Tag Archives: Rice University

To make carbon nanotubes (CNTs), reach like a giraffe

Caption: There are dozens of varieties of nanotubes, each with a characteristic diameter and structural twist, or chiral angle. Carbon nanotubes are grown on catalytic particles using batch production methods that produce the entire gamut of chiral varieties, but Rice University scientists have come up with a new strategy for making batches with a single, desired chirality. Their theory shows chiral varieties can be selected for production when catalytic particles are drawn away at specific speeds by localized feedstock supply. The illustration depicts this and an analogous process 19th-century scientists used to describe the evolution of giraffes’ long necks due to the gradual selection of abilities to reach progressively higher for food. Credit: Illustration by Ksenia Bets/Rice University

A November 9, 2022 Rice University news release (also on EurekAlert) announces the Holy Grail (I’ve lost track of how many have been reached) has been achieved for growing batches of carbon nanotubes,

Like a giraffe stretching for leaves on a tall tree, making carbon nanotubes reach for food as they grow may lead to a long-sought breakthrough.

Materials theorists Boris Yakobson and Ksenia Bets at Rice University’s George R. Brown School of Engineering show how putting constraints on growing nanotubes could facilitate a “holy grail” of growing batches with a single desired chirality.

Their paper in Science Advances describes a strategy by which constraining the carbon feedstock in a furnace would help control the “kite” growth of nanotubes. In this method, the nanotube begins to form at the metal catalyst on a substrate, but lifts the catalyst as it grows, resembling a kite on a string.

Carbon nanotube walls are basically graphene, its hexagonal lattice of atoms rolled into a tube. Chirality refers to how the hexagons are angled within the lattice, between 0 and 30 degrees. That determines whether the nanotubes are metallic or semiconductors. The ability to grow long nanotubes in a single chirality could, for instance, enable the manufacture of highly conductive nanotube fibers or semiconductor channels of transistors.

Normally, nanotubes grow in random fashion with single and multiple walls and various chiralities. That’s fine for some applications, but many need “purified” batches that require centrifugation or other costly strategies to separate the nanotubes.

The researchers suggested hot carbon feedstock gas fed through moving nozzles could effectively lead nanotubes to grow for as long as the catalyst remains active. Because tubes with different chiralities grow at different speeds, they could then be separated by length, and slower-growing types could be completely eliminated.

One additional step that involves etching away some of the nanotubes could then allow specific chiralities to be harvested, they determined.

The lab’s work to define the mechanisms of nanotube growth led them to think about whether the speed of growth as a function of individual tubes’ chirality could be useful. The angle of “kinks” in the growing nanotubes’ edges determines how energetically amenable they are to adding new carbon atoms.

“The catalyst particles are moving as the nanotubes grow, and that’s principally important,” said lead author Bets, a researcher in Yakobson’s group. “If your feedstock keeps moving away, you get a moving window where you’re feeding some tubes and not the others.”

The paper’s reference to Lamarck giraffes — a 19th-century theory of how they evolved such long necks — isn’t entirely out of left field, Bets said.  

“It works as a metaphor because you move your ‘leaves’ away and the tubes that can reach it continue growing fast, and those that cannot just die out,” she said. “Eventually, all the nanotubes that are just a tiny bit slow will ‘die.’”

Speed is only part of the strategy. In fact, they suggest nanotubes that are a little slower should be the target to assure a harvest of single chiralities.

Because nanotubes of different chiralities grow at their own rates, a batch would likely exhibit tiers. Chemically etching the longest nanotubes would degrade them, preserving the next level of tubes. Restoring the feedstock could then allow the second-tier nanotubes to continue growing until they are ready to be culled, Bets said.

“There are three or four laboratory studies that show nanotube growth can be reversed, and we also know it can be restarted after etching,” she said. “So all the parts of our idea already exist, even if some of them are tricky. Close to equilibrium, you will have the same proportionality between growth and etching speeds for the same tubes. If it’s all nice and clean, then you can absolutely, precisely pick the tubes you target.”

The Yakobson lab won’t make them, as it focuses on theory, not experimentation. But other labs have turned past Rice theories into products like boron buckyballs.

“I’m pretty sure every single one of our reviewers were experimentalists, and they didn’t see any contradictions to it working,” Bets said. “Their only complaint, of course, was that they would like experimental results right now, but that’s not what we do.”

She hopes more than a few labs will pick up the challenge. “In terms of science, it’s usually more beneficial to give ideas to the crowd,” Bets said. “That way, those who have interest can do it in 100 different variations and see which one works. One guy trying it might take 100 years.”

Yakobson added, “We don’t want to be that ‘guy.’ We don’t have that much time.”

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

Single-chirality nanotube synthesis by guided evolutionary selection by Boris I. Yakobson and Ksenia V. Bets. Science Advances 9 Nov 2022 Vol 8, Issue 45 DOI: 10.1126/sciadv.add4627

This paper is open access.

Even a ‘good’ gene edit can go wrong

An October 24, 2022 news item on ScienceDaily highlights research into better understanding problems with ‘good’ CRISPR (clustered regularly interspaced short palindromic repeats) gene editing,

A Rice University lab is leading the effort to reveal potential threats to the efficacy and safety of therapies based on CRISPR-Cas9, the Nobel Prize-winning gene editing technique, even when it appears to be working as planned.

Bioengineer Gang Bao of Rice’s George R. Brown School of Engineering and his team point out in a paper published in Science Advances that while off-target edits to DNA have long been a cause for concern, unseen changes that accompany on-target edits also need to be recognized — and quantified.

