E-textiles¶
This week's topic is E-Textiles, where we explore how textiles can stop being passive surfaces and become interactive interfaces, capable of sensing, responding and communicating. The exploration focuses on understanding the basic principles of electronics and translating them into soft materials: conductive threads, conductive fabrics and textile components that replace cables, switches and sensors.
1. Objective¶
weekly assignment
- Understand the basic principles of electric circuits and how they can be built with soft and conductive materials.
- Differentiate between digital and analog sensors, and how each one reads information from the body and the environment.
- Build a textile object that integrates one digital sensor and one analog sensor, connected to an output (LED).
2. References, research & inspiration¶
When I think about e-textiles, I remember that for a long time electronics and textiles were seen as two separate worlds: one rigid, cold and technical, the other soft, close to the body and deeply cultural. What I find interesting about this field is precisely the meeting point between both, where the textile is no longer only a support for electronics, but becomes the electronic component itself.
These are some of the works and researchers that I feel communicate this idea very well, from a more experimental and artisanal approach to a more industrial and fashion-oriented one:
Leah Buechley – Developed the LilyPad Arduino (2007), a sewable microcontroller designed to be stitched with conductive thread. It made e-textiles accessible to designers, artists and educators, and is still a reference for soft circuit construction.
KOBAKANT (Hannah Perner-Wilson & Mika Satomi): Their online archive How To Get What You Want is probably the most complete open library of DIY textile sensors, switches and actuators. Their approach is very close to craft: crochet, knitting, embroidery and felting as ways of building electronics.
## Key Concepts
Before moving on to the process, it was necessary to understand some basic principles of electronics, since everything we build in e-textiles depends on them.
What are e-textiles?¶
We can distinguish between two approaches:
Wearables / attached electronics: conventional components (LEDs, batteries, boards) are attached or sewn onto the textile. Textile electronics: the textile itself becomes the component. A piece of conductive fabric can be a switch, a resistive fabric can be a sensor, and a stitch made with conductive thread can be a wire.
The electric circuit¶
A circuit is a closed path through which electric current flows. For it to work, it needs at least:
A power source (battery): provides the energy, measured in volts (V). A conductor (thread, fabric, wire): the path through which current travels. A load or output (LED, motor, speaker): the element that transforms energy into light, movement, sound, etc. A control element (switch or sensor): decides when and how much current passes.
If the path is interrupted, the circuit is open and nothing happens. When the path is complete, the circuit is closed and the current flows.
The three basic magnitudes are related through Ohm's Law:
This is especially important in e-textiles because conductive threads and fabrics have much more resistance than a copper wire, and this resistance increases with the length of the stitched path. A circuit that works on a small sample may not work the same way when the path is longer.
Conductive materials¶
Conductive thread: usually made of stainless steel fibers or nylon/polyester coated with silver. Stainless steel is more resistant to oxidation; silver-plated thread has lower resistance and is softer to sew, but can tarnish over time. Conductive fabrics: woven or knitted fabrics coated with copper, nickel or silver (for example, conductive ripstop or taffeta). They are ideal for creating contact surfaces and pads. Resistive / piezoresistive materials: materials whose electrical resistance changes when they are pressed, bent or stretched, such as Velostat, Eeontex fabrics or conductive yarn blends. These are the basis of most soft analog sensors. Conductive hardware: metal snaps, hooks, zippers and rivets, which can work as connectors or switches.
Inputs and outputs¶
Inputs (sensors): capture information from the body or environment: touch, pressure, stretch, bending, proximity, light, temperature. Outputs (actuators): the visible or perceivable response: LEDs, vibration motors, speakers, heating elements, thermochromic inks, shape-memory alloys.
Digital vs. analog sensors¶
This was the core concept of the week.
Digital sensors work like switches. Two conductive parts either touch or don't. Typical textile examples are snaps, zippers, Velcro with conductive fabric, tilt sensors with a metal bead, or two conductive pads that close the circuit when pressed together. With a microcontroller, these are read with digitalRead(), which returns HIGH or LOW. Analog sensors are variable resistors. Their resistance changes gradually depending on how much they are pressed, stretched or bent, so the current that passes through them also changes. This allows us to read intensity, not only presence. With a microcontroller, these are read with analogRead(), which in an Arduino returns a value between 0 and 1023.
LEDs and polarity¶
LEDs are polarized: current only flows in one direction.
The anode (+) is the longer leg (or the side marked with "+" on sewable LEDs). The cathode (−) is the shorter leg, usually next to the flat side of the LED.
If the LED is connected backwards, it simply won't light up. It is also common to use a current-limiting resistor to protect the LED, depending on the voltage of the power source.
Tools¶
- Conductive thread
- Eeontex conductive/piezoresistive fabric Metal snaps (press studs)
- LEDs
- Battery [complete: e.g. CR2032 3V coin cell + holder]
- Microcontroller XIAO RP2040
- Resistors
- Multimeter
- Sewing needles, scissors, fabric and bag materials
Process and workflow¶
First tests: circuits on fabric¶
The first thing we did was experiment with simple circuits to understand how current travels through conductive thread. [Describe your first samples: swatches, a simple LED circuit, tests with the multimeter, etc.]
Using the multimeter, we measured the resistance of the conductive materials. This helped me understand why some materials work better than others depending on the function they are going to have in the circuit: low resistance for paths that act as wires, and variable resistance for sensors.
Personal exercise: the bag¶
For the integral exercise, I wanted to work with an object that is part of our everyday life and that is in constant relationship with the body: a bag. A bag is opened and closed many times a day, it carries our things and, in a way, it also carries part of our weight. I found it interesting to think of it as an object that could communicate its own state: whether it is open or closed, and whether it is carrying too much.
So, the bag integrates two sensors:
- A digital sensor, built with metal snaps, which turns the LED lights on and off when the bag is opened or closed.
- An analog sensor, built with Eeontex fabric sewn to the handle, which turns on an LED when the bag becomes too heavy and pulls on the handle.
Circuit design
Before sewing, I drew the circuit to define the path of the positive and negative lines, the position of the LEDs, the battery and the sensors, trying to make sure that the lines would never cross.
Results¶
Code¶
Use the three backticks to separate code.
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);
}
// the loop function runs over and over again forever
void loop() {
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000); // wait for a second
digitalWrite(LED_BUILTIN, LOW); // turn the LED off by making the voltage LOW
delay(1000); // wait for a second
}