12. Soft robotics¶
It is becoming more clear to me that Fabricademy is also a materials research study program. This aspect of the program...where we explore the fabrication and manipulation of different materials is fascinating to me. This week, we consider robotics that would engage with the body in a gentle and pleasing way. Soft Robotics is discussed in contrast to the Hard Robotics that is typically considered synonymous with the word Robotics. In the talk, The Incredible Potential of Flexible Soft Robots Giada Gerboni does an incredible job of laying out the meaning and possibilities.
The posited question...do all robots have to be heavy, hard...and potentially dangerous to the fragile human body? For example, servo motors common to robotic construction can produced a significant amounts of torque and very fast motion. If not properly tuned...a robotic armature constructed of multiple servos (and contained in rigid frame to enhance precision and repeatability) can achieve frighteningly speedy motion. A body in the way of that motion...would surely suffer injury.
So in this week, we are asked to explore the construction of robots are soft to the touch...and maybe less dangerous. Robots that are friendly to the human body. Maybe even robots that are worn.
Bend it. Squish it. Stretch it. (...sounds like the beginning of a Daft Punk song)
Inspiration & Research¶
aidesign.png¶
Conincidentally, I discovered the channel aidesign.png on Instagram this week...self-described as "artificial intelligence generated concepts {biomimicry outdoor fashion & weird design}". Many of their high-fashion garments featured puffy, inflated shapes that I found incredibly creative and interesting...with a hint of utility...and was in alignment in aesthetic concept with the topic of this week's assignment.
Montserrat Ciges¶
Also coincidetally, Fabricademy alum...Montse Ciges...visited my lab, where she gave a brief lecture. Soft Robotics were featured in her talk...along with reconstructions of Squid and Octopus chromatophores and liquid actuated inflatable cells. Needless to say...Montse's work is exceptional and I could see the potential of soft robotics in the context of Fabricademy.
Octopus Color Transformation - National Geographics
- Expand or contract millions of pigment cells...Chromatophores...in the skin to change colors
- Tiny muscles in the skin can be manipulated to change skin texture
* [Montserrat Ciges Final Project](https://class.textile-academy.org/2019/Montserrat/project.html)
* [Montserrat Ciges Soft Robotics](https://class.textile-academy.org/2019/Montserrat/week11.html)
Baymax¶
And of course, can't think about Soft Robotics without thinking of this guy...
It is easy to dismiss Baymax as a childish cartoon character, but I found him rather inspirational (the movie was about a maker lab afterall...it would be impossible for me not to find romance and resonance with it!). So, Baymax is hard robotics wrapped in an inflatable, warm & cuddly skin. The 'Softness' is a mitigant...between severe technology and the humans Baymax is designed to interact with and serve. I believe that the resulting design is exceptionally successful.
Dune > Fremen Still Suit¶
Then lastly, I recalled a wearable from a favorite science fiction story...the Fremen Suit from the story Dune. This unique suit is water reclaimation and processing device powered by human motion...designed to assist the wearer to survive the harsh conditions of a desert planet. Constructed of water filled cells connected with tubes and held together with a soft and elastic armature...the Fremen Suit is perfect soft robotic factory with unmatched aesthetics and exceptional utility.
Wet Matter/Harvard Design Magazine
Wing Suit¶
From the desert to the air, the Wing Suit is an extreme sport device that takes advantage of inflation to allow for exhilerating human flight.
It is hard for me to watch videos of the Wing Suit in action and not be simultaneously excited and terrified.
## Spider Hydraulics
Spider legs don't have muscles...they use hydrolics to move their legs. Air into dead spider legs allow gripping action. Dead spiders into mechanical grippers. Scientists Are Turning Dead Spiders Into 'Necrobots'
Assignment¶
Soft Robotics > Gripper¶
Attempt 1¶
My initial attempts at using silicone to make soft robotics was pretty much a disaster.
I didn't use Smooth-On Ecoflex. I didn't have it and it was expensive. I chose to look for a locally (Japan) made alternative. I purchased a liquid silicone rubber called Silopren...and the resulting casts were problematic. Silopren consists of 2 liquids...the primary rubber silicone and a curing accelerant...mixed on a 100 to 1 ratio.
Looking online for inspiration, I found some some pre-modeled, 3D printable, soft robotic gripper casting molds. I printed it out using PLA filament.
Silopren was mixed and poured into the mold...and left to cure overnight. But demolding proved VERY difficult. Silopren cures rather hard...with a texture of semi-stiff rubber. Removing the cast from the mold resulted in both the mold and cast becoming broken.
Attempt 2¶
I thought that perhaps Silopren could be made to work if the mold was wider...so I modeled a mold in TinkerCAD.
And I 3D printed it.
It significanly wider than the thingiverse model and I hoped that it would make demolding the cast silicone easier.
Unfortunately, it didn't go well and the cast failed again.
Silopren is not a good option.
