8. Soft robotics¶

Inspiration¶

Adi Meyer, Sirou Peng, and Silvia Rueda explore emotion-driven interaction through soft robotic silicone masks, where air pressure and movement translate human feelings into sculptural facial motion.
Sheguang Hu pushes the boundaries of wearable form with architectural, body-morphing silhouettes that evoke the mechanical expressiveness of kinetic or pneumatic motion.
HARRI (Harikrishnan) uses inflatable latex structures to exaggerate proportion and volume, transforming the body into a soft robotic vessel of air and playfulness.
Issey Miyake pioneers fabric memory and pleated motion, where material behaviour itself becomes a kind of gentle, programmable movement.
Comme des Garçons (Rei Kawakubo) sculpts organic, bulging forms that challenge anatomy-anticipating the tactile, inflated morphologies now explored in soft robotics.

More Inspo Tajah Ellis ¶

Research¶

Alginate inflatable balls by Hala Amer ¶

This demonstrates how air, pressure, and flexible materials can act as a new kind of digital fabric - Alignate, animating garments and accessories with gentle, organic motion.

It shows experimenting with inflatable silicone structures, textile actuators, and pneumatic chambers that expand, contract, and pulse, almost as if the clothing were breathing or responding emotionally. The motion isn’t mechanical or rigid; it’s soft, lifelike, and expressive, blurring the boundary between body and machine.

Materials¶

Toolbox¶

Category	Items
Pressing & Cutting	Heat press vinyl • Baking paper • Scissors
Assembly & Sealing	PTU (polyurethane tubing) • Straws • Air compressor • Inflation pump
Casting & Forming	Silicone • Gelatine • Moulds

Usage Notes
- Baking paper prevents vinyl or silicone from sticking during heat sealing.
- Air compressor or pump used for inflatables and pneumatic tests.
- Silicone and gelatine serve as base materials for moulding or flexible structures.
- Keep scissors sharp and clean for precision cuts.

Process:¶

Make design on baking paper (ensure you leave a blow opening) and create a vinyl outer design, making sure to cover the baking paper (any exposed baking paper will create holes).
Place baking paper design in between vinyl (both shiny sides facing out and matt sides in) &wrap in baking paper
Put in heat press (285 degrees C for 22 seconds)
Take out + peel off the plastic protective layer carefully & ready to inflate!

Prototypes:¶

Prototypes in motion:¶

Elephant trunk¶

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Venus fly trap¶

A Pneumatic linear actuator¶

The Tri-Spiral¶

THE FISH¶

Fails:¶

This one failed as the TPU layer was a little too small, so there were gaps & the baking paper was exposed. Extra TPU to cover the gaps did not work.

Laser Cutting Setup¶

Dimensions for TPU and baking paper pieces used in the heat-press inflatables.

Material	Dimensions (mm)	Notes
TPU sheet	160.0 × 25.0	Main inflatable strip for sealing and air channels.
Baking paper	100.0 × 20.0	Heat barrier between TPU layers during pressing.

TPU piece is longer and wider than the baking paper.
Baking paper sits inside the TPU area to protect from sticking and burning.
Use these as your laser-cut sizes before pressing.

Moulds - Soft Robotics¶

Soft robotics prototypes often rely on silicone or gelatine moulds to create inflatable structures that can expand, contract, or bend with controlled air flow.
These moulds are typically cast in two layers: a flexible membrane and a structural backing.

Silicone Recipe¶

Ingredients
- Silicone, Part A: Part B
- 1:1 ratio
- Optional: a few drops of pigment in either part A or part B

Method
1. Prepare the mould - clean and dry the cavity (3D-printed or laser-cut).
2. Mix the silicone - combine Part A and Part B thoroughly for 2–3 minutes, avoiding bubbles.
3. Degas (optional) - place in vacuum chamber for 1–2 minutes if available. If not an air presser will do. 4. Pour slowly into the mould and tap gently to release trapped air.
5. Cure at room temperature for ~4 hours.
6. Demould carefully - flex the sides to release without tearing the thin walls.
7. Optionally, bond two cured halves with a thin layer of uncured silicone to form inflatable chambers.

