8. Soft robotics¶

✂︎Research & Ideation✂︎¶

Okay, I know I say this every week but I am SO SO SO excited for soft robotics week! A major interest of mine is kinetic sculpture and biomimetic movement. There are so many exciting projects in the world of soft robotics that inspired me to start my fabricademy journey. This week I really want to get my head around the basics of creating movement so that I can start to go deeper into how you can make more complex, organic movements.

My main interests for this week are:

Biomimetic movement (informed by our amazing lecture from Lily Chamber and Adrianna Cabrera).
Hard and Soft Connections (How the interplay of different materials can increase or constrain the drama of a movement?)
Folding and Gathering ( How this can turn simple actuations into more complex movements?)

I'm hoping this week will give me building blocks for lots and lots of projects. I have included references below of other practitioners who explore these questions in their work:

U-Ram Chloe's kinetic sculptures inspire me for their delicate, weightless animation. I think this is largely owed to the soft materials he incorperates that allow many of his artworks to move elegantly and organically in contrast to the metallic sheen of other parts.
Casey Curran's work always comes up for me. He uses gears, cranks, pullies, fishing line and other simple mechanism to animate complex frameworks and upscale them to full room installations. Again, the naturalness of the movement he is able to create using paper, dura lar and fabrics is mesmerizing to me.
Cyerce elegans. For this week, I am finding lots of inspiration in gelatinouis and transparent sea slugs, in their form and movement. When I first saw examples of silicon grippers, these critter immediately came to mind.
Matthew Szosz inflatables are made of glass, cast in an instantanious process and capturing the cast of the inflated movement forever. The forms he achieves are really nice
Mikela Holmes' Blossoming Flowers, I really like the combination of 3D printing TPU and mechanical actuation. I think you can create very natural movements.
Unknown Source for Image

I had an absolute wealth of inspiration for this week. I am interested in how folding, gathering and joints can be used to create more complex movements with soft robotics. Particularly movements that unfurl, twist, open and close.

Studio Drift's Shylights interest me in the way they use the folding and gathering of fabric to create dance like movements:

Kirigami (incorperating folds and cuts) is something I am thinking a lot about and how in combination with inflatables and other actuation you could create very complex patterns and movements:

Fluid driven origami movement is also SO COOL:

✙Documentation Workflow✙¶

Assignment Criteria: Week 8

Document the concept, sketches, references also to artistic and scientific publications
Learn the fabrication of soft actuators, sensors and grippers using novel materials, artificial muscles and performative locomotion design
Make a soft robotic sample, develop the pattern for the Inflatable and draw a sketch of the air flow
Develop a pneumatic wrist brace (basic level) or
Develop a Soft Gripper (intermediate level) or
Built a Pneumatic, digitally controlled system (advanced level)
Experiment with different materials, such as silicones, 3d printing, parchment paper, thermoadesive vynil, bioplastic , document your achievements and unexpected outcomes
Upload a small video of your inflatable working
EXTRA POINT Integrate it into a project

Top Tip!!!

Really consider scale in your designs! Does it fit in the heat press in one go? How hard will it be to inflate? Are your air channels big enough?

Oh and also- if you are asthmatic... bring your inhaler this week! :)

Inspiration!!!

Monteserrat Ciges. I love her final project and the way it considers inspiration from nature alongside contexts that affect humans in the digital age in terms of self-transformation. Plus! the design is gorgeous!
Amanda Jarvis. I think her design is so cool. The way she was able to disguise the electronics and inflatable structure so that the blooming movement was really elegant and foregrounded is very impressive.
Viviane Labelle. I love how this project developed throughout the assignment and i think the polarized affect is magical.
Saskia Helinska experimented with so much and the documentation is just stella for explaining the basics.

