Tag Archives: electrochemistry

400 nm thick glucose fuel cell uses body’s own sugar

This May 12, 2022 news item on Nanowerk reminds me of bioenergy harvesting (using the body’s own processes rather than batteries to power implants),

Glucose is the sugar we absorb from the foods we eat. It is the fuel that powers every cell in our bodies. Could glucose also power tomorrow’s medical implants?

Engineers at MIT [Massachusetts Institute of Technology] and the Technical University of Munich think so. They have designed a new kind of glucose fuel cell that converts glucose directly into electricity. The device is smaller than other proposed glucose fuel cells, measuring just 400 nanometers thick. The sugary power source generates about 43 microwatts per square centimeter of electricity, achieving the highest power density of any glucose fuel cell to date under ambient conditions.

Caption: Silicon chip with 30 individual glucose micro fuel cells, seen as small silver squares inside each gray rectangle. Credit Image: Kent Dayton

A May 12, 2022 MIT news release (also on EuekAlert) by Jennifer Chu, which originated the news item, describes the technology in more detail, Note: A link has been removed,

The new device is also resilient, able to withstand temperatures up to 600 degrees Celsius. If incorporated into a medical implant, the fuel cell could remain stable through the high-temperature sterilization process required for all implantable devices.

The heart of the new device is made from ceramic, a material that retains its electrochemical properties even at high temperatures and miniature scales. The researchers envision the new design could be made into ultrathin films or coatings and wrapped around implants to passively power electronics, using the body’s abundant glucose supply.

“Glucose is everywhere in the body, and the idea is to harvest this readily available energy and use it to power implantable devices,” says Philipp Simons, who developed the design as part of his PhD thesis in MIT’s Department of Materials Science and Engineering (DMSE). “In our work we show a new glucose fuel cell electrochemistry.”

“Instead of using a battery, which can take up 90 percent of an implant’s volume, you could make a device with a thin film, and you’d have a power source with no volumetric footprint,” says Jennifer L.M. Rupp, Simons’ thesis supervisor and a DMSE visiting professor, who is also an associate professor of solid-state electrolyte chemistry at Technical University Munich in Germany.

Simons and his colleagues detail their design today in the journal Advanced Materials. Co-authors of the study include Rupp, Steven Schenk, Marco Gysel, and Lorenz Olbrich.

A “hard” separation

The inspiration for the new fuel cell came in 2016, when Rupp, who specializes in ceramics and electrochemical devices, went to take a routine glucose test toward the end of her pregnancy.

“In the doctor’s office, I was a very bored electrochemist, thinking what you could do with sugar and electrochemistry,” Rupp recalls. “Then I realized, it would be good to have a glucose-powered solid state device. And Philipp and I met over coffee and wrote out on a napkin the first drawings.”

The team is not the first to conceive of a glucose fuel cell, which was initially introduced in the 1960s and showed potential for converting glucose’s chemical energy into electrical energy. But glucose fuel cells at the time were based on soft polymers and were quickly eclipsed by lithium-iodide batteries, which would become the standard power source for medical implants, most notably the cardiac pacemaker.

However, batteries have a limit to how small they can be made, as their design requires the physical capacity to store energy.

“Fuel cells directly convert energy rather than storing it in a device, so you don’t need all that volume that’s required to store energy in a battery,” Rupp says.

In recent years, scientists have taken another look at glucose fuel cells as potentially smaller power sources, fueled directly by the body’s abundant glucose.

A glucose fuel cell’s basic design consists of three layers: a top anode, a middle electrolyte, and a bottom cathode. The anode reacts with glucose in bodily fluids, transforming the sugar into gluconic acid. This electrochemical conversion releases a pair of protons and a pair of electrons. The middle electrolyte acts to separate the protons from the electrons, conducting the protons through the fuel cell, where they combine with air to form molecules of water — a harmless byproduct that flows away with the body’s fluid. Meanwhile, the isolated electrons flow to an external circuit, where they can be used to power an electronic device.

The team looked to improve on existing materials and designs by modifying the electrolyte layer, which is often made from polymers. But polymer properties, along with their ability to conduct protons, easily degrade at high temperatures, are difficult to retain when scaled down to the dimension of nanometers, and are hard to sterilize. The researchers wondered if a ceramic — a heat-resistant material which can naturally conduct protons — could be made into an electrolyte for glucose fuel cells.

“When you think of ceramics for such a glucose fuel cell, they have the advantage of long-term stability, small scalability, and silicon chip integration,” Rupp notes. “They’re hard and robust.”

