Underwater exploration gets its own battery free sensing system

A battery-free underwater “piezoelectric” sensor invented by MIT researchers transmits data by absorbing or reflecting sound waves back to a receiver, where a reflected wave decodes a 1 bit and an absorbed wave decodes a 0 bit — and simultaneously stores energy. Image courtesy of the researchers

Submerged system uses the vibration of “piezoelectric” materials to generate power and send and receive data.

To investigate the vastly unexplored oceans covering most our planet, researchers aim to build a submerged network of interconnected sensors that send data to the surface — an underwater “internet of things.” But how to supply constant power to scores of sensors designed to stay for long durations in the ocean’s deep?

MIT researchers have an answer: a battery-free underwater communication system that uses near-zero power to transmit sensor data. The system could be used to monitor sea temperatures to study climate change and track marine life over long periods — and even sample waters on distant planets. They are presenting the system at the SIGCOMM conference this week, in a paper that has won the conference’s “best paper” award.

The system makes use of two key phenomena. One, called the “piezoelectric effect,” occurs when vibrations in certain materials generate an electrical charge. The other is “backscatter,” a communication technique commonly used for RFID tags, that transmits data by reflecting modulated wireless signals off a tag and back to a reader.

In the researchers’ system, a transmitter sends acoustic waves through water toward a piezoelectric sensor that has stored data. When the wave hits the sensor, the material vibrates and stores the resulting electrical charge. Then the sensor uses the stored energy to reflect a wave back to a receiver — or it doesn’t reflect one at all. Alternating between reflection in that way corresponds to the bits in the transmitted data: For a reflected wave, the receiver decodes a 1; for no reflected wave, the receiver decodes a 0.

“Once you have a way to transmit 1s and 0s, you can send any information,” says co-author Fadel Adib, an assistant professor in the MIT Media Lab and the Department of Electrical Engineering and Computer Science and founding director of the Signal Kinetics Research Group. “Basically, we can communicate with underwater sensors based solely on the incoming sound signals whose energy we are harvesting.”

The researchers demonstrated their Piezo-Acoustic Backscatter System in an MIT pool, using it to collect water temperature and pressure measurements. The system was able to transmit 3 kilobytes per second of accurate data from two sensors simultaneously at a distance of 10 meters between sensor and receiver.

Applications go beyond our own planet. The system, Adib says, could be used to collect data in the recently discovered subsurface ocean on Saturn’s largest moon, Titan. In June, NASA announced the Dragonfly mission to send a rover in 2026 to explore the moon, sampling water reservoirs and other sites.

“How can you put a sensor under the water on Titan that lasts for long periods of time in a place that’s difficult to get energy?” says Adib, who co-wrote the paper with Media Lab researcher JunSu Jang. “Sensors that communicate without a battery open up possibilities for sensing in extreme environments.”

Preventing deformation

Inspiration for the system hit while Adib was watching “Blue Planet,” a nature documentary series exploring various aspects of sea life. Oceans cover about 72 percent of Earth’s surface. “It occurred to me how little we know of the ocean and how marine animals evolve and procreate,” he says. Internet-of-things (IoT) devices could aid that research, “but underwater you can’t use Wi-Fi or Bluetooth signals … and you don’t want to put batteries all over the ocean, because that raises issues with pollution.”

That led Adib to piezoelectric materials, which have been around and used in microphones and other devices for about 150 years. They produce a small voltage in response to vibrations. But that effect is also reversible: Applying voltage causes the material to deform. If placed underwater, that effect produces a pressure wave that travels through the water. They’re often used to detect sunken vessels, fish, and other underwater objects.

“That reversibility is what allows us to develop a very powerful underwater backscatter communication technology,” Adib says.

Communicating relies on preventing the piezoelectric resonator from naturally deforming in response to strain. At the heart of the system is a submerged node, a circuit board that houses a piezoelectric resonator, an energy-harvesting unit, and a microcontroller. Any type of sensor can be integrated into the node by programming the microcontroller. An acoustic projector (transmitter) and underwater listening device, called a hydrophone (receiver), are placed some distance away.

Say the sensor wants to send a 0 bit. When the transmitter sends its acoustic wave at the node, the piezoelectric resonator absorbs the wave and naturally deforms, and the energy harvester stores a little charge from the resulting vibrations. The receiver then sees no reflected signal and decodes a 0.

However, when the sensor wants to send a 1 bit, the nature changes. When the transmitter sends a wave, the microcontroller uses the stored charge to send a little voltage to the piezoelectric resonator. That voltage reorients the material’s structure in a way that stops it from deforming, and instead reflects the wave. Sensing a reflected wave, the receiver decodes a 1.

