Power/Performance Bits: April 15

Smaller is not always better
While Moore’s Law-esque shrinking has allowed for economies of scale in many industries, when it comes to nanomedicine, however, smaller is not always better, according to researchers at UCLA. They have determined that the diminutive size of nanowire-based biosensors — that healthcare workers use to detect proteins that mark the onset of heart failure, cancer and other health risks — is not what makes them more sensitive than other diagnostic devices. What does matter is the interplay between the charged ions in the biological sample being tested and the charged proteins captured on the sensors’ surface.

This finding counters years of conventional wisdom that a biosensor can be made more sensitive simply by reducing the diameter of the nanowires that make up the device. This assumption has driven hundreds of costly research-and-development efforts in the field of nanomedicine — in which tiny materials and devices are used to detect, diagnose and treat disease. The research suggests new directions for designing biosensors to improve their sensitivity and make them more practical for doctors — and, eventually, patients themselves — to use.

The researchers believe this is the first time the understanding of why nanowire biosensing works has been challenged. The advantage is not from the fact that the wires are nanoscale, but rather how their geometry reduces the ability of the ions to inhibit protein detection. This research could be a step toward developing sophisticated, cost-efficient and portable devices to accurately detect a range of illnesses.

A molecular approach to solar power
The problem with solar power today is that sometimes the sun doesn’t shine, but a team of researchers from MIT and Harvard University are working to change that. They’ve come up with an ingenious workaround — a material that can absorb the sun’s heat and store that energy in chemical form, ready to be released again on demand.

They admit the technology is not a solar-energy panacea. While it could produce electricity, it would be inefficient at doing so. But for applications where heat is the desired output — whether for heating buildings, cooking, or powering heat-based industrial processes — this could provide an opportunity for the expansion of solar power into new realms.

One of the researchers explained that this could change the game, since it makes the sun’s energy, in the form of heat, storable and distributable.

The principle is simple: Some molecules, known as photoswitches, can assume either of two different shapes, as if they had a hinge in the middle. Exposing them to sunlight causes them to absorb energy and jump from one configuration to the other, which is then stable for long periods of time.

But these photoswitches can be triggered to return to the other configuration by applying a small jolt of heat, light, or electricity — and when they relax, they give off heat. In effect, they behave as rechargeable thermal batteries: taking in energy from the sun, storing it indefinitely, and then releasing it on demand.

A powerful arc lamp is used to simulate sunlight on a sample of photoswitchable molecules, driving structural changes at the molecular level. A portion of the light’s energy is stored with each structural change. The progress of these changes can be tracked by monitoring the molecules’ optical properties. (Source: MIT)

The working cycle of a solar thermal fuel is depicted in this illustration, using azobenzene as an example. When such a photoswitchable molecule absorbs a photon of light, it undergoes a structural rearrangement, capturing a portion of the photon’s energy as the energy difference between the two structural states. When the molecule is triggered to switch back to the lower-energy form, it releases that energy difference as heat. (Source: MIT)

Further exploration of materials and manufacturing methods will be needed to create a practical system for production, but a commercial system is now a big step closer.