Our muscles expand and contract to allow us to move. But it's a challenge to create artificial muscles. At the University of Texas they're using twisted and coiled yarns constructed from carbon nanotubes and filled with paraffin wax. A flash of light can be enough to melt the wax, causing it to expand, increasing the volume of the yarn and making the yarn's length contract. The artificial muscles can lift more than 100,000 times their own weight and generate 85 times more mechanical power than the same size natural muscle. Although they're not suitable for use in the human body, the muscles could be used in robots, toys, mechanical systems and intelligent materials. Excellent lateral thinking there, to convert a straight motion with a twist.

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FIVE BY DOTS: How much data can we cram onto a hard disk? The magnetised regions on a disk are already packed so close together it seems impossible to fit any more in without magnetic interference wrecking things. But perhaps physically separate dots of magnetic material would allow much denser storage? Current manufacturing techniques still can't pack them in densely enough. US researchers may have the answer, with blocks of copolymers that can assemble themselves into regular densely packed repeating patterns. Those patterns can be used as templates for the magnetic dots on a hard disk platter. The new technique could allow hard drives to store data at five times their current density. Though surely there's a trend away from disk drives. Technology Review has more.

WALK THIS WAY: The Rapid Rehab system is a shoe insole designed to gather data while helping to correct walking problems. A custom gel insole includes force sensors, accelerometers and gyroscopes to detect a person's gait. The system monitors footsteps and provides continuous feedback during every step via a smartphone app. This could help physical therapists correct walking problems, and help prevent falls in people with hip replacements. The system could also be used to help sportspeople during training. There could be some innovative uses around specialised training too, such as high-wire walkers. University of Utah details.

NO MORE HEAT THAN LIGHT: When light and heat are mentioned in the same breath it's usually to put them in opposition. But researchers at the University of Texas created a hybrid nanomaterial from copper sulfide nanoparticles and single-walled carbon nanotubes that converts both light and thermal energy into electrical current. They hope to use the material to produce milliwatts of power — enough for sensors or medical devices. The material is more efficient yet less expensive and more environment-friendly than similar hybrids. It's good to see the end of at least one oppositional duality. University of Texas explains.

THROUGH A GLASS DARKLY: Startup View's auto-tinting window system uses electrochromatic glass to both save energy and make people more comfortable. The windows reduce glare and heat, while letting in as much natural light as possible. The production process adds metal oxide gases onto glass to create a ceramic coating. The finished windows include a second glass pane and are wired to a device that connects them to a wifi network. That means they can be controlled from a smartphone. In commercial systems though sensors connect to a building management system that controls the windows automatically. Arguments over the window remote could be truly annoying. Technology Review finds.

Miraz Jordan, knowit.co.nz