Long-term deep-sea sensing

The transmitter and receiver must have power but can be planted on ships or buoys, where batteries are easier to replace, or connected to outlets on land. One transmitter and one receiver can gather information from many sensors covering one area or many areas.

“When you’re tracking a marine animal, for instance, you want to track it over a long range and want to keep the sensor on them for a long period of time. You don’t want to worry about the battery running out,” Adib says. “Or, if you want to track temperature gradients in the ocean, you can get information from sensors covering a number of different places.”

Another interesting application is monitoring brine pools, large areas of brine that sit in pools in ocean basins, and are difficult to monitor long-term. They exist, for instance, on the Antarctic Shelf, where salt settles during the formation of sea ice, and could aid in studying melting ice and marine life interaction with the pools. “We could sense what’s happening down there, without needing to keep hauling sensors up when their batteries die,” Adib says.

Polly Huang, a professor of electrical engineering at Taiwan National University, praised the work for its technical novelty and potential impact on environmental science. “This is a cool idea,” Huang says. “It’s not news one uses piezoelectric crystals to harvest energy … [but is the] first time to see it being used as a radio at the same time [which] is unheard of to the sensor network/system research community. Also interesting and unique is the hardware design and fabrication. The circuit and the design of the encapsulation are both sound and interesting.”

While noting that the system still needs more experimentation, especially in sea water, Huang adds that “this might be the ultimate solution for researchers in marine biography, oceanography, or even meteorology — those in need of long-term, low-human-effort underwater sensing.”

Next, the researchers aim to demonstrate that the system can work at farther distances and communicate with more sensors simultaneously. They’re also hoping to test if the system can transmit sound and low-resolution images.

Learn more: A battery-free sensor for underwater exploration


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New material approach means piezoelectric energy harvesting could see a 10 fold increase

A 10-fold increase in the ability to harvest mechanical and thermal energy over standard piezoelectric composites may be possible using a piezoelectric ceramic foam supported by a flexible polymer support, according to Penn State researchers.
Image: Wang Lab/Penn State

A 10-fold increase in the ability to harvest mechanical and thermal energy over standard piezoelectric composites may be possible using a piezoelectric ceramic foam supported by a flexible polymer support, according to Penn State researchers.

In the search for ways to harvest small amounts of energy to run mobile electronic devices or sensors for health monitoring, researchers typically add hard ceramic nanoparticles or nanowires to a soft, flexible polymer support. The polymer provides the flexibility, while the piezo nanoparticles convert the mechanical energy into electrical voltage. But these materials are relatively inefficient, because upon mechanical loading the mechanical energy is largely absorbed by the bulk of the polymer, with a very small fraction transferred to the piezo nanoparticles. While adding more ceramic would increase the energy efficiency, it comes with the tradeoff of less flexibility.

“The hard ceramics in the soft polymer is like stones in water,” said Qing Wang, professor of materials science and engineering, Penn State. “You can slap the surface of the water, but little force is transferred to the stones. We call that strain-transfer capability.”

Almost three decades ago, the late Penn State materials scientist Bob Newnham came up with the concept that the connectivity of the piezo filler determined the efficiency of the piezoelectric effect. A three-dimensional material would be more efficient than what he classified as zero-dimensional nanoparticles, one-dimensional nanowires or two-dimensional films, because the mechanical energy would be transported directly through the three-dimensional material instead of dissipating into the polymer matrix.

“Bob Newnham was a legend in the field of piezoelectrics,” said Wang. “so everybody in the ceramic community knew of his approach, but how to achieve that 3-D structure with a well-defined microstructure remained a mystery.”

The secret ingredient to solve the mystery turned out to be a cheap polyurethane foam dusting sheet that can be purchased at any home improvement store. The small uniform protrusions on the sheet act as a template for forming the microstructure of the piezoelectric ceramic. The researchers applied the ceramic to the polyurethane sheet in the form of suspended nanoparticles in solution. When the template and solution are heated to a high enough temperature, the sheet burns out and the solution crystalizes into a solid 3-D microform foam with uniform holes. They then fill the holes in the ceramic foam with polymer.

“We see that this 3-D composite has a much higher energy output under different modes,” said Wang. “We can stretch it, bend it, press it. And at the same time, it can be used as a pyroelectric energy harvester if there is a temperature gradient of at least a few degrees.”

Sulin Zhang, professor of engineering science and mechanics, Penn State is the other corresponding author on the paper that appears in Energy and Environmental Science. Zhang and his students were responsible for extensive computational work simulating the piezoelectric performance of the 3-D composite.