Tools¶

GENERAL:

Air pump
Straws

HEAT PRESS VINYL:

Baking Paper
Vinyl Sheets
Scissors
Heat Press
Laser Cutter
Cricut Machine
Rhino
Adobe Illustrator

TPU WELDING

TPU
Laser Cutter
Rhino
Adobe Illustrator

SILICON CASTING

Eco Flex Silicon Rubber
Acrylic Sheet
Laser cutter
Acryclic Glue
Cups and stirring utensils
Weighing Scale

BIO SILICION CASTING

Gelatin
Glycerin
Water
Acrylic Sheet
Laser cutter
Acryclic Glue
Cups and stirring utensils
Weighing Scale

ALGINATE INFLATABLES

Alginate
Water
Calcium Chloride
One way valve air pump
Plastic Tubing
Syringe
Embroidery hoop
Permeable Fabric

♒︎Heat Press Vinyl♒︎¶

We started the week getting to know the basics with good old fashioned paper and scissors. Heat press vinyls are by far the fastest way to create an inflatable and to learn how to design air channels that will actuate a specific movement.

The basic process is sandwiching a baking paper air channel design in between two pieces of vinyl. When you heat press the 3 layers together. The vinyl will stick in places where the baking paper isn't blocking the touch of the two layers. This creates a gap for the air to pass through.

Illustration by Adriana Cabrera from her Introduction to inflatables lecture

Top: Saskia Helinska, Soft Robotics Assignment. Bottom: Asli Aksan, Soft Robotics Assignment, experiments with bending and twisting

Hinge Mechanisms:

To get our heads around how we can affect the movement of our inflatables using air channel design we looked at lots of examples. Asli Aksan's experiments in bending and twisting movements from last year were particularly helpful. We were able to see how you can use diamond shapes to create joints:

The thinner the diamond the more the hinge will bend. The longer the diamond, the longer the joint will be but the bend will be less. The rotation of the diamond will determine the direction of the bend. A great article that explains this is "AeroMorph- Heat-sealing Inflatable Shape-change Materials for Interaction Design" is linked below ¹.

Illustration from "aeroMorph- Heat-sealing Inflatable Shape-change Materials for Interaction Design" by Jifei Ou, Mélina Skouras, Nikolaos Vlavianos, Felix Heibeck, Chin-Yi Cheng, Jannik Peters and Hiroshi Ishii

It is also important to consider while you design:

Where will the air enter your inflatable? Have you left a hole for the air pump?
Where will the air flow? Where should be sealed?
Are the air channels wide enough to have a good airflow throughout your inflatable?
Have you left a big enough border of vinyl so that it can be stuck well and hold?

I wanted to start by seeing if I could make something curl in and out again. I wanted to make a flower shape.

I decided to use each "petal" to test a different air channel design to see which would curl up the best. I varied the lengths of each air channel and how many there were.

Heat Press settings:

We set the heat press to 285 Farenheit and pressed the layers for 22 seconds.

Make sure to have a layer of baking paper on the bottom and top of your sandwich, inbetween your inflatable and the heat press bed to avoid everything getting very sticky!

Results:

It is clear from both of these videos that no. 3 created the most curl. I think the gradually increasing length of the channels helped the upward bend of the vinyl. I think if I put the channels closer together and thinner the curl would be tighter.

Alginate Inflatables¶

Asli Aksan had seen this project "Re-humanising Sensing" by Hala Amer in which they made inflatables from Alginate. Having loved playing with the alginate during biomaterials week and with lots left over, we decided to give it a try.

Image from Hala Amer's Fabricademy thesis

Amer helpfully uploaded a full tutorial to her fabricademy page which we were able to adapt and experiment with given the resources we had available to us.

PROCESS:

Our experiment differs from Hala Amer's in the sense that we use a cold process for making the Alginate rather than a hot one. This allows us to do two things:

The cold process Alginate can be stored and used again at a later date. This allowed us to make our alginate inflatables over the course of a few days.
We were able to make an opaque mixture by adding a drop of sunflower oil to our recipe. This gave us greater scope for the aesthetic of our inflatables as they could be more opaque or transparent. However, we think this is why the alignate shrank so much (another variable that can be played with).

Mix up some Alginate:

For this we used our left over alginate from Biofabricating Materials week.

The ingredients are as follows:

Sodium alginate powder - 6 gr
Glycerine - 10 gr
Water - 200 ml/gr
Water and Calcium chloride solution at a 90% to 10% ratio
A drop of sunflower oil if you want your mixture to be opaque.

