MIT Study: Discarded Silk Can Replace Microplastics

For the study, published in Small, the researchers tested the silk coating material in existing spray-based manufacturing equipment by creating a water-soluble microencapsulated herbicide product. When the product was sprayed on corn in a greenhouse, not only did it work as well as existing products, but it also significantly reduced crop damage.

Fortunately, the new silk coating could replace microplastics for more than just chemicals. In fact, the researchers discovered that the silk is so tunable that they can change properties of the resulting coating once it dries and hardens. For example, the material can be hydrophobic even though it is made in a water solution, or it can be hydrophilic—or anywhere in between. It can even be made to match the characteristics of the material it is being used to replace.

“To encapsulate different materials, we have to study how the polymer chains interact and whether they are compatible with different active materials in suspension,” said co-author and MIT postdoc Muchun Liu. “The payload material and the coating material are mixed together in a solution and then sprayed. As droplets form, the payload tends to be embedded in a shell of the coating material, whether that’s the original synthetic plastic or the new silk material.”



These scanning electron microscope images show silk-coated microcapsules containing vitamin C, at different scales of detail. On the left, and top center, samples made by spray drying, a method already widely used in industry. On the right and at bottom center, samples made by ultrasonic spray freeze drying, a method used by the researchers to reveal greater detail of the process involved. Credit: SEM images by Muchun Liu, edited by MIT News


Lab products used in this environmental research:

  • Merlin High-resolution SEM- Zeiss
  • UV-1600PC spectrophotometer- VWR
  • Spectrum 65 with ATR accessory- PerkinElmer
  • Zetasizer Nano-ZS- Malvern Panalytical
  • Milli-Q- MilliporeSigma
  • Mini spray dryer SD-18A- LABFREEZ Instruments
  • ECHO ultrasonication generator- Sono-tek
  • PARSource HID grow lights- Parsource Lighting Solutions
  • New-Tech Spray Chamber- New-Tech

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