Supplying power to and communicating with body surface sensors via 2D communication through clothing!

LANGUAGE ≫ Japanese

NODA Akihito

Specialized field: Microwave engineering, Radio frequency circuits, Wireless communications, Wireless power transfer

For Details

New wearable devices for broader and more intensive measurement of body data...

Recently trends have moved beyond smartphones, and smartwatches have become commonplace. Device features include touchscreens, speakers, microphones for calling, notification vibrators, and even functions for measuring heart rate, and it's not unusual for users to employ these devices for health management. Computers attached to a person's body are called "wearable devices," and pursuing new device functions is one of the research themes of Associate Professor Akihito Noda. "We can measure heart rate with a smartwatch--through functions concentrated at a single point on the wrist--because we have just one heart. However, if we want to monitor the state of tension of muscles all over the body, we need to capture nerve signals as muscles move at each individual body part." To achieve this, Dr. Noda is developing distributed wearable systems with numerous flexible, miniature, clothing-embeddable electronic devices dispersed over the body surface. He aims to develop devices that allow gathering of more detailed bio-information during daily life by wearing the system as clothing, like a smartwatch is worn on the arm. We can expect to see applications of the realized system in various domains such as health management and preventive medicine, and it should also boost sports science, and the virtual reality (VR) industry in combination with head-mounted displays.

2D communication for power supply and communication, using clothing itself as the transmission line

Centralized wearable devices like smartwatches and smartglasses employ wireless communication via radio waves, with a battery as the power source. For distributed wearable systems, however, this sort of configuration is not realistic.

Dr. Noda: "The distributed units are not large devices with touch panels, like smartwatches. Rather, a few dozen or a few hundred integrated circuit (IC) chips serving as sensors, and about the size of a pea, are mounted all over the body. If each of these pea-sized devices had a battery and wireless communication circuit, you can imagine how the non-sensor parts would be much heavier, and the system would be cumbersome." Other issues also arise such as battery charging/replacement, and the loss of immediacy and data transmission reliability due to crowding and interference between multiple wireless communication modules. On the other hand, using individual wired connections from a central processing device for data collection/control, or from a power supply, to each element also has the disadvantages like the risk of disconnection, and degraded flexibility and wearability of clothing.

To solve these problems, Dr. Noda's design supplies power to and communicates with elements, without using a battery or antenna, by employing clothing made from conductive fibers as a two-dimensional (2D) transmission line.

"This is an application of a technology called 2D communication--a research topic I've been working on since graduate school. By letting the clothing itself be the transmission line, we can connect small-scale electronic circuits like pin-back buttons at any location on the clothing. Power supply and communication can be achieved without individual wiring. Power is supplied from a single source to the entire transmission line, and each element operates without a battery by receiving power from the transmission line ."

Data is also transmitted via the same transmission line, and radio waves for communication are not emitted to the outside. Thus, 2D communication has features not found in ordinary wired/wireless connection methods.

(T-shirt with LEDs attached, developed as an application of technology for simultaneous power supply and communication with sensors on clothing via 2D communication. Clothing is made of conductive fibers.)

Realizing a network with a high degree of freedom while avoiding issues specific to flexible materials

Extensive R&D has already been done in technical fields where electronic circuits are formed on flexible materials, such as clothing, fabrics, and films. In conventional approaches, numerous individual signal lines are formed on clothing. With the 2D communication that Dr. Noda is working on, on the other hand, the entire garment is used as a single transmission line. Dr. Noda highlights an issue in previous research, "If we make a circuit in the same way as with an ordinary hard circuit board, just replacing the board with a soft material, a new problem appears. Since the material is fabric, short-circuit faults may occur due to the fabric folding or wrinkling, or due to the formation of electrically conductive fuzz."

"With the 2D communication approach we are studying, the elements are not connected with many wires that are individually isolated. Everything is connected in parallel, so such faults due to short-circuits do not occur. This is because everything is already connected in the first place."

There are other advantages to avoiding individual wiring and connecting everything in parallel with a uniform material. "Fabric is made through a standardized process of weaving or knitting, so it can be mass produced in rolls. We can make pants or jackets, or long sleeves or short sleeves, all from the same fabric. Also, finished clothing can be freely modified, by changing the mounting location of electronic circuits, or adding and removing circuits."

However, since the same transmission line is used for both power supply and data transmission, a system of multiplex transmission is needed. In Dr. Noda's research, continuous DC power supply and data communication are performed simultaneously through a technology called frequency division multiplexing (FDM).

"Simultaneity is a key point. It allows the system to meet greater demand for power and communication compared to systems which stop power supply during communication. In that respect, a creative approach is needed regarding circuits."

Dr. Noda has also developed new circuit techniques to provide compatibility with existing serial communication methods through the addition of a few electronic circuits. Compatibility with widely-used, existing communication systems allows as-is use of things like commercially-available sensor ICs, which is advantageous for using sophisticated functions built into ICs and existing communication software libraries.

High expectations for applications to health management and preventive medicine, and for boosting growth of the VR industry

The wearable networks that are the focus of Dr. Noda's R&D can simultaneously supply power to and communicate with sensors on clothing, so there is excellent potential for industrial applications, and high expectations in areas like health management and preventive medicine.

"With this technology, we can gather comprehensive data by attaching and operating sensors and other devices at various locations on the surface of the human body. This means we can achieve more precise measurement. If, in the future, we can mount devices on clothing worn routinely as casual wear, then, for example, we will be able to say to manual laborers: 'The activity of your muscles clearly indicates a high load. Please take a rest.'"

This is not a subjective indicator like fatigue or an indirect indicator like working hours. Health management can be done based on objective, direct numeric values, for a safer and more secure work environment. The technology can also support home healthcare for the elderly, and capture detailed body data, so we are also likely to see applications to sports science, and to systems for handling full-body tactile sensation in VR.

Dr. Noda: "In developing such applied systems for solving social problems and creating new industries, there will need to be a lot of trial and error, and I'm looking forward to doing that in earnest with the students at Kochi University of Technology, where I assumed my current position last year." To enable his students to conduct research freely, Dr. Noda wants to establish an environment which is as free as possible from constraints, and focused on creative work.

When asked about what attracts him to his research, Dr. Noda says: "It's the sense of achievement. I notice something--'hmm, maybe it's possible if I proceed this way'--then I verify it with my knowledge, and voila! it works."

"The 'idea' that I want to establish in my research overturns the settled thinking of electronics. It's a paradigm shift, from steadily increasing integration density and packing higher functionality into palm-of-the-hand size devices, to achieving new functions by dispersing simple circuits over a wider area or the whole body."

While producing research results to meet social and industrial needs in areas like medicine and VR, Dr. Noda will continue working to establish his idea, and highlight the potential for a new paradigm in the field of electronics.

Date of posting: November, 2023/ Date of interview: November, 2022