Bao noted a 2018 Nature Biotechnology paper indicated the presence of large deletions. “That’s when we started looking into what we can do to quantify them, due to CRISPR-Cas9 systems designed for treating sickle cell disease,” he said.

An October 24, 2022 Rice University news release (also on EurekAlert), which originated the news item, details the concerns (Note: Links have been removed),

Bao has been a strong proponent of CRISPR-Cas9 as a tool to treat sickle cell disease, a quest that has brought him and his colleagues ever closer to a cure. Now the researchers fear that large deletions or other undetected changes due to gene editing could persist in stem cells as they divide and differentiate, thus have long-term implications for health.

“We do not have a good understanding of why a few thousand bases of DNA at the Cas9 cut site can go missing and the DNA double-strand breaks can still be rejoined efficiently,” Bao said. “That’s the first question, and we have some hypotheses. The second is, what are the biological consequences? Large deletions (LDs) can reach to nearby genes and disrupt the expression of both the target gene and the nearby genes. It is unclear if LDs could result in the expression of truncated proteins. 

“You could also have proteins that misfold, or proteins with an extra domain because of large insertions,” he said. “All kinds of things could happen, and the cells could die or have abnormal functions.”

His lab developed a procedure that uses single-molecule, real-time (SMRT) sequencing with dual unique molecular identifiers (UMI) to find and quantify unintended LDs along with large insertions and local chromosomal rearrangements that accompany small insertions/deletions (INDELs) at a Cas9 on-target cut site. 

“To quantify large gene modifications, we need to perform long-range PCR, but that could induce artifacts during DNA amplification,” Bao said. “So we used UMIs of 18 bases as a kind of barcode.”

“We add them to the DNA molecules we want to amplify to identify specific DNA molecules as a way to reduce or eliminate artifacts due to long-range PCR,” he said. “We also developed a bioinformatics pipeline to analyze SMRT sequencing data and quantified the LDs and large insertions.”

The Bao lab’s tool, called LongAmp-seq (for long-amplicon sequencing), accurately quantifies both small INDELs and large LDs. Unlike SMRT-seq, which requires the use of a long-read sequencer often only available at a core facility, LongAmp-seq can be performed using a short-read sequencer.

To test the strategy, the lab team led by Rice alumna Julie Park, now an assistant research professor of bioengineering, used Streptococcus pyogenes Cas9 to edit beta-globin (HBB), gamma-globin (HBG) and B-cell lymphoma/leukemia 11A (BCL11A) enhancers in hematopoietic stem and progenitor cells (HSPC) from patients with sickle cell disease, and the PD-1 gene in primary T-cells.  

They found large deletions of up to several thousand bases occurred at high frequency in HSPCs: up to 35.4% in HBB, 14.3% in HBG and 15.2% in BCL11A genes, as well as on the PD-1 (15.2%) gene in T-cells. 

Since two of the specific CRISPR guide RNAs tested by the Bao lab are being used in clinical trials to treat sickle cell disease, he said it’s important to determine the biological consequences of large gene modifications due to Cas9-induced double-strand breaks. 

Bao said the Rice team is currently looking downstream to analyze the consequences of long deletions on messenger RNA, the mediator that carries code for ribosomes to make proteins. “Then we’ll move on to the protein level,” Bao said. “We want to know if these large deletions and insertions persist after the gene-edited HSPCs are transplantation into mice and patients.”  

Co-authors of the study from Rice are graduate students Mingming Cao and Yilei Fu, alumni Yidan Pan and Timothy Davis, research specialist Lavanya Saxena, microscopist/bioinstrumentation specialist Harshavardhan Deshmukh and Todd Treangen, an assistant professor of computer science, and Emory University’s Vivien Sheehan, an associate professor of pediatrics. 

Bao is the department chair and Foyt Family Professor of Bioengineering, a professor of chemistry, materials science and nanoengineering, and mechanical engineering, and a CPRIT Scholar in Cancer Research.

The National Institutes of Health (R01HL152314, OT2HL154977) supported the research.

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

Comprehensive analysis and accurate quantification of unintended large gene modifications induced by CRISPR-Cas9 gene editing by So Hyun Park, Mingming Cao, Yidan Pan, Timothy H. Davis, Lavanya Saxena, Harshavardhan Deshmukh, Yilei Fu, Todd Treangen, Vivien A. Sheehan, and Gang Bao. Science Advances Vol 8, Issue 42 DOI: 10.1126/sciadv.abo7676 First published online: 21 Oct 2022 Published in print: March 3, 2023

This paper is behind a paywall.

Implantable living pharmacy

I stumbled across a very interesting US Defense Advanced Research Projects Agency (DARPA) project (from an August 30, 2021 posting on Northwestern University’s Rivnay Lab [a laboratory for organic bioelectronics] blog),

Our lab has received a cooperative agreement with DARPA to develop a wireless, fully implantable ‘living pharmacy’ device that could help regulate human sleep patterns. The project is through DARPA’s BTO (biotechnology office)’s Advanced Acclimation and Protection Tool for Environmental Readiness (ADAPTER) program, meant to address physical challenges of travel, such as jetlag and fatigue.

The device, called NTRAIN (Normalizing Timing of Rhythms Across Internal Networks of Circadian Clocks), would control the body’s circadian clock, reducing the time it takes for a person to recover from disrupted sleep/wake cycles by as much as half the usual time.

The project spans 5 institutions including Northwestern, Rice University, Carnegie Mellon, University of Minnesota, and Blackrock Neurotech.

Prior to the Aug. 30, 2021 posting, Amanda Morris wrote a May 13, 2021 article for Northwestern NOW (university magazine), which provides more details about the project, Note: A link has been removed,

The first phase of the highly interdisciplinary program will focus on developing the implant. The second phase, contingent on the first, will validate the device. If that milestone is met, then researchers will test the device in human trials, as part of the third phase. The full funding corresponds to $33 million over four-and-a-half years. 