The step by step Alginate recipe can be found on my assignment page.

Mix up some Calcium Chloride solution

Its important to have lots of Calcium Chloride solution as this is what you are going to use at every step of the process to cure your inflatable.

Prepare the solution as per my biofabrication week recipe: a 90% to 10% ratio of Water to Calcium Chloride and have it ready in a large spray bottle and also a syringe.

Prepare your set up

Prepare an embroidery hoop with a thick, absorbant material. We used a denim. It is important that the material is absorbant and has a dense weave so that the calcium chloride can pool and isn't pushed through the pores of the fabric by the Alginate. Similarly, the dense weave means it doesn't leave a texture on your inflatable.

This embroidery hoop will be the container for your alginate inflatable and its shape will determine the basic shape of your inflatable but it will be considerably smaller.

Place your hoop on a clean surface and soak it with Calcium chloride. Use enough so that there is some pooling at the bottom of your container and ensure you spray the sides thoroughly.

You will also need to prepare your set up with the spray bottle and syringe of Calcium Chloride, an airpump, a small cutting of thin plastic tubing and a one way air valve.

Pour your alginate

Slowly pour the alignate mixture into your embroidery hoop. It is important to keep pouring in the same spot because otherwise the seperate pools will cure and not join when they become in contact with the Calcium Chloride.

As soon as you have poured it you need to start the curing process by spraying the whole surface with your Calcium Chloride solution, very quickly you will see a skin starting to form and the alginate begin to shrink. Spray the sides as it shrinks.

Its amazing how quickly it becomes a little bao bun!

Inflate

Your alginate is ready to inflate when you touch the outside and it feels completely cured but it still feels liquid in between. As long as you can feel two distinct layers with liquid between you should be okay.

You can now use a sharp object to pierce a small hole in the side of your alginate bubble. Then feed your short cutting of platic tubing into the hole. Make sure not to push it in too far and lose it in your bubble!

Importantly, move the tube in and out of the hole gently and push slightly on the bubble until some of the liquid alginate inside the bubble seeps out of the hole around the tube. You are looking to seal the hole around the tube. When enough has been pushed out to seal the tube in the opening you should quickly spray the entire hole with calcium chloride solution and cure the excess liquid so it forms a air tight plug around the tube.

When this has sufficiently cured, carefully insert a one way air valve into the end of the plastic tubing and attached to your air pump to the valve.

You can now slowly inflate your alginate bubble but make sure not to go to much or too fast and risk bursting your bubble. When it seems stretched to its maximum stop adding air. From here the one way air valve and sealed hole should stop the air escaping and you should have an inflated alginate bubble.

Cure the inside of your bubble

Now we have to carefully pour calcium chloride solution into the bubble to cure the inside. We do this by pinching the plastic tubing and detaching the air valve and pump from your bubble.

Still pinching tightly, get your syringe full of calcium chloride solution.

Quickly and carefully insert the syringe into the plastic tubing and squirt the calcium chloride inside your bubble.

Next, pinch the tube again and remove the syringe.

Try to gently pick up your alginate bubble and swirl the calcium chloride around inside the bubble, ensuring to flip it over and get both the bottom and top surfaces of the bubble to cure completely. Give this some time and be gentle around the tube and opening to ensure you don't create any leaks and holes in your bubble.

Inflate again

Finally, you can reverse this process by pinching the tube and reinserting the air valve and pump. Inflate the bubble again so it is at it's maximum inflation and leave it this way while it fully cures and begins to dry out.

The results were amazing!! We were so happy with our little bubbles. We could definitely experiment more with adjusting the thickness and getting maximum stretch out of them but the basic process was reliable and repeatable and gave us really nice results.

Adding texture

One thing we really wanted to try was adding textures to the surface of the bubble so that when it inflated you could see the pattern stretch and become clear.

We decided to try putting a patterned surface in our embroidery hoop before we poured the alginate on top.

We experimented with:

Acrylic cut out
Textured fabric
3D printed surface

The Acrylic cut out sort of worked but we saw that the edges were too sharp and they created little weak points in our alginate bubble as it cured. Similarly we think the acrylic we used was too thick because there were weaknesses were created where the alginate was stretched over too high a step. It is also clear that the acrylic is too smooth and non absorbant so the calcium chloride didn't stay on its surface as well. As a result the alginate did not cure in places and caused further flaws.

