8. Soft robotics¶

I. References & Inspiration¶

II. Introduction to Soft Robotics¶

Soft Robots are flexible, compliant systems made from materials that can bend, stretch, and deform during movement, allowing them to interact gently with their surroundings. In this context, compliance refers to the robot’s softness, its ability to bend, squish, and adapt its shape rather than remain rigid.

Actuation: Soft robots often use non traditional actuation methods. Common approaches include: Pneumatic and Hydraulic systems, where air or fluid pressure causes soft chambers to inflate or contract, producing motion. Other actuation methods involve shape-memory alloys and polymers,thermal or magnetic-responsive materials. In many cases, actuation is embedded within the structure itself, blurring the boundary between material and machine.

III. Class Experimentation¶

After getting introduced to soft robotics we carried by prototyping some through using the following techniques:

1. Molding and Casting¶

Within this experiment we used some of the already fabricated molds in the lab for testing.

Sequence:

Tools Needed

Ecoflex Silicon Rubber, Carton Cups, Stirring Sticks, Weighing Scale, Air Pump or Straw

Step 1: Design the actuator: Design a mold that includes internal air chambers (ribbed channels) and a designated inlet port for air injection, within class experimentation we used some of the previous students 3d printed molds, however in my assignment workflow we will get into more depth how I designed my mold using Rhino and Illustrator.

Step 2: Fabricate the Mold: Either 3d print the mold or laser cut it.

Step 3: Prepare the mold: Clean it, apply mold release if needed.

Step 4: Measure Ecoflex: Weigh Part A and Part B 1:1 (by weight), per the datasheet.

Step 5: Mix: Stir thoroughly (scrape sides/bottom) for each part alone and afterwards pour them on one another and mix them until the mix is uniform.

Step 6: Pour: Pour Ecoflex slowly from height in a thin stream into the mold to avoid trapping air in the channels.

Step 7: Cure: Let it cure fully (room temp cure).

Step 8: Demold: Carefully remove the soft part without tearing thin chamber walls.

Step 9: Prepare the sealing layer: Use a thin silicone sheet OR cast a flat Ecoflex layer on a smooth surface.

Step 10: Bond (seal the channels): Spread a thin fresh Ecoflex mix as “silicone glue” on the mating surfaces, Align and press together, clamp lightly, and cure again.

Step 11: Add the air inlet: Punch a small hole at the inlet point (if not molded), insert tubing and seal around it with a small amount of Ecoflex (cure).

Step 12: Test: Inject air with a syringe/pump slowly. (patch with ecoflex if needed).

Result:

Notes

The experimentation phase was challenging at the start, especially during air inlet testing. Adding too little Ecoflex while bonding the mold pieces caused a crack to form, making it necessary to remake one of the molds.

2. Heat-Pressing Vinyl with Baking Paper¶

Sequence:

Tools Needed

Vinyl Sheets, Baking Paper, Heat Press, Vinyl Cutter, Blade or Scissors, Laser Cutting Machine, Air Pump or Straw

Step 1: Prepare the design: Design the air channel pattern that will define the internal pathways of the soft robot. Cut this pattern from baking paper using laser cutter or with scissors, ensuring clean edges and continuous channels. Afterwards design the vinyl layers that will sandwich the air channel pattern in between. Don't forget to take into consideration the air inlet.

Step 2: Cut the vinyl layers: Cut two identical pieces of heat press vinyl slightly larger than the baking paper design to allow for proper sealing around the edges.

Step 3: Assemble the sandwich:Place one vinyl sheet on the heat press surface, then position the baking paper air channel design on top. Align the second vinyl sheet over it, creating a three-layer sandwich.

Step 4: Heat press the layers: Set the heat press to the appropriate temperature (150 degrees) and time (1 minute) for the vinyl material. Apply heat and pressure evenly to fuse the vinyl layers together. During pressing, the vinyl bonds everywhere except where the baking paper blocks contact between the two layers. This prevents sealing in those areas and forms hollow air channels.