Nicknamed the “living pharmacy,” the device could be a powerful tool for military personnel, who frequently travel across multiple time zones, and shift workers including first responders, who vacillate between overnight and daytime shifts.

Combining synthetic biology with bioelectronics, the team will engineer cells to produce the same peptides that the body makes to regulate sleep cycles, precisely adjusting timing and dose with bioelectronic controls. When the engineered cells are exposed to light, they will generate precisely dosed peptide therapies. 

“This control system allows us to deliver a peptide of interest on demand, directly into the bloodstream,” said Northwestern’s Jonathan Rivnay, principal investigator of the project. “No need to carry drugs, no need to inject therapeutics and — depending on how long we can make the device last — no need to refill the device. It’s like an implantable pharmacy on a chip that never runs out.” 

Beyond controlling circadian rhythms, the researchers believe this technology could be modified to release other types of therapies with precise timing and dosing for potentially treating pain and disease. The DARPA program also will help researchers better understand sleep/wake cycles, in general.

“The experiments carried out in these studies will enable new insights into how internal circadian organization is maintained,” said Turek [Fred W. Turek], who co-leads the sleep team with Vitaterna [Martha Hotz Vitaterna]. “These insights will lead to new therapeutic approaches for sleep disorders as well as many other physiological and mental disorders, including those associated with aging where there is often a spontaneous breakdown in temporal organization.” 

For those who like to dig even deeper, Dieynaba Young’s June 17, 2021 article for Smithsonian Magazine (GetPocket.com link to article) provides greater context and greater satisfaction, Note: Links have been removed,

In 1926, Fritz Kahn completed Man as Industrial Palace, the preeminent lithograph in his five-volume publication The Life of Man. The illustration shows a human body bustling with tiny factory workers. They cheerily operate a brain filled with switchboards, circuits and manometers. Below their feet, an ingenious network of pipes, chutes and conveyer belts make up the blood circulatory system. The image epitomizes a central motif in Kahn’s oeuvre: the parallel between human physiology and manufacturing, or the human body as a marvel of engineering.

An apparatus in the embryonic stage of development at the time of this writing in June of 2021—the so-called “implantable living pharmacy”—could have easily originated in Kahn’s fervid imagination. The concept is being developed by the Defense Advanced Research Projects Agency (DARPA) in conjunction with several universities, notably Northwestern and Rice. Researchers envision a miniaturized factory, tucked inside a microchip, that will manufacture pharmaceuticals from inside the body. The drugs will then be delivered to precise targets at the command of a mobile application. …

The implantable living pharmacy, which is still in the “proof of concept” stage of development, is actually envisioned as two separate devices—a microchip implant and an armband. The implant will contain a layer of living synthetic cells, along with a sensor that measures temperature, a short-range wireless transmitter and a photo detector. The cells are sourced from a human donor and reengineered to perform specific functions. They’ll be mass produced in the lab, and slathered onto a layer of tiny LED lights.

The microchip will be set with a unique identification number and encryption key, then implanted under the skin in an outpatient procedure. The chip will be controlled by a battery-powered hub attached to an armband. That hub will receive signals transmitted from a mobile app.

If a soldier wishes to reset their internal clock, they’ll simply grab their phone, log onto the app and enter their upcoming itinerary—say, a flight departing at 5:30 a.m. from Arlington, Virginia, and arriving 16 hours later at Fort Buckner in Okinawa, Japan. Using short-range wireless communications, the hub will receive the signal and activate the LED lights inside the chip. The lights will shine on the synthetic cells, stimulating them to generate two compounds that are naturally produced in the body. The compounds will be released directly into the bloodstream, heading towards targeted locations, such as a tiny, centrally-located structure in the brain called the suprachiasmatic nucleus (SCN) that serves as master pacemaker of the circadian rhythm. Whatever the target location, the flow of biomolecules will alter the natural clock. When the solider arrives in Okinawa, their body will be perfectly in tune with local time.

The synthetic cells will be kept isolated from the host’s immune system by a membrane constructed of novel biomaterials, allowing only nutrients and oxygen in and only the compounds out. Should anything go wrong, they would swallow a pill that would kill the cells inside the chip only, leaving the rest of their body unaffected.

If you have the time, I recommend reading Young’s June 17, 2021 Smithsonian Magazine article (GetPocket.com link to article) in its entirety. Young goes on to discuss, hacking, malware, and ethical/societal issues and more.

There is an animation of Kahn’s original poster in a June 23, 2011 posting on openculture.com (also found on Vimeo; Der Mensch als Industriepalast [Man as Industrial Palace])

Credits: Idea & Animation: Henning M. Lederer / led-r-r.net; Sound-Design: David Indge; and original poster art: Fritz Kahn.

‘Necrobotic’ spiders as mechanical grippers

A July 25, 2022 news item on ScienceDaily describes research utilizing dead spiders,

Spiders are amazing. They’re useful even when they’re dead.

Rice University mechanical engineers are showing how to repurpose deceased spiders as mechanical grippers that can blend into natural environments while picking up objects, like other insects, that outweigh them.

Caption: An illustration shows the process by which Rice University mechanical engineers turn deceased spiders into necrobotic grippers, able to grasp items when triggered by hydraulic pressure. Credit: Preston Innovation Laboratory/Rice University

A July 25, 2022 Rice University news release (also on on EurekAlert but published August 4, 2022), which originated the news item, explains the reasoning, Note: Links have been removed,

“It happens to be the case that the spider, after it’s deceased, is the perfect architecture for small scale, naturally derived grippers,” said Daniel Preston of Rice’s George R. Brown School of Engineering. 