The textured fabric worked really well! It was flat and soft enough that it didn't rip our alginate or cause any weaknesses. The texture was the reverse of the fabrics pattern and gave the alginate bubble a really tactile and organic surface.

Finally, I tried casting one on a 3D print I made on textile for computational coutre week! This was a bit of experiment but I thought because the design was only about 1-2mm thick it would be safe to test with the alginate! And it worked really well. The pattern printed nicely and this opens up so much possibility for the kind of designs you could print on its surface!

In the future I would love to try making custom moulds to see if we can create different shapes for our inflatables and more intricate textures!

♙Moulding and Casting Inflatables♙¶

We wanted to have a go at making a Silicon and Biosilicon inflatable. We looked examples of silicon soft grippers and other inflatables made by past participants to better understand how to design the air channels and the 2 parts of the mould. As silicon is a very unsustainable material, we didn't want to recreate anything that we could already see and experiment with here in the lab, so we decided to not make a gripper like the one below:

Right to left: Soft Gripper produced by participants from 2023/24; 6 armed gripped produced by participants from 2023/24 and Silicon Bubble Inflatable produced by Riley Cox

Having explored the options we decided we wanted to make an inflatable like Riley's bubble inflatable.

For this, Asli designed a mould in Rhino using a Voronoi Grasshopper Definition we used in Computational Coutre week. We wanted to see if we could get the voronoi modules to pop out.

When designing the mould we had to ensure that we could get the cast silicon out of the mould and that there was a clear air pathway and entry point for the air pump.

We used the laser cutter to cut out the pieces for our mould and used acrylic glue Acrifix to stick it together. I found this an incredibly difficult glue to work with as it drys very fast but is very hard to spread precisely. (Foreshadowing: this may have lead to the demise of our silicon inflatable).

You can find the .dxf file for the Voronoi mould below ² and we used the following settings on the laser cutter:

Speed: 15.00
Max power: 40.00
Min Power: 20.00

Eco Flex Silicon Rubber Casting

We prepared the Ecoflex Rubber silicon. This is not a sustainable material but it does produce very detailed casts that are elastic and inflatable.

The process is very simple but you have to be very precise to get good results and ensure thorough curing.

Measure parts A and B of the eco- flex. The measurements are a easy 1:1 ratio.
Mix very well. It is crucial that the two parts are thoroughly mixed so that you don't have sticky, uncured parts in your cast. To do this you can colour 1 part to see the difference better but we just poured it into another cup and stired again to ensure we got the bottom of the mixture. The mixyure doesn't start curing for 45 minutes so there is no rush but it is not possible to reuse the mixture after this time.
We then placed the mixture on a vibrating machine in order to get the airbubbles to rise to the top and . We want to avoid airbubbles as they will create weaknesses and leaks in your cast. It is important to be gentle when you are mixing the parts by folding not stirring.
Pour into your mould. Pour slowly in the center and let it spread out. We wanted a very thin layer for the part that does not have the pattern so that it could stretch and inflate. It is important not to put so much mixture.
Then we let it cure over night but the minimum cure time is 4 hours.
When we returned it was no longer sticky to the touch so we thought it was safe to remove. we carefully poressed and pulled at the edge until we could release the silicon from the mould.

Results

Unfortunately, we did not get good results with this cast. We used too much acrylic glue when sticking our mould together and the excess seemed to have interfered with the silicon curing. There were lots of holes and rounding of edges in our cast and a lot of the inside was still sticky despite curing over night.

We mixed up some more eco- flex and applied it to the edges of the two parts and glued them together. We left this sandwiched under a compress to see if we could make the cast airtight despite its flaws and test it as inflatable.

As you can see when we attached it to our airpump and tested it, there were far too many holes and leaks for the silicon to inflate properly. Similarly because of the glue leaving parts of our silicon uncured the two parts would not stick together and many of the air channels inside were unclosed. This meant we got large air bubbles instead of the intricate air channel design we had created.

