First self-powered device with wireless data transmission

First self-powered device with wireless data transmission

  9:55:00 AM    Science Lover

---

Scientists are reporting development of the first self-powered nano-device that can transmit data wirelessly over long distances. In a study in ACS's journal Nano Letters, they say it proves the feasibility of a futuristic genre of tiny implantable medical sensors, airborne and stationary surveillance cameras and sensors, wearable personal electronics, and other devices that operate independently without batteries on energy collected from the environment.

Zhong Lin Wang and colleagues explain that advances in electronics have opened the door to developing tiny devices that operate battery-free on minute amounts of electricity that can be harvested from the pulse of a blood vessel, a gentle breeze, or the motions of a person walking. "It is entirely possible to drive the devices by scavenging energy from sources in the environment such as gentle airflow, vibration, sonic wave, solar, chemical, and/or thermal energy," the scientists explain.

The device consists of a nanogenerator that produces electricity from mechanical vibration/triggering, a capacitor to store the energy, and electronics that include a sensor and a radio transmitter similar to those in Bluetooth mobile phone headsets. Their device transmitted wireless signals that could be detected by an ordinary commercial radio at distances of more than 30 feet.

More information: “Self-Powered System with Wireless Data Transmission” Nano Lett., 2011, 11 (6), pp 2572–2577 DOI: 10.1021/nl201505c

Abstract

We demonstrate the first self-powered system driven by a nanogenerator (NG) that works wirelessly and independently for long-distance data transmission. The NG was made of a free cantilever beam that consisted of a five-layer structure: a flexible polymer substrate, ZnO nanowire textured films on its top and bottom surfaces, and electrodes on the surfaces. When it was strained to 0.12% at a strain rate of 3.56% S–1, the measured output voltage reached 10 V, and the output current exceeded 0.6 μA (corresponding power density 10 mW/cm3). A system was built up by integrating a NG, rectification circuit, capacitor for energy storage, sensor, and RF data transmitter. Wireless signals sent out by the system were detected by a commercial radio at a distance of 5–10 m. This study proves the feasibility of using ZnO nanowire NGs for building self-powered systems, and its potential application in wireless biosensing, environmental/infrastructure monitoring, sensor networks, personal electronics, and even national security.

Provided by American Chemical Society

Read More

New Artificial Skin Could Make Prosthetic Limbs and Robots More Sensitive

New Artificial Skin Could Make Prosthetic Limbs and Robots More Sensitive

  9:24:00 AM    Science Lover

---

The light, tickling tread of a pesky fly landing on your face may strike most of us as one of the most aggravating of life's small annoyances. But for scientists working to develop pressure sensors for artificial skin for use on prosthetic limbs or robots, skin sensitive enough to feel the tickle of fly feet would be a huge advance. Now Stanford researchers have built such a sensor.

The sensor is sensitive enough to easily detect this Peruvian butterfly (Chorinea faunus) with transparent wings and red-tipped tails, positioned on a sheet of the sensors. (Credit: Linda Cicero, Stanford University News Service)

By sandwiching a precisely molded, highly elastic rubber layer between two parallel electrodes, the team created an electronic sensor that can detect the slightest touch.

"It detects pressures well below the pressure exerted by a 20 milligram bluebottle fly carcass we experimented with, and does so with unprecedented speed," said Zhenan Bao, an associate professor of chemical engineering who led the research.

The key innovation in the new sensor is the use of a thin film of rubber molded into a grid of tiny pyramids, Bao said. She is the senior author of a paper published Sept. 12 online by Nature Materials.

Previous attempts at building a sensor of this type using a smooth film encountered problems.

"We found that with a very thin continuous film, when you press on it, the material does not have room to expand," said Stefan Mannsfeld, a former postdoctoral researcher in chemical engineering and a coauthor. "So the molecules in the continuous rubber film are forced closer together and become entangled. When pressure is released, they cannot go back to the original arrangement, so the sensor doesn't work as well."

"The microstructuring we developed makes the rubber behave more like an ideal spring," Mannsfeld said. The total thickness of the artificial skin, including the rubber layer and both electrodes, is less than one millimeter.

The speed of compression and rebound of the rubber is critical for the sensor to be able to detect -- and distinguish between -- separate touches in quick succession.

The thin rubber film between the two electrodes stores electrical charges, much like a battery. When pressure is exerted on the sensor, the rubber film compresses, which changes the amount of electrical charges the film can store. That change is detected by the electrodes and is what enables the sensor to transmit what it is "feeling."

The largest sheet of sensors that Bao's group has produced to date measures about seven centimeters on a side. The sheet exhibited a great deal of flexibility, indicating it should perform well when wrapped around a surface mimicking the curvature of something such as a human hand or the sharp angles of a robotic arm.

Bao said that molding the rubber in different shapes yields sensors that are responsive to different ranges of pressure. "It's the same as for human skin, which has a whole range of sensitivities," she said. "Fingertips are the most sensitive, while the elbow is quite insensitive."

The sensors have from several hundred thousand up to 25 million pyramids per square centimeter. Under magnification, the array of tiny structures looks like the product of an ancient Egyptian micro-civilization obsessed with order and gone mad with productivity.

But that density allows the sensors to perceive pressures "in the range of a very, very gentle touch," Bao said. By altering the configuration of the microstructure or the density of the sensors, she thinks the sensor can be refined to detect subtleties in the shape of an object.