An open-access study in Advanced Science outlines the process by which Preston and lead author Faye Yap harnessed a spider’s physiology in a first step toward a novel area of research they call “necrobotics.”

Preston’s lab specializes in soft robotic systems that often use nontraditional materials, as opposed to hard plastics, metals and electronics. “We use all kinds of interesting new materials like hydrogels and elastomers that can be actuated by things like chemical reactions, pneumatics and light,” he said. “We even have some recent work on textiles and wearables. 

“This area of soft robotics is a lot of fun because we get to use previously untapped types of actuation and materials,” Preston said. “The spider falls into this line of inquiry. It’s something that hasn’t been used before but has a lot of potential.”

Unlike people and other mammals that move their limbs by synchronizing opposing muscles, spiders use hydraulics. A chamber near their heads contracts to send blood to limbs, forcing them to extend. When the pressure is relieved, the legs contract. 

The cadavers Preston’s lab pressed into service were wolf spiders, and testing showed they were reliably able to lift more than 130% of their own body weight, and sometimes much more. They had the grippers manipulate a circuit board, move objects and even lift another spider.  

The researchers noted smaller spiders can carry heavier loads in comparison to their size. Conversely, the larger the spider, the smaller the load it can carry in comparison to its own body weight. Future research will likely involve testing this concept with spiders smaller than the wolf spider, Preston said

Yap said the project began shortly after Preston established his lab in Rice’s Department of Mechanical Engineering in 2019.

“We were moving stuff around in the lab and we noticed a curled up spider at the edge of the hallway,” she said. “We were really curious as to why spiders curl up after they die.”

A quick search found the answer: “Spiders do not have antagonistic muscle pairs, like biceps and triceps in humans,” Yap said. “They only have flexor muscles, which allow their legs to curl in, and they extend them outward by hydraulic pressure. When they die, they lose the ability to actively pressurize their bodies. That’s why they curl up. 

“At the time, we were thinking, ‘Oh, this is super interesting.’ We wanted to find a way to leverage this mechanism,” she said.

Internal valves in the spiders’ hydraulic chamber, or prosoma, allow them to control each leg individually, and that will also be the subject of future research, Preston said. “The dead spider isn’t controlling these valves,” he said. “They’re all open. That worked out in our favor in this study, because it allowed us to control all the legs at the same time.”

Setting up a spider gripper was fairly simple. Yap tapped into the prosoma chamber with a needle, attaching it with a dab of superglue. The other end of the needle was connected to one of the lab’s test rigs or a handheld syringe, which delivered a minute amount of air to activate the legs almost instantly. 

The lab ran one ex-spider through 1,000 open-close cycles to see how well its limbs held up, and found it to be fairly robust. “It starts to experience some wear and tear as we get close to 1,000 cycles,” Preston said. “We think that’s related to issues with dehydration of the joints. We think we can overcome that by applying polymeric coatings.”

What turns the lab’s work from a cool stunt into a useful technology?

Preston said a few necrobotic applications have occurred to him. “There are a lot of pick-and-place tasks we could look into, repetitive tasks like sorting or moving objects around at these small scales, and maybe even things like assembly of microelectronics,” he said. 

“Another application could be deploying it to capture smaller insects in nature, because it’s inherently camouflaged,” Yap added. 

“Also, the spiders themselves are biodegradable,” Preston said. “So we’re not introducing a big waste stream, which can be a problem with more traditional components.”

Preston and Yap are aware the experiments may sound to some people like the stuff of nightmares, but they said what they’re doing doesn’t qualify as reanimation. 

“Despite looking like it might have come back to life, we’re certain that it’s inanimate, and we’re using it in this case strictly as a material derived from a once-living spider,” Preston said. “It’s providing us with something really useful.”

Co-authors of the paper are graduate students Zhen Liu and Trevor Shimokusu and postdoctoral fellow Anoop Rajappan. Preston is an assistant professor of mechanical engineering.

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

Necrobotics: Biotic Materials as Ready-to-Use Actuators by Te Faye Yap, Zhen Liu, Anoop Rajappan, Trevor J. Shimokusu, Daniel J. Preston. Advanced Science
DOI: https://doi.org/10.1002/advs.202201174 First published: 25 July 2022

As noted in the news release, this paper is open access.

Why can’t they produce graphene at usable (industrial) scales?

Kevin Wyss, PhD chemistry student at Rice University, has written an explanation of why graphene is not produced in quantities that make it usable in industry in his November 29, 2022 essay for The Conversation (h/t Nov. 29, 2022 phys.org news item), Note: Links have been removed from the following,

“Future chips may be 10 times faster, all thanks to graphene”; “Graphene may be used in COVID-19 detection”; and “Graphene allows batteries to charge 5x faster” – those are just a handful of recent dramatic headlines lauding the possibilities of graphene. Graphene is an incredibly light, strong and durable material made of a single layer of carbon atoms. With these properties, it is no wonder researchers have been studying ways that graphene could advance material science and technology for decades.

Graphene is a fascinating material, just as the sensational headlines suggest, but it is only just starting be used in real-world applications. The problem lies not in graphene’s properties, but in the fact that it is still incredibly difficult and expensive to manufacture at commercial scales.

Wyss highlights the properties that make graphene so attractive, from the November 29, 2022 essay (Note: Links have been removed from the following),

… The material can be used to create flexible electronics and to purify or desalinate water. And adding just 0.03 ounces (1 gram) of graphene to 11.5 pounds (5 kilograms) of cement increases the strength of the cement by 35%.