Unfortunately, this material may take more experimenting and time to get a good silicon cast inflatable.

Bio Silicon Inflatable Casting

We wanted to try out a more sustainable alternative to Eco-flex which would still give us good enough stretch and elasticity to make an inflatable. We decided to make a gelatine bio-silicon inflatable using a flower acrylic mould that had been previously made in the lab.

We used the Bio Silicon recipe we followed in Bio-fabricating materials week with Cecilai Raspanti. The Bio-silicon recipe had the most Glycerin in the recipe and therefore had the most elasticity.

We heated the ingredients until we got a syrupy consistency and poured it into our moulds. We tapped the moulds gently to help the air bubbles rise to the surface:

When the bio-sillicon had cured long enough to take it out of the mould we applied some more bio-silicon around the edges of each part to glue them together and create a tight seal. We left this under a compress over night before attmepting to inflate.

Unfortunately, we had the sticky hand of failure strike again! Our cast bio-silicon was much too thick to inflate and we didn't see any change at all when we inserted the air pump. We should have kept both layers much thinner and perhaps not cooked the bio-silicon for so long. This is another experiment we will have to repeat to see if we can get success with our sustainable inflatable dreams!

♨︎TPU Welding♨︎¶

TPU is a polyurethane plastic which is thermosensative and melts when heated.

TPU WELDING with the Laser Cutter

You can use the laser cutter out of focus to weld two pieces of TPU together. You achieve this by unfocusing the laser. This is essentially moving the lens further away from the material. This creates a thicker line which gives more area for the two materials to stick together. We did many tests but found that it worked best when we had the laser head the furthest it could go from the material.

Then we had to do lots AND lots AND lots of testing to find the right laser cutting settings to weld the TPU sheets together but not cut through or burn holes. It was important to test it on curves and straight lines to insure the min power was also correct.

Eventually we arrived at these settings for the yellow TPU. However, annoyingly every colour has slightly different settings so it is always important to run a test first.

CUT: 
Speed: 180.00
Max Power: 25.00
Min Power: 12.00

WELD: 
Speed: 170.00
Max Power: 25.00
Min Power: 12.00

Remember to refocus the lens when you are cutting and unfocus again when welding!

We tested this method with a cute little balloon:

I later tried this method with an origami design I had created. Unfortunately I found it very difficult to do a more intricate bigger design. The new laser cutter doesn't have enough space to move the lens as far away as necessary to unfocus the laser properly. For this process and even with the lens as far away from the TPU surface as we could go the laser still cutting holes instead of welding the TPU. I found it too hard to proceed with this process as the limitations of our machine were working against us.

Although this method failed with air actuation as it is not air tight it is possible this would work with fluid actuation.

TPU WELDING with the Heat Press:

You can also weld TPU in the same way we welded the vinyl in the heat press. We can sandwich a baking paper air channel design between two layers of TPU which weld together when in the heat press.

First we cut out our TPU and baking paper with the laser using these settings:

Yellow TPU: 
Speed: 180
Max Power: 25
Min Power:12

Baking Paper: 
Speed: 170
Max Power: 25
Min Power:12

Then we moved to the heat press:

After playing around a bit we found good settings to weld the TPU with the heat press:

285 Farenheit
For 25 seconds

Make sure to give it some time to cool after other wise you might pull it apart before it has fully hardened and stuck together.

I found this process much easier and gave me much better result than when I welded with the laser. I decided to create a few projects to explore the possibilities of this process:

☘︎ORIGAMI INFLATABLE☘︎¶

I was really inspired by the fluid origami and kirigami skin robotics I had seen and wanted to see if I could make an inflatable that would fold in a specific pattern.

I took a origami crease pattern, a flasher and translated it into an approximate diamond pattern in rhino.

In my first attempt (The design to the left in the screenshot below), I made the diagonal diamonds much too long and thin and I didn't achieve a good crease and no folding motion at all. Unfortunately, my TPU wasn't welded strong enough on this one and it immediately split the TPU and created lots of air bubbles before I could take a picture or video.

