Engineering for Human Health

Tufts is a leader in the development of cutting-edge biodegradable, biocompatible, and biomimetic devices to monitor our environment and safeguard our health. Engineers from multiple disciplines are teaming up to create edible sensors that can detect diseases in our bodies and toxins in our water, robots made entirely of soft tissue that could slither inside bombs to defuse them or repair our internal organs from the inside, and silk-based scaffolding for growing human blood vessels.

Soft-bots

A team of Tufts scientists is inching its way to a major breakthrough in robotics. They are designing robots made entirely of soft, biocompatible, and biodegradable materials—no exoskeletons, no hinges or metal joints, and nothing toxic. The research could lead to robots that can shimmy along wires, crumple their way into tiny crevices to defuse improvised explosive devices, or even explore internal organs and blood vessels to make surgical repairs. Their inspiration is a thumb-sized green caterpillar known as Manduca sexta, or the tobacco hornworm, a creature that has long fascinated the team's leader, neurobiologist Barry Trimmer, a professor of biology who also holds appointments in biomedical engineering and Tufts Graduate School of Biomedical Sciences.

Trimmer heads up the Biomimetic Devices Laboratory operating in Tufts' Advanced Technology Laboratory (ATL), 40,000 square feet providing lab space for interdisciplinary research. Other research groups there are dedicated to advanced integrated circuits, the mechanics of soft materials, micro and nano fabrication, nanoscale integrated sensors, and tissue engineering. This lab is also the center of the Soft Material Robotics | IGERT doctoral program funded by the National Science Foundation.

The ATL is the perfect home for the soft-bot project, because all sorts of expertise is needed to mimic the tobacco hornworm—from creating computational models of the caterpillar crawling along various surfaces, to recreating its stretchy skin, to building a central nervous system that can control its complex movements and react to its environment.

This last task fell to Valencia Koomson, a professor of electrical and computer engineering. The caterpillar uses relatively few neurons to produce a wide variety of movements, and Joyner has been building micro-scale circuits to approximate this incredibly flexible natural system.

"I can design a circuit that gives out an action potential that looks the same as that stimulated by the caterpillar muscle, but this requires control to ensure then you have to control that so that you're getting actual movement," she says. Another challenge was incorporating sensory feedback, that tells the caterpillar's brain where its legs are in relation to its body while crawling on different kinds of surfaces. To solve this, Koomson teamed up with mechanical engineer Robert White, who designed hair-like sensors that attach to the robot's feet to detect small displacements and feed this information into Koomson's circuits.

Edible optics

Biomedical engineers Fiorenzo Omenetto and David Kaplan are developing biocompatible and biodegradable sensors able to detect everything from body temperature to food-borne bacteria to water pollution. The collaboration began, as many do, with the initiative of a graduate student. A student in Kaplan's lab was working on using silk as a replacement cornea and needed to make tiny, precise cuts in thin silk films. He and Kaplan sought out Omenetto, who has expertise in lasers. And Omenetto, in turn, became fascinated by the optical properties of the films.

Unlike the materials used for most current photonics devices, silk is deemed biocompatible by the Food and Drug Administration, so silk-based sensors could be injected into groundwater systems or integrated into food packaging and could detect the presence of pathogens or toxic chemicals by simply changing color. Plus, the devices Omenetto and Kaplan are creating can be stored at room temperature for long periods without losing their biological activity.

"It's a material, with multiple functionality, that you can eat and that will be reabsorbed by your body," says Omenetto. "This gives us a range of possible sensor applications that didn't exist before."

Metabolic engineering

The goal is to genetically engineer bacteria into tiny factories manufacturing everything from antibiotics to biofuels to anti-cancer drugs. It's not just about rearranging a few genetic sequences. Cell metabolism is an interactive web of chemical reactions. Nothing can be changed in isolation.

"Some reactions we want to shut down and some we want to proceed faster," says Kyongbum Lee, a professor of chemical and biological engineering. "It's analogous to managing traffic in a complex network of streets."

The team now has a working computational model, which Lee calls "a blueprint," for genetically engineering bacteria to produce any number of compounds. "The next step will be to have molecular biologists and molecular engineers follow that blueprint."