Tag Archives: John Madden

Everlasting dirt-powered sensors for agriculture?

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Caption: The fuel cell’s 3D printed cap peeks above the ground. The cap keeps debris out of the device while enabling air flow. Credit: Bill Yen/Northwestern University

A January 12, 2024 Northwestern University news release (also received via email and also on EurekAlert both published January 15, 2024) describes this dirt-powered research from the US, Note: Links have been removed,

*New fuel cell harnesses naturally occurring microbes to generate electricity

*Soil-powered sensors to successfully monitor soil moisture and detect touch

*New tech was robust enough to withstand drier soil conditions and flooding

*Fuel cell could replace batteries in sensors used for precision agriculture

EVANSTON, Ill. — A Northwestern University-led team of researchers has developed a new fuel cell that harvests energy from microbes living in dirt. 

About the size of a standard paperback book, the completely soil-powered technology could fuel underground sensors used in precision agriculture and green infrastructure. This potentially could offer a sustainable, renewable alternative to batteries, which hold toxic, flammable chemicals that leach into the ground, are fraught with conflict-filled supply chains and contribute to the ever-growing problem of electronic waste.

To test the new fuel cell, the researchers used it to power sensors measuring soil moisture and detecting touch, a capability that could be valuable for tracking passing animals. To enable wireless communications, the researchers also equipped the soil-powered sensor with a tiny antenna to transmit data to a neighboring base station by reflecting existing radio frequency signals.

Not only did the fuel cell work in both wet and dry conditions, but its power also outlasted similar technologies by 120%.

The research will be published today (Jan. 12 [2024]) in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies. The study authors also are releasing all designs, tutorials and simulation tools to the public, so others may use and build upon the research.

“The number of devices in the Internet of Things (IoT) is constantly growing,” said Northwestern alumnus Bill Yen, who led the work. “If we imagine a future with trillions of these devices, we cannot build every one of them out of lithium, heavy metals and toxins that are dangerous to the environment. We need to find alternatives that can provide low amounts of energy to power a decentralized network of devices. In a search for solutions, we looked to soil microbial fuel cells, which use special microbes to break down soil and use that low amount of energy to power sensors. As long as there is organic carbon in the soil for the microbes to break down, the fuel cell can potentially last forever.”

“These microbes are ubiquitous; they already live in soil everywhere,” said Northwestern’s George Wells, a senior author on the study. “We can use very simple engineered systems to capture their electricity. We’re not going to power entire cities with this energy. But we can capture minute amounts of energy to fuel practical, low-power applications.”

Wells is an associate professor of civil and environmental engineering at Northwestern’s McCormick School of Engineering. Now a Ph.D. student at Stanford University, Yen started this project when he was an undergraduate researcher in Wells’ laboratory.

Solutions for a dirty job

In recent years, farmers worldwide increasingly have adopted precision agriculture as a strategy to improve crop yields. The tech-driven approach relies on measuring precise levels of moisture, nutrients and contaminants in soil to make decisions that enhance crop health. This requires a widespread, dispersed network of electronic devices to continuously collect environmental data.

“If you want to put a sensor out in the wild, in a farm or in a wetland, you are constrained to putting a battery in it or harvesting solar energy,” Yen said. “Solar panels don’t work well in dirty environments because they get covered with dirt, do not work when the sun isn’t out and take up a lot of space. Batteries also are challenging because they run out of power. Farmers are not going to go around a 100-acre farm to regularly swap out batteries or dust off solar panels.”

To overcome these challenges, Wells, Yen and their collaborators wondered if they could instead harvest energy from the existing environment. “We could harvest energy from the soil that farmers are monitoring anyway,” Yen said.

‘Stymied efforts’

Making their first appearance in 1911, soil-based microbial fuel cells (MFCs) operate like a battery — with an anode, cathode and electrolyte. But instead of using chemicals to generate electricity, MFCs harvest electricity from bacteria that naturally donate electrons to nearby conductors. When these electrons flow from the anode to the cathode, it creates an electric circuit.

