System Bits: June 30

Implanted chip for drug delivery; cuttlefish key to next-gen displays; flexing graphene.


Implantable drug-delivery chip
An implantable, microchip-based device developed by MIT spinout Microchips Biotech may soon replace the injections and pills now needed to treat chronic diseases. The company partnered with Teva Pharmaceutical to commercialize its wirelessly controlled, implantable, microchip-based devices that store and release drugs inside the body over many years.

A version of Microchip Biotech's implantable, wirelessly controlled microchip. When an electrical current is delivered to one of the chip's tiny reservoirs, a single dose of therapeutics is released into the body. (Source: Microchips Biotech)

A version of Microchip Biotech’s implantable, wirelessly controlled microchip. When an electrical current is delivered to one of the chip’s tiny reservoirs, a single dose of therapeutics is released into the body. (Source: Microchips Biotech)

The microchips were invented by Microchips Biotech co-founders Michael Cima, the David H. Koch Professor of Engineering, and Robert Langer, the David H. Koch Institute Professor, and consist of hundreds of pinhead-sized reservoirs, each capped with a metal membrane that store tiny doses of therapeutics or chemicals. An electric current delivered by the device removes the membrane, releasing a single dose. The device can be programmed wirelessly to release individual doses for up to 16 years to treat, for example, diabetes, cancer, multiple sclerosis, and osteoporosis.

Are cuttlefish the key to next-generation displays?
Professor Stephen Allen Boppart and researchers at the University of Illinois believe the evasive cuttlefish may improve next-generation display technology.

Cuttlefish are known as the chameleons of the sea because of their ability to control the dynamics of their skin colorations, patterns, and textures, and the researchers believe those dynamics can be imaged in new ways to understand the mechanisms of control.

But by raising cuttlefish and investigating the dynamic optical and mechanical properties, the researchers hope to learn about cuttlefish skin and apply that knowledge to the next generation of displays: tactile displays.

The idea is that by studying these animals that have succeeded in both colorizing and texturizing their skin, researchers can find a way to incorporate the cuttlefishes’ techniques into modern display technology.

They explained that the problem with current screens of different shapes – for example, in phones with curved screens – is that the picture is warped, pixelated, and unclear. Cuttlefish skin has incorporated texture and color so the “picture” it displays is clear and natural. This is something the team has discovered through research.

But no one has studied live cuttlefish skin at the cellular level and in 3D, Boppart said, so he’s using technology he developed for imaging tissues in real time to do so. This allows the research team to identify the cuttlefishes’ different types of cells and optical properties.

They’ve found that cuttlefish optically match within 3 to 5 percent error to their surroundings. So these animals aren’t simply hiding  – they’re actually mimicking and matching their surroundings’ optical wavelengths.

Calculating the electrical properties of carbon cones
According to calculations by theoretical physicists at Rice University and in Russia, flexing graphene may be the most basic way to control its electrical properties.

The Rice lab of Boris Yakobson in collaboration with researchers in Moscow found the effect is pronounced and predictable in nanocones and should apply equally to other forms of graphene. They said it may be possible to access what they call an electronic flexoelectric effect in which the electronic properties of a sheet of graphene can be manipulated simply by twisting it a certain way.

This should be of interest to those considering graphene elements in flexible touchscreens or memories that store bits by controlling electric dipole moments of carbon atoms.

Perfect graphene – an atom-thick sheet of carbon – is a conductor, as its atoms’ electrical charges balance each other out across the plane. But curvature in graphene compresses the electron clouds of the bonds on the concave side and stretches them on the convex side, thus altering their electric dipole moments, the characteristic that controls how polarized atoms interact with external electric fields.

(Source: Rice University)

(Source: Rice University)

The researchers discovered they could calculate the flexoelectric effect of graphene rolled into a cone of any size and length.

Density functional theory was used to compute dipole moments for individual atoms in a graphene lattice and then figure out their cumulative effect. They suggested their technique could be used to calculate the effect for graphene in other more complex shapes, like wrinkled sheets or distorted fullerenes, several of which they also analyzed.

Yakobson sees potential uses for the newly found characteristic. “One possibly far-reaching characteristic is in the voltage drop across a curved sheet,” he said. “It can permit one to locally vary the work function and to engineer the band-structure stacking in bilayers or multiple layers by their bending. It may also allow the creation of partitions and cavities with varying electrochemical potential, more ‘acidic’ or ‘basic,’ depending on the curvature in the 3-D carbon architecture.”

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