends and to which wires are connected. A difference of potential occurs. A low-voltage current, which is quite enough to light a low-power LED, begins to flow through the wires.

In order to replicate the “lemon battery” design, the researchers decided to attach zinc and copper electrodes to the surface of a conventional medical ingestible sensor. As in the case of a lemon, an electric current begins to be generated. It is enough to ensure the operation of the sensor and the 900 MHz transmitter.