But in order for microbial fuel cells to operate without disruption, they need to stay hydrated and oxygenated — which is tricky when buried underground within dry dirt.

“Although MFCs have existed as a concept for more than a century, their unreliable performance and low output power have stymied efforts to make practical use of them, especially in low-moisture conditions,” Yen said.

Winning geometry

With these challenges in mind, Yen and his team embarked on a two-year journey to develop a practical, reliable soil-based MFC. His expedition included creating — and comparing — four different versions. First, the researchers collected a combined nine months of data on the performance of each design. Then, they tested their final version in an outdoor garden.

The best-performing prototype worked well in dry conditions as well as within a water-logged environment. The secret behind its success: Its geometry. Instead of using a traditional design, in which the anode and cathode are parallel to one another, the winning fuel cell leveraged a perpendicular design.

Made of carbon felt (an inexpensive, abundant conductor to capture the microbes’ electrons), the anode is horizontal to the ground’s surface. Made of an inert, conductive metal, the cathode sits vertically atop the anode. 

Although the entire device is buried, the vertical design ensures that the top end is flush with the ground’s surface. A 3D-printed cap rests on top of the device to prevent debris from falling inside. And a hole on top and an empty air chamber running alongside the cathode enable consistent airflow.  

The lower end of the cathode remains nestled deep beneath the surface, ensuring that it stays hydrated from the moist, surrounding soil — even when the surface soil dries out in the sunlight. The researchers also coated part of the cathode with waterproofing material to allow it to breathe during a flood. And, after a potential flood, the vertical design enables the cathode to dry out gradually rather than all at once.

On average, the resulting fuel cell generated 68 times more power than needed to operate its sensors. It also was robust enough to withstand large changes in soil moisture — from somewhat dry (41% water by volume) to completely underwater.

Making computing accessible

The researchers say all components for their soil-based MFC can be purchased at a local hardware store. Next, they plan to develop a soil-based MFC made from fully biodegradable materials. Both designs bypass complicated supply chains and avoid using conflict minerals.

“With the COVID-19 pandemic, we all became familiar with how a crisis can disrupt the global supply chain for electronics,” said study co-author Josiah Hester, a former Northwestern faculty member who is now at the Georgia Institute of Technology. “We want to build devices that use local supply chains and low-cost materials so that computing is accessible for all communities.”

The study, “Soil-powered computing: The engineer’s guide to practical soil microbial fuel cell design,” was supported by the National Science Foundation (award number CNS-2038853), the Agricultural and Food Research Initiative (award number 2023-67021-40628) from the USDA National Institute of Food and Agriculture, the Alfred P. Sloan Foundation, VMware Research and 3M.

Here’s a link to and a citation for the paper,

Soil-Powered Computing: The Engineer’s Guide to Practical Soil Microbial Fuel Cell Design by Bill Yen, Laura Jaliff, Louis Gutierrez, Philothei Sahinidis, Sadie Bernstein, John Madden, Stephen Taylor, Colleen Josephson, Pat Pannuto, Weitao Shuai, George Wells, Nivedita Arora, Josiah Hester. Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies Volume 7 Issue 4 Article No.: 196 pp 1–40 DOI: https://doi.org/10.1145/3631410 Published: 12 January 2024

This paper is open access.

Ionic skin for ‘smart’ skin

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An April 28, 2022 University of British Columbia (UBC) news release (also on EurekAlert) announces a step forward in the attempt to create ‘smart’ skin, Note: Links have been removed,

In the quest to build smart skin that mimics the sensing capabilities of natural skin, ionic skins have shown significant advantages. They’re made of flexible, biocompatible hydrogels that use ions to carry an electrical charge. In contrast to smart skins made of plastics and metals, the hydrogels have the softness of natural skin. This offers a more natural feel to the prosthetic arm or robot hand they are mounted on, and makes them comfortable to wear.

These hydrogels can generate voltages when touched, but scientists did not clearly understand how — until a team of researchers at UBC devised a unique experiment, published today in Science.

