GOALS:

We decided to use this project to help us test and prepare for the final projects we are currently working on.  The goal was to create a dyed felted fabric that changes color in specific areas and patterns in a more controlled way than our previous experiments.  By using an arduino, an additional power supply,  and circuits that contain a mosvet, resistor  we are able to control specific areas of the fabric using different pins on the arduino. Our hope for the near future and for our final project is to be able use out side data (specifically weather and temperature) to control these changes.

PROCESS:

Knitting

The first step to creating this fabric was to knit a large sample on the knitting machine. This sample was  knit with a light weight cotton yarn (purple) and a heavy wool yarn (white). The differences in the yarn weights allowed for the yarns to variegate creating an interesting striped pattern.

Sewing and Felting:

Before felting the piece lines of steel were sewn into the fabric in a zig zaz pattern. Before sewing the lines were mapped out  with tape as channels on the fabric.

After the sewing was completed the fabric was thrown into the wash to felt.

Dyeing

The next step was dyeing the fabric. Instead of vinegar like we used here we used lemon juice. After some research on natural dyes we determined a different process to use. This process involved first boiling the fabric with a fixer (lemon juice) then rinsing the fabric and letting it soak in the thermochroomic dye overnight. After soaking it was hung in the sun to dry . Dye Process

This process seemed to take much better than the vinegar dye used for the first experiment in dyeing yarns. It also does not smell as pungent and seems more wash-fast.

CHALLENGES:

Heat actuator Water Crystallization SMALL

Water droplets were frozen at -78C for 10-30 minutes, before being imaged under 625x microscope.  Some water droplets were subjected to negative pressure for the freezing process (.5 and .33 atm respectively), and their crystal size compared with 1atm frozen water.  Glycerin and PEG (Poly ethylene glycol) were also frozen.

The point to take away from these images is that the ice crystals (the small, granular, sharp angled shapes) melt, turning into water droplets, followed by water droplets conglomerating into a larger droplet.  The first part of the crystal to melt are the fractal “arms” which extend past the center of the crystal; these are pointed out in a couple images.  The effect of the greater “stickiness” (surface attraction) from the wetted crystals, as well as a bulk amount of liquid outside the focus of the microscope, causes more crystals to move into the focus of the microscope as the melt continues.  The end of the melt process results in many individual domains of mini-water droplets; these then combine to form macroscopic droplets.  The initial size of these droplets is indicative of general crystal size; lower pressure results in smaller crystals.  These smaller crystals are somewhat difficult to image as droplets, as there is greater surface tension and thus reason to form larger droplets quickly.  In general, there were issues with imaging since the ice melted so quickly; using a controlled, sub-zero C environment for the entire microscope set-up and environment would help with this issue, and allow for greater time to find a perfect focus and thus greater possible resolution.  In such a scenario, direct measurements and analysis of the ice crystals could be readily performed, as opposed to the analysis of their post-melt state.

Neither PEG nor Glycerol formed large crystals similar to those of the water.  The glycerol is either very poorly crystalline or amorphous; it seems as though the PEG has an even weaker trend towards crystallinity.

Ice is a readily available material that illustrates many of the principles behind designing solid-liquid heat controlled actuators.

This is a paper spring, folded, essentially, using a very similar technique. I learned it on YouTube. Look up, ‘Origami Spring’. It’s a bit tedious to get the folds, but with a small push on the center, you can get very impressive actuation.

This is the crease pattern for the spring. You do this part first.

This is the process of folding the spring. It’s more unpleasant as it goes on.

And efforts at actuation. A number of different configurations were tried, to try and maximize the degree of change, given the relatively small contraction of the flexinol. Attaching flexinol threads to the back of the pleated sheet didn’t give a particularly noticeable actuation (though the nitinol contracted effectively):

Experiments with a scissor-style lever arrangement worked much better:

And on a larger scale:

Ultimately, to maximize the actuation of the miura fold, the entire sheet was sandwiched between a large lever, which was actuated close to the fulcrum with a looped piece of flexinol:

Presentation link (sans videos)

Working either individually or in a small group (2-3 people), you will experiment with material actuators in a hands-on project. For Tuesday’s class you should prepare a 5-10 minute presentation and a blog post that documents your project.

Your presentation and blog post should include:

• A description of your project.
• Images and/or videos that document your process.
• A discussion of challenges, frustrations, and/or epiphanies.
• Reflections on how you might use the material or technique in your practice in the future.

Add your blog post to the the Actuators Project category. Bring your project to class on Tuesday for an in person demonstration and discussion.

The voiceover and subtitles explains how this works, where a soft rubber pouch is actuated by pressured air. The simplified demonstration below shows this, a syringe of air changing the dimensions of the finger-pouch:

I decided to use a medical syringe as the air pump, examination gloves as the membrane, rubber bands to provide a seal, and soaked cotton balls as the jamming content. I used a bunch of lightweight dental sticks as pickup objects.

So after snipping off the fingers of the glove, I made this:

a surrealistic little finger.

I wanted to test it with unsoaked cotton ball first, as well as a combination of unsoaked cotton ball and ground black pepper.

Finger with Cotton and Pepper

The finger failed to pick up the stick when actuated with air.

I had much more success with water-soaked cotton.

Successful Pickup with Water Soaked Cotton

It also manages to pick two up, albeit a little badly.

Pickup of Two Sticks

I tried fluids with different viscosity, first honey, and then soy milk.

But viscosity changes the effectiveness dramatically, such that I seem to achieve a stronger suction effect, but without a corresponding increase in successful pickups.

Unsuccessful Pickup with Soy Milk

I wanted to experiment with the thermochromatic ink that Leah showed us last week.  Just a reminder: thermo  = heat and chroma = colour.  It is an ink that changes its behavior when the temperature rises over a certain base level.  For example:

I was also inspired by pictures of silhouettes, and so I decided to make a picture of something in silhouette with a very colorful background.  I wasted a bit of time trying to figure out what to do, and finally decided on making a silhouette of MIT.

Process

First, I started with this drawing on autocad:

Next, I cut out this stencil from a 12″ x 12″ sheet of paper with the laser cutter:

Then, I sprayed the base layer of black paint on a 12″ x 12″ piece of acrylic:

After that, I used the stencil to map out the layer of conductive ink, that would activate the thermochromatic ink:

Then, I sprayed on the second layer of black paint to mask the conductive ink.  Unfortunately, something went wrong and the paint got messed up.  I’m not sure what happened, but some suggestions are that because I used two different kinds of inks for the black layers, they reacted badly:

Lastly, I used the stencil again to paint on the thermochromatic ink, and voila!:

Lessons Learned

Unfortunately, it was not the layer of conductive ink that caused the wonderful colors to show.  It was a regular hair-dryer.  There are three possible reasons for why this did not work

1. the area I was trying to heat up was too big
2. the black paint successfully shielded the thermochromatic ink from the conductive ink
3. the voltage I was using was too low

Future Applications

I still want to use thermochromatic ink in my final project (and not require a hair dryer) so I’m going to experiment a little more.  But instead of using conductive ink, I want to try sinking a strand of steel thread in a trace on the acrylic and seeing if that works.

Presentation: Crouching Beaver Hidden Institute

Inspired by the hydro skeletons and muscular hydrostats in nature (e.g. elephant trunk, starfish, octopus arm, etc.), the kinematics are based on the combination of elastic material body actuator and pneumatic pressure feedback system.

[Module and Power Source Feedback Loop]

[Kinetic Study Process Sketches]

[Table of Kinetic types, material and Geometry]

[Mold Fabrication Process]

[Kinetic Study Demonstration Video]
Bend 01

Bend 02

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