Tag Archives: wearable

High Power Generator Utilizes Thermal Difference Of Only 5ºC

Objects in our daily lives, such as speakers, refrigerators, and even cars, are becoming “smarter” day by day as they connect to the internet and exchange data, creating the Internet of Things (IoT), a network among the objects themselves. Toward an IoT-based society, a miniaturized thermoelectric generator is anticipated to charge these objects, especially for those that are portable and wearable.

Due to advantages such as its relatively low thermal conductance but high electric conductance, silicon nanowires have emerged as a promising thermoelectric material. Silicon-based thermoelectric generators conventionally employed long, silicon nanowires of about 10-100 nanometers, which were suspended on a cavity to cutoff the bypass of the heat current and secure the temperature difference across the silicon nanowires. However, the cavity structure weakened the mechanical strength of the devices and increased the fabrication cost. To address these problems, a team of Japanese researchers from Waseda University, Osaka University, and Shizuoka University designed and successfully developed a novel silicon-nanowire thermoelectric generator, which experimentally demonstrated a high power density of 12 microwatts per 1cm2, enough to drive sensors or realize intermittent wireless communication, at a small thermal difference of only 5ºC.

Because our generator uses the same technology to manufacture semiconductor integrated circuits, its processing cost could be largely cut through mass production,” says Professor Takanobu Watanabe of Waseda University, the leading researcher of this study. “Also, it could open up a pathway to various, autonomously-driven IoT devices utilizing environmental and body heats. For instance, it may be possible to charge your smartwatch during your morning jog someday.”

The newly developed thermoelectric generator lost the cavity structure but instead shortened the silicon nanowires to 0.25 nanometers, since simulations showed that the thermoelectric performance improved by minimizing the device. Professor Watanabe explains that despite its new structure, the new thermoelectric generator demonstrated the same power density as the conventional devices. More surprisingly, thermal resistance was suppressed, and the power density multiplied by ten times by thinning the generator’s silicon substrate from the conventional 750 nanometers to 50 nanometers with backside grinding.

Source: https://www.waseda.jp/

Nanoscale Transistor

Flexible televisions
, tablets and phones as well as ‘truly wearable’ smart tech are a step closer thanks to a nanoscale transistor created by researchers at The University of Manchester and Shandong University in China. The international team has developed an ultrafast, nanoscale transistor – known as a thin film transistor, or TFT, – made out of an oxide semiconductor. The TFT is the first oxide-semiconductor based transistor that is capable of operating at a benchmark speed of 1 GHz. This could make the next generation electronic gadgets even faster, brighter and more flexible than ever before. A TFT is a type of transistor usually used in a liquid crystal display (LCD). These can be found in most modern gadgets with LCD screens such as smart phones, tablets and high-definition televisions.

How do they work? LCD features a TFT behind each individual pixel and they act as individual switches that allow the pixels to change state rapidly, making them turn on and off much more quickly. But most current TFTs are silicon-based which are opaque, rigid and expensive in comparison to the oxide semiconductor family of transistors which the team from the UK and China are developing. Whilst oxide TFTs will improve picture on LCD displays, it is their flexibility that is even more impressive.

Aimin Song, Professor of Nanoelectronics in the School of Electrical & Electronic Engineering, The University of Manchester, explains:

TVs can already be made extremely thin and bright. Our work may help make TV more mechanically flexible and even cheaper to produce. “But, perhaps even more importantly, our GHz transistors may enable medium or even high performance flexible electronic circuits, such as truly wearable electronics. “Wearable electronics requires flexibility and in many cases transparency, too. This would be the perfect application for our research. “Plus, there is a trend in developing smart homes, smart hospitals and smart cities – in all of which oxide semiconductor TFTs will play a key role.

Oxide-based technology has seen rapid development when compared to its silicon counterpart which is increasingly close to some fundamental limitations. Prof Song says there has been fast progress in oxide-semiconductors in recent years and extensive efforts have been made in order to improve the speed of oxide-semiconductor-based TFTs. So much so some oxide-based technology has already started replacing amorphous silicon in some gadgets. Prof Song thinks these latest developments have brought commercialisation much closer.

Source: http://www.manchester.ac.uk/