“How hydrogel sensors work is they produce voltages and currents in reaction to stimuli, such as pressure or touch – what we are calling a piezoionic effect. But we didn’t know exactly how these voltages are produced,” said the study’s lead author Yuta Dobashi, who started the work as part of his master’s in biomedical engineering at UBC.

Working under the supervision of UBC researcher Dr. John Madden, Dobashi devised hydrogel sensors containing salts with positive and negative ions of different sizes. He and collaborators in UBC’s physics and chemistry departments applied magnetic fields to track precisely how the ions moved when pressure was applied to the sensor.

“When pressure is applied to the gel, that pressure spreads out the ions in the liquid at different speeds, creating an electrical signal. Positive ions, which tend to be smaller, move faster than larger, negative ions. This results in an uneven ion distribution which creates an electric field, which is what makes a piezoionic sensor work.”

The researchers say this new knowledge confirms that hydrogels work in a similar way to how humans detect pressure, which is also through moving ions in response to pressure, inspiring potential new applications for ionic skins.

“The obvious application is creating sensors that interact directly with cells and the nervous system, since the voltages, currents and response times are like those across cell membranes,” says Dr. Madden, an electrical and computer engineering professor in UBC’s faculty of applied science. “When we connect our sensor to a nerve, it produces a signal in the nerve. The nerve, in turn, activates muscle contraction.”

“You can imagine a prosthetic arm covered in an ionic skin. The skin senses an object through touch or pressure, conveys that information through the nerves to the brain, and the brain then activates the motors required to lift or hold the object. With further development of the sensor skin and interfaces with nerves, this bionic interface is conceivable.”

Another application is a soft hydrogel sensor worn on the skin that can monitor a patient’s vital signs while being totally unobtrusive and generating its own power.

Dobashi, who’s currently completing his PhD work at the University of Toronto, is keen to continue working on ionic technologies after he graduates.

“We can imagine a future where jelly-like ‘iontronics’ are used for body implants. Artificial joints can be implanted, without fear of rejection inside the human body. Ionic devices can be used as part of artificial knee cartilage, adding a smart sensing element.  A piezoionic gel implant might release drugs based on how much pressure it senses, for example.”

Dr. Madden added that the market for smart skins is estimated at $4.5 billion in 2019 and it continues to grow. “Smart skins can be integrated into clothing or placed directly on the skin, and ionic skins are one of the technologies that can further that growth.”

The research includes contributions from UBC chemistry PhD graduate Yael Petel and Carl Michal, UBC professor of physics, who used the interaction between strong magnetic fields and the nuclear spins of ions to track ion movements within the hydrogels. Cédric Plesse, Giao Nguyen and Frédéric Vidal at CY Cergy Paris University in France helped develop a new theory on how the charge and voltage are generated in the hydrogels.

Interview language(s): English (Dobashi, Madden), French (Plesse, Madden), Japanese (Dobashi)

Here’s a link to and a citation for the paper,

Piezoionic mechanoreceptors: Force-induced current generation in hydrogels by
Yuta Dobashi, Dickson Yao, Yael Petel, Tan Ngoc Nguyen, Mirza Saquib Sarwar, Yacine Thabet, Cliff L. W. Ng, Ettore Scabeni Glitz, Giao Tran Minh Nguyen, Cédric Plesse, Frédéric Vidal, Carl A. Michal and John D. W. Madden. Science • 28 Apr 2022 • Vol 376, Issue 6592 • pp. 502-507 • DOI: 10.1126/science.aaw1974

This paper is behind a paywall.

Aussies, Yanks, Canucks, and Koreans collaborate on artificial muscles

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I received a media release (from the University of British Columbia [UBC]) about artificial muscles. I was expecting to see Dr. Hongbin Li’s name as one of the researchers but this is an entirely different kind of artificial muscle. Dr. Li works with artificial proteins to create new biomaterials (my May 5, 2010 posting). This latest work published in Science Express, Oct. 13, 2011,  involves carbon nanotubes and teams from Australia, Canada, Korea, and the US. From the Oct. 13, 2011, UBC media release,

An international team of researchers has invented new artificial muscles strong enough to rotate objects a thousand times their own weight, but with the same flexibility of an elephant’s trunk or octopus limbs.

