Rheological Matter

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The project is based on creating a structural system that reacts to certain stimuli and changes its configuration within a given space. The nature of responsiveness can occur after the structure is erected, resulting in real-time reactions to its local users. We experimented with different materials which were activated with various stimuli such as shear force, electricity, and magnetic fields. The problem was that in order to achieve bigger viscosity we had to apply continuous. One answer to this question were materials with photorheological (PR) properties, which get stiffer when you apply UV light and stay stiff until you apply a different UV light. However, due to the high cost and rarity of the aforementioned PR materials we are working with microcrystalline wax insted, which also allows us to create an optimized system without exerting a lot of energy.

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For our prototype we designed 2 silicone molds of 200 x 200 x 7 mm. Both are based on a grid system; one has continuous interlocking lines whislt the other is made up of individualy separated capsules. Varied densities were also given in respect to the wax / silicone ratio and distribution around the centre / perimiter in order to test their effect on the mold’s malleability. Nichrome, a resitance heating alloy, was then interlaced through the silicone mold and in the cavities where the wax was to be poured. We previously tested various thicknesses of wire and the relationship in respect to voltage and average temperature. In our square silicone molds, we needed around 20 Volts DC @ 2.4 Amps to reach our required 84-88° celsius melting point for the microcrystalline wax. We then distributed a layer of hemp fibres on top, which after our material testing, proved to significantly increase the strength and durability of the previously brittle wax in its solid state. Finally we poured the melted wax over top and sealed it with another thin 2mm layer of silicone.

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Our tests in melting the wax in the square molds gave way to interesting results. While we were able to reach melting point quite quickly and liquify the immediate surrounding area of the nichrome quite efficiently, the rest of the wax / fibre composite was too stiff to assess the mold’s potential to change form and hold shape. What we have learned from these prototypes will inform how to push our material and system research:

1) Searching for more efficient alternatives to the silicone mold with wax combination. The material we are most interested in pursuing is a Shape Memory Polymer, which under the influence of heat is able to change state to a soft rubbery state, whilst being able to hold a new shape after cooling.

2) Using more optimal heatwires, potentially Constantan wire.

3) Exploring singular or bi-directional actuation movement instead of the 4-cornered grid. Candidates for actuation include motors or muscle wires (flexinol, nitinol)

4) Exploring fabrics as a potential shell for the phase-changing material to be held within, and understanding how a larger fabric system would function, keeping responsive actuation in mind.

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