The world is distinctly rising towards the new era, an era of smart and intelligent discoveries; problem solving and creativity − the smart automobile vehicles (cars, metro system), intelligent jets, smart homes and amongst from many of such aristocratic paradigms, the ‘Smart and Intelligent Textiles’.Before going further, a clarification of the term and definition of smart and intelligent textile is essential. There is a substantive difference between the terms, ‘Smart’ and ‘Intelligent’, Smart materials or textiles can be defined as the materials and structures which have sense or can sense the environmental conditions or stimuli, whereas intelligent textiles can be defined as textile structures which not only can sense but can also react and respond to environmental conditions or stimuli . These stimuli as well as response , could be thermal, chemical, mechanical, electric, magnetic or from other source . According to the manner of reaction, they can be divided into passive smart, active smart and very smart
1. Passive smart materials can only sense the environmental conditions or stimuli; they are sensors.
2. Active smart materials will sense and react to the conditions or stimuli, besides the
3. sensor function, they also have actuation characteristics;
4. Very smart materials can sense, react and adapt themselves accordingly;
5. An even higher level of intelligence can be achieved from those intelligent materials
6. and structures capable of responding or activated to perform a function in a manual or pre-programmed manner.
Several circuits have been built on and with fabric to date, including busses to connect various digital devices, microcontroller systems that sense proximity and touch, and all-fabric keyboards and touchpads. In the microcontroller circuit shown in Figure 1, a PIC16C84 microcontroller and its supporting components are soldered directly onto a square of fabric. The circuit uses the bidirectional I/O pins on the PIC to control LEDs and to sense touch along the length of the fabric, while providing musical feedback to reinforce the sense of interaction. Building systems in this way is easy because components can be soldered directly onto the conductive yarn. The addressability of conductors in the fabric make it a good material for prototyping, and it can simply be cut where signals lines are to terminate.
One kind of fabric keyboard uses pieced conductive and nonconductive fabric, sewn together like a quilt to make a row- and column-addressable structure. The quilted conductive columns are insulated from the conductive rows with a soft, thick fabric, like felt, velvet, or quilt batting. Holes in the insulating fabric layer allow the row and column conductors to make contact with each other when pressed. This insulation also provides a rewardingly springy, button-like mechanical effect. Contact is made to each row and column with a gripper snap, and each snap is soldered to a wire which leads to the keyboard encoding circuitry. This keyboard can be wadded up, thrown in the wash, and even used as a potholder if desired. Such row-and-column structures can also be made by embroidering or silk-screening the contact traces.
All-fabric capacitive keyboard.
Keyboards can also be made in a single layer of fabric using capacitive sensing [Baxter97], where an array of embroidered or silk-screened electrodes make up the points of contact. A finger's contact with an electrode can be sensed by measuring the increase in the electrode's total capacitance. It is worth noting that this can be done with a single bidirectional digital I/O pin per electrode, and a leakage resistor sewn in highly resistive yarn. Capacitive sensing arrays can also be used to tell how well a piece of clothing fits the wearer, because the signal varies with pressure.
The keypad shown here has been mass-produced using ordinary embroidery techniques and mildly conductive thread. The result is a keypad that is flexible, durable, and responsive to touch. A printed circuit board supports the components necessary to do capacitive sensing and output keypress events as a serial data stream. The circuit board makes contact with the electrodes at the circular pads only at the bottom of the electrode pattern. In a test application, 50 denim jackets were embroidered in this pattern. Some of these jackets are equipped with miniature MIDI synthesizers controlled by the keypad. The responsiveness of the keyboard to touch and timing were found by several users to be excellent.