All posts by Daniel Davies

DARPA is sending brain implants on a voyage round the body to power artificial limbs

A DARPA-funded research team has created a brain implant that can be transported to the brain through blood vessels and take control of artificial limbs.

The new device – dubbed the stentrode –was developed under DARPA’s Reliable Neural-Interface Technology (RE-NET) program, and offers new potential for safely expanding the use of brain-machine interfaces to treat physical disabilities and neurological disorders.

“DARPA has previously demonstrated direct brain control of a prosthetic limb by paralyzed patients fitted with penetrating electrode arrays implanted in the motor cortex during traditional open-brain surgery,” said program manager for RE-NET, Doug Weber.

“By reducing the need for invasive surgery, the stentrode may pave the way for more practical implementations of those kinds of life-changing applications of brain-machine interfaces.”


Traditional brain implants have been implanted into the brain through invasive surgical procedures that require opening the skull.

However, because of the stentrode’s flexibility and durability it can transported via blood vessels, which are used as portals for accessing deep structures while greatly reducing the trauma associated with open surgery.

Proof-of-concept results, from a study conducted in sheep, are described in an article published in Nature Biotechnology.

The article describes how measurements taken from the motor cortex using the stentrode are quantitatively similar to measurements made by commercially available brain implants that require open-brain surgery.

Image and featured image courtesy of DARPA

Image and featured image courtesy of DARPA

The research into brain-machine interfaces is the defence agency’s latest foray into the health industry having previously created an artificial limb, which communicates directly with the wearer’s neural system, a prosthetic hand that can connect directly to the brain and a number of tiny implantable nerve stimulation devices that can monitor, diagnose and treat the nervous system.

Super-strong, super-stretchy material to be used as artificial skin

A new stretchy material has been developed that can lift an object one-thousand times its weight while still maintaining the ability to revert back to its original shape, when heated at body temperature.

Scientists at the University of Rochester believe that because of its flexibility their shape-memory polymer will be used as artificial skin but could also be useful when applying sutures, for body-heat assisted medical dispensers and for use as a wearable self-fitting apparel.

“Our shape-memory polymer is like a rubber band that can lock itself into a new shape when stretched,” said lead researcher, Mitch Anthamatten. “But a simple touch causes it to recoil back to its original shape.”

Image and featured image courtesy of Adam Fenster, University of Rocheste

Image and featured image courtesy of Adam Fenster, University of Rocheste

The shape-memory polymer works by controlling the crystallisation that occurs when the material is cooled or stretched.

As the material is deformed, polymer chains are stretched, and small segments of the polymer align in the same direction in small areas called crystallites.

These crystallites fix the material into a temporarily deformed shape, but as the number of crystallites grows, the polymer shape becomes more and more stable, making it increasingly difficult for the material to revert back to its initial shape.

To avoid the material becoming fixed in a deformed state the research team inserted molecular linkers to connect the individual polymer strands.

Anthamatten’s group discovered that linkers inhibit, but don’t stop, crystallisation when the material is stretched.

By altering the number and types of linkers used, as well as how they’re distributed throughout the polymer network, the university researchers were able to adjust the material’s structure and precisely set the point at which the material’s shape can be reverted.


As well as being able to stretch and revert back to its original shape the new material has been optimised so that it can store as much elastic energy as possible.

As a result, the shape-memory polymer is capable of lifting an object one-thousand times its weight. For example, a polymer the size of a shoelace – which weighs about a gram – could lift a litre of soda.

“Tuning the trigger temperature is only one part of the story,” said Anthamatten. “We also engineered these materials to store large amount of elastic energy, enabling them to perform more mechanical work during their shape recovery”

Full details of the shape-memory polymer can be found in the Journal of Polymer Science Part B: Polymer Physics.