9. E-Textiles and Wearables II#

Objectives from Fabricademy website:

Create a swatch using an ATtiny with one input and one output of your choice#

Create 2 actuator swatches + test them with the Arduino or ATtiny#

Document your swatches including your code and a schematic of your components#

Record a small video of your circuit working#

Design a wearable concept and make its prototype#

Learning outcomes

• Understand more advanced components and materials for creating soft sensors and actuators
• Inputs and outputs
• Explore possible applications for soft circuits in the fashion and textile industry
• Learn different components and types of interaction

Wearable Concept#

Self lifting sleeve - using smocking technique and shape memory alloy (SMA).

Shape Memory Alloy Actuator#

Materials#

Initial Materials:
- Pliers (pinzas)
- Needle
- Conductive connection that has a low resistance (I used Karl Grimm, a conductive copper thread that has a low resistance)
- Natural, lightweight fabric (cotton or silk)
- SMA (I used Nitinol, 1mm diameter and activated temp of 70C)
- Ruler

Prepare SMA edges (Step 4):
- Metal crimp beads

Train SMA wire (Step 5):
- Screws (to wrap SMA around to “train” the shape)
- Metal clamps
- A heat gun or bunsen burner
- Protective gloves

Arduino and circuit board testing:
- Bread board
- Jumper cables
- Diode
- Resistors
- LED
- MOSFET
- Laboratory power supply (our machine is the PeakTech 1080)
- Aligator clips
- Arduino Uno

ATtiny:#

Step 1: Research smocking techniques#

“Smocking is an old textile technique that gathers fabric in certain pattern to create 3D decorative pattern on textile” - Kobakant

I need to determine: - How many gathering points I want
- How far apart the gathering points are from one another (and will this be an equidistant spacing…or no)
- What smocking technique to do
- What the length of the SMA wire will be

Techniques to try:
- Tubular/Lozenge smocking
- Lattice smocking

I familiarized myself with the Smocking SMA tutorials on Kobakant

Resources:
- SMA Smocking Swatch Example - Kobokant
- SMA Smocking - Kobakant
- Modern Smocking Lozenge Pattern
- Lozenge Smocking Tutorial

Step 2: Find a fabric that works well for SMA + smocking#

Smocking requirements:
“Smocking requires lightweight fabric with a stable weave that gathers well. Cotton and silk are typical fiber choices..” - Kobakant

SMA requirements: - Liza reccommends light weight fabric to produce the best results. - DO NOT use a high-content polyester fabric. The SMA could melt the polyester.

I wasn’t sure which of the lightweight fabrics we had in our inventory were natural, I did a “burn test”. By burning the edge of the fabric, you can tell if the fabric is synthetic or natural.
- Synthetic fabrics = will melt
- Natural fabrics = will burn quicker, and the burnt part will flake off like ash.

Natural fabric

Step 3: Cut fabric#

• Cut my fabric to A3 size, as done in the Kobakant summer camp
• Drew the template onto the fabric (diagonals = 10.5 cm)

References:
- http://etextile-summercamp.org/2014/wp-content/uploads/2014/06/Smock-patterns-workshop-2-straight-fabric.pdf

I did iron my fabric, but it easily wrinkles :)

Step 4: Prepare SMA edges#

• Cut the wire and made loops with crimp beads

References: - https://www.kobakant.at/DIY/?p=6684

Step 5: Train SMA into a coil shape#

• From lecture, Liza says the trained Flexinol can contract to 10%

Additional variables/considerations when working with SMA:
- As you increase the length of the wire, you also increase the resistance. My wire is at 10.5 cm long, which is oover double the length of the wire done in the Kobakant tutorials. I may want to decrease the length if it becomes a problem later.
- If you go higher than a diameter of 0.008, you’ll need to increase your amount of power

