The Eco-Ride was developed by Tokyo University and doesn't run on ordinary tracks.

, its speed controlled by aerodynamics and curves. At stations it's stopped and started by rotating wheels between the rails that catch a fin under the train. It uses its own inertia to climb slopes, though it may need to be winched up steeper inclines. With no engine, the train is lightweight, so it doesn't take a lot of energy to run. Now for the swings and roundabouts.

LIGHT FALL: Kerosene lamps are vital in developing countries but create harmful smoke and are a fire risk. The GravityLight could be an alternative. It's a low cost light with no ongoing running costs. Fill a bag with rocks or sand and hang it from the light. As the bag drops it generates enough power for around 30 minutes of light. No batteries means no problems with replacing them. Some mechanical clocks used to work like that, didn't they?


PUT ALGAE TO WORK: Wastewater in a commercial building usually just goes down the drain. In one highrise office block in Paris though, they're growing algae in wastewater in panels on the side of the building. The algae use the nutrients in the water for their own growth, which takes 24 to 48 hours. That helps clean up the water. Once grown, the algae are used as biomass to produce energy. That's a great way to clean up.

SWEATY TATTOO: If you have to wear a monitor, perhaps to check your skin's pH levels in response to metabolic stress from exertion, then why not make it fun? A sensor from the University of Toronto looks and works like a temporary tattoo. It uses standard screen printing techniques and commercially available transfer tattoo paper, and is shaped like a smiley face. Unlike bulky sensors that may fall off during exercise or when the wearer's sweating, these sensors stay in place. By using different sensing materials, the tattoos can be modified to detect other components of sweat. It's good to see some fun in the serious work.

PLASTIC PHONE: Dai Nippon Printing hope their new plastic will replace the glass covers on smartphone displays. The plastic resists abrasion and fingerprints yet is flexible and lets a lot of light through. They aim to start shipping in volume early in 2013. But does it feel as good as glass?