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Soft Robotics

Past Experience + Intro

I actually did research in soft robotics when I was an engineering student. I too was new to it but it blew my mind! I didn't work with pneumatic soft robotic principles because I was designing a soft robot for handling assemblies and tasks in space. So the gripping technology was more advanced and, well, it was actuated by what's known as shape memory alloy or SMA wire, which changes shape through changes in current and/or subsequently temperature. Pneumatics mean death in space - they wouldn't survive.

But that was once upon a time ago. As Bob Dylan once said, I was older then, I'm much younger than that now.

If you're wondering what soft robotics are, let me tell you! They're robotics.. that are soft. Yes. Traditional robotics are those that work with rigid materials (aluminum, stepper motors, wires, machined parts, etc.). They also operate on an XYZ plane meaning their programmable movement is limited to X, Y, and Z directions. Soft robots are made of soft materials - silicone, rubber, biosilicone, textiles, etc. and actuated usually pneumatically which means they move by way of compressed air or fluid.

As described with the SMA wire, soft robots can be actuated in other ways - chemically, biologically, thermally, electrically, magnetically, and a combination of the previous listed - but most of the wider research out there has focused on pneumatic actuation. The other thing about soft robotics, which is both a plus and a continuing challenge, is the planes and degrees of freedom in which soft robots move and possess are infinite. They move within the XYZ planes, sure, but they're range of motion is more unpredictable and thus more difficult to program and configure practically.

SR Introduction

Soft Robotics - Brief Breakdown

SR Actuation

Soft Robotics - Actuation

Now, there's a soft robotics conference that happens every year called RoboSoft so go check it out! :)

I've explored the soft robotics world at a largely engineering perspective so I'm excited to incorporate a little more design and artistic experimentation this week.

Research + Inspiration

These were a few works that I came across that stuck out to me.

SMA Jacket Wearable

Shape Memory Alloy Soft Robotic Wearable, University of Minnesota Wearable Technology Lab

E-textiles lend themselves to soft robotics and to wearables and thrice versa (I made that up). But I really love seeing soft robotics interesecting with knitted/woven textiles.

Knitted Robotics

Textile Technology for Soft Robotic and Autonomous Garments, Vanessa Sanchez, Advanced Functional Materials

MIT Origami Gripper

MIT Origami Gripper

There's also this work done at MIT in breathable and programmable fibers.

One of our lecturers, Adriana Cabrera, also showed us some work on sustainable interactive surfaces that are are folded in origami configurations and have embedded within them shape memory alloy wire or nitinol. Really cool stuff and near and dear to my heart :)

Soft Interactive Surfaces - Adriana Cabrera's Work

Soft Interactive Surfaces, Adriana Cabrera

I've always loved these types of Elizabethan, accordion style, ruff collars. In typical fashion I love the idea of combining them with punk wear and soft robotic principles so we'll see how that goes.

The potential for soft robotics in creating a collar like this is exciting and feasible :)

Elizabethan Ruff Collars

With this, I'm going into this assignment excited and with many ideas!

Weekly Assignment
  • Document the concept, sketches, references (also to artistic and scientific articles)
  • Make a soft robotic sample, develop the pattern for the Inflatable and draw a sketch of the air flow:
    • Build a pneumatic wrist brace (basic level) or
    • Build a Soft Gripper (intermediate level) or
    • Build and document a Pneumatic, digitally controlled system, electronics schematic, electronic control and code (advanced level)
  • Design your own version of an inflatable / soft robot
  • Experiment with different materials, such as silicone, 3d printing, parchment paper, thermoadesive vynil, TPU fabrics, bioplastic, document your achievements and unexpected outcomes
  • Make a small video of your inflatable/soft robot working
  • Upload your digital design files (if any)
  • Build the electronic circuit to control your inflatable/soft robot (extra credit)
What You'll Need
  • Vinyl cutter
  • Iron
  • Heat Press
  • Digital scale
  • 3D printer / laser cutter
  • Soldering iron
  • Arduino + Arduino IDE
  • 2D Drawing Software: Inkscape, Illustrator
  • 3D Modelling Software: Fusion 360, Rhino 3D, Grasshopper, Solidworks
  • Thermoadesive vinyl
  • Parchment paper
  • Silicone Eco-flex (00-30) or you can make your own biosilicone!
  • PLA filament
  • Tubing and hand pump
  • 3V/6V Pump
  • Heat shrink tubing

Explorations

Sample Gripper

I printed a sample gripper from the Instructables I linked below under References and tested with it a bit.

Sample Soft Robot "Finger"

Sample Soft Robot "Finger" I casted with EcoFlex

3D (Not Printed) Laser Cut Molds

Well, the 3D printer dieties were not on my side this time around. All my CAD designed molds were complete and utter failures on my friend's precious Ender 3 printer. 3 TIMES I tried printing. Yes, you read that right. Anyway, I've prepared my files for lasercutting from some acrylic board and/or MDF. I did 3D print an adjustable square mold to paste on top of a flat surface to pour and cure EcoFlex into. Here they are.

