Woven eTextiles

While advancing technologies make the entire world around us more digital, the human longing for tactile experiences persists. Our experiences with the physical world are diminishing as screens are the default interface to the digital realm. This development opens new world of possibilities for textile designers. As technologies advance unforeseen functions are being integrated into textile materials. Hereafter textiles can serve as an intuitive bridge between the physical and digital world – interfaces that invite people to touch. And while offering new possibilities, this development also poses new demands for the textile design process. Rapidly evolving textile-like conductive materials enable the integration of electronic components into textile structures more delicately than before.

In my own work, I use the reflective weaving practice as my main method to explore new ways to integrate electronics and sensor structures into woven fabrics, from textile designer’s point of view. I truly believe, that although the new functions broaden the domain of textiles capabilities, the important basic qualities, such as the feel and the look of textile materials, will remain essential for the user. Thus, while fields such as electronic engineering and interaction design influence textile design process, the deep understanding of textile structures, techniques and materials should be the solid foundation to explore this emerging field of eTextiles.

Woven circuit board

One essential question driving my research is, how the whole structure of the woven fabric can be designed to support the creation of a woven circuit board, that combines different components into the same electric circuit. Especially pocket weaves and interlaced multilayer structures offer a plethora of interesting opportunities. Weaving multiple layers simultaneously, and using the selected bindings to connect the layers with each other at selected points allows for the development of structures similar to multilayer circuit boards. As fabrics can be created with multiple threads with various properties, it is possible to create fabrics with computational, sensorial and actuating properties.

These cross-sections of woven multilayered fabric and a multilayered circuit board illustrate the similarities of typical circuit boards and woven structures. In the woven fabric, single yarns can move between different layers to connect, but also isolate where necessary, in a controlled manner.Certain similarities between the two can be recognize.

Since the processor-yarn is designed to be used in the weft, another fundamental element for the development process has been the design of the conductive warp system. The intent is that by using a certain pattern the processor-yarn connects with a direct contact to the conductive lines in the warp (the grey lines in the picture above on the right). These conductive lines are used for multiple purposes, such as programming the processor, and control other component modified similarly than the processor. Once the processor-yarn is woven in, the warp will act as a base enabling other yarn-components to connect to the same circuit. The resulting structure equals to a circuit board, where the components are part of the textile structure that contains a working circuit.

Testing the processor-fabric. The integrated processor controls the led-lights embedded into the same circuit. Video of the fabric can be watched here.

One of the key objectives of my work is to question how electronic components could be designed better to mee the needs of the weaving process. The major difference that needs to be addressed is the dynamic nature of the textile materials. From a textile designer’s point of view the most natural way to attach a component into the fabric is to simply weave it into the structure, similarly as it is done with normal yarns. To create a base for versatile woven circuits, a processor was first modified into a yarn-like form.

Related publication:Mikkonen J. and Pouta E. Flexible wire-component fo weaving electronic textiles in Proc. 2016 IEEE 66t Electronic Components and Technology Conferenc (ECTC), Las Vegas, NV, USA, 2016, pp. 1656-1663

Woven two-layer circuit

The first attempt to explore the use of reflective weaving practice in the creation of woven circuit boards contains a circuit able to detect changes in the magnetic field. The two-layered woven structure hides magnetic field sensors, led-lights and singnal traces inside the two interlaced layers of the fabric, powered by external power supply though two conductive signal lines in the warp. The components were first soldered into liz-wire, and inserted into the woven structure similarly as weft yarns during weaving.

Left: Conductive warp system.
Right: Components were modified into weavable form by using Litz-wire and epoxy resin.

Watch a video of the circuit being tested here.

Related publication:
Mikkonen J. and Pouta E. Weaving electronic circuit into two-layer fabric. In Adjunct Proceedings of the 2015 ACM interna
tional Joint Conference on Pervasive and Ubiquitous Computing and Proceedings of the 2015 ACM international Symposium on Wearable Computers

Woven sensor structures

Weaving as a technique is very suitable for exploring various sensor structures, especially designed for sensing touch. Complex structures can be created by utilizing different bindings and combining both conductive and non-conductive yarns suitable for weaving. Especially digital Jacquard-looms allow the use of multiple warp systems freely, and thus the creation of several layers for conductive signals. Surely it is not only the technique that makes woven fabrics particularly suitable for sensing touch: soft and smooth materials naturally invite us to touch them. I personally consider textiles as one of the most meaningful materials in people’s lives: textiles protect our body, decorate our homes and are present in our everyday life in many different forms. This versatility and close connection with the human body offers countless opportunities to create more tactile and emotionally rich ways of interacting with technology through the soft materials around us. These reasons have inspired me to explore various capacitive sensor structures capable to sense the touch of a hand by sensing the electrical field of the human body.

In the more complex structures multiple electrodes are used to construct a single sensor or a sensor matrix. This picture shows an example of a multi-layered fabric with an integrated woven sensor matrix. The capacitive matrix detects the order and the amount of overlapping conductive layers, and recognizes different qualities of touch, such as pressure and different hand gestures.
Early prototypes of the capacitive multi-layered sensor structure.

These sensors contain of one or multiple woven conductive areas, electrodes. In the simplest structures one single woven electrode detects when it is being touched, and multiple conductive areas work as independent sensors, as in this Rose-sensor fabric shown above. The electrodes are part o the pattern design: each of the rose motifs will separately detect when being touched. The conductive pattern is created by usin the fil coupé-technique, where the fabric incorporates the jacquard pattern that is interwoven by using weft floats. The floating conductive weft creates the rose design on the surface of the fabric, and the floats between the motifs are being cut after weaving.
Watch the sensor being tested here.

In the early prototypes the different sensor fabrics can be connected to the same circuit with the processor fabric through snap buttons.

2019 Emmi Pouta