Introduction: Hot Seat: Build a Colour-Changing Heated Cushion

About: e-textile researcher

Want to keep yourself toasty on cold winter days? Hot Seat is a project that uses two of the most exciting e-textile possibilities - colour change and heat! We will be building a seat cushion that warms up, and when it's ready to go it will reveal the message "HOT SEAT" to let you know.

In this project we will be using LOOMIA Packs and Parts, which are flexible components for prototyping soft interfaces.

Note: This is an advanced project that uses heat and requires adult supervision. Do not leave your project unsupervised, and unplug when not using.


For this project you will need:

Step 1: How Does It Work?

To make this seat cushion we will have 3 main component layers: a stool, a heating pad, and a cushion with thermochromic fabric or dye. If we break down the word thermochromic, thermo = heat, and chromic = colour changing, which means a fabric material that changes colour when heated. So when heat is applied with the heating pad the fabric above will then change colour, revealing our message. In our case this colour change will let us know when the heating pad is warm enough for us to feel it, because the thermochromic fabric will feel it first!

Step 2: Gather Supplies and Strip Your Cushion

Our first step is to strip our cushion and re-use the parts we can. For this stool, I'm going to be re-using the elastic around the edges for my new cushion cover to make sure it will have a tight and secure fit around the heating pad and stool.

Step 3: Pick a Fabric That Matches Your Thermochromic Material

Now we are going to start building our cushion top. For mine I want my thermochromic material and regular fabric to be the same colour. This will make the message text stand out more when the cushion is warmed up.

Step 4: Build Your Test Circuit

We are going to be building a simple circuit using the LOOMIA heating pad and a 3.7V LiPo rechargeable battery. This will enable us to then test the heating pad with the specific thermochromic fabric we want to use before sewing everything in place. To build out this circuit I used alligator clips to hold the circuit temporarily in place.

Step 5: Test Thermochromic Fabric

Make sure your LiPo battery is all charged up, and then we will use our testing circuit to test our fabric. Thermochromic fabrics and dyes all change colour at different heats, so before sewing your project in place you want to make sure that your specific heating pad gets warm enough to change the colour of your material. For the Shadow Shifter fabric I'm using it changes colour quite quickly (for example with a warm touch or with perspiration) so it'll start changing colour almost immediately once the heating pad warms up.

Step 6: Cut & Sew the Cushion

Once you've picked your message (in this case "HOT SEAT"), the next step is to cut it out and sew it onto your cushion fabric. Make sure that the text space isn't larger than the marked our square on the LOOMIA heating pad. Anything outside the marked space will not change colour. Next, I added the elastic from the previous cushion to the edge of the base fabric so that it will lay close and secure around the heating pad.

Step 7: Place Cushion Cover Over the Heating Pad and Enjoy!

Now we are ready to bring it all together. Pull your seat cushion over the heating pad, plug in your battery, watch the colour change, and get cosy!

Remember: Make sure to always unplug your battery when you are not using your seat. Do not leave your circuit unsupervised.