Load/Path

A reactor's fuel comes in assemblies, bundles of fuel rods that are lifted in and out as one unit. On 30 August, one tipped over inside the reactor at Palisades in Michigan. It leaned at about 30°, its bottom still in its slot and its top resting on the core shroud, the wall around the core. Getting it out needed a purpose-built tool.

Holtec, which owns the plant, designed a custom lifting device and a special transfer canister. Engineers in New Jersey designed it and a factory in Pittsburgh made it. Crews lifted the assembly into the canister, sealed the lid in the reactor cavity, then moved the canister to the spent fuel pool. Holtec says the lifting device took about two weeks to design, build and deliver. The US Nuclear Regulatory Commission approved the method through a licence change.

Burning waste in air makes flue gas that is only about 8–15% CO₂. Most of the rest is nitrogen from the air. Pulling CO₂ out of such a weak mix needs a big capture plant.

Japanese engineering firm Kanadevia has finished a pilot plant at the Shinagawa incineration plant in Tokyo that burns waste in oxygen instead. The oxygen is mixed with recycled flue gas. With no nitrogen to dilute it, the flue gas should be 30–60% CO₂, so the capture plant can be much smaller. The pilot handles 2 tonnes of waste a day. In lab tests, the process recovered more than 90% of the CO₂, at over 95% purity. Test runs start in November.

Acrylic glass (Plexiglas) is mostly recycled by heating it above 400 °C. That breaks the polymer down, but the monomer that comes out has up to 3% impurities. Other chemical routes needed solvents, catalysts, UV light or specially modified plastic.

Chemists at ETH Zurich add one cheap reagent that is already sold commercially. It attacks the polymer chains and starts them "unzipping" into monomer. The reaction then keeps itself going, with no solvent, from just over 200 °C. Up to 98% of the plastic comes back as monomer. New acrylic made from it is as good as the original, even when the waste was dyed or dirty. ETH has filed a patent.

Every radio has to make a signal, and making a signal costs power. Yet everything around us already gives off thermal noise, the faint static from electrons jiggling with heat.

A Stanford team built a transmitter that sends no signal at all. Its antenna flips between open circuit and short circuit. In one state it absorbs the noise around it; in the other it reflects it. A receiver nearby sees the noise get slightly "hotter" or "colder", and reads 1s and 0s. Tuning the setup with their new model of the channel made data flow 100 times faster than at first. The paper is in PNAS.

Gallium nitride (GaN) chips switch power efficiently, in chargers and power supplies. They are often grown on sapphire, which is cheap but poor at carrying heat away. Heat limits how hard a chip can work.

Researchers at the University of Bristol and Germany's Ferdinand-Braun-Institut grew GaN diodes on sapphire, then removed the sapphire with a laser. They bonded the GaN to tungsten with a silver-tin layer that melts and then sets solid. Tungsten was a compromise: it conducts heat and electricity well enough, it is available, and it expands with heat at a similar rate to GaN. Thermal resistance was 3.1 times lower than for the same diodes still on sapphire. To measure temperature, they coated the chips with tiny titanium dioxide particles and read how they scattered laser light.

Screens are flat. Fabric is made of thin, round fibres, and building circuits on a curved fibre is hard.

A team at the National University of Singapore made each fibre a row of pixels and a touch sensor in one. A laser exposes the joint points on insulated wire, so molten solder bonds only there. The LED strip is then heated and drawn out into a fibre about 1 mm thick, with a touch layer underneath. Each fibre has its own control channel, so one fault doesn't knock out its neighbours. Fifty-four fibres, woven into a sleeve, make a 96 × 54-pixel screen that plays video and survives 50 washes. The paper is in Nature.

A walking robot that weighs over 120 kg has to be safe around the people it works beside. Agility Robotics' co-founder Jonathan Hurst wrote in IEEE Spectrum about how that shaped Digit 5.

When a person approaches, Digit 5 stops, puts its load down, sits on the floor and cuts power to its motors. Safety-rated sensors and separate safety computers make that decision. Safety and product standards shaped the whole design. It got humanlike knees instead of backward-bending legs. Its battery and cooling take about 75% of the torso, for 90 minutes of work and a 9-minute recharge. It can work up to 20 hours a day, lifting 23 kg bins onto 1.75 m shelves.

Prosthetic arms often read the electrical signals from muscles (electromyography, or EMG) through sensors on the skin. Some of these need recalibrating every day, according to the company Phantom Neuro.

Its implant is a flexible silicone strip, 2 cm by 10 cm, with two rows of electrodes. It sits under the skin, sends data out wirelessly, and is powered through a coil from outside the body, like a cochlear implant. Two patients in Melbourne have it. The second operation took about 45 minutes, without general anaesthetic. The company says one calibration might last months.

Lab-grown muscle can contract, but usually the movement is too small to be useful. ETH Zurich's Soft Robotics Lab designed the muscle and its soft scaffold together, in simulation, as one system. (The paper came out in September; ETH publicised it this week.)

The scaffolds are 3D-printed with light in about a minute each. Grooves in them line up the muscle fibres. The resulting actuators are about 1.5 cm long and move up to 11 times further than earlier designs with similar muscle. One jumps about 5 mm per contraction. Another walks at 6.2 mm a second, which ETH says is the fastest, for its size, of any walking robot of this kind.