6. Biofabricating

This week we learned about bio plastics- plastics derived from natural materials. Bio materials can have many properties and applications thereby making them a viable alternative to petroleum based plastics. Bio plastics can be made from an array of natural materials including- mushroom, fish skins, fruit, and gelatin. Below are some examples of bio materials + fibers that I came across in my research.

Field Trip

We also had the opportunity to learn about some exciting research happening right in our backyard, at the Tufts University Silk Lab. We got a tour of the facilities, learned about some cutting edge research and applications. Silk derived from silk worms have incredible properties and has applications in advanced medical therapeutics, implantables, sensors, food preservation, the list goes on ! More on the Tufts Silk lab here and their research here. Visiting this lab has me thinking about how I can apply this new knowledge to my final project. Specifically, I am interested in 3D printing with silk fibers.

Various Silk Worm Specimens seen at the Silk Lab

A TED Talk about Silk

Assignment

I decided to create my own bio-plastic material using arrowroot starch and gelatine as my polymer and vegetable glycerine as my plasticizer. What is arrowroot anyway? According to Mountain Rose Herbs, arrowroot:

Arrowroot powder is a natural powdered root starch that is white in color and very lightweight. It is derived from the tropical South American plant Maranta arundinacea. This starchy root was a staple in the diet of the Arawak people, and they called it 'aru-ruta' which led to the name arrowroot as we know it.

The Awawak people are an indigenous peoples of South America and of the Caribbean. I was interested in using this starch because of where it is derived from. Because arrowroot starch is used as an alternative to cornstarch in cooking, I wondered if it could be used as a replacement for a cornstarch/potato starch and glycerine bio plastic.

Materials:

  • Food Scale
  • Food Thermometer
  • Silicon Mold
  • Water
  • Arrowroot starch
  • Pigment of choice (I used hybiscus)
  • White vinegar
  • Vegetable Glycerine
  • Gelatine

Gelatine/Glycerine Bio-Resin Recipe

  • Preparing the hibiscus dye

    • Bring ~ 300 mL of water to boil. Add 9 g of dried hibiscus and let simmer for ~20 minutes on med/low heat. Stir occassionaly. Drain to separate flowers from colored water.

  • Making the bio-resin

    • Bring approximately 240 mL of dyed water to a boil. Add 24 grams of gelatine and stir until the gelatin completely dissolves. Add 4 g of glycerine. Allow to simmer. Continue to stir and do not let the mixture exceed 90C. When the mixture becomes a syrup-like consistency, remove from heat. Pour into chosen cast and allow to cool.

Arrowroot Bio-plastic Recipe

  • Bring approximately 160 mL of dyed water to a boil. Add 4 grams of arrowroot and stir until the arrowroot completely dissolves for approximately 15- 20 minutes. Add 40 g of glycerine. Allow to simmer. Continue to stir and do not let the mixture exceed 90C. When the mixture becomes a syrup-like consistency, remove from heat. Pour into chosen cast and allow to cool.

1. Some tools for bio-plastic synthesis. 2. Gelatine/Glycerine Bio-Resin 3. Arrowroot Bio-plastic.

Results

Below is a table summarizing my preliminary results.

  • Gelatine/Glycerine Bio-Resin
    • The first resin I made happened to be by accident. I made a resin film after letting my pot boil over. The result was a thin film that formed on my stove top. This film was very brittle and dissolved readily in water (do not handle with wet hands !)
    • The second resin I made was poured into a mold and allowed to air dry. The 3rd resin was placed in a silicon mold in the oven at 76C for ~4 hours. The resin that was air dried had a jelly like texture after 4 hours of drying.

1.Gelatine/Glycerine Bio-Resin 2. Film 3. Soild, jelly-like 4. Hardened, air bubbles

  • Arrowroot Bio-plastic
    • After pouring the arrowroot bio-plastic into a mold, I put it in the oven for approximately 4 hours at 76C. I also left a sample to air dry as a control. After 4 hours of drying under these conditions there wasn’t much difference between both samples. Both were sticky to the touch yet gel like. It is possible that I didn’t use enough arrowroot powder or too much plasticizer. I will continue to monitor the drying and changes in properties over time.

Arrowroot Bio-plastic

Future Work

  • Both bio-plastics can stand to lose more water. I am interested in seeing how both plastics behave over time as they dry. I would also like to investigate using a dehydrator instead of the oven to control and speed up the drying process.
  • I am interested in characterizing these bio plastics I made. I am interested in there mechanical properties as I know that would dictate performance. I am also interested in the chemophysical properties as well as some imaging via microscopy of the bio materials I made. These properties include: thermal analysis, LOD (loss on drying), etc.
  • I am interested in exploring arrowroot to glycerine ratios more as the results from my experiment did not generate a fleixble plastic but rather a very gel like substance.

Resources