Silicone mould inflatable:¶

Gelatine Recipe (Bio-soft Robotics Alternative) go to Maddie Olsen's method ¶

Ingredients
- 100 grams Gelatin
- 100 grams Glycerine
- 500 ml water
- Optional: natural dye or food colouring

Method
1. Hydrate the gelatine.
2. Heat gently (≈ 60–70 °C) until the mixture is smooth - do not boil.
3. Add glycerine and stir until fully dissolved.
4. Pour into your mould (acrylic, silicone, or 3D-printed).
5. Let it set at room temperature for 24 hours, then demould slowly.
6. For longer lifespan, dehydrate slightly in a dry cabinet, remove air bubbles or use a thin beeswax coating.

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Notes & Tips¶

Gelatine moulds are ideal for bio-fabrication or biodegradable soft robots.
Silicone moulds are more durable and can be connected to pneumatic systems (syringe or air pump).
Always design with chamber thickness between 1–3 mm for flexibility and control.
Seal seams with thin layers of silicone or heat-press TPU film for airtightness.

Alginate Bio-Inflatable Balls aka JELLYFISH CELLS with Tajah Ellis ¶

Alginate inflatables combine biopolymer casting with soft-robotic air channels.
Unique/Lab alginate forms flexible membranes when cross-linked with calcium ions - perfect for lightweight, biodegradable inflatables.

The process¶

Recipe - Alginate Mix¶

Ingredients
- 400 ml Water
- 12g Alginate powder
- 20ml Glycerine (adds elasticity)
- Optional: Natural dye or food colouring

Method
1. Blend alginate powder gradually into cold water using a hand blender.
- Mix until fully dissolved and slightly viscous.
2. Add glycerine and mix again until uniform.
3. (Optional) Warm gently (≈ 40 °C) to dissolve gelatine if using.
4. Let rest to remove bubbles, preferably for a day.
5. Pour into an embroidered loop, for shape.

Cross-linking Bath¶

Solution
- Water
- Calcium Chloride (CaCl₂)
- 1:3 ratio

Steps
1. Prepare the bath in a separate container with a sprayer.
2. Gently submerge the filled moulds or extrude alginate drops directly into the bath.
3. Allow to set for 1 minute until the surface becomes firm.
4. Rinse briefly with clean water to remove excess calcium.

Inflation & Soft-Robotic Setup¶

Materials
- Air compressor
- Syringe pump
- Poke stick

Method
1. Once the alginate ball has set, insert tubing before complete hardening.
2. Seal the entry point with a drop of fresh alginate mix.
3. Connect to an inflation pump and slowly add air.
4. Observe membrane expansion - thin layers (≈ 1 mm) yield a soft, organic inflation.
5. For reusability, store hydrated in sealed containers or coat with glycerine film.

Notes¶

Adding more glycerine increases flexibility but reduces structural strength.
If the mix is too watery, reheat gently and add a little extra alginate (≈ 1 g per 50 ml).
Gelatine addition improves elasticity and prevents cracking on drying.
Avoid over-inflation - bio-membranes rupture faster than silicone.

What Went Wrong¶

Issue	Observation	Likely Cause	Adjustment
Mixture too watery	The alginate didn’t hold shape and tore easily when inflating.	Too much water / too little alginate.	Use 6 g alginate per 200 ml of water. Let it rest longer to thicken.
Holes forming on surface	Small air pockets burst during curing.	Poured too quickly or trapped air in mix.	Mix slowly, rest 30 minutes, tap moulds to release bubbles.
Weak or sticky film	Membrane stayed tacky after drying.	Incomplete cross-linking or too much glycerine.	Reduce glycerine slightly; extend CaCl₂ bath time.
Broke on inflation	Burst before expanding properly.	Walls too thin or edges not sealed.	Use thicker layer or add a second coating of alginate.
Uneven curing	One side firmer than the other.	Uneven contact with calcium bath.	Rotate or submerge evenly during cross-linking.

Key takeaway: The alginate ratio must be exact. Allow the mixture to rest for a few minutes to thicken, and always test a small batch before full casting.

Hydrogels¶

Hydrogels are networks of water-holding polymers - materials that can absorb and retain large amounts of water while staying soft and flexible.
They behave like a cross between a liquid and a solid, which makes them perfect for soft-robotic membranes, sensors, and bio-materials. Hydro gels are small but will expand and push against the walls in water. They were swirling and push against each other, which will cause a motion.

What They Are Made Of¶

Most hydrogels are based on natural or synthetic polymers that form cross-links - tiny bridges that trap water inside a three-dimensional mesh.

References¶

Hala Amer - bio-material soft structures
Fab Lab Material Recipes