Fabrication Files¶
Soft Gripper Model - Outer Mold
Soft Gripper Model - Inner Mold
Soft Robotics > Tartigrade¶
A Fablab Kamakura, Fabacademy student Kat working on her Wildcard Week project > Soft Robotics...came to my lab with Smooth ON Ecoflex and Mold Star Fast
...and we worked together on creating silicone Soft Robots.
I downloaded 3D printable molds from the Fabacademy student Adrian Torres Wildcard Week documentation.
We followed the instructions on Adrian's page and casted using both Ecoflex and Mold Star.
Result
The Mold Star silicone is very similar to Silopren...and is too dense and resistant to stretching and inflation. When air is pumped into the mold...the seams failed...and air escaped.
The Ecoflex silicone on the other hand...ended up working VERY well (once we created a proper cast).
Inflatables > Heat Transfer Vinyl¶
Initially frustrated with my silicone casts with Silopren...I gave Heat Transfer Vinyl (HTV) Inflatables a try. It proved to be so much fun.
The procedure was simple...
-
Hand draw up a shape with pencil on a sheet of ordinary A4 paper that has been folded in half...ensuring to draw a channel to insert the inflation pump and one or multiple inflation chambers connected by narrow inflation pathways.
-
Cut out the shape out of the folded paper using scissors...resulting in 2 identical cutouts that should be stacked one on top of the other.
-
Cut 2 pieces of HTV.
-
Sandwich the stacked paper shapes between the 2 pieces of HTV...making sure that the shiny side of the HTV is not facing the paper shapes.
-
Put another sheet of A4 paper over the HTV/Paper Shape sandwich...and use a hot clothes iron to melt the glue side of the HTV together...trapping the paper shapes inside.
-
Trim the HTV so that it takes on the shape of the paper shapes inside...but leave a border of around 5mm. Make sure that the top and bottom HTV layers at this 5mm are properly adhered to one another (no air gaps)...or run the iron over it one more time.
-
Insert the pump into the insertion channel of the inflatable and pump air in between the 2 pieces of paper trapped inside.
The Snow Tree shape contracts in length when inflated...could be used as a linear actuator to pull something
The Diamond Shape doesn't do anything particularly interesting
The Gekko Foot behaves almost like a gripper when inflated...each one of its toes bending towards the center
Here is the SVG of the Gekko's Foot (all other shapes were just hand drawn)...
Obviously my attempt at inflatables was very amateurish. More research should be conducted to see how different shapes could create motion that is more predictable and useful.
Class Notes¶
Lecture by Lily Chambers & Adriana Cabrera
Soft Robots = systems that are compliant and flexible, have a feedback sensory and control system
Soft Actuators = systems that are compliant and flexible. Can be used for shape changes, joining and locomotion
Directional control using multiple air modules...each with different amount of inflation.
An imbedded origami structure in the air chamber...to control the contracted shape of the air bladder.
Actuation Medium:
- Air/Gas
- Liquid
All mediums will expand in heat and contract in cold...to varying amounts. Expansion and contraction can also occur through 'State Change'...from gas to liquid and vice versa
Nylon Fishing Line & Nylon Sewing Thread
When twisted...the nylon takes on Artificial Muscle properties...expanding and contracting when cooled (with air) or heated (with electricity). This material is fascinating!! And gives some justifications for plastic.
Thermo-actuated Artificial Muscle: Nylon Fishing Line and Sewing Thread
Artificial Muscle from Fishing Line and Sewing Thread
Fishing Line Artificial Muscle
Power Fabric from Fishing Line Artificial Muscle
High Performance Robotic Muscles form Conductive Nylon Sewing Thread
How to Make Cavatappi Artificial Muscle
- Soft PVC (Tygon) Tube: inner dia 1/16", outer dia 1/8"
- Nylon monofilament for fabrication..0.03" dia (0.8mm)...3x longer than PVC tube
- Mandrel 1.0mm dia
- Mineral Oil...PVC tube lubrication for monofilament insertion
Woven into fabric
Dielectric Elastomer
The Basics of Dielectric Elastomer
- carbon grease and rubber block
- parallel plate capacitor...can function as strain sensor
Dielectric Elastomer Actuator - Opensoftmachines
- 5.5 kV of voltage required
Conductive Thread by Adafruit
- Stainless Steel yarn to convert knited glove tips to be able to activate mobile phone screens
- Silver-plated nylon thread will eventually tarnish (oxidize) and stop working
- Conductive threads are like uninsulated wire
- Running stitch for conductive thread traces...clear nail polish on tag-ends to seal
- Clear nail-polish as a sealant over exposed electronic boards...mitigate short-circuits
- Conductive thread not a good option for power and ground wires where many high electricity draw components (neopixels) are connected
- Zipper Switch
Soft Robotics Applications
- Soft Mechanisms & Motion Systems
- Thermoregulation
- Sensory interface
- Medical and Therapeutic
Form + Acuation + Sensing + Body
Paper Inflatable Bladder
Pneumatic Shape/Structure Manipulation
Pneumatic Hinges
Heat Sealing Heat Transfer Sheets
Baking Paper
Lasercut Mold