Peak power

The researchers designed a glucose fuel cell with an electrolyte made from ceria, a ceramic material that possesses high ion conductivity, is mechanically robust, and as such, is widely used as an electrolyte in hydrogen fuel cells. It has also been shown to be biocompatible.

“Ceria is actively studied in the cancer research community,” Simons notes. “It’s also similar to zirconia, which is used in tooth implants, and is biocompatible and safe.”

The team sandwiched the electrolyte with an anode and cathode made of platinum, a stable material that readily reacts with glucose. They fabricated 150 individual glucose fuel cells on a chip, each about 400 nanometers thin, and about 300 micrometers wide (about the width of 30 human hairs). They patterned the cells onto silicon wafers, showing that the devices can be paired with a common semiconductor material. They then measured the current produced by each cell as they flowed a solution of glucose over each wafer in a custom-fabricated test station.

They found many cells produced a peak voltage of about 80 millivolts. Given the tiny size of each cell, this output is the highest power density of any existing glucose fuel cell design.

“Excitingly, we are able to draw power and current that’s sufficient to power implantable devices,” Simons says.

“It is the first time that proton conduction in electroceramic materials can be used for glucose-to-power conversion, defining a new type of electrochemstry,” Rupp says. “It extends the material use-cases from hydrogen fuel cells to new, exciting glucose-conversion modes.”

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

A Ceramic-Electrolyte Glucose Fuel Cell for Implantable Electronics by Philipp Simons, Steven A. Schenk, Marco A. Gysel, Lorenz F. Olbrich, Jennifer L. M. Rupp. Advanced Materials https://doi.org/10.1002/adma.202109075 First published: 05 April 2022

This paper is open access.

Carbon nanotubes can scavenge energy from environment to generate electricity

A June 7, 2021 news item on phys.org announces research into a new method for generating electricity (Note: A link has been removed),

MIT [Massachusetts Institute of Technology] engineers have discovered a new way of generating electricity using tiny carbon particles that can create a current simply by interacting with liquid surrounding them.

The liquid, an organic solvent, draws electrons out of the particles, generating a current that could be used to drive chemical reactions or to power micro- or nanoscale robots, the researchers say.

“This mechanism is new, and this way of generating energy is completely new,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT. “This technology is intriguing because all you have to do is flow a solvent through a bed of these particles. This allows you to do electrochemistry, but with no wires.”

A June 7, 2021 MIT news release (also on EurekAlert), which generated the news item, delves further into the research,

In a new study describing this phenomenon, the researchers showed that they could use this electric current to drive a reaction known as alcohol oxidation — an organic chemical reaction that is important in the chemical industry.

Strano is the senior author of the paper, which appears today [June 7, 2021] in Nature Communications. The lead authors of the study are MIT graduate student Albert Tianxiang Liu and former MIT researcher Yuichiro Kunai. Other authors include former graduate student Anton Cottrill, postdocs Amir Kaplan and Hyunah Kim, graduate student Ge Zhang, and recent MIT graduates Rafid Mollah and Yannick Eatmon.

Unique properties

The new discovery grew out of Strano’s research on carbon nanotubes — hollow tubes made of a lattice of carbon atoms, which have unique electrical properties. In 2010, Strano demonstrated, for the first time, that carbon nanotubes can generate “thermopower waves.” When a carbon nanotube is coated with layer of fuel, moving pulses of heat, or thermopower waves, travel along the tube, creating an electrical current.

That work led Strano and his students to uncover a related feature of carbon nanotubes. They found that when part of a nanotube is coated with a Teflon-like polymer, it creates an asymmetry that makes it possible for electrons to flow from the coated to the uncoated part of the tube, generating an electrical current. Those electrons can be drawn out by submerging the particles in a solvent that is hungry for electrons.

To harness this special capability, the researchers created electricity-generating particles by grinding up carbon nanotubes and forming them into a sheet of paper-like material. One side of each sheet was coated with a Teflon-like polymer, and the researchers then cut out small particles, which can be any shape or size. For this study, they made particles that were 250 microns by 250 microns.

When these particles are submerged in an organic solvent such as acetonitrile, the solvent adheres to the uncoated surface of the particles and begins pulling electrons out of them.

“The solvent takes electrons away, and the system tries to equilibrate by moving electrons,” Strano says. “There’s no sophisticated battery chemistry inside. It’s just a particle and you put it into solvent and it starts generating an electric field.”

Particle power

The current version of the particles can generate about 0.7 volts of electricity per particle. In this study, the researchers also showed that they can form arrays of hundreds of particles in a small test tube. This “packed bed” reactor generates enough energy to power a chemical reaction called an alcohol oxidation, in which an alcohol is converted to an aldehyde or a ketone. Usually, this reaction is not performed using electrochemistry because it would require too much external current.