Determined my wire was 1mm in diameter Nitinol. I researched what temperature I needed to heat the Nitinol to in order to “train” or “shape”.
- From my research, I found 500-550 F would do.
But there was a lot of varying information (that you only had to do it at 200 F, that you had to hold it over the heat source for 8-10 minutes, or 20 minutes, or you could just blast it with heat until the wire turns red hot, only a minute over the heat source, also mention that you could permanently deform the shape if it was too hot, also you could make the wire too hot and break it.
- Determined I needed to shape my wire into coil shapes. I also determined that my heat source would be our heat gun which had a setting of 550 F (Proxxon Heat Gun).
- Secured the wire (the crimp beads fell off in the process)
- Applied heat to the wire via heat gun

• Created a system to hold my wire in place

Wait for it…

• The heat gun immediately died
• Had to figure out a new system

Attempt 2:
- Decided to use our Bunsen burner in the Biolab (open flame). I could no longer use my wooden system because the wood catches on fire
- I didn’t have any bolts, or good metal clamps to hold the wire, so I ended up twisting the wire around the one round end of the pliers and physically keeping the wire taught and holding it over the flame with pliers. I may have burned my hands, and knicked my fingers with the pliers a couple times. I held it about 20 cm above the flame, as low as the flame would go without dying out, for 4-5 minutes, rotating the pliers so as to bake the wire evenly.
** I didn’t have any way of measuring the exact temperature of the flame, so had to guesstimate. Some of my attempts did not work, due to this experimental error.

Left to right:

• Immediately tossed the wire into cold water
• Boiled water and tested if the wire properly shaped

• It does! But it has to be boiling water 100C. Now I knew for sure that the activation is 70C, and not 40C. See many, many failed attempts below.

At first I thought none of my wire had shaped, but it was just because I didn’t have the water hot enough. The water was just warm, but not boiling and it didn’t work.

Resources:
- https://www.kobakant.at/DIY/?p=6682
- https://smartwires.eu/index.php?id_cms=9&controller=cms&id_lang=1
- https://www.materialsampleshop.com/products/shape-memory-alloy —> “500°C before it is rapidly cooled. The metal is available as wire, bar, tube, or sheet. It can be machined to obtain other geometries. It is possible to change the composition of the alloy, so that the metal returns to its original shape at temperatures between -100°C and +110°C” 
- http://jmmedical.com/resources/251/Nitinol-Shape-Setting.html —> “In general, temperatures as low as 400 deg.C and times as short as 1-2 minutes can set the shape, but generally one uses a temperature closer to 500 deg.C and times over 5 minutes” and “Higher heat treatment times and temperatures will increase the actuation temperature of the part and often gives a sharper thermal response (in the case of shape memory elements). However, there is usually a concurrent drop either in peak force (for shape memory elements) or in plateau stresses (for superelastic elements). There is also an accompanying decrease in the ability of the Nitinol element to resist permanent deformation.”
- https://smartwires.eu/index.php?id_product=13&controller=product&id_lang=1

Step 6: Circuitry and Arduino coding#

• Determined what components I would need to build this circuit (see Materials list below)
• First tested the wire just with the Arduino as the power supply. It didn’t work because the Arduino is not enough volts for the Nitinol, Nitinol requires A LOT of voltage, which we already knew but wanted to double check. opened Arduino and used this code: “TestNitinol” by copy and pasting the “Analogwrite” code and adjusting it from LED to Nitinol: https://www.arduino.cc/reference/en/language/functions/analog-io/analogwrite/
• We need the external power supply, so we hooked it up to the Laboratory power supply. Started with 3.4 V, and an ampage less than 0.5

• Found we couldn’t go up to 6V because the MOSFET got too hot

• Schematic diagrams to reference/cross-reference: https://programmingsketches.wordpress.com/2012/11/28/diagram-for-a-nano-muscle-wire-control/ (this is the best one)

• Then we wanted to regulate the current, so that it happened in pulses. This is the way to prevent the MOSFET and other components from overheating and from the circuit burning out. For this we need “Pulse width modulation”. Found the code for Arduino.
• Added in a component to regulate the PWM —> button. Had to research what each of the legs were on the button —> https://forum.arduino.cc/index.php?topic=395958.0

• Definition of PWM: https://www.arduino.cc/en/Tutorial/PWM

• Need a resistor, determined it was 250 ohm resistor by the colour bands (we only had the colour bands to go off of, from the schematic we were looking at: https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-band

• We left the code so that you have to press and hold the button to keep contracting the wire. This way you can let go of the button when your sleeve is at the desired height you want it.

