Project 4: Creating the case

In the planning, this week I had to put all of my components to the phone in such a way that it would hold AND feel nice:

  1. Put sensors and foam unto phone
  2.  (if time) 3D-Print phone case that can hold Arduino, sensors and foam

From the beginning one of my main goals was to make the phone feel soft and squishy and really different from, for example, touch screens:

My project is to develop a soft and squishy device for the iPhone 5 that feels good in your hands

Now that I had to think of putting the elements to the phone, I considered my options for this requirement:

  1. Use silicone
    Michael Wesseley had given me a lot of information on how to make my own silicone parts. This would be the best option in terms of the squishiness I wanted, but too time-consuming for this project. I would have to make my own mould, pour the silicone liquid inside, wait and all this without pre-knowledge and no time to reiterate.
  2. 3D-Print a flexible case
    This seemed an easier option. I knew there were students in the Fab Lab making the exact same phone case and that there was a more flexible 3D printing material.
  3. 3D-Print a flexible case + add foam under it
    Although the material seemed more flexible, it would still not feel really squishy. thus, I had bought really soft foam of about 20 mm thick from BHV Le Marais.

Now that there was few time left, I went with option 3 and tried to do that as good as possible.

Test print material

I was given a very good tip: instead of printing the whole case and finding out the FSR does not register pressure through the case, I could better print a simple test square of the material that fits on the FSR. This was also a good opportunity to test how the envisioned structure (phone+FSR+foam+case) would work and feel.

Thus, I made a small, 40×40 mm test square using 123D Design, netfabb and Cura (see Assignment 3a). Luckily, it felt very flexible and thin and the FSR worked perfectly under it, both with foam and without.

Print extended phone case

Luckily, Kevin had already made a very nice flexible iPhone 5 case in his project and he was so nice to share his .stl file with me. Thus, all the credits for the original phone case go to him.

I still had to calculate the extra space that I needed though:

Kevin’s Case:
Case: 2.5 mm
iPhone: 7.6 mm
iPhone+Case: 10.1 mm

My Case:
Arduino: 7 mm
Foam : +-2 mm extra (embedding Arduino)
Arduino+Foam: 9 mm
Phone+Arduino+Foam: 16.6 mm
Phone+Arduino+Foam+Case: 19.1 mm
Extra down: 9 mm

In the end I needed about 9 mm of extra space. I took Kevin’s file, moved the phone up for 9mm and tried extruding the phones bottom down. It didn’t work. After a lot of trying I figured out I needed to press-pull the exact bottom down, avoiding to create any other unwanted rims.

Another part I had to think about was creating an extra whole for Arduino Nano. I could have done this very precisely, but now just cut a larger whole where the Arduino port simply had to fit in.

The last problem was the printing itself. I did not pay attention to the spool on the back of the printer. This is why it got stuck, and the printer was unable to « suck up » more material. My first print failed, leaving behind the vague structure of a half-printed bottom. I had to fix the spool and test print some material by the 3D printer while it heated up. Next time I will definitely keep an eye on this.

Cut and add foam

I cut the foam in the shape of an iPhone, but then I figured out that I needed the foam to be 9 mm (embedding the Arduino with 2 extra mm) instead of 20. I therefore drew a line to cut the foam in half…

However, cutting this foam was a very, very disillusioning experience. Using a sharp Stanley knife to cut in as small dimensions was near to impossible. Even cutting out a whole in the foam was hard, because the foam was very tough. In the end, what worked better was to precut and then rip tears of foam apart. This created a very roughly shaped foam, still nice on one side but randomly shaped on the other.


The foam cut (left) and uncut (right)


In the end I used sticky foam to stick the Arduino to the case, which was way easier than putting it directly on my phone.Then, I added the foam on top of it, with a whole to let the Arduino Nano through (embedding with 2mm foam was impossible). When I put my phone there in the end it felt quite good, since finally Arduino, the case and the phone were one holdable object.


After I finished the whole project, one drawback I found was the flexibility of the phone case. Although this was one of the most flexible materials, It still felt quite stiff and plastic-alike on the back. If I would continue the project, I would definitely want to try making a silicone part with a mold to make it more soft and squishy.

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