"If we can make this in higher resolution, then potentially we should be able to have the image on a coin read by the sensor," she said. A robotic hand covered with the electronic skin could feel a surface and know rough from smooth.

That degree of sensitivity could make the sensors useful in a broad range of medical applications, including robotic surgery, Bao said. In addition, using bandages equipped with the sensors could aid in healing of wounds and incisions. Doctors could use data from the sensors to be sure the bandages were not too tight.

Automobile safety could also be enhanced. "If a driver is tired, or drunk, or falls asleep at the wheel, their hands might loosen or fall off the wheel," said Benjamin Tee, graduate student in electrical engineering and a coauthor. "If there are pressure sensors that can sense that no hands are holding the steering wheel, the car could be equipped with some automatic safety device that could sound an alarm or kick in to slow the car down. This could be simpler and cost less than other methods of detecting driver fatigue."

The team also invented a new type of transistor in which they used the structured, flexible rubber film to replace a component that is normally rigid in a typical transistor. When pressure is applied to their new transistor, the pressure causes a change in the amount of current that the transistor puts out. The new, flexible transistors could also be used in making artificial skin, Bao said.

As Bao's team continues its research, the members may find applications not yet considered as well as other ways to demonstrate the sensitivity of their sensors. They have already expanded their stable of insects beyond the bluebottle fly to include some beautiful, delicate looking -- albeit slightly heavier -- butterflies.

But if the researchers wanted an even more ethereal demonstration, could the sensors detect the bubbles rising in a glass of champagne?

"If the bubbles coming out from the champagne impinge onto the pressure sensor, that might be possible," Bao said. "That would be an interesting experiment to do in the lab."

Read More

Robot fish to detect pollution in waters

Robot fish to detect pollution in waters

  1:12:00 AM    Science Lover

---

The robotic fish, equipped with sensors that detect hazardous elements, can operate underwater for over eight hours at a time

Scientists in the UK have developed new robotic fish to detect water pollution in rivers, lakes and seas.

The robots – costing around $29,000 each – are being built by Professor Huosheng Hu and his robotics team at the School of Computer Science and Electronic Engineering, University of Essex.

The life-like creatures, which will mimic the undulating movement of real fish, will be equipped with tiny chemical sensors to find the source of potentially hazardous pollutants in the water, such as leaks from vessels in the port or underwater pipelines.

The fish will then transmit their data through Wi-Fi technology when they dock to charge their batteries, which last around eight hours.

Rory Doyle, senior research scientist at technology consultancy BMT Group, has described the project as a “world first”.

“In using robotic fish, we are building on a design created by hundreds of millions of years’ worth of evolution which is incredibly energy efficient. This efficiency is something we need to ensure that our pollution detection sensors can navigate in the underwater environment for hours on end,” he said.

“We will produce a system that allows the fish to search underwater, meaning that we will be able to analyse not only chemicals on the surface of the water, but also those that are dissolved in the water,” he added.

Doyle and Hu hope to release five of the bots into the water by the end of next year.

If you like this post, buy me a beer at $3!

Read More

Watchful windows

Watchful windows

  10:20:00 PM    Science Lover

---

New light-sensitive sensor technology could enable your windows to detect intruders and sound an alarm

Ever had that sinking feeling that someone is sneaking around in front of your window, probably trying to break in? With new technology crafted by researchers in Germany, windows and doors might soon be able to detect whether there’s suspicious activity outside your house, and accordingly, sound an alarm.

A novel motion sensor developed by the Fraunhofer Institutes for Applied Polymer Research (IAP) in Potsdam-Golm enables window panes and glass doors to detect movements, thanks to a special coating.

If anything changes in front of a pane, or someone sneaks up to it, an alarm is soon sounded.

“The glass is coated with a fluorescent material,” explains IAP group manager Dr Burkhard Elling. “The coating contains nanoparticles that convert light falling on the window into fluorescent radiation.”

How it works

The principle is as follows: The invisible light of an ultraviolet (UV) lamp “illuminates” the window panes, and generates fluorescent radiation in the coating. Sensors in the edges of the window detect this radiation, and thus keep a tab on activities.

A single sensor can perform simple applications: For example, if someone steps into the light of the lamp, less light reaches the coating and less fluorescent radiation is produced – thus triggering the sensor.

If several sensors are installed on all four sides of the window frame, conclusions can be drawn from the data as to how fast and in what direction an object is moving. Its size, too, can be estimated by the sensors.

The invisible light of a UV lamp ‘illuminates’ the window panes and generates fluorescent radiation in the coating. This radiation is detected by sensors in the edges of the window

“This is especially useful in warding off false alarms. For instance, by setting a threshold for the alarm, moving objects that are the size of birds do not set off any sirens,” Elling says.

Likewise, the smart sensors do not react to light from passing cars, as the researchers have developed a software application that can interpret different light signals. This enables the system to easily distinguish between a UV lamp and the slowly changing light from a passing headlight.

“The system has further advantages: For one, it does not infringe on anybody’s personal rights, as it only detects the change in radiation, and not who triggered it,” Elling points out.

“It is also cost-efficient, because the coating can be sprayed onto the windows by airbrush or glued on as a film,” he adds.

A demonstrator system has already been made, and the boffins are aiming to market it at places such as museums.

If you like this post, buy me a beer at $3!

Read More