Textiles are the new integrated circuits for the smart wearable. Today, technology can provide textiles the ability to sense their surroundings and help the fabrics respond to the outer stimuli by adapting to the conditions and maintaining their fabric properties.
These intelligent textile (e-textile) or smart textiles, using soft-computing, sensors, and wearable technologies, has gained tremendous demands in recent times, especially in the military, medicine, sports, automotive, aerospace, and security, where we can see a trend of integrating our daily environment with intelligence since these wearable systems can make daily efficient with all the needed information on the go.
Different methods are used to process these wearable textiles with several materials. The primary components used for smart textiles are sensors, actuators, data processors, communicators, energy supply, and advanced technologies like fire-resistant, breathable, or ultra-strong fibers.
There are three classifications of smart textiles based on their applications:
- Passive smart textiles – that sense environmental conditions.
- Active smart textiles – both sensing and reacting to environmental conditions.
- Very smart textiles – that senses react and adapt the environmental conditions.
This post will examine three smart fabrics sensors used in smart textiles.
Capacitive Pressure Sensors
In capacitive pressure sensors, conductive materials which act as conductive plates are used as textile capacitors and are separated by dielectrics, such as synthetic foams, fabric spacers, and/or soft non-conductive polymers. These sensors can be woven, sewn, embroidered with conductive thread/fabrics, painted, printed, sputtered, or screened with conductive inks or conductive polymers.
Capacitive fibers can also be made with techniques similar to those used in flexible electronics, such as sputtered metals on silicon fiber. The area of two conductive parallel plans, the conductive material, and the distance between them determine the capacitance of a capacitive pressure sensor. The capacitance will change by varying the distance between the conductive plates while maintaining the same area for the conductive plates. When the distance between the conductive plates decreases, the capacitance decreases, and the distance between the conductive plates increases, the capacitance increases.
Resistive Pressure Sensors
There is a relationship between pressure and electrical resistance in resistive pressure sensors. These sensors can be made of various conductive materials in various structures using various manufacturing techniques. The variable resistive materials can be sewn, embroidered, or glued to the textile substrate to measure pressure. A resistive pressure sensor’s working principle is based on increased electric resistance as the resistive material is stretched or compressed. A higher resistance increases the output voltage for the same electric current, according to Ohm’s Law (V = R*I). In this way, the stretch or compression can be linked to the voltage.
Optical Textile Sensors
The variation of light intensity or amplitude sensed by a fiber Bragg grating (FBG) sensor is the working principle of optical textile sensors. These materials are suitable for seamless textile integration with industrial processes due to their small glass optical fiber diameters (micron range). A small light emission diode (LED) can be used as the optical fiber light source, and the light amplitude at the fiber’s end can be sensed with a small photodetector. The light amplitude will change in response to the movement of the textile, allowing for the detection of textile displacements and pressures. Optical textile sensors can detect textile displacements and pressures in applications where electrical currents cannot pass through textile substrates. The light amplitude passing through the fiber increases as the elastic fabric is stretched, increasing the output voltage from the photodetector.
New wearable e-textile products with various useful functions are introduced to the market every day. These smart textiles provide a novel means to sense and interact with the wearer’s body through sensors; they can monitor according to the environment. Thus it has great growth and opportunity in the stream of sports, science, exercise, and many more areas.