As of late 2022, Ford Motor Co., with which I worked as part of my doctoral research, is one of the the only companies to use graphene at industrial scales. Starting in 2018, Ford began making plastic for its vehicles that was 0.5% graphene – increasing the plastic’s strength by 20%.

There are two ways of producing graphene as Wyss notes in his November 29, 2022 essay (Note: Links have been removed from the following),

Top-down synthesis [emphasis mine], also known as graphene exfoliation, works by peeling off the thinnest possible layers of carbon from graphite. Some of the earliest graphene sheets were made by using cellophane tape to peel off layers of carbon from a larger piece of graphite.

The problem is that the molecular forces holding graphene sheets together in graphite are very strong, and it’s hard to pull sheets apart. Because of this, graphene produced using top-down methods is often many layers thick, has holes or deformations, and can contain impurities. Factories can produce a few tons of mechanically or chemically exfoliated graphene per year, and for many applications – like mixing it into plastic – the lower-quality graphene works well.

Bottom-up synthesis [emphasis mine] builds the carbon sheets one atom at a time over a few hours. This process – called vapor deposition – allows researchers to produce high-quality graphene that is one atom thick and up to 30 inches across. This yields graphene with the best possible mechanical and electrical properties. The problem is that with a bottom-up synthesis, it can take hours to make even 0.00001 gram – not nearly fast enough for any large scale uses like in flexible touch-screen electronics or solar panels, for example.

Current production methods of graphene, both top-down and bottom-up, are expensive as well as energy and resource intensive, and simply produce too little product, too slowly.

Wyss has written an informative essay and, for those who need it, he has included an explanation of the substance known as graphene.

Detangling carbon nanotubes (CNTs)

An April 27, 2022 news item on ScienceDaily announces research into a solution to a vexing problem associated with the production of carbon nanotubes (CNTs),

Carbon nanotubes that are prone to tangle like spaghetti can use a little special sauce to realize their full potential.

Rice University scientists have come up with just the sauce, an acid-based solvent that simplifies carbon nanotube processing in a way that’s easier to scale up for industrial applications.

The Rice lab of Matteo Pasquali reported in Science Advances on its discovery of a unique combination of acids that helps separate nanotubes in a solution and turn them into films, fibers or other materials with excellent electrical and mechanical properties.

The study co-led by graduate alumnus Robert Headrick and graduate student Steven Williams reports the solvent is compatible with conventional manufacturing processes. That should help it find a place in the production of advanced materials for many applications.

An April 22, 2022 Rice University news release (received via email and also published on April 27, 2022 on EurekAlert), which originated the news item, delves further into how the research has environmental benefits and into its technical aspects (Note Links have been removed),

“There’s a growing realization that it’s probably not a good idea to increase the mining of copper and aluminum and nickel,” said Pasquali, Rice’s A.J. Hartsook Professor and a professor of chemical and biomolecular engineering, chemistry and materials science and nanoengineering. He is also director of the Rice-based Carbon Hub, which promotes the development of advanced carbon materials to benefit the environment.

“But there is this giant opportunity to use hydrocarbons as our ore,” he said. “In that light, we need to broaden as much as possible the range in which we can use carbon materials, especially where it can displace metals with a product that can be manufactured sustainably from a feedstock like hydrocarbons.” Pasquali noted these manufacturing processes produce clean hydrogen as well.

“Carbon is plentiful, we control the supply chains and we know how to get it out in an environmentally responsible way,” he said.

A better way to process carbon will help. The solvent is based on methanesulfonic (MSA), p-toluenesulfonic (pToS)and oleum acids that, when combined, are less corrosive than those currently used to process nanotubes in a solution. Separating nanotubes (which researchers refer to as dissolving) is a necessary step before they can be extruded through a needle or other device where shear forces help turn them into familiar fibers or sheets. 

Oleum and chlorosulfonic acids have long been used to dissolve nanotubes without modifying their structures, but both are highly corrosive. By combining oleum with two weaker acids, the team developed a broadly applicable process that enables new manufacturing for nanotubes products.

“The oleum surrounds each individual nanotube and gives it a very localized positive charge,” said Headrick, now a research scientist at Shell. “That charge makes them repel each other.”

After detangling, the milder acids further separate the nanotubes. They found MSA is best for fiber spinning and roll-to-roll film production, while pToS, a solid that melts at 40 degrees Celsius (104 degrees Fahrenheit), is particularly useful for 3D printing applications because it allows nanotube solutions to be processed at a moderate temperature and then solidified by cooling.

The researchers used these stable liquid crystalline solutions to make things in both modern and traditional ways, 3D printing carbon nanotube aerogels and silk screen printing patterns onto a variety of surfaces, including glass. 

The solutions also enabled roll-to-roll production of transparent films that can be used as electrodes. “Honestly, it was a little surprising how well that worked,” Headrick said. “It came out pretty flawless on the very first try.”

The researchers noted oleum still requires careful handling, but once diluted with the other acids, the solution is much less aggressive to other materials. 

“The acids we’re using are so much gentler that you can use them with common plastics,” Headrick said. “That opens the door to a lot of materials processing and printing techniques that are already in place in manufacturing facilities. 

“It’s also really important for integrating carbon nanotubes into other devices, depositing them as one step in a device-manufacturing process,” he said.

They reported the less-corrosive solutions did not give off harmful fumes and were easier to clean up after production. MSA and pToS can also be recycled after processing nanotubes, lowering their environmental impact and energy and processing costs.

Williams said the next step is to fine-tune the solvent for applications, and to determine how factors like chirality and size affect nanotube processing. “It’s really important that we have high-quality, clean, large diameter tubes,” he said.

