Our team worked with Katlyn, a student at the Levy Special Education High School in Wichita, KS. Katlyn has Cerebral Palsy (CP) and is nonverbal, so to communicate with the world she recently began using an app called Proloquo2go on her iPad. However, to use the app, she must manually press buttons and icons on the iPad screen. She must use a stylus because her physical capabilities due to CP renders her range of motion and finger strength ineffective for such a task. She struggles with using commercially available styluses and our team believed that a custom-made stylus would benefit her greatly such that it allows her to use the Proloquo app on her iPad much more effectively, therefore giving her the ability to communicate with her world just like you and I are able to.

This Instructable will include details on the manufacturing process that was utilized to build the custom styli and a little backstory to the reasons behind the design approach for the stylus.

Supplies

iPad or Android Tablet
Proloquo2go App
Ultimaker 3D Printer (or another applicable 3D printer)
PLA 3D Printing Material
Sandpaper (optional - for smoothing out the plastic)
Aluminium Tape
MEKO 0.30“ (Dia) Hybrid Stylus Replacement Fiber Tip; bought on Amazon.com

Step 1: Design Approach

Katlyn had been previously using a variety of styli. She had a few which were the regular pen styli and a custom make stylus which was basically a stylus tip jammed into a wiffle ball. She found the wiffle ball stylus to be most effective for her grip. Based on this the team decided a stylus with a ball like end would be the best choice.

The first step was to get the measurements for the stylus she was using and measurements of Katlyn's range of motion which were measured with the help of a physical therapist who works with her. Using these measurements, the team developed a CAD model for the stylus. The stylus was designed with AutoCAD Fusion 360 (Free student version).

We noticed in our observations of Katlyn initially using her original stylus that she occasionally had to readjust the stylus in her hand. Sometimes the stylus was completely backwards and she would struggle with flipping the stylus around in order to use it properly. So we designed the stylus to be reversible by adding two sides to the stylus. We found that this would also provide a more stable grip as the back end of the stylus would stabilize with her hand. However, we quickly found out after a 1 week trial run that she did not like to hold it from where we intended, but instead opted to hold it from the very back, making the stylus far too long for what it was meant for.

After this discovery, we went back to the drawing boards and redesigned the stylus to be a little bit shorter and removing the double-sided feature. She ended up really liking the second version and we were very happy to see that it was precisely what she was looking for.

When we first 3D printed our stylus, we found that although the tip was a silver mesh, high sensitivity tip, it was still having trouble responding with the iPad. Through our research we also found that iPads work with a capacitive touch screen. What this means is that there is a small charge stored on the surface of the screen that is released and analyzed through the iPad whenever you touch the screen. Your body is mostly made of water and is therefore very conductive. Since the 3D printed stylus was non conductive plastic between the hand and the tip, we needed to find a way to bridge the conductivity so that it would be basically as if you touched the screen with your finger when the tip of the stylus made contact. Our solution to this was a long strip of aluminum tape that we designed a small flat surface for on the stylus itself. The solution worked flawlessly and the stylus was as highly sensitive as we could hope for.

Step 2: 3D Printing Instructions

The final stylus has a 1.5" diameter sphere for the handle end, a 0.35" diameter for the shaft and an M5 thread for the stylus tip hole.

Since every 3D printer has a different software, the exact instructions on how to print the stylus will be slightly different between each device. However, if you need to reprint the stylus in the future, simply drop the .STL file that will be included in this Instructable into the slicer software that your 3D printer uses. Be sure to use approximately 25% support density and approximately 20% infill density for the stylus. The overall length of the file should be exactly 4'' in length from the stylus tip to the back end of the handle so be sure to check that the model in your slicer (3D printer software) is scaled uniformly to 4". The stylus was printed with PLA and uses aluminum tape to create conductivity from the tip to the end.