CONnected TEXTiles for on body-centric communications – CONTEXT

The project aims to develop smart textiles with integrated radiofrequency technologies (RF) and electronic components for on-body communications in Wireless Body Area Networks (WBAN). Based on existing technologies in smartphones, two issues will be treated in the project:

1 - The first one is an energy transfer using the Near Field Communication technology (NFC) at 13.56 MHz with the goal to supply a sensor away from the smartphone. This part of the project answers the issues of the use of battery in smart textiles and the washability. For energy transfer, the project will develop antennas, transmission lines, and integrated organic components into a textile technology. In the basic principle, antenna will couple the smartphone and textile, and it will be connected to a sensor by a transmission line made of textile. Sensor will be supplied by a textile-integrated RF/DC rectifying circuit in organic technology. Such an organic technology components is chosen because it is appropriate for a textile integration purpose. Every RF and electronic element will be studied and characterized with the final goal to produce a prototype validating the battery-less supplying of a wireless textile-integrated sensor by a smartphone. For the final application, a wireless electrocardiogram sensor could be worn in the underwear of the subject and the smartphone on a pocket of a garment. The proposed system should be completely transparent for the subject and no modification of subject’s way of using his underwear should be undertaken. It is important to note that this system will be a life style device and not a medical one, it could just suggest consulting a general practitioner in the case of troubles.

2 - The second issue of the project will be to transmit data between a sensor and a smartphone. Depending on the previous technology for energy transfer, the NFC band will be also considered in the project, provided that the link-budget favorably demonstrates the feasibility of data transmission. However, data transmission by using the Industrial, Scientific, and Medical band (ISM) at 2.4 GHz is expected to be more efficient especially in terms of high flow rate. By taking inspiration from metamaterials, the project will intend to use textile as a waveguide for surface waves. Three technological ways will be explored to produce surfaces with reactive impedance: (i) an Artificial Magnetic Conductor (AMC) type structure; (ii) a corrugated ground plane by using woven or sewn metallic yarns; and (iii) woven metasurfaces with phase-advance. Each technological route will need to produce specific textiles by lamination, weaving or knitting, and using enameled or bare metallic yarns. Such reactive impedance surfaces can guide surface waves with a Transverse Magnetic (TM) polarization. To launch such surface waves, textile antennas operating at 2.4 GHz will be developed and produced. Besides the wave polarization, textile antennas will have to lower any interactions with human body for complying with the medical standards about the wave absorption. In the project, such interactions will be not precisely studied; particularly the Specific Absorption Rate (SAR) from antennas and waveguides will not be measured. However, RF components will be designed to reduce body interactions to facilitate future transfer of developed technologies to industrial applications. At last, each RF structures in the ISM band will be studied and optimized to produce a final prototype validating a RF data transmission by a guided surface wave onto a textile between two antennas.

On the whole, exotic electromagnetic properties emerging from metamaterials will be considered as a potential solution for reducing the footprint of antennas and of the system, or to engineer waveguides of surface waves.