4. Biofabricating Dyes and Materials#
This week I worked on (click on item below to jump to section):
Natural dye synthesis#
Below is an image of the biodye swatch book created for the group assignment.
Five biodyes were used:
- Annato
- Black bean
- Blue corn / "Maiz morada"
- Hibiscus
- Tumeric
Three textiles were used:
- Muslin (woven cotton)
- Felt (cotton)
- Silk
- Method 1: Stainless steel pot + meat thermometer
- Method 2: Pantelligent pan + iOS app to monitor the heat variation in processing the bioplastic. (Note: as of 10/22/18, I noticed that Pantelligent isn't being sold anymore, but this product seems similar. The only drawback is that it only works with an induction stove).
- In terms of viscosity, a balance between integrating the bioplastic precursor with the textile while maintaining it in the overmold must be achieved. Too low of viscosity (like water) means the textile can be soaked with the bioplastic precursor. Too high of a viscosty (like honey) means that the bioplastic precursor will stay in the mold and never fully integrate with the textile and peel off when finally cured.
- Gelatin-based bioplastics, while curing, can be re-melted if direct heat is applied to it.
Bioplastic fabrication#
Overview#
I experimented with two different types of bioplastic formulations: (1) starch-based, and (2) gelatin-based. The goal was to find a suitable bioplastic that could be integrated with textiles using an over-molding process.
Formulations#
The protocol for fabricating each type of bioplastic can be found here.
Starch-based results#
Generally, I found the starch-based bioplastics easier to work with. In comparison to the gelatin-based formulations, the starch powders needed more time to dissolve and thus the gellification of the plastic while heating was slower. Because of this, I found that integration of starch-based bioplastics with textile was much easier.
Figure 1. Fabricademy mini-intern (my 2-yr old daughter) smushing the cornstarch-based bioplastic into the mold
Figure 2. Left: Sweet rice flour-based (left) and tapoica flour-based (right, darker of the bioplastics) in the overmold. Right: final product after post-processing
Table 1 below outlines the different formulations pursued based on percent. For dry ingredients, this was mass-based; for liquid ingredients (with the exception of glycerol), it was volume based (the assumption here is that the liquids have a density of 1 g/mL).
| Recipe ID | Starch ingredient | Dye | % Starch | % Glycerol | % Vinegar | % Water | Final characteristics |
|---|---|---|---|---|---|---|---|
| A | Cornstarch | Annatto seed + tumeric | 10.7 | 14.3 | 3.6 | 71.4 | Squishy |
| B | Sweet rice flour | Beet juice | 10.4 | 7.5 | 7.5 | 74.6 | Sticky |
| C | Tapioca flour | Beet juice | 10.4 | 7.5 | 7.5 | 74.6 | Rigid |
Gelatin-based results#
When working with the gelatin-based formulations, I found that, regardless of gelatin-content, the heated mixtures before gelling (‘precursor’) were less viscous than the starch-based bioplastics. In the first formulation I had tried (Recipe D in Table 2 below), I accidentally put more water than required, and this made the precursor have a water-like consistency. Because of this consistency, when overmolding was attempted, the precursor quickly soaked the textile rather than sit in the mold above the textile. Refer to the over-molding section for more information.
Figure 3. Gelatin-based bioplastics. Left: Knox®-based (Recipe D); right: agar-based (Recipe E)
| Recipe ID | Gelatin ingredient | Dye | % Gelatin | % Glycerol | % Water | Final characteristics |
|---|---|---|---|---|---|---|
| D | Knox® gelatin | Beet juice | 8.7 | 4.3 | 87.0 | Thin, flexible |
| E | Agar | Beet juice | 9.4 | 3.6 | 87.0 | Rigid, strong |
| F | Knox® gelatin | Blue food coloring | 15.8 | 5.0 | 79.2 | Rigid, strong |
Bioplastic processing#
Cooking the formulation#
I used two different methods of cooking up my bioplastic formulations:
The 2nd method was pursued because, as a classically trained chemical engineer, I wanted more insight over the processing parameters of my materials. :) It is very hard to control the heat for an electric stove!
Figure 4. How I monitored temperature in real-time using Method 2.
Since I had insight on the temperature profile of my mixture, this inspired another study I pursued with Recipe F (gelatin-based material [see Table 2]). Basically, I wanted to see how the material properties of the precursor changed based on how long I waited to take it out of the pan. When I was following the original recipe, there were no details on how to work with the material as you cook it. I feel this is such an important detail that should not be overlooked.
Figure 5. How temperature and elapsed time after precursor mixture reached ‘frothiness’ affected gelatin bioplastic consistency
time = 0 is the time at which the precursor mixture started to froth, which, according to protocol, is when it’s advised to remove from heat. I tried to maintain the temperature of the pan at 203°F to remove precursor material from the pan. As time elapsed, the rigidity and viscosity of the resulting bioplastic increased. This was to be expected, since water is the main ingredient in the mixture, it was most likely evaporating off.
Overmolding on textile#
The inspiration for integrating bioplastic with textile was suggested by Nuria, our Fabricademy mentor. She suggested using a laser cut acrylic mold and a textile with openings in it.
Figure 6. Acrylic mold laser cut design with epilog laser cutter at Dassault Systemes. (The mold is not finished being cut in this picture)
Two types of ‘open’ textiles were pursued: (1) embroidery fabric, and (2) tulle. I found that the more ‘open’ the textile was, the easier the bioplastic precursor integrated with it.
Figure 7. Textiles pursued for integration. Left: embroidery fabric; right: tulle.
Some things I found while integrating the bioplastic precursor with each textile:
Figure 8. Bioplastic-textile integration. Top: bioplastic precursor had ‘too high’ of viscosity (would not integrate with textile and started peeling off the textile when drying). Bottom: precursor with just the right viscosity.
Post-processing#
Bioplastics take a few days to come to their final form. If you have access to a dehydrator that can accomodate your material, use it! At first, I let my material dry on its own. Being the impatient person that I am, I started to use a hair dryer to speed up drying. This was a disappointment: the material melted! I read about how one could dehydrate food at home by turning on your oven at the lowest temperature state (‘keep warm’ setting), which totally sped up the drying. But this involved having my oven on for 8 hours, which is probably energy-intensive, so waiting is the most sustainable bet :)
Other applications#
Since the plastic came out more rigid than I wanted it, I found that another use of the bioplastic could be toward beads for jewelry. The soft nature of the plastic as it cures allows one to poke holes through the bead so that one could use it for a necklace or earrings. See below.
Figure 9. Jewelry made with agar-based bioplastic