Taking inspiration from comic books, the team developed a material that solidifies into a string that adheres to and lifts objects — much like Spider-Man's web-slinging capabilities.

Source: Mario Lo Presti/Tufts University

To create the sticky fibers, which were produced at the Tufts University Silklab, the team used silk from moth cocoons that were boiled in a solution and broken down into proteins known as fibroin. The researchers explained that the silk fibroin solution, mixed with the appropriate additives, can be extruded through narrow needles to form a stream that solidifies into a fiber once it is exposed to air.

Specifically, the team noted that the introduction of dopamine — used in adhesive production — to the silk fibroin allowed for near-instant solidification of the material. Further, when mixed rapidly, the silk solution instantly produced fibers with tremendous tensile strength and stickiness. This is because dopamine and its polymers employ the same chemical process as barnacles to create fibers that stick tightly to surfaces.

The next step involved spinning the fibers in the air. Researchers then integrated dopamine into the silk fibroin solution, thereby accelerating the transition from liquid to solid by removing water from the silk. As such, once the solution is ejected through a coaxial needle, a thin silk stream is enveloped by acetone, thus triggering solidification.

The acetone then evaporates mid-air and leaves behind the sticky fiber that can attach to anything it contacts. The researchers noted that adding chitosan from insect exoskeletons made the fibers up to 200 times stronger while a borate buffer made them stick 18 times better.

While the diameter of the fibers can vary from that of human hair to about half a millimeter, according to the needle used, the device can shoot fibers that can reportedly lift objects over 80 times their own weight. This was demonstrated in the lab where researchers used the device to lift a cocoon, a steel bolt, a floating lab tube, a scalpel partially buried in sand as well as a wooden block from a distance of about 12 cm.

The team is eyeing their silk-shooting technology for applications in robotics, medicine and sustainable materials.

An article detailing the silk-shooting technology, “Dynamic Adhesive Fibers for Remote Capturing of Objects,” appears in the journal Advanced Functional Materials.