In the second attempt (design to the right), I made the diagonal diamonds much shorter and wider and did manage to improve the crease! Sadly, neither design showed any signs of folding up into a flasher like I had hoped. I realised I may have set my expectations too high in expecting the air to actuate both valley and mountain folds with no distinction! I think I would like to try this design out with fluid origami in the future as I would be able to encase the origami in the material already folded and the force of the fluid would be strong enough to make it expand and contract.

Here is my best version of this inflatable, although it doesn't work how I imagined, I do like the design and was happy with the strength and durability of the TPU heat press welding:

You can download the .dxf file for the origami inflatable here ³

⚘SMOCKING INFLATABLE⚘¶

I was really inspired by this Fabricademy project by Amanda Jarvis in which she creates a 3D smocking pattern that scrunches the fabric together with inflation and could be used as a robotic scaffold for a 3D printed pattern.

I started by creating a geometric pattern. I imagined Trapezoid shapes which would be scrunched closer together both horizontally and vertically when inflated.

I started with diamond shapes which I planned on seperating into 2 trapezoids with folds. I connected the diamonds together horizontally and vertically and started adding small diamond shapes where I wanted the piece to fold and scrunch. This part would be my inner layer cut out of baking paper. I then added a 5mm offset to the whole design to create the outer layer I would cut out of TPU. I also designed and extruded parts I wanted to 3D print and secure to the pattern later.

Everything about my first attempt was flawed! My scaling was way off and my inflatable ended up being far to big to fit in the heat press! For this reason I had to remove some modules to test it out. Similarly the spacing between the big diamond modules was way to large, so the effect of the movement was not very dramatic. The spacers between the shapes impedimented the movement as the spaces on the vertical coloumns didn't have a hinge and the hinges on the spacers in the horizontal rows were much too small to create a crease.

For my second attempt it was important to reduce the space between the columns and the rows and to scale the whole piece down significantly

In my new design I overlapped the diamonds instead of having rectangular spacers. This was to make the individual modules closer and make the movement more dramatic. The angles of the diamond modules had to be adjusted so that the airchannels around the diamond hinges were wide enough. Although I scaled the whole thing down massively, I scaled the hinge sizes less in hopes of achieveing a more dramatic movement.

I made this inflatable in both welded TPU and heat pressed vinyl and was very happy with the results!

I did the vinyl version last and added some extra improvements such as an additonal row of hinges. I also folded the baking paper along the lines I wanted it to crease before I heat pressed it all together. This worked wonderfully and I think the vinyl material is also the most suited for this design as the movement and shapes are slightly more pronounced.

I would love to complete this project with a 3D printed layer which could be brought closer together with the inflation. Unfortunately, Soft robotics week is only 1 week and there isn't enough time. I am super excited for all the possibilities that could come from this though!

You can download the .dxf file for the smocking inflatable here ⁴

⭐︎SEA SLUG INFLATABLE⭐︎¶

For my final little project, I wanted to create a inflatable that was more 3D. I was thinking about concertinas and had the idea to make something that started 2D and inflated open to a 3D shape.

This brought me to the idea of making a sea slug sort of creature that would slowly sway, furl and unfurl:

I made some ruidmentry models in paper and heat press welded TPU to try out different ways of creating the shape and movement:

I established that the motion could be achieved by joining individual pockets in the round, leaving a hole at the bottom to insert the air pump. The first pocket on the pile would inflate first and its lift would encourage the rest to unfurl.

The challenge here was how to join each individual pocket without welding them all together or melting them with the laser cutter or heat press.

The answer was to use the IRON and individually fold and weld each part.

I got to designing a basic shape for my pockets in rhino and also baking paper shapes which could be used to stop certain section of the TPU sticking together as I ironed.

I then lasered each section out from either TPU or Baking paper. The settings I used were:

Pink TPU: 
Speed: 180
Max Power: 25
Min Power:12

Baking Paper: 
Speed: 170
Max Power: 25
Min Power:12

Once I had all my components, I began to carefully iron each pocket together and then connect it to the next in the round. I had to make sure there was always baking paper between parts I didn't want to weld together as I went. Moreover, I had to be careful how long I kept the iron on the TPU. In my first attempt I melted a lot of the TPU and created a sticky mess. From then I was very careful and put the iron settings low on its SEIDE setting.