“We were able to show theoretically that the piezoelectric performance of nanoparticle/nanowire composites is critically limited by the large disparity in stiffness of the polymer matrix and piezoceramics, but the 3-D composite foam is not limited by stiffness,” said Zhang. “This is the fundamental difference between these composite materials, which speaks to the innovation of this new 3-D composite. Our extensive simulations further demonstrate this idea.”

Currently, Wang and his collaborators are working with lead-free and more environmentally friendly alternatives to the current lead-zirconium-titanate ceramic.

“This is a very general method,” said Wang. “This is to demonstrate the concept, based on Bob Newnham’s work. It is good to continue the work of a Penn State legend and to advance this field.”

Learn more: Flexible, highly efficient multimodal energy harvesting


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New surface acoustic wave device is up to six times faster for the IoT

VIA Nanowerk

New embedded transducer approach allows surface acoustic wave device to transmit signals with six times the speed of most commercially used devices.

In today’s “internet of things,” devices connect primarily over short ranges at high speeds, an environment in which surface acoustic wave (SAW) devices have shown promise for years, resulting in the shrinking size of your smartphone. To obtain ever faster speeds, however, SAW devices need to operate at higher frequencies, which limits output power and can deteriorate overall performance. A new SAW device looks to provide a path forward for these devices to reach even higher frequencies.

A team of researchers in China has demonstrated a SAW device that can achieve frequencies six times higher than most current devices. With embedded interdigital transducers (IDTs) on a layer of combined aluminum nitride and diamond, the team’s device was also able to boost output significantly. Their results are published this week in Applied Physics Letters, from AIP Publishing.

“We have found the acoustic field distribution is quite different for the embedded and conventional electrode structures,” said Jinying Zhang, one of the paper’s authors. “Based on the numerical simulation analysis and experimental testing results, we found that the embedded structures bring two benefits: higher frequency and higher output power.”

Surface acoustic wave devices transmit a high-frequency signal by converting electric energy to acoustic energy. This is often done with piezoelectric materials, which are able to change shape in the presence of an electric voltage. IDT electrodes are typically placed on top of piezoelectric materials to perform this conversion.

Ramping up the operational frequency of IDTs — and the overall signal speed — has proven difficult. Most current SAW devices top out at a frequency of about 3 gigahertz, Zhang said, but in principle it is possible to make devices that are 10 times faster. Higher frequencies, however, demand more power to overcome the signal loss, and in turn, some features of the IDTs need to be increasingly small. While a 30 GHz device could transmit a signal more quickly, its operational range becomes limited.

“The major challenge is still the fabrication of the IDTs with such small feature sizes,” Zhang said. “Although we made a lot of efforts, there are still small gaps between the side walls of the electrodes and the piezoelectric materials.”

To ensure that the transducers had the proper feature size, Zhang’s team needed a material with a high acoustic velocity, such as diamond. They then coupled diamond, a material that changes its shape very little with electric voltage, with aluminum nitride, a piezoelectric material, and embedded the IDT inside their new SAW device.

The resulting device operated at a frequency of 17.7 GHz and improved power output by 10 percent compared to conventional devices using SAWs.

“The part which surprised us most is that the acoustic field distribution is quite different for the embedded and conventional electrode structures,” Zhang said. “We had no idea at all about it before.”

Zhang said she hopes this research will lead to SAW devices used in monolithic microwave integrated circuits (MMICs), low-cost, high-bandwidth integrated circuits that are seeing use in a variety of forms of high speed communications, such as cell phones.

Learn more: Acoustic device makes piezoelectrics sing to a different tune


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Low-cost biomaterial generates electricity

Mobile phone speakers and motion detectors in cars and video games may soon be powered by electricity generated from low cost and sustainable biomaterials, according to research carried out at University of Limerick (UL), Ireland. Scientists at UL’s Bernal Institute have discovered that the biomolecule glycine, when tapped or squeezed, can generate enough electricity to power electrical devices in an economically viable and environmentally sustainable way. The research was published on Dec. 4, 2017 in leading international journal Nature Materials. Pictured is Sarah Guerin, Science Foundation Ireland funded post-graduate researcher at the Bernal Institute, UL.

Irish researchers squeeze low-cost electricity from sustainable biomaterial

Mobile phone speakers and motion detectors in cars and video games may soon be powered by electricity generated from low cost and sustainable biomaterials, according to research carried out at University of Limerick (UL), Ireland.

