A flat-screen panel that resembles a TV on your living room wall could one day remotely charge any device within its line of sight, according to new research.

In a published Oct. 23, 2016, on the arXiv pre-print repository, engineers at the 91Ě˝»¨, Duke University and Intellectual Ventures’ Invention Science Fund (ISF) show that the technology already exists to build such a system — it’s only a matter of taking the time to design it.

“There is an enormous demand for alternatives to today’s clunky charging pads and cumbersome cables, which restrict the mobility of a smart phone or a tablet. Our proposed approach takes advantage of widely used LCD technology to seamlessly deliver wireless power to all kinds of smart devices,” said co-author , 91Ě˝»¨associate professor of electrical engineering and of computer science and engineering.

“The ability to safely direct focused beams of microwave energy to charge specific devices, while avoiding unwanted exposure to people, pets and other objects, is a game-changer for wireless power. And we’re looking into alternatives to liquid crystals that could allow energy transfer at much higher power levels over greater distances,” Reynolds said.

Some wireless charging systems already exist to help power speakers, cell phones and tablets. These technologies rely on platforms that require their own wires, however, and the devices must be placed in the immediate vicinity of the charging station.

This is because existing chargers use the resonant magnetic near-field to transmit energy. The magnetic field produced by current flowing in a coil of wire can be quite large  close to the coil and can be used to induce a similar current in a neighboring coil. Magnetic fields also have the added bonus of being considered safe for human exposure, making them a convenient choice for wireless power transfer.

The magnetic near-field approach is not an option for power transfer over larger distances. This is because the coupling between source and receiver — and thus the power transfer efficiency — drops rapidly with distance. The wireless power transfer system proposed in the new paper operates at much higher microwave frequencies, where the power transfer distance can extend well beyond the confines of a room.

To maintain reasonable levels of power transfer efficiency, the key to the system is to operate in the Fresnel zone — a region of an electromagnetic field that can be focused, allowing power density to reach levels sufficient to charge many devices with high efficiency.

“As long as you’re within a certain distance, you can build antennas that gather electromagnetic energy and focus it, much like a lens can focus a beam of light,” said lead author , professor and chair of the Department of Electrical and Computer Engineering at Duke. “Our proposed system would be able to automatically and continuously charge any device anywhere within a room, making dead batteries a thing of the past.”

The problem to date has been that the antennas in a wireless power transfer system would need to be able to focus on any device within a room. This could be done, for example, with a movable antenna dish, but that would take up too much space, and nobody wants a big, moving satellite dish on their mantel.

Another solution is a phased array — an antenna with a lot of tiny antennas grouped together, each of which can be independently adjusted and tuned. That technology also exists, but would cost too much and consume too much energy for household use.

The solution proposed in the new paper instead relies on metamaterials — a synthetic material composed of many individual, engineered cells that together produce properties not found in nature.

“Imagine you have an electromagnetic wave front moving through a flat surface made of thousands of tiny electrical cells,” said Smith. “If you can tune each cell to manipulate the wave in a specific way, you can dictate exactly what the field looks like when it comes out on the other side.”

Smith and his laboratory used this same principle to create the world’s first cloaking device that bends electromagnetic waves around an object held within. Several years ago, Nathan Kundtz, a former graduate student and postdoc from Smith’s group, led an ISF team that developed the metamaterials technology for satellite communications. The team founded Kymeta, which builds powerful, flat antennas that could soon replace the gigantic revolving satellite dishes often seen atop large boats. Three other companies, Evolv, Echodyne and Pivotal have also been founded using different versions of the metamaterials for imaging, radar and wireless communications, respectively.

In the paper, the research team works through calculations to illustrate what a metamaterials-based wireless power system would be capable of. According to the results, a flat metamaterial device no bigger than a typical flat-screen television could focus beams of microwave energy down to a spot about the size of a cell phone within a distance of up to ten meters. It should also be capable of powering more than one device at the same time.

There are, of course, challenges to engineering such a wireless power transfer system. A powerful, low-cost, and highly efficient electromagnetic energy source would need to be developed. The system would have to automatically shut off if a person or a pet were to walk into the focused electromagnetic beam. And the software and controls for the metamaterial lens would have to be optimized to focus powerful beams while suppressing any unwanted secondary “ghost” beams.

But the technology is there, the researchers say.

“All of these issues are possible to overcome — they aren’t roadblocks,” said Smith. “I think building a system like this, which could be embedded in the ceiling and wirelessly charge everything in a room, is a very feasible scheme.”

For more information, contact Reynolds at matt.reynolds@ee.washington.edu or Ken Kingery at Duke University’s Pratt School of Engineering at ken.kingery@duke.edu.

This news release was adapted from a

A complementary way robots can “sense” what is around them is through the use of small radio-frequency identification, or RFID, tags tuned to ultra-high frequencies. Inexpensive, self-adhesive tags can be stuck on objects, allowing an RFID-equipped robot to search a room for the correct tag’s signal. Once the tag is detected, the robot knows the object isn’t far away.

“But RFID doesn’t tell the robot where it is,” said , a professor at Georgia Institute of Technology. “To actually find the object and get close to it, the robot has to be more clever.”