Step 5: Cool and inspect: Allow the pressed piece to cool completely before handling, the remove the plastic sheets from both sides. Check that all sealed areas are fully bonded and that the air channels remain open.

Step 6: Test inflation: Gently introduce air using a pump or straw to verify that the channels inflate evenly and that there are no leaks.

Result:

IV. Assignment Workflow¶

1. The Hearts Row (Molding and Casting)¶

Conception and Design

I enjoy incorporating simple heart forms into my design experiments, so in this project I aimed to inflate a row of hearts. The process began with a 2D mold sketch in Illustrator, followed by 3D modeling in Rhino and final fabrication through 3D printing.

Slicing Setting

Open Stl. file with Ultimaker Cura.
Set Printer: Ultimaker S5.
Set Material: PLA
Make sure the model is placed flat on the build plate (Z = 0).
Adjust scale.
Adjust print settings:
Basic Settings Layer Height: 0.2 mm Wall Thickness: 1.2 mm Top/Bottom Thickness: 0.8 mm. Infill Density: 15–20% (Gyroid or Cubic infill).
Supports Generate Support: Disabled
Adhesion Build Plate Adhesion Type: Brim (8 mm) Z Hop When Retracted: Enabled — avoids hitting existing layers.
Temperature & Cooling Printing Temperature: 200 °C (PLA). Build Plate Temperature: 60 °C. Fan Speed: 100% after the first 3 layers for smooth surface finish.
Speed Print Speed: 45–55 mm/s. Wall Speed: 25 mm/s for improved accuracy. Initial Layer Speed: 10 mm/s to ensure good bed adhesion.
Retraction & Quality Retraction Distance: 6.5 mm (Bowden) or 1 mm (Direct Drive). Retraction Speed: 25 mm/s. Combing Mode: Within Infill. Enable Coasting: Optional — reduces stringing on curved surfaces.
Optional Post-Processing Support Interface Density: 100% for cleaner undersides. Ironing: Enable on top layers for smoother finish. Use Tree Supports (Experimental): Ideal for organic shapes — minimizes scarring and material use.
Click Slice and save the file.

Row of Hearts Mold by Simone Kiswani on Sketchfab

Fabrication Process
Result

Notes

During the air inlet testing. Adding too little Ecoflex while bonding the mold pieces seperated the two bonded pieces, making it necessary to remake one of the molds. (the small one)

Despite that the design was a row of hearts, when inflated they turnes=d into rather spheres.

2. Inflatable Yoke (Vinyl with Baking Paper)¶

Conception and Design

Heat pressing vinyl and baking paper was hands down my favorite technique for creating soft robots! In this experiment I aimed to create an inflatable yoke that mimics helical fiber movement. The process began with a simple sketch, followed by a more measured design developed in Illustrator from which PDF files were exported to cut both the vinyl and the baking paper.

Fabrication Process

Step 1: Cut the Vynil pieces:

Vynil Cutting Steps

Prepare design: Create a vector file (SVG/AI/PDF), outline strokes, mirror if using heat-transfer vinyl
Open CutStudio (or Illustrator + Roland plugin) and send file to cutter
Power on cutter and connect via USB
Load vinyl:

Lower lever

Insert vinyl (face up)

Align pinch rollers within white guides

Raise lever to lock

Select material type on machine (ROLL / EDGE / PIECE)
Set blade force & speed (start moderate)
Run TEST cut and adjust force if needed
Set origin using arrow keys → press ENTER
Send cut job from software
Wait for cut to finish

Step 2: Cut the baking paper pattern:

Suitable Settings for Baking Paper

 Cut; Power:25.00 - Speed:4.0 - HZ:1000

 Note: The baking paper must be firmly taped on the laser cutting bed.

Step 3: Assemble the sandwich and heat press the layers:

Result

V. Fabrication files¶

File: 3D Model Row of Hearts ↩
File: Inflatable Yoke Baking Paper 2d Pattern ↩
File: Inflatable Yoke Vinyl 2d Pattern ↩