Co-authors of the paper are alumna Lauren Taylor and graduate students Oliver Dewey and Cedric Ginestra of Rice; graduate student Crystal Owens and professors Gareth McKinley and A. John Hart at the Massachusetts Institute of Technology; alumna Lucy Liberman, graduate student Asia Matatyaho Ya’akobi and Yeshayahu Talmon, a professor emeritus of chemical engineering, at the Technion-Israel Institute of Technology, Haifa, Israel; and Benji Maruyama, autonomous materials lead in the Materials and Manufacturing Directorate, Air Force Research Laboratory.

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

Versatile acid solvents for pristine carbon nanotube assembly by Robert J. Headrick, Steven M. Williams, Crystal E. Owens, Lauren W. Taylor, Oliver S. Dewey, Cedric J. Ginestra, Lucy Liberman, Asia Matatyaho Ya’akobi, Yeshayahu Talmon, Benji Maruyama, Gareth H. McKinley, A. John Hart, Matteo Pasquali. Science Advances • 27 Apr 2022 • Vol 8, Issue 17 • DOI: 10.1126/sciadv.abm3285

This paper is open access.

3D-printed ‘smart helmets’ for the military

Caption: The Rice University-designed smart helmet is intended to modernize standard-issue military helmets by 3D-printing a nanomaterial-enhanced exoskeleton with embedded sensors to actively protect the brain against kinetic or directed-energy effects. Credit: Rice University

Hopefully this will limit the number of head injuries suffered by soldiers.

Some years ago I was at dinner with friends when one of them, a doctor at the local hospital, told me that the Canadian military, which was in Afghanistan at the time, was dealing with a high number of head injury cases, in part due to the soldiers’ own protective gear.

For example, the protective helmet meant you were less likely to receive a catastrophic injury to your cranium (e.g., metal cracking through bone) but your head would be shaken and that isn’t good for anyone’s brain.

It would seem this project at Rice University (Texas, US) is designed to limit the problem of your own protective gear causing injury, from a November 10, 2021 Rice University news release (also on EurekAlert), Note: Links have been removed,

Rice University researchers have received $1.3 million from the Office of Naval Research through the Defense Research University Instrumentation Program to create the world’s first printable military “smart helmet” using industrial-grade 3D printers. 

Led by principal investigator Paul Cherukuri, executive director of Rice’s Institute of Biosciences and Bioengineering, the Smart Helmet program aims to modernize standard-issue military helmets by 3D-printing a nanomaterial-enhanced exoskeleton with embedded sensors to actively protect the brain against kinetic or directed-energy effects. 

Rice will utilize Carbon Inc.’s L1 printer to develop a strong-but-light military-grade helmet that incorporates advances in materials, image processing, artificial intelligence, haptic feedback and energy storage. The printer enables rapid prototyping that in turn simplifies the process of incorporating the sensors, cameras, batteries and wiring harnesses the program requires, Cherukuri said. 

“Current helmets have evolved little since the last century and are still heavy, bulky, passive devices,” he said. “Because of advances in sensors and additive manufacturing, we’re now reimagining the helmet as a 3D-printed, AI-enabled, ‘always-on’ wearable that detects threats near or far and is capable of launching countermeasures to protect soldiers, sailors, airmen and Marines. Essentially, we’re building J.A.R.V.I.S.”

The Smart Helmet program will use technology drawn from projects like the FlatCam, a system developed by co-investigator and electrical and computer engineer Ashok Veeraraghavan and his colleagues that incorporates sophisticated image processing to eliminate the need for bulky lenses, as well as Cherukuri’s Teslaphoresis, a kind of tractor beam for nanomaterials that could help create physical and electromagnetic shields inside the helmets. 

“A smart helmet task force has been assembled from some of the finest minds at Rice to tackle the challenge of creating a self-contained, intelligent system that protects the warfighter at all times,” Cherukuri said. The task force includes the labs of materials scientist Pulickel Ajayan, civil and environmental engineer and Rice Provost Reginald DesRoches, mechanical engineer Marcia O’Malley, chemist James Tour and Veeraraghavan.

While the location of the L1 has yet to be determined, a Carbon M2 printer will be located at the Oshman Engineering Design Kitchen (OEDK), where it will be available for projects other than the helmet. Rice undergraduates who design and build their mandated capstone projects at the OEDK are taking part in the helmet project, working alongside graduate students and postdoctoral researchers to develop the heads-up display.   

“We’ve got a lot of innovative tech in university labs that has never seen the light of day,” Cherukuri said. “We’re simply developing that technology into a device that gives the men and women protecting our country a real chance at coming home safe and sound. This is for them.”

A gas, gas, gas for creating semiconducting nanomaterials?

A June 14, 2021 news item on phys.org highlights some new research from Rice University (Texas, US),

Scientific studies describing the most basic processes often have the greatest impact in the long run. A new work by Rice University engineers could be one such, and it’s a gas, gas, gas for nanomaterials.

Yes, I ‘stole’ the phrase from the news item/release for my headline. For anyone unfamiliar with the word gas’ used as slang, it mean something is good or wonderful (See Urban Dictionary).

Getting back to science, gas, and nanomaterials, a June 11, 2021 Rice University news release (also on EurekAlert), which originated the news item, answers some questions about how manufacturing nanomaterial used in electronics could be more easily manufactured,

Rice materials theorist Boris Yakobson, graduate student Jincheng Lei and alumnus Yu Xie of Rice’s Brown School of Engineering have unveiled how a popular 2D material, molybdenum disulfide (MoS2), flashes into existence during chemical vapor deposition (CVD).

