11. Soft robotics#
Making an iron-on inflatable on textile#
Intro - Background & motivation#
This week I created soft robotic structures based on inflatable textiles. I wanted to explore the concept of creating actuated pores (circular valves) within a textile, and what kinds of architectures would enable that. Cameras have a type of lens called 'leaf shutter lens,' and I wanted to recreate that in a textile because it has an actuated way of opening and closing while being in a flat structure.
Example of different types of leaf shutter designs
Concept, sketches, and references#
Desired mechanism of actuation#
Past work in textile soft robotics#
Robotic sample, inflatable pattern, sketch of airflow#
Robotic sample and findings#
The ratio of inflatable triangle size needs to overpower the width of the sealed wall channel. [to be quantitatively determined!]
Left: First working prototype. Right: explorations in changing design parameters.
Inflatable pattern and sketch of airflow#
Below are the designs pursued for changing up the number of triangles within the shutter design. The concept of airflow is shown in the first design denoted by the purple arrows.
How I made it#
The textile soft robotic was made from (1) iron-on vinyl, (2) parchment paper, and (3) textile (stretch cotton knit). The procedure is as follows:
- I designed my patterns in Illustrator. Designs for vinyl were exported as PNG to be cut on vinyl cutter; Parchment paper design was exported as AI for laser cutter. Manufacturing settings listed below.
- A bottom vinyyl pattern was ironed onto the textile.
- The parchment paper design was carefully placed on top of the ironed on vinyl.
- The top vinyl pattern was ironed on top to seal the whole inflatable.
- A rotary blade cutter was used to manually cut the triangles over the sealed vinyl
Experimentation with silicone#
For my final project, I had been experimenting with making an inflatable using silicone. Below is an example of it working as I pump air into it to inflate. Montserrat gave me advice on how to construct the inflatable. I made two separate layers -- a top layer that had the shape (circle with airflow input), and a bottom layer that was a 6mm thick of silicone. The two layers were adhered to each other using a thin layer of silicone (some that were leftover from making a batch of the two layers). One thing that I found difficult with making the silicone inflatable was making sure that the two layers were adhered well so that the shape I wanted to inflate was crisp at the edges. It's not a big deal, if it's just air, but if liquid is pumped into the inflatable (especially a colored liquid), it ruins the aesthetics.
Making a silicone gripper#
I followed the instructions for making a silicone gripper via the soft robotics toolkit, but modified it so that I could use acrylic as a mold instead of cardboard as listed on the website. To save the time, I also used a laser cutter to cut my mold and textile out instead of using plane scissors because... why not?
- Acrylic - 3mm and 6mm thick
- Muslin fabric
- Ecoflex 00-30
- Acrylic glue
Lasercut your components - acrylic mold and textile
- Using the vector files in the following section, cut the files for the specific materials indicated. I used a Trotec Speedy flex 400, and the settings for each material are as follows:
- Acrylic, 6mm thick -- Power, 75%; Speed, 0.35; Frequency, 5000 Hz
- Acrylic, 3mm thick -- Power, 60%; Speed, 0.50; Frequency, 5000 Hz
- Muslin fabric (with a 3mm thick plywood underneath) -- Power, 50%; Speed, 90; Frequency, 2000 Hz
- Make two molds from the cut acrylic pieces
- Mold #1 will be constructed of just 6mm thick pieces, and
- Mold #2 will be just like #1, but you'll glue the pattern you cut from 3mm thick acrylic in the middle of the 'plus.' Make sure that the 3mm thick acrylic pattern doesn't touch the 6mm thick acrylic walls.
- When molds are ready, make silicone by pouring equal parts of A and B from your Ecoflex 00-30 kit. For this, I poured 10g each of A and B. I also used a freebie sun-activated pigment powder that came along with thermochromic pigment ordered for our lab, about 0.2 g of it to color my silicone, just for fun. I stirred the whole mixture vigourously for ~1 min, poured it into my molds, stuck the filled molds into a vacuum chamber and waited for all the bubbles to leave ("degas").
- Place the lasercut muslin fabric over the uncured silicone that's in the mold without the 3mm thick acrylic pattern in it
- Once silicone is degassed, place each mold in an oven preheated to 150F for 10 mins
- Remove the molds, touch with your finger to check silicone is cured, and peel the silicone from the mold. Your silicone pieces should look as follows.
- Use what's left of your uncured silicone to glue the cured silicone pieces together. You'll want to make sure that: (1) for the silicone piece with the fabric - you're gluing the NON-fabric side, and (2) for the silicone piece with the 3mm acrylic molded pattern - you're gluing the side with the patterned air chamber.
- Place sandwiched silicone pieces in 150F oven for another 10 minutes
- Let cool, then insert tubing into one of the inside corners of the gripper, being mindful to make sure the tube doesn't pierce the thin wall that will inflate.
- Connect a large syringe or DC air pump to your tubing, and inflate. If gripper is not properly inflating, check for holes, and plug those holes up with more silicone.
(Right-click files below, and Save link as... to your computer)