This process was very fiddly and unfortunately the TPU came apart quite a lot at the bottom and top of the shape as I had to be very careful how much I ironed the TPU so it wouldn't melt. It was very difficult to get everything aligned just right and to keep the baking paper from moving during the process. For this reason, I had to use a bit of tape to keep the pockets together at the top of the inflatable. However, as a proof of concept I am happy with it. When inflated the pockets unfurl in order just as I wanted to and I see potential for further protyping with this design:

You can download the .dxf file for the sea slug inflatable here ⁵

♧Tapioca Experiment♧¶

At Dutch Design Week this year myself, Carolina and Asli came across Aquamorph, a project exploring the fabrication of shapeshifting hydrogel structures printed by means of FDM.

They use hydrogels for their reversible shape changing properties which self-actuate when they come into contact with water. They were able to prototype different containers that would have different movements and shapes when they are immersed in water and the enclosed hydrogels begin to expand.

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We were really excited about this idea and knew it was something we wanted to try for ourselves in Soft Robotics week.

Asli began quickly creating a prototype for us in rhino based on the Aquamorph Twisting design. You can download this model via sketch fab below:

tapıoca by issy2842 on Sketchfab

In the Aquamorph design they use hydrogel beads which are super absorbant polymers which when exposed to liquid, they absorb large amounts of the liquid without dissolving. This expansion inside a FDM printed container creates a lot of pressure which can be harnessed to create actuation.

Unfortunately, we couldn't get our hands on any Hydrogel beads so we had to get CREATIVE. Instead we decided to use TAPIOCA. We ran to the nearest oriental supermarket and bought a range of different Tapioca balls and pearls to test as we knew from our bubble tea drinking experience that Tapioca would absorb liquid and expand much like a hydrogel.

We did a test to see how much the tapioca would expand. Following the instructions and cook time for each one, boiling the larger boba boils for 5 mins and the tapioca pearls for 20 mins. It was clear that whilst the larger boba balls were bigger, the smaller tapioca pearls almost doubled in size. They would be easier to put inside the containers and would cumulatively exert more pressure as they all expanded.

We also boiled a peice of tpu filament along with the tapioca to ensure that our 3D printed container could survive the cooking process.

With our Tapioca and Rhino file in hand all that was left to do was print it and give it a try

We prepared our rhino file for printing in Prusa slicer. We decided to use the 98A Fillamentum Flexfill TPU filament to print to give it enough flexibility. We also chose these print settings for our Prusa i3 mk3s.

We also added a pause in our print schedule so that we could add the tapioca balls before the printer closed each component.

Printing went pretty well, most of the challenges occured after the scheduled pause and we added the tapioca balls. We had to insert them carefully and ensure none of them were sticking out too high so that we could resume printing.

We repeatedly got holes in the first few modules because the nossle took some time to reheat and get into good flow after the pause but overall we were happy with the printing.

We ended up printing 3 different versions which we tested:

The first was a small test had a straight connection between the modules. We were looking to see if the tapioca created enough pressure for it to expand.

To prepare it we soldered holes into the TPU to let water enter the modules and we soaked it in cold water first to ensure the water could reach inside as after the tapioca expands it blocks the holes and doesn't allow water to reach the center of the modules.

This test was a success in 20 minutes our tapioca robot expanded from 3 to 5 cm!

For our second test we made it longer and we made the connectors follow a helix trace which makes 1 turn in order to encourage it to twist!

This test also showed signs of twisting and was a more interesting actuation to our first one.

BUT WE STILL WANTED MORE! We decided that the modules were too far away from each other so the modules couldn't push against each other enough when they expanded

So, for our final test we kept the same design but made the connectors smaller. We hoped this would increase the pressure the modules exerted against each other and encourage more twisting.

It worked! We saw a definite twisting motion (yes its slow and you have to squint! but its there). We were so excited to see it and think that this was the most effective design. We would love to try it with hydragels or thermo reversible hydragels in the future to make the motion reversible and quicker.

