8. Soft robotics

Research & Understanding

Basic concepts

New week, new topic for me. This class focused on soft robotics, a field of robotics inspired by nature and living organisms. Unlike traditional rigid robots made of metal and hard joints, soft robots are made of flexible and elastic materials that can bend, stretch, and move more like living bodies.

Soft actuators, sensors and grippers enable movement and interaction in soft robotics: actuators create motion, sensors provide feedback and grippers allow safe object handling.

References & Inspiration

Active Textile by Suzumori Endo Lab
A soft robotic textile made of thin artificial muscles and strings that bends and moves when activated, showing how robots can be woven into flexible materials.

SONŌ – Mads Bering Christiansen & Jonas Jørgensen
A soft robotic entity that moves and produces sound in real time, interacting with its surroundings through its material deformations and generated audio.

Exo‑biote – Jonathan Pêpe
A soft robotic installation featuring hybrid inflatable sculptures that swell and move with air, creating the impression of breathing forms.

Credit: Jonathan Pêpe

Fabricademy Alumni

• On her page, Alessia Pasquini from TextileLab Amsterdam clearly explains how to test vinyl materials and I was fascinated by the motifs she created using the TPU laser welding technique.

Credit: Alessia Pasquini

• In “UNFLATABLES”, Saskia Helinska explores soft-robotic inflatables for wearables and e-textiles, focusing on material-driven actuators. The project highlights the difference between visual and touch-based interaction.

Screenshot from Dr. Lily Chambers and Adriana Cabrera lecture

Nuragic Sardinian symbols

• The Pintadera: an ancient terracotta tool used during the Nuragic era to decorate and “brand” bread. A Sardinian bank later adopted the pintadera as its symbol and it is also used today as a decorative motif for silver jewellery.
  

• The ‘Dea Madre di Porto Ferro’: discovered near Alghero, this figurine depicts a standing nude female and represents an icon of Sardinian prehistory. The original was carved in stone during the Neolithic era, but today the figure is often reinterpreted in silver jewellery.
  

Credits to Pinterest: 1 & 2

Results

This weekly assignments required to:

• Make a soft robotic sample by designing an inflatable pattern and sketching the airflow.
  

• Experiment with different materials, such as silicone, parchment paper and thermoadesive vynil.

As outputs, I worked on inflatable actuators and casting technique with silicone.

Process and workflow

For personal reasons, I was able to work in the lab for only two days, so I completed part of the assignments once back in the Lyon lab, and there is still more to experiment with.

Inflatable actuators: baking paper and thermo vinyl

To create them, I used only two materials: baking paper and thermo vinyl, plus a pump to inflate (or just my breath). I followed this tutorial by Adriana Cabrera and used her slides as a reference for the building process.

Credit to Adriana Cabrera

Process I followed

1. Draw a design on baking paper. The drawn part is the one that will inflate.
   

2. Cut two equal, slightly larger pieces of vinyl to enclose the design.
   

3. Place the baking paper with your design between the two vinyl sheets, making sure the shiny sides face outward. Remember to include a channel to blow air.
   

4. Use an iron or a heat press to seal the three layers together.
   

5. Once cooled, peel off the protective film.
   

6. Insert the pump in the channel and inflate your element.
   

I decided to reproduce the two Sardinian elements shown in the References & Inspiration.

After cutting and testing the two vinyl pieces, I realized they were not heat-sensitive and therefore unsuitable for the experiment, although I appreciated their shiny, jewel-like appearance.

I tested the shapes using heat-sensitive material and designed minimal cuts to maximize the available surface. The experiment was successful.

Casting: silicone and molds

Diana and I experimented with soft robotics using silicone casting, creating inflatable soft actuators that expand and deform when filled with air. We also explored a gripper variation by integrating textile elements into the silicone structure to improve grip.

We used 3D-printed molds available in the lab and followed Adriana Cabrera's tutorial for the silicone recipe. Each actuator is made from two mold halves joined together, and secondary molds like embroidery hoops were used to create additional matching pieces.

The main part of the recipe is the silicone. Each silicone product is a dual-component system: Component A (base) + Component B (catalyst/curing agent), typically mixed with a 50:50 ratio but refer to the product’s technical sheet.

In our lab we have three types of silicone and chose Ecoflex 00-30 (Smooth-On) as faster to dry and easy to mix. It is important not to mix silicones from different brands, as incompatibilities between formulations can prevent proper curing.

Silicone options and their properties

• R PRO 30 (Reschimica): : 1:1 mix ratio, 45 min pot life, 3 h cure, yellow color.

• RTV 181 (Esprit Composite): 2–5% catalyst, 24 h cure, heat resistant up to 180 °C, white color.

• Ecoflex 00-30 (Smooth-On): 1:1 mix ratio, soft and transparent, cures in 4 h (45 min pot life).

