Since I am responsible for designing and building many of the back-end technologies, I looked into how we can not only make the shirt a reality, but also maximize its re-usability.
We considered using technologies such as:
- Lilypad arduino – a dedicated tool for wearable technologies, the Lilypad will be used to power & control the T-shirt functions.
- Conductive thread – For connections between Lilypad/LEDs/Sensors, more robust and dedicated for the task (compared to soldering wires, which may snap under stress!)
- RGB LEDs and LED strips – For creating lighting & light patterns within the T shirt. If strips are used, the LEDs within them need to be individually addressable.
- Bluetooth or GPS – For tracking proximity to other T-shirts in the area and transmitting data between them.
If we decide to use the Lilypad Arduino over the NodeMCU board, we will have to consider other problems, such as internet connectivity.
Using conductive thread
The best conductive thread for machine or hand sewing is silver plated fiber. It has good sew-ability and a clean finish, and is less likely to get stuck in thread take-up of a sewing machine, unlike stainless steel fibers. For machine sewing, a “z-twist” direction should be used. For hand stitching, however, either type can be used. (Instructables.com, 2017)
To avoid shorts in conductive thread, power and ground lines should be kept a good distance apart. During stitching, fabric should be kept taut and flat . All thread should be tested with a multimeter prior to use. (Stern, 2017)
Waterproofing and wash-ability
Since we are making wearable technologies, we have extra points to consider, such as durability & the ability to wash it.
Washing LED T-shirts
Shirts that have an LED panel should be hand-washed only, to prevent cracking the panel. Battery packs and other water-sensitive parts should be removed prior to washing. Many of these shirts have an interior pocket that allows the wearer to remove the battery pack. (Flashion Statement, 2017)
Shirts that have non-removable electronics are generally dry clean only. (Christmasjumpercompany.co.uk, 2017)
Conductive Thread & Washing
Silver plated fibers are not as suitable for washing as oxidation can occur, however stainless steel fibers can be washed without risk. (Instructables.com, 2017)
The thread has to be dried thoroughly to reduce the risks of shorting (particularly for plated fiber kinds of thread, which may stay damp inside). (Stern, 2017)
Flashion Statement. (2017). Washing Instructions – Flashion Statement. [online] Available at: https://www.flashionstatement.com/light-up-t-shirts/washing-instructions/ [Accessed 19 Nov. 2017].
Christmasjumpercompany.co.uk. (2017). Product Care Instructions for your purchase – Christmas Jumper Company 2017. [online] Available at: http://www.christmasjumpercompany.co.uk/care-instructions/4586923675 [Accessed 19 Nov. 2017].
Instructables.com. (2017). Selection Guide of Conductive Thread for Machine Sewing. [online] Available at: http://www.instructables.com/id/Selection-Guide-of-Conductive-Thread-for-Machine-S/ [Accessed 19 Nov. 2017].
Stern, B. (2017). Overview | Conductive Thread | Adafruit Learning System. [online] Learn.adafruit.com. Available at: https://learn.adafruit.com/conductive-thread/overview [Accessed 19 Nov. 2017].
Stern, B. (2017). Preventing short circuits | Conductive Thread | Adafruit Learning System. [online] Learn.adafruit.com. Available at: https://learn.adafruit.com/conductive-thread/preventing-short-circuits [Accessed 19 Nov. 2017].