Knowing how the process works will give scientists and engineers a way to optimize the bulk manufacture of MoS2 and other valuable materials classed as transition metal dichalcogenides (TMDs), semiconducting crystals that are good bets to find a home in next-generation electronics.

Their study in the American Chemical Society journal ACS Nano focuses on MoS2’s “pre-history,” specifically what happens in a CVD furnace once all the solid ingredients are in place. CVD, often associated with graphene and carbon nanotubes, has been exploited to make a variety of 2D materials by providing solid precursors and catalysts that sublimate into gas and react. The chemistry dictates which molecules fall out of the gas and settle on a substrate, like copper or silicone, and assemble into a 2D crystal.

The problem has been that once the furnace cranks up, it’s impossible to see or measure the complicated chain of reactions in the chemical stew in real time.

“Hundreds of labs are cooking these TMDs, quite oblivious to the intricate transformations occurring in the dark oven,” said Yakobson, the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry. “Here, we’re using quantum-chemical simulations and analysis to reveal what’s there, in the dark, that leads to synthesis.”

Yakobson’s theories often lead experimentalists to make his predictions come true. (For example, boron buckyballs.) This time, the Rice lab determined the path molybdenum oxide (MoO3) and sulfur powder take to deposit an atomically thin lattice onto a surface.

The short answer is that it takes three steps. First, the solids are sublimated through heating to change them from solid to gas, including what Yakobson called a “beautiful” ring-molecule, trimolybdenum nonaoxide (Mo3O9). Second, the molybdenum-containing gases react with sulfur atoms under high heat, up to 4,040 degrees Fahrenheit. Third, molybdenum and sulfur molecules fall to the surface, where they crystallize into the jacks-like lattice that is characteristic of TMDs.

What happens in the middle step was of the most interest to the researchers. The lab’s simulations showed a trio of main gas phase reactants are the prime suspects in making MoS2: sulfur, the ring-like Mo3O9 molecules that form in sulfur’s presence and the subsequent hybrid of MoS6 that forms the crystal, releasing excess sulfur atoms in the process.

Lei said the molecular dynamics simulations showed the activation barriers that must be overcome to move the process along, usually in picoseconds.

“In our molecular dynamics simulation, we find that this ring is opened by its interaction with sulfur, which attacks oxygen connected to the molybdenum atoms,” he said. “The ring becomes a chain, and further interactions with the sulfur molecules separate this chain into molybdenum sulfide monomers. The most important part is the chain breaking, which overcomes the highest energy barrier.”

That realization could help labs streamline the process, Lei said. “If we can find precursor molecules with only one molybdenum atom, we would not need to overcome the high barrier of breaking the chain,” he said.

Yakobson said the study could apply to other TMDs.

“The findings raise oftentimes empirical nanoengineering to become a basic science-guided endeavor, where processes can be predicted and optimized,” he said, noting that while the chemistry has been generally known since the discovery of TMD fullerenes in the early ’90s, understanding the specifics will further the development of 2D synthesis.

“Only now can we ‘sequence’ the step-by-step chemistry involved,” Yakobson said. “That will allow us to improve the quality of 2D material, and also see which gas side-products might be useful and captured on the way, opening opportunities for chemical engineering.”

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

Gas-Phase “Prehistory” and Molecular Precursors in Monolayer Metal Dichalcogenides Synthesis: The Case of MoS2 by Jincheng Lei, Yu Xie, and Boris I. Yakobson. ACS Nano 2021, 15, 6, 10525–10531 DOI: https://doi.org/10.1021/acsnano.1c03103 Publication Date: June 9, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.

Stronger concrete with graphene derived from tires

I’ve become strangely fascinated with concrete these last few months. Possibly, this is a consequence of a lot more ‘concrete’ research being published. Here’s a March 29, 2021 news item on phys.org featuring work from Rice University (Texas, US),

This could be where the rubber truly hits the road.

Rice University scientists have optimized a process to convert waste from rubber tires into graphene that can, in turn, be used to strengthen concrete.

The environmental benefits of adding graphene to concrete are clear, chemist James Tour said.

“Concrete is the most-produced material in the world, and simply making it produces as much as 9% of the world’s carbon dioxide emissions,” Tour said. “If we can use less concrete in our roads, buildings and bridges, we can eliminate some of the emissions at the very start.”

A March 29, 2021 Rice University news release (also on EurekAlert), which originated the news item, provides context for the work and more technical details,

Recycled tire waste is already used as a component of Portland cement, but graphene has been proven to strengthen cementitious materials, concrete among them, at the molecular level.

While the majority of the 800 million tires discarded annually are burned for fuel or ground up for other applications, 16% of them wind up in landfills.

“Reclaiming even a fraction of those as graphene will keep millions of tires from reaching landfills,” Tour said.

The “flash” process introduced by Tour and his colleagues in 2020 has been used to convert food waste, plastic and other carbon sources by exposing them to a jolt of electricity that removes everything but carbon atoms from the sample.

Those atoms reassemble into valuable turbostratic graphene, which has misaligned layers that are more soluble than graphene produced via exfoliation from graphite. That makes it easier to use in composite materials.

Rubber proved more challenging than food or plastic to turn into graphene, but the lab optimized the process by using commercial pyrolyzed waste rubber from tires. After useful oils are extracted from waste tires, this carbon residue has until now had near-zero value, Tour said.

Tire-derived carbon black or a blend of shredded rubber tires and commercial carbon black can be flashed into graphene. Because turbostratic graphene is soluble, it can easily be added to cement to make more environmentally friendly concrete.

The research led by Tour and Rouzbeh Shahsavari of C-Crete Technologies is detailed in the journal Carbon.