The 91Ě˝»¨’s , an associate professor of electrical engineering and of computer science and engineering, teamed with Kemp and former Georgia Tech student to develop a new search algorithm that improves a robot’s ability to find and navigate to tagged objects. The team has implemented its system on a type of robot called a , allowing it to travel through a home and correctly locate different types of tagged household objects, including a medication bottle, TV remote, phone and hair brush.

The this month at the in Chicago.

The researchers equipped a PR2 robot with articulated, directionally sensitive antennas and a new algorithm that allows the robot to successfully find and navigate to an object. These antennas tend to receive stronger signals from a tag when they are closer to it and pointed more directly at it.

By moving the antennas around on its shoulders and driving around the room, the robot can figure out the direction it should move to get a stronger signal from a tag and thus become closer to a tagged object.

In essence, the robot plays the classic childhood game of “Hotter/Colder,” with the tag telling the robot when it’s getting closer to the target object.

“While we have demonstrated this technology with a few common household objects, the RFID tags can uniquely identify billions of different objects with essentially zero false positives. This is important because many objects look alike, yet must be uniquely identified,” Reynolds said.

In contrast to other approaches, the robot doesn’t explicitly estimate the 3-D location of the target object, which significantly reduces the complexity of the algorithm.

“Instead, the robot can use its mobility and our special behaviors to get close to a tag and orient toward it,” said Deyle, who conducted the study in Kemp’s lab while earning his doctoral degree.

Deyle, who currently works at Google Inc., says the research has implications for future home robots and is particularly compelling for applications like helping people take medicine.

“This could allow a robot to search for, grasp and deliver the right medication to the right person at the right time,” Deyle said. “RFID provides precise identification, so the risk of delivering the wrong medication is dramatically reduced. Creating a system that allows robots to accurately locate the correct tag is an important first step.”

This research was funded by the National Science Foundation and the Willow Garage PR2 Beta Program.

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For more information, contact Reynolds at matt.reynolds@ee.washington.edu.

This story was adapted from a Georgia Institute of Technology .

What’s coming next, say 91Ě˝»¨ researchers, is the ability to interact with our devices not just with touchscreens, but through gestures in the space around the phone. Some smartphones are starting to incorporate 3-D gesture sensing based on cameras, for example, but cameras consume significant battery power and require a clear view of the user’s hands.

91Ě˝»¨engineers have developed a new form of low-power wireless sensing technology that could soon contribute to this growing field by letting users “train” their smartphones to recognize and respond to specific hand gestures near the phone.

The technology – developed in the labs of and , 91Ě˝»¨associate professors of electrical engineering and of computer science and engineering – uses the phone’s wireless transmissions to sense nearby gestures, so it works when a device is out of sight in a pocket or bag and could easily be built into future smartphones and tablets.

“Today’s smartphones have many different sensors built in, ranging from cameras to accelerometers and gyroscopes that can track the motion of the phone itself,” Reynolds said. “We have developed a new type of sensor that uses the reflection of the phone’s own wireless transmissions to sense nearby gestures, enabling users to interact with their phones even when they are not holding the phone, looking at the display or touching the screen.”

Team members will present their project, called , and a Oct. 8 at the Association for Computing Machinery’s in Honolulu.

When a person makes a call or an app exchanges data with the Internet, a phone transmits radio signals on a 2G, 3G or 4G cellular network to communicate with a cellular base station. When a user’s hand moves through space near the phone, the user’s body reflects some of the transmitted signal back toward the phone.

The new system uses multiple small antennas to capture the changes in the reflected signal and classify the changes to detect the type of gesture performed. In this way, tapping, hovering and sliding gestures could correspond to various commands for the phone, such as silencing a ring, changing which song is playing or muting the speakerphone. Because the phone’s wireless transmissions pass easily through the fabric of clothing or a handbag, the system works even when the phone is stowed away.

“This approach allows us to make the entire space around the phone an interaction space, going beyond a typical touchscreen interface,” Patel said. “You can interact with the phone without even seeing the display by using gestures in the 3-D space around the phone.”

A group of 10 study participants tested the technology by performing 14 different hand gestures – including hovering, sliding and tapping – in various positions around a smartphone. Each time, the phone was calibrated by learning a user’s hand movements, then trained itself to respond. The team found the smartphone recognized gestures with about 87 percent accuracy.

There are other gesture-based technologies, such as “” and “” recently developed at the UW, but researchers say there are important advantages to the new approach.

“SideSwipe’s directional antenna approach makes interaction with the phone completely self-contained, because you’re not depending on anything in the environment other than the phone’s own transmissions,” Reynolds said. “Because the SideSwipe sensor is based only on low-power receivers and relatively simple signal processing compared with video from a camera, we expect SideSwipe would have a minimal impact on battery life.”

The team has filed patents on the technology and will continue developing SideSwipe, integrating the hardware and making a “plug and play” device that could be built into smartphones, said , project lead and a 91Ě˝»¨doctoral student in electrical engineering.

Other co-authors are Ke-Yu Chen, a 91Ě˝»¨doctoral student in electrical engineering, and Md Tanvir Islam Aumi, a doctoral student in computer science and engineering.

This research was funded by the UW.

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For more information, contact Reynolds at matt.reynolds@ee.washington.edu or 206-616-5046.