♌︎Electronic Set up♌︎¶

Finally is TO BE CONTINUED project. Our instructor Michelle Vossen set up an electronically controlled, 2 way air valve set up for us so we could experiment and allowed us to have programmable airflow!

This set up has 2 motors and a 2 way air valve attached to an Arduino Nano. One valve is programmed to push in air and one to suck air out. We can use the code to adjust parameters such as the time air is pushed in and pushed out and the delay inbetween. The code Michelle used is below:

// L293D as motor driver for the two motors
// Motor A - inflating
const int motorPin1 = 5;     // Pin 14 of L293
const int motorPin2 = 6;     // Pin 10 of L293
const int motorPinEn12 = 3;  // PWM pin

// Motor B - deflating
const int motorPin3 = 10;     // Pin  7 of L293
const int motorPin4 = 9;      // Pin  2 of L293
const int motorPinEn34 = 11;  // PWM pin

// Solenoid valve
// The middle port with the flange is the 'common' connection.
// When powered (HIGH), the common middle port and the plastic end port closest to it are connected and the metal end port is closed (no air flow in or out).
// When de-powered (LOW), the common middle port and the metal end port are connected, and the plastic end port is closed (no air flow in or out).
const int valvePin = 2;

//This will run only one time.
void setup() {
Serial.begin(9600);
// Motor A - inflating
pinMode(motorPin1, OUTPUT);
pinMode(motorPin2, OUTPUT);
pinMode(motorPinEn12, OUTPUT);

// Motor B - deflating
pinMode(motorPin3, OUTPUT);
pinMode(motorPin4, OUTPUT);
pinMode(motorPinEn34, OUTPUT);

// Solenoid valve
pinMode(valvePin, OUTPUT);
}

void loop() {
digitalWrite(motorPin1, LOW);
digitalWrite(motorPin2, LOW);
digitalWrite(motorPin3, LOW);
digitalWrite(motorPin4, LOW);

// valvePin HIGH for inflating, LOW for deflating
Serial.println("INFLATING");
digitalWrite(valvePin, HIGH);  // HIGH - inflate

// Pump inflating: motorPin1, motorpin2; Pump deflating: motorpin3, motorpin4

analogWrite(motorPinEn12, 255);  // set speed to highest setting (0-255)

digitalWrite(motorPin1, HIGH);
digitalWrite(motorPin2, LOW);
delay(5000);  // how long it should inflate in milliseconds

// Turn off motors
digitalWrite(motorPin1, LOW);
digitalWrite(motorPin2, LOW);

// analogWrite(motorPinEn12, 180); // set speed to lower setting
// digitalWrite(motorPin1, HIGH);
// digitalWrite(motorPin2, LOW);
// delay(3000);
// Stop inflating
// digitalWrite(motorPin1, LOW);
// digitalWrite(motorPin2, LOW);
// delay(1000);

// // PWM inflation speed; this also works, can be nice for gradual inflation. In the lower range it's hard to notice any inflation
// for (int i = 0; i < 255; i++) {
//   analogWrite(motorPinEn12, i);
//   digitalWrite(motorPin1, HIGH);
//   digitalWrite(motorPin2, LOW);
//   delay(10);
// }
// // Gradually Decrease Duty Cycle
// for (int i = 255; i > 0; i--) {
//   analogWrite(motorPinEn12, i);
//   digitalWrite(motorPin1, HIGH);
//   digitalWrite(motorPin2, LOW);
//   delay(10);
// }

Serial.println("DEFLATING");
digitalWrite(valvePin, LOW);     // set solenoid to LOW to enable air flow to the deflating pump
analogWrite(motorPinEn34, 255);  // set speed to highest setting (0-255)

// Turn on the deflating pump
digitalWrite(motorPin3, HIGH);
digitalWrite(motorPin4, LOW);
delay(2000);

// And this stops deflating
digitalWrite(motorPin3, LOW);
digitalWrite(motorPin4, LOW);

// Short optional pause between inflating and deflating
delay(500);
}

This is how it worked set up with my origami inflatable:

I didn't get to the point of really understanding the complexity of this set up but this is something I would like to learn more about going into Wearables.

Overall a fantastic, ram packed week which I wish was 3!! or 4!!