• Adjusted the code: (button code](https://github.com/mikst/code/blob/master/heat_button_control/heat_button_control.ino]

• At this point we also swapped out our MOSFET to the TIP120, and it worked better

• Tried swapping out the diode for the LED, but when we did this, the LED blinked but the button no longer worked. So we had to adjust the circuitry (so that now everything has its own PIN) and adjust the code. LED (0.5 mm green): calculated what resistance we needed from the datasheet. https://www.sparkfun.com/datasheets/Components/LED/COM-09592-YSL-R531K3D-D2.pdf, Forward Current = 20 mA, and we know our voltage is 5V. Calculate the resistance using this calculator http://www.ohmslawcalculator.com/ohms-law-calculator, which gives us a resistance of 250 ohms. Couldn’t find 250k so I used 270k resistor.

• Need to have ampage between 0.5 and 1 amps

Step 7: Draw schematic diagrams#

Transfer everything I currently have hooked up to Arduino to wanting to ATtiny

Step 8: Fritzing program schematic#

Step 9: Sew SMA into my swatch, adding conductive thread#

Step 10: Hook up to external power source to test#

But then there were problems and we needed to troubleshoot!
- LED wasn’t lighting up in the circuit
- Diode was super hot in the circuit, so put in a new diode
- Had WAY too big of a resistor on my LED, because I thought it was 270 ohms, but it was acutally 270 MEGA ohms meaning it was taking all the current. This makes sense why the LED wasn’t lighting up!
- The connection points between the wire and the thread is too weak. We tested it with the voltmeter. I need to connect these two pieces stronger. Ruled out it was the thread because the wire had a low resistance when tested with voltmeter. Also ruled out it was the wire, because when we hooked up the power supply to just the wire (and not the thread) the wire contracted properly.

Left: Incorrect bread board, Right: Correct bread board! LED is now lighting up.

Left: Kobakant tutorial, Right: My connections

• Changes in Arduino code:
• Adjusted the codefor “Button state LOW” and “Button state HIGH”
• Realized I didn’t actually have PWM, so changed “SeriesWrite” to say “AnalogWrite”
• I had my LED as “Input” when it should be an “Output”

Step 11: Migrate my code to ATtiny#

Step 12: Sew circuitry, button, and all components to swatch#

Additional Resources#

• [“Materializing Interaction”] by Marcelo Coelho (https://dam-prod.media.mit.edu/x/files/thesis/2013/coelho-phd.pdf)
• [Materials of Interaction Responsive Materials in the Design of Transformable Interactive Surfaces] by Marcelo Coelho (https://pdfs.semanticscholar.org/c5d7/39fc4f0840802c22e10672b86d3f36d6574c.pdf)
• http://portfolio.newschool.edu/artisanaltech/2014/10/07/6-thermochromic-nitinol/ (makes reference to fritzing)

Initial testing with ServoMotor#

Before I realized Shape Memory Alloy was the best way to create my desired result, I tested with a ServoMotor.

My line of brainstorming: - Use the Servo motor like a spinning bobbin, that reels in the thread attached to the shirt sleeve
- The circuitry will be sewn on the inside of the sleeve
- Maybe it’s not possible to fold the garment, maybe I can only lift up and down like blinds?
- I would need 3 ranges:
-turn once CW = one fold
-turn twice CW = two folds (3/4 length sleeve)
-turn thrice CW = three folds (t-shirt sleeve)
PLUS a range that goes down from the t-shirt sleeve setting:
-turn once CCW = goes back down to 3/4 length sleeve
-turn twice CCW= goes back down to one fold
-turn thrice CCW = goes to unfolded

What I learned#

Although I abondoned this idea because it was way too complicated, it led me to revisiting SMA. In the learning process I explored:
- orgami folding systems
- how to program and set up a circuit board with a ServoMotor
- Potentiometers
- Arduino functions Sweeper and Knob

Resources
- Code
- Tutorial
- Schematic

Lecture reflections#

“Second Skins”
Presented by Liza Stark
Lecture 9