Ricoh Invents Green, Flexible Energy-Generating Material

Japanese electronics maker Ricoh has invented a flexible, energy-generating material that could replace the lead-bearing ceramics used in many sensors, and is durable enough to be widely used in Internet of Things (IoT) devices.

The “energy-generating rubber”, as Ricoh calls it, is a piezoelectric material, meaning that, like quartz, certain crystals and some biologically occurring materials, it produces an electric charge when a mechanical stress is applied. The worldwide market for such devices reached estimated at $14.8 billion in 2013, according to Acmite Market Intelligence, which said it continues to show strong growth.

Piezoelectric materials were first used industrially during the First World War for ultrasonic submarine detectors, which used transducers made of thin quartz crystals. A lightweight piezoelectric crystal mechanism was used in creation of aviation radio during the Second World War, facilitating the development of mass coordinated air strikes.

Today, piezoelectric ceramics are widely used in sensors, for instance in medical instruments or in automobiles for the echolocation devices found in parking systems, but such materials are relatively fragile, and also contain lead, a toxic material. Piezoelectric polymers are also commonly used in industry, but while flexible, they generate a relatively low electric charge.

Ricoh said its new material combines the advantages of both materials, generating a higher charge while being lead-free and having the flexibility of a polymer.
Ricoh said these features should make the new material well-suited to connected devices, allowing sensors or other piezoelectric devices to be built into a wide range of Internet of Things gadgets. It is easier to manufacture than ceramics, since it doesn’t require a high-temperature process, and can be manufactured as a flexible sheet, allowing it to be installed in large spaces, the company said.

“Flexible, high-output, durable, workable and productive, ‘energy-generating rubber’ can be installed in various locations and large spaces,” Ricoh stated. “It can therefore be used for various purposes in the wider market compared with ceramics and polymers.”

Energy harvesting

The company didn’t reveal details of the material’s electricity-generating mechanism, only saying it is different from that of previous materials. The company said it is collaborating with the Tokyo University of Science on a molecular-level mechanism analysis of the material using computational chemistry techniques, a study it expects to help develop new industrial applications.

Acmite said with polymer piezoelectrics are currently showing the strongest growth due to their low weight and small size, characteristics Ricoh said are shared by its new material.

Japan has been a leader in the development of piezoelectric devices since the Second World War, when Japanese scientists independently developed ferroelectric materials, a type of lead-bearing synthetic piezoelectric material, at the same time as their peers in Russia and the US – Ricoh itself dates from around this time, having been founded in 1936. Japanese scientists were, for instance, behind the development of piezoceramic igniters for engines, as well as the piezoelectric ultrasonic transducers used in early television remote controls.

Japan has been behind energy-harvesting projects using piezoelectrics, including piezoelectric floors that have been trialled in two Japanese train stations, Tokyo and Shibuya, since 2007, which use the electricity generated from foot traffic to power automatic ticket gates and electronic display systems.

A Kings Cross-area nightclub called Surya, which opened in 2008, employs a similar technique, using the power generated by piezoelectric crystals in its dancefloor to power lights and air conditioning. The US military research organisation DARPA has also trialled energy-harvesting techniques, building piezoelectric materials into soldiers’ boots to power battlefield equipment, but abandoned the approach due to the discomfort of this footwear.

A piezoelectric transducer was used in the penetrometer instrument on the Huygens probe that landed on Saturn’s moon Titan in 2005, while piezoelectric materials also power acoustic-electric guitar pickups and sensors for medical imaging.

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