I designed 2 bubble molds to laser cut - a bubble cluster and a bubble size gradient. I used Inkscape and Fusion 360 to design these.

Bubble Cluster - Laser Cut

Bubble Cluster

Bubble Gradient - Laser Cut

Bubble Gradient
  • EcoFlex in Scrap + DIY Molds

Cast Bubble Cluster Cast Bubble Gradient


I will say ever since Fabricademy started my efforts to find a stable fab lab to do my work have proven tiring and somewhat unsuccessful. I used a laser cutter at work and I'm not entirely allowed to laser cut myself. Someone at work had to laser cut these files for me which is honestly not great when you want to lasercut, refine the design, and lasercut again. Not to mention to 3D printer I borrowed from my friend is experiencing some sort of bug because, as I said earlier, my 3D molds failed 3 times and well I don't have all the time in the world.

All that to say, I did as best I could with the time and resources I currently have :,)

Heat Transfer Vinyl

I used Heat Transfer Vinyl (HTV) mainly for most of my designs.

First, I wanted to experiment a bit with a kind of fish skeleton design.

  • "Fish skeleton" Design!

"Fish Skeleton" Design


Fish Skeleton HTV Process

Fish Skeleton HTV Process

Steps to make this: 1. Make your design. Laser cut it on parchment(baking) paper or print it, trace on parchment paper, and manually cut it out. 2. Cut your desired shape on vinyl to enclose baking paper design. 3. Sandwich your baking paper design between the 2 vinyl pieces, shiny sides on the outside. 4. Use an iron or heat press to 140C for about 15 seconds. I used my old school iron that does not indicate temperature but I set it on a somewhat medium to low setting. I would press it for about 30sec to a minute to not fry the vinyl. 5. Ready to go!

I also reversed the chambers in which air flows.

I also made another origami tessellation design to experiment with. Because of my lack of stable laser cutter access, I did not get to lasercut this or laser weld it onto TPU. Maybe that'll change in the next day or 2.

  • Waterbomb Design!

Waterbomb Design


TPU + 3D Printed Mold

I thought of a cool idea. Of course at the time when I'm winding this project down. I wanted to design and 3D print another design (should luck have been on my side), cast it with EcoFlex, and sandwich the design between 2 pieces of fabric. I thought if I applied aire through the chambers, it may compress the fabric in the right way to create the ruff/pleated collar I envisioned. I did not have time for this so I decided to cast EcoFlex in the reference grip finger I printed as a sample and attach it to a piece of organza.

Fabric + EcoFlex Mold

It didn't work but there's promise here. I can feel it.

Soft Ruff Collar on HTV + Circuit for Arduino-Controlled Air Pump

I attempted to make the ruff collar by folding the HTV but doing this with my iron did not work. My iron may not have applied heat evenly across the HTV sandwiched together. Maybe I'll have better luck with more time. Thank you, Fabricademy alumnus (Charlotte Bracho)[https://class.textile-academy.org/2022/charlotte-bracho/X-Research/week12/] for your documentation on this! I was unable to execute it here. I mean, I was somewhat successful. The first design I fried with an iron that was too hot. The second design sort of worked but because of my uneven heat iron possibly, the vinyl did not adhere quite well to the other vinyl piece so the air chambers did not quite form well. Air would escape.

Failed Vinyl Ruffs

Somewhat Fails?

I made 2 more off the cuff designs for what a ruff collar could look like - 2 sheets of HTV sandwiched together with a kind of sine wave in the middle that would compress and act like a ribbon, creating pleats in the vinyl.

Paper Circuit for Arduino Controlled Air Pump

9V Circuit for Air Pump

The paper circuit above is to apply 9V to a 3.3V air pump. I didn't have a battery holder to hold 6V worth of batteries. I'm pretty sure this air pump can withstand 3.3-6V, right? Anyway, make sure of this on the air pump datasheet. Now, 9V would bust this air pump for sure. But the transistor helps with this temporarily. At least enough to demo this. If you do this, I would make sure you have the correct transistors and/or resistors in your circuit.

NOTE: CAUTION. Not all transistor/MOSFETs are the same. If your circuit isn't working, make sure the connections on the left, middle, and right pins of your MOSFET are wired correctly. And also note that the diode you have may be unidirectional which means current flows in one direction. There is a right way your diode has to be oriented if the latter is the case.

Then I made a circuit for the correct 3.3V to be applied to the air pump. Not very strong so be sure to get uh.. a stronger air pump. My suggestion.

3.3V Arduino Circuit

3.3V Circuit for Air Pump

Code for Pneumatic Actuation

This is the code I used. Thank you to my instructor for sharing it in her documentation. 

int air=9; // signal pin in Arduino
// the setup function runs once when you press reset or power the board
void setup() {
  // initialize analog pin "air" as an output.
  pinMode(air, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(air, HIGH);   // turn the air pump on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(air, LOW);    // turn the air pump off by making the voltage LOW
  delay(1000);                       // wait for a second
}

References

Some Files