Skip to Content

How Cocoons Are Turned Into Optical Devices

A simple process turns cocoons into optical devices with biological applications.
December 22, 2008
Preda stirs cut-up cocoons in a salt solution. The cocoons are boiled in a beaker over a hot plate to dissolve the protein that holds them together, sericin. The silk fibers, now pure fibroin protein, will be dissolved in another salt solution.
Using a syringe, Preda loads the syrupy silk solution into a dialysis cartridge. The cartridge will be placed in a beaker of water, which will draw the salt out through the cartridge’s clear window. Finally, Preda will use a syringe to suck out the pure water-fibroin solution left behind, which she’ll store in the fridge.
To make a hologram, a researcher deposits the water-based solution of pure silk fibroin onto a mold with a pipette. Fibroin makes a good optical material because it’s translucent when it dries, and it conforms well to both the nanoscale and macro­scale details of molds like this one.
After drying for several hours, silk optical devices like the hemoglobin-containing card in the researcher’s left hand can be peeled off their molds. Each iridescent square has been molded into a different device. One is a diffraction grating that can act as an oxygen sensor.

Keep Reading

Most Popular

light and shadow on floor
light and shadow on floor

How Facebook and Google fund global misinformation

The tech giants are paying millions of dollars to the operators of clickbait pages, bankrolling the deterioration of information ecosystems around the world.

illustration of Psyche spacecraft
illustration of Psyche spacecraft

NASA wants to use the sun to power future deep space missions

Solar energy can make space travel more fuel-efficient. 

egasus' fortune after macron hack
egasus' fortune after macron hack

NSO was about to sell hacking tools to France. Now it’s in crisis.

French officials were close to buying controversial surveillance tool Pegasus from NSO earlier this year. Now the US has sanctioned the Israeli company, and insiders say it’s on the ropes.

wet market selling fish
wet market selling fish

This scientist now believes covid started in Wuhan’s wet market. Here’s why.

How a veteran virologist found fresh evidence to back up the theory that covid jumped from animals to humans in a notorious Chinese market—rather than emerged from a lab leak.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.