The Rice lab flashed tire-derived carbon black and found about 70% of the material converted to graphene. When flashing shredded rubber tires mixed with plain carbon black to add conductivity, about 47% converted to graphene. Elements besides carbon were vented out for other uses.

The electrical pulses lasted between 300 milliseconds and 1 second. The lab calculated electricity used in the conversion process would cost about $100 per ton of starting carbon.

The researchers blended minute amounts of tire-derived graphene — 0.1 weight/percent (wt%) for tire carbon black and 0.05 wt% for carbon black and shredded tires — with Portland cement and used it to produce concrete cylinders. Tested after curing for seven days, the cylinders showed gains of 30% or more in compressive strength. After 28 days, 0.1 wt% of graphene sufficed to give both products a strength gain of at least 30%.

“This increase in strength is in part due to a seeding effect of 2D graphene for better growth of cement hydrate products, and in part due to a reinforcing effect at later stages,” Shahsavari said.

Set of tires on a sky background

I’m not sure where I got this stock shot but it is pretty (if tires can ever be described that way).

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

Flash Graphene from Rubber Waste by Paul A. Advincula, Duy Xuan Luong, Weiyin Chen, Shivaranjan Raghuraman, Rouzbeh Shahsavari, James M.Tour. Carbon Available online 28 March 2021 In Press, Journal Pre-proof DOI: https://doi.org/10.1016/j.carbon.2021.03.020

This paper is behind a paywall.

Soap and water for creating 2D nanoflakes (hexagonal boron nitride [hBN] sheets)

Rice University (Texas, US) has a pretty image illustrating the process of making 2D nanoflakes,

Caption: The image displays the exfoliation of hexagonal boron nitride into atomically thin nanosheets aided by surfactants, a process refined by chemists at Rice University. Credit: Ella Maru Studio

A January 27, 2021 news item on Nanowerk announces the Rice University news,

Just a little soap helps clean up the challenging process of preparing two-dimensional hexagonal boron nitride (hBN).

Rice University chemists have found a way to get the maximum amount [number] of quality 2D hBN nanosheets from its natural bulk form by processing it with surfactant (aka soap) and water. The surfactant surrounds and stabilizes the microscopic flakes, preserving their properties.

Experiments by the lab of Rice chemist Angel Martí identified the “sweet spot” for making stable dispersions of hBN, which can be processed into very thin antibacterial films that handle temperatures up to 900 degrees Celsius (1,652 degrees Fahrenheit).

A brief grammatical moment: I can see where someone might view it as arguable (see second paragraph of the above excerpt) but for me ‘amount’ is for something like ‘flour’ for an ‘amount of flour’. ‘Number’ is for something like a ‘number of sheets’. The difference lies in your ability to count the items. Generally speaking, you can’t count the number of flour, therefore, it’s the amount of flour, but you can count the number of sheets. Can count these hexagonal boron nitride (hBN) sheets? If not, is what makes this arguable.

A January 27, 2021 Rice University news release (also on EurekAlert), which originated the news item, delves into details,

The work led by Martí, alumna Ashleigh Smith McWilliams and graduate student Cecilia Martínez-Jiménez is detailed in the American Chemical Society journal ACS Applied Nano Materials.

“Boron nitride materials are interesting, particularly because they are extremely resistant to heat,” Martí said. “They are as light as graphene and carbon nanotubes, but you can put hBN in a flame and nothing happens to it.”

He said bulk hBN is cheap and easy to obtain, but processing it into microscopic building blocks has been a challenge. “The first step is to be able to exfoliate and disperse them, but research on how to do that has been scattered,” Martí said. “When we decided to set a benchmark, we found the processes that have been extremely useful for graphene and nanotubes don’t work as well for boron nitride.”

Sonicating bulk hBN in water successfully exfoliated the material and made it soluble. “That surprised us, because nanotubes or graphene just float on top,” Martí said. “The hBN dispersed throughout, though they weren’t particularly stable.

“It turned out the borders of boron nitride crystals are made of amine and nitric oxide groups and boric acid, and all of these groups are polar (with positive or negative charge),” he said. “So when you exfoliate them, the edges are full of these functional groups that really like water. That never happens with graphene.”

Experiments with nine surfactants helped them find just the right type and amount to keep 2D hBN from clumping without cutting individual flakes too much during sonication. The researchers used 1% by weight of each surfactant in water, added 20 milligrams of bulk hBN, then stirred and sonicated the mix.

Spinning the resulting solutions at low and high rates showed the greatest yield came with the surfactant known as PF88 under 100-gravity centrifugation, but the highest-quality nanosheets came from all the ionic surfactants under 8,000 g centrifugation, with the greatest stability from common ionic surfactants SDS and CTAC.

DTAB — short for dodecyltrimethylammonium bromide — under high centrifugation proved best at balancing the yield and quality of 2D hBN. The researchers also produced a transparent film from hBN nanosheets dispersed in SDS and water to demonstrate how they can be processed into useful products.

“We describe the steps you need to do to produce high-quality hBN flakes,” Martí said. “All of the steps are important, and we were able to bring to light the consequences of each one.”

Understanding the Exfoliation and Dispersion of Hexagonal Boron Nitride Nanosheets by Surfactants: Implications for Antibacterial and Thermally Resistant Coatings by Ashleigh D. Smith McWilliams, Cecilia Martínez-Jiménez, Asia Matatyaho Ya’akobi, Cedric J. Ginestra, Yeshayahu Talmon, Matteo Pasquali, and Angel A. Martí. ACS Appl. Nano Mater. 2021, 4, 1, 142–151 DOI: https://doi.org/10.1021/acsanm.0c02437 Publication Date: January 7, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.