Conductive Fabric Garment for a Cable-Free Body Area Network

Abstract

O f the many wearable computing applications, health-monitoring systems open a world of ways to improve our quality of life by supporting continuous measurement of physiological signals such as limb motion, respiration, and skin temperature. Such systems can expedite recovery and rehabilitation, immediately address a sudden decline in health, and assist those in need until they have access to a health professional. For such wearable systems to become widely accepted, they must be minimally invasive and minimally intrusive. This is a crucial requirement particularly for elderly outpatients, 1 fitness professionals, 2 and soldiers in the battlefield.Placing sensor nodes on the body requires careful consideration of the components' physical connections, their bulk and weight, and the routing of wires along the body. 3,4 When evaluating how to locate system components on the body, you must also consider metrics such as relative movement, load-carrying capacity, and shape. 5 We've devised a unique approach to addressing these issues by applying DC power-line communication technology to a wearable monitoring system. DC-PLC technology uses a single, shared DC bus to provide power to each node and to simultaneously facilitate data transmission between nodes in an electrical network. 6 For maximum comfort, the DC bus must be flexible and lightweight. This precludes the use of traditional metal wiring. Instead, we use electrically conductive fabrics sewn into a garment, where they behave like normal fabrics and thus don't restrict the wearer's body movement. 7,8 This distributed transmission medium serves as the physical layer of the DC-PLC bus. We've designed the system so that users can go about their daily business in the comfort of their home while being monitored remotely over the Internet.In this article, we focus on a novel method for the analysis and design of these conductive-fabric (CF), sensor-network garments, including a discussion of our method for applying DC-PLC to a wearable garment, a method of analyzing the garment characteristics, and the details of the physical implementation. DC-PLC on the bodyThe garment design reflects our ability to simultaneously transmit power and information over a single medium, commonly known as power-line carrier communication. The DC-PLC bus consists of a power and data supply line, which we call the consolidated power-signal (CPS) line, and a ground line for electrical return. Sensor nodes are connected to this DC-PLC bus, and the system superimposes the modulated physiological data they collect on the CPS. The sensor nodes, embedded in the garment at various locations, transmit data along the bus to a master node that transmits all sensor information wirelessly to a local capture and storage mechanism, such as a personal computer.Theoretical analysis and experimentation show that a prototype body area network composed of 2D electrically conductive fabric sheets can transmit both signals and DC power sufficient for implementing a cable-free network in a garment.

Evaluating capacitive touch input on clothes

“…Metal wires are rather inflexible, however, and can reduce the wearablitity of the garment. Wade and Asada [30] describe a setup of a cable-free body area network which is based on conductive fabrics that are supposed to behave like normal fabrics. They provide a two wire bus that transmits power and data to sensor nodes.…”

Inter-IC for Wearables (I2We): Power and Data Transfer Over Double-Sided Conductive Textile

“…Nonetheless, combination with a double-sided conductive textile would be suitable for wearable systems, because it provides freedom of sensor location along with lower resistance and higher current capacity while using a fairly flexible conductive textile for comfortable wearability. Advantages of such a two-dimensional (2-D) conductive material over a 1-D conductive strand are discussed in detail in [14]. The resistance between two points on the 2-D material is approximately proportional to the logarithm of the distance between the two points, while the resistance of a 1-D conductor is proportional to its length.…”

“…TextileNet [15] enables dc power supply and serial communication on the transmission line by temporally switching the power supply state and the pulse transfer state; thus, the power supply is intermittent and only singleplexed signal transfer is supported. Wade et al proposed a dc powerline communication (DC-PLC) on a layered conductive textile [14], [21], using a modulation/demodulation (modem) circuitry specially developed by themselves [22]. Continuous dc power supply and amplitude modulated signal, using a carrier in a frequency range of 2-10 MHz, are simultaneously transferred on the same textile medium.…”

A method to control LED blinking for position detection of devices on conductive clothes

“…As researches on systems using conductive fabrics, Networked Vest [5] uses conductive fabric on both sides of the wear, and the devices attached to the vest have DC-PLC (Power Line Communi- cation) modems that provide DC power from a single power supply as well as modulated analog signal communication. Electronic Textiles [6] uses a conductive thread with an insulator coating for horizontal and vertical directions as well as insulator thread.…”