Three mold configurations were created: standard, with pigment, and with textile (mesh) to influence shape and simulate gripper-like movement.

ingredientstoolssilicone molds recipe

* Silicone (Ecoflex 00-30 in our case)
* Anti-Stick spray (e.g. CoolSlip)
* Pigments (optional)
* A piece of mesh fabric (optional)

* A precision balance
* A spatula or mixting stick
* 3D molds
* Mixing/dosing containers
* Gloves (we forgot to use them, but luckily the silicone we used was harmless)

* Weigh 50 g of Part A and 50 g of Part B of your silicone. Then mix them gently until the color and texture are uniform. Avoid introducing air bubbles.

* Spray the anti-stick spray inside the mold to prevent adhesion and facilitate demolding.

* Pour the mixture into your molds and remove bubbles with a mixing stick.

* Let the silicone cure according to the product instructions. To speed up drying, you can use an oven or a dehydrator set at a low temperature (around 40–50 °C), making sure not to overheat.

* Adding pigments (optional): If you want to color the silicone, mix up to 2% pigment (relative to the total weight of A + B). Add the pigment first to one component (e.g. Part A), mix well, then add Part B and mix gently.

• Adding pigments (optional): If you want to color the silicone, mix up to 2% pigment (relative to the total weight of A + B). Add the pigment first to one component (e.g. Part A), mix well, then add Part B and mix gently.

• Adding fabric (optional): Use your smooth mold (like the closing part), pour a first thin layer of silicone into the mold. Place the fabric on top and cover it with a second layer of silicone. The embedded fabric enhances flexibility and control over the silicone’s movement and behavior.
  

A speeded video showing the process to prepare the molds.

Even after waiting over 4 hours and using a dehydrator, some molds took several days to fully cure. In some cases, like the one containing a mesh, they did not dry at all.

Controlling the components with Arduino UNO

In this part, I explored the possibility of inflating the silicone components created earlier using an air pump controlled by an Arduino Uno. I replicated the configuration developed by Louise Massacrier at Le Textile Lab, based on a circuit created during Wearable Week.

The circuit included:
- a transistor: acts as an electronic switch between the Arduino and the air pump. When the Arduino sends a signal, it allows current to flow and powers the pump.
- a resistor: placed at the base to limit the current into the transistor.
- a diode: added across the pump to protect the circuit from any reverse voltage spikes caused by the motor’s inductance.

Credit to Louise Massacrier

Configuration tested in the lab

With Capucine, I ran a first test using elements already available in the lab, while waiting for the molds to dry. Once the Arduino code was running and the circuit connected, the pump made a small noise and inflated the element.

Unfortunately, the tests with our molds did not work as expected: some had holes, inflated irregularly or were too wet to be tested.

Credit to Diana Castillo

What's Next: more to explore

I would like to retest the casting technique using bio-silicone and a mold of my own design. I plan to experiment with an alginate mixture, inspired by Isobel Leonard’s work, since the Fabricademy recipe is gelatin-based and I am more interested in plant-based alternatives.

Wool application: I am also exploring ways to integrate wool into the experiments. Capucine suggested creating a 3D felted shape that follows the form of the soft actuator and acts as a decorative outer cushion. This was scheduled for Friday, when I couldn’t be in the lab, but I look forward to trying it soon. As a reference, below a video Diana recorded.

Credit to Diana Castillo

Laser Welding: I’m intrigued by the tactile quality and flexibility of this technique, as demonstrated in Alessia Pasquini’s work above. The material used is TPU, which wasn’t available in the lab, and since it is plastic, I would prefer to explore more natural alternatives.

Update: mold design

In January, once back from the break, I found some time to design and print my own mold, as I hadn’t been able to cover this part during Phase 1 of the program.

For the material, I selected a leftover plexiglass panel (cast acrylic, to be precise) suitable for laser cutting.

The mold is composed of several pieces, which are then glued together with acrylic adhesive to form Mold A and Mold B, with Mold B to be added on top.

For Mold A, I designed three elements:

• a base
  
• a frame, which keeps the silicone in place while pouring, preventing any overflow
  
• a middle insert with a line design (I printed two copies just in case).

For Mold B, I only needed to replicate the base and the frame.

I tried to optimize the use of the material as much as possible, but later realized I had created some extra parts that can still be used for future projects.

Mold PDF version

I printed the design following the settings below, and it took less than 10 minutes:

Power	Speed
100.00	2.00

The next step will be to complete the silicone casting and test the resulting molds.

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Images: Martina Muroni unless otherwise stated.

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Tools & Resources

• Arduino UNO
• Arduino IDE
• Lecture resources
• Previous years tutorials

Arduino code

/int motor = 3;

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(motor, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(motor, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(3000);                       // wait for a second
  digitalWrite(motor, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}