“Because the packed bed reactor is compact, it has more flexibility in terms of applications than a large electrochemical reactor,” Zhang says. “The particles can be made very small, and they don’t require any external wires in order to drive the electrochemical reaction.”

In future work, Strano hopes to use this kind of energy generation to build polymers using only carbon dioxide as a starting material. In a related project, he has already created polymers that can regenerate themselves using carbon dioxide as a building material, in a process powered by solar energy. This work is inspired by carbon fixation, the set of chemical reactions that plants use to build sugars from carbon dioxide, using energy from the sun.

In the longer term, this approach could also be used to power micro- or nanoscale robots. Strano’s lab has already begun building robots at that scale, which could one day be used as diagnostic or environmental sensors. The idea of being able to scavenge energy from the environment to power these kinds of robots is appealing, he says.

“It means you don’t have to put the energy storage on board,” he says. “What we like about this mechanism is that you can take the energy, at least in part, from the environment.”

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

Solvent-induced electrochemistry at an electrically asymmetric carbon Janus particle by Albert Tianxiang Liu, Yuichiro Kunai, Anton L. Cottrill, Amir Kaplan, Ge Zhang, Hyunah Kim, Rafid S. Mollah, Yannick L. Eatmon & Michael S. Strano. Nature Communications volume 12, Article number: 3415 (2021) DOI: https://doi.org/10.1038/s41467-021-23038-7Published 07 June 2021

This paper is open access.

A biohybrid artificial synapse that can communicate with living cells

As I noted in my June 16, 2020 posting, we may have more than one kind of artificial brain in our future. This latest work features a biohybrid. From a June 15, 2020 news item on ScienceDaily,

In 2017, Stanford University researchers presented a new device that mimics the brain’s efficient and low-energy neural learning process [see my March 8, 2017 posting for more]. It was an artificial version of a synapse — the gap across which neurotransmitters travel to communicate between neurons — made from organic materials. In 2019, the researchers assembled nine of their artificial synapses together in an array, showing that they could be simultaneously programmed to mimic the parallel operation of the brain [see my Sept. 17, 2019 posting].

Now, in a paper published June 15 [2020] in Nature Materials, they have tested the first biohybrid version of their artificial synapse and demonstrated that it can communicate with living cells. Future technologies stemming from this device could function by responding directly to chemical signals from the brain. The research was conducted in collaboration with researchers at Istituto Italiano di Tecnologia (Italian Institute of Technology — IIT) in Italy and at Eindhoven University of Technology (Netherlands).

“This paper really highlights the unique strength of the materials that we use in being able to interact with living matter,” said Alberto Salleo, professor of materials science and engineering at Stanford and co-senior author of the paper. “The cells are happy sitting on the soft polymer. But the compatibility goes deeper: These materials work with the same molecules neurons use naturally.”

While other brain-integrated devices require an electrical signal to detect and process the brain’s messages, the communications between this device and living cells occur through electrochemistry — as though the material were just another neuron receiving messages from its neighbor.

A June 15, 2020 Stanford University news release (also on EurekAlert) by Taylor Kubota, which originated the news item, delves further into this recent work,

How neurons learn

The biohybrid artificial synapse consists of two soft polymer electrodes, separated by a trench filled with electrolyte solution – which plays the part of the synaptic cleft that separates communicating neurons in the brain. When living cells are placed on top of one electrode, neurotransmitters that those cells release can react with that electrode to produce ions. Those ions travel across the trench to the second electrode and modulate the conductive state of this electrode. Some of that change is preserved, simulating the learning process occurring in nature.

“In a biological synapse, essentially everything is controlled by chemical interactions at the synaptic junction. Whenever the cells communicate with one another, they’re using chemistry,” said Scott Keene, a graduate student at Stanford and co-lead author of the paper. “Being able to interact with the brain’s natural chemistry gives the device added utility.”

This process mimics the same kind of learning seen in biological synapses, which is highly efficient in terms of energy because computing and memory storage happen in one action. In more traditional computer systems, the data is processed first and then later moved to storage.

To test their device, the researchers used rat neuroendocrine cells that release the neurotransmitter dopamine. Before they ran their experiment, they were unsure how the dopamine would interact with their material – but they saw a permanent change in the state of their device upon the first reaction.

“We knew the reaction is irreversible, so it makes sense that it would cause a permanent change in the device’s conductive state,” said Keene. “But, it was hard to know whether we’d achieve the outcome we predicted on paper until we saw it happen in the lab. That was when we realized the potential this has for emulating the long-term learning process of a synapse.”