Scientists at UL’s Bernal Institute have discovered that the biomolecule glycine, when tapped or squeezed, can generate enough electricity to power electrical devices in an economically viable and environmentally sustainable way. The research was published on December 4, 2017 in leading international journal Nature Materials.

Glycine is the simplest amino acid. It occurs in practically all agro and forestry residues. It can be produced at less than one per cent of the cost of currently used piezoelectric materials.

Piezoelectric materials generate electricity in response to pressure, and vice versa. They are widely used in cars, phones, and remote controls for games consoles. Unlike glycine, these materials are normally synthetic and often contain toxic elements such as lead or lithium.

“It is really exciting that such a tiny molecule can generate so much electricity,” said lead author Sarah Guerin, a post-graduate student at the Department of Physics and the Bernal Institute, UL.

“We used computer models to predict the electrical response of a wide range of crystals and the glycine number was off the charts. We then grew long, narrow crystals of glycine in alcohol,” she added, “and we produced electricity just by tapping them.”

Sarah’s PhD supervisor Dr Damien Thompson, adds, “The predictive models we are developing can save years of trial-and-error lab work. The modelling data tells us what kinds of crystals to grow and where best to cut and press those crystals to generate electricity.”

Co-author and Science Foundation Ireland (SFI) Centre for Medical Devices (CURAM) investigator Professor Tofail Syed said: “We also have a pending patent that translates our findings to applications such as biodegradable power generation, devices detecting diseases inside of the body and physiologically controlled drug pumps”.

Previously, Bernal scientists discovered piezoelectricity in the globular protein lysozyme, found in tears, egg-white and saliva, and hydroxyapatite, a component of bone.

“The current finding extends the technology towards pragmatic, low-cost, renewable sources for electricity generation,” according to Professor Luuk van der Wielen, Director of the Bernal Institute and Bernal Professor of Biosystems Engineering and Design. “The finding translates the earlier Bernal scientists’ world-leading contribution in bio-piezoelectricity towards a large-scale and affordable application potential.”

Professor Edmond Magner, Dean of Science and Engineering at UL, said: “UL’s Department of Physics and Bernal Institute researchers continue to pioneer the use of biological crystals for electrical applications. This work places them at the forefront in the development of bio-piezoelectric devices”.

Learn more: Researchers generate electricity from low-cost biomaterial


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Next-gen pacemakers may be powered by unlikely source: the heart

via University at Buffalo

via University at Buffalo

The implantable pacemaker, a medical marvel that has extended millions of lives since its invention nearly 60 years ago, is getting a 21st century makeover.

First came a wireless version; these pacemakers, which are AAA battery-sized and placed inside the heart via a catheter through the leg, are being tested in humans in the United States, Canada and Australia.

Now, researchers are developing technology to make these devices battery-free. The advancement is based upon a piezoelectric system that converts vibrational energy – created inside the chest by each heartbeat – into electricity to power the pacemaker.

“Essentially, we’re creating technology that will allow pacemakers to be powered by the very heart that they are regulating,” says M. Amin Karami, PhD, assistant professor of mechanical engineering at the University at Buffalo School of Engineering and Applied Sciences, who is leading the research.

The technology may eliminate the medical risks, costs and inconvenience of having a battery replacement every five to 12 years for millions of people worldwide.

From the beginning

The development of pacemakers dates back nearly a century. At the beginning, most efforts focused on devices that patients would carry outside their body.

Surgeons first successfully implanted a pacemaker in a human in 1960 in Buffalo, New York. The device, invented by UB alumnus Wilson Greatbatch, enabled the patient to survive another 18 months. (Note: A patient in Sweden received an implantable pacemaker in 1958, but the device failed after three hours.)

While there have been advancements since 1960 – the devices are smaller, the batteries last longer, there are even “smart” pacemakers that are linked to computers – the basic design from Greatbatch is the same. About the size of a pocket watch, pacemakers are implanted under the skin through an incision in the chest. Wires, also called leads, connect the device to the heart and deliver electrical signals that regulate the heart’s activity.

The new wireless option does not require leads because it rests inside the heart. This removes a potential point of failure, but the device still relies on a battery that must be replaced as often as the batteries that conventional pacemakers use.

A state of constant motion

The idea of heart-powered pacemakers came to Karami after doing PhD work on piezoelectric applications for unmanned aerial vehicles and bridges. He wanted to apply that knowledge to the human body. The heart was an obvious choice because of its relative strength and constant motion.

“To see the heart in motion – even an animation – is to be awestruck,” says Karami. “It moves significantly. In turn, that movement creates energy that we’re just now figuring out how to harvest.”

Read more: Next-gen pacemakers may be powered by unlikely source: the heart



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