In a paper published online today on Science Express, the scientists and engineers from the University of British Columbia, the University of Wollongong in Australia, the University of Texas at Dallas and Hanyang University in Korea detail their innovation. The study elaborates on a discovery made by research fellow Javad Foroughi at the University of Wollongong.

Using yarns of carbon nanotubes that are enormously strong, tough and highly flexible, the researchers developed artificial muscles that can rotate 250 degrees per millimetre of muscle length. This is more than a thousand times that of available artificial muscles composed of shape memory alloys, conducting organic polymers or ferroelectrics, a class of materials that can hold both positive and negative electric charges, even in the absence of voltage.

Here’s how the UBC media release recounts the story of these artificial muscles (Aside: The Australians take a different approach; I haven’t seen any material from the University of Texas at Dallas or the University of Hanyang),

The new material was devised at the University of Texas at Dallas and then tested as an artificial muscle in Madden’s [Associate Professor, John Madden, Dept. of Electrical and Computer Engineering] lab at UBC. A chance discovery by collaborators from Wollongong showed the enormous twist developed by the device. Guided by theory at UBC and further experiments in Wollongong and Texas, the team was able to extract considerable torsion and power from the yarns.

The Australians, not unnaturally focus on their own contributions, and, somewhat unexpectedly discuss nanorobots. From the ARC (Australian Research Council) Centre of Excellence for Electromaterials Science (ACES) at the University of Wollongong news release (?) [ETA Oct. 17, 2011: I forgot to include a link to the Australian news item; and here’s a link to the Oct. 16, 2011 Australian news item on Nanowerk] ,

The possibility of a doctor using tiny robots in your body to diagnose and treat medical conditions is one step closer to becoming reality today, with the development of artificial muscles small and strong enough to push the tiny Nanobots along.

Although Nanorobots (Nanobots) have received much attention for the potential medical use in the body, such as cancer fighting, drug delivery and parasite removal, one major hurdle in their development has been the issue of how to propel them along in the bloodstream.

An international collaborative team led by researchers at UOW’s Intelligent Polymer Research Institute, part of the ARC Centre of Excellence for Electromaterials Science (ACES), have developed a new twisting artificial muscle that could be used for propelling nanobots.   The muscles use very tough and highly flexible yarns of carbon nanotubes (nanoscale cylinders of carbon), which are twist-spun into the required form.  When voltage is applied, the yarns rotate up to 600 revolutions per minute, then rotate in reverse when the voltage is changed.

Due to their complexity, conventional motors are very difficult to miniaturise, making them unsuitable for use in nanorobotics.  The twisting artificial muscles, on the other hand, are simple and inexpensive to construct either in very long, or in millimetre lengths.

Interesting, non?

There’s an animation illustrating the nanorobots and the muscles,

In the animated video below, you first see a few bacteria like creatures swimming about. Their rotating flagella are highlighted with some detail of the flagella motor turning the “hook” and “filament” parts of the tail. We next see a similar type of rotating tail produced by a length of carbon nanotube thread that is inside a futuristic microbot. The yarn is immersed in a liquid electrolyte along with another electrode wire. Batteries and an electrical circuit are also inside the bot. When a voltage is applied the yarn partially untwists and turns the filament. Slow discharging of the yarn causes it to re-twist. In this way, we can imagine the micro-bot is propelled along in a series of short spurts.

I think the graphics resemble conception complete with sperm and eggs but I can see the nanorobots too. Here’s your chance to take a look,

ETA Oct. 14, 2011 11:20 am PST: I found a copy of the University of Texas at Dallas news release posted on Oct. 13, 2011 at Nanowerk. No mention of nanobots but if you’re looking for additional technical explanations, this would be good to read.