A first step

This biohybrid design is in such early stages that the main focus of the current research was simply to make it work.

“It’s a demonstration that this communication melding chemistry and electricity is possible,” said Salleo. “You could say it’s a first step toward a brain-machine interface, but it’s a tiny, tiny very first step.”

Now that the researchers have successfully tested their design, they are figuring out the best paths for future research, which could include work on brain-inspired computers, brain-machine interfaces, medical devices or new research tools for neuroscience. Already, they are working on how to make the device function better in more complex biological settings that contain different kinds of cells and neurotransmitters.

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

A biohybrid synapse with neurotransmitter-mediated plasticity by Scott T. Keene, Claudia Lubrano, Setareh Kazemzadeh, Armantas Melianas, Yaakov Tuchman, Giuseppina Polino, Paola Scognamiglio, Lucio Cinà, Alberto Salleo, Yoeri van de Burgt & Francesca Santoro. Nature Materials (2020) DOI: https://doi.org/10.1038/s41563-020-0703-y Published: 15 June 2020

This paper is behind a paywall.

Creating cheap, small carbon nanotubes

The excitement fairly crackles off the video,

A May 24, 2018 news item on Nanowerk announces the research,

Imagine a box you plug into the wall that cleans your toxic air and pays you cash.

That’s essentially what Vanderbilt University researchers produced after discovering the blueprint for turning the carbon dioxide into carbon nanotubes with small diameters.

Carbon nanotubes are supermaterials that can be stronger than steel and more conductive than copper. The reason they’re not in every application from batteries to tires is that these amazing properties only show up in the tiniest nanotubes, which are extremely expensive. Not only did the Vanderbilt team show they can make these materials from carbon dioxide sucked from the air, but how to do this in a way that is much cheaper than any other method out there.

I’m not sure what ‘small’ means in this context. I’ve heard of long and short carbon nanotubes (CNTs) and also of single-walled, multi-walled, and double-walled CNTs. I wish there’d been an an explanation and measurements for ‘small diameter CNTs’. That nitpick aside, a May 23, 2018 Vanderbilt University news release by Heidi Hall adds a few more technical details,

These materials, which Assistant Professor of Mechanical Engineering Cary Pint calls “black gold,” could steer the conversation from the negative impact of emissions to how we can use them in future technology.

“One of the most exciting things about what we’ve done is use electrochemistry to pull apart carbon dioxide into elemental constituents of carbon and oxygen and stitch together, with nanometer precision, those carbon atoms into new forms of matter,” Pint said. “That opens the door to being able to generate really valuable products with carbon nanotubes.

“These could revolutionize the world.”

In a report published today in ACS [American Chemical Society] Applied Materials and Interfaces, Pint, interdisciplinary material science Ph.D. student Anna Douglas and their team describe how tiny nanoparticles 10,000 times smaller than a human hair can be produced from coatings on stainless steel surfaces. The key was making them small enough to be valuable.

“The cheapest carbon nanotubes on the market cost around $100-200 per kilogram,” Douglas said. “Our research advance demonstrates a pathway to synthesize carbon nanotubes better in quality than these materials with lower cost and using carbon dioxide captured from the air.”

But making small nanotubes is no small task. The research team showed that a process called Ostwald ripening — where the nanoparticles that grow the carbon nanotubes change in size to larger diameters — is a key contender against producing the infinitely more useful size. The team showed they could partially overcome this by tuning electrochemical parameters to minimize these pesky large nanoparticles.

side-by-side photos showing stainless steel plate becoming covered in carbon nanotubes (which look like lumps of ash or mud)
Small diameter carbon nanotubes grown on a stainless steel surface. (Pint Lab/Vanderbilt University)

This core technology led Pint and Douglas to co-found SkyNano LLC, a company focused on building upon the science of this process to scale up and commercialize products from these materials.

“What we’ve learned is the science that opens the door to now build some of the most valuable materials in our world, such as diamonds and single-walled carbon nanotubes, from carbon dioxide that we capture from air through our process,” Pint said.

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

Toward Small-Diameter Carbon Nanotubes Synthesized from Captured Carbon Dioxide: Critical Role of Catalyst Coarsening by Anna Douglas, Rachel Carter, Mengya Li, and Cary L. Pint. ACS Appl. Mater. Interfaces, Article ASAP DOI: 10.1021/acsami.8b02834 Publication Date (Web): May 1, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

Regarding the start-up, SkyNano, which Douglas and Pint have co-founded, it looks to be at a  very early stage.