Updates and Some Nanotechnology Developments

In doing research for an upcoming published paper, I ran across an interesting article.  In September 2019, a research article was published that postulated the worst case situation for a worldwide pandemic, of unknown origins, might have a devastating impact on the world.  This was the first annual report by the Global Preparedness Monitoring Board [Ref. 1].  This paper was published before the evidence of the coronavirus (COVID-19) was detected.  Consequently, these hypothetical findings were transferred to the projections of coronavirus impact.

In a related area, it appears that there are more instances of publications of faulty or purposely misleading scientific and medical research, even by prestigious researchers [Ref. 2, 3].  Whether it is researchers who refuse to provide details on their models or experts that have a segment of researchers in their field insisting on retracting papers, the overall effect is to build a distrust in any research that is published.  This will have serious consequences when the general public develops an attitude that all scientific pronouncements are not to be believed.

Back to nanotechnology.  A team from Binghamton University lead by Pu Zhang developed a liquid metal lattice material [Ref. 4].  The basic concept of the material is that a silicone shell holds the metal composite together, so the material can be crushed but is able to return to its original form.  The metal composite has a melting point of 62C, which enables a restructuring possible using heated water.  The concept relies on the shell to return to its original form.  Without that shell, the liquid metal would become a blob of metal.  In its solid form, the material is very strong and stable.  If is much more resistant to deformation than similar property-type polymers that are able to be reshaped.    

From Queensland University of Technology comes some computational studies that diamond-like carbon nanothreads could be employed in a strained mechanical battery system [Ref. 5].  As described in the referenced article: First described in 2015,  nanothreads joined a catalogue of carbon nanomaterials that have emerged over the past four decades. Nanothreads are 1D structures with carbon atoms linked by single bonds (like those in diamond) to three other carbon atoms and a hydrogen atom. Where the hydrogen atom is missing, the carbon atom may bond to a fourth carbon atom in an adjacent thread. This bonding contrasts with the hexagonal carbon lattices found in buckyballs, carbon nanotubes and graphene. In these materials, electron orbitals from each carbon atom are shared between just three other carbon atoms.” It is interesting to note that Penn State University has a National Science Foundation Center for Nanothread Chemistry.  There should be some interesting research coming from this new Center.

Medicine is moving into the nano realm to study and obtain insights about amyloid plaques [Ref. 6].  These amyloid plaques are characteristic of neurodegenerative diseases.  (Diseases like Parkinson’s and Alzheimer’s.)  These plaques are abnormal aggregates that have been linked to numerous diseases.  The goal of the research was to understand the structure of the plaques.  In order to accomplish their study, it required for the development of a new aspect of microscopy.  Their “super” resolution microscopy involves the latest in high resolution equipment with the addition of a dual channel polarized fluorescence light.  With their invention, they are able to observe the working of the molecules interacting with the plaques. 

There is the annual SEMICon West conference occurring next month (July).  This year it is virtual.  There will be a number of presentations on the issues/challenges as semiconductor devices have to overcome as the dimensions go lower into the single digit nanometers.  This is one area where nanotechnology is very much in the forefront of new developments.

References:

  1. https://apps.who.int/gpmb/assets/annual_report/GPMB_annualreport_2019.pdf
  2. https://www.wsj.com/articles/the-lancets-politicized-science-on-antimalarial-drugs-11591053222?mod=hp_opin_pos_3
  3. https://www.washingtontimes.com/news/2020/may/9/covid-19-puts-spotlight-science-scientists-often-l/
  4. https://physicsworld.com/a/new-material-could-be-used-to-make-a-liquid-metal-robot/?
  5. https://physicsworld.com/a/diamond-nanothreads-could-beat-batteries-for-energy-storage-theoretical-study-suggests/?
  6. https://physicsworld.com/a/super-resolution-microscopy-reveals-nanoscale-details-of-amyloid-protein-structures/?

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Research Impacts at the End of the Great Shutdown

As the world starts to come out of the Covid–19 shutdown, there are many things that will be required for research organizations to address prior to beginning their research again. Businesses have a similar but different process that needs to be completed as the organizations come out of the Great Shutdown. There are opportunities to reevaluate processes and procedures during the restart.

The items that need to be addressed from the research perspective include the workforce, equipment maintenance and calibration, material purity and integrity, and the validity of the most recent research. The initial consideration will include any new rules, regulations, and procedures the overall organization has developed and required to be implemented.  The challenge will be that all of these things need to be accomplished simultaneously. This is one of those times when a fast start may require additional assistance from recently retired personnel or external experts.

The workforce has several components that need to be addressed. The first one is the question of whether all personnel will be returning to the organization. It is possible that those not returning could have had a serious or deadly effect of Covid-19, still be recovering, found a new position, or have decided not to return to work until some later time. It is obvious that the new people who would need to be employed to replace people no longer available will require training. The returning people will need to go through a refresher training since it has been three months or more since they last use the equipment or processes, they will be working on. In addition, there may be regulations on social distancing that require changes in the workplace.

The equipment maintenance and calibration are an important part of any research effort. Since it has been months that the equipment has been non-operating, the equipment needs to have a thorough maintenance update. (I recall returning from a two-week shutdown to find that several of our wire binders had rust on parts of the mechanism. The temperature and humidity controlled rooms keep a level of moisture in the atmosphere all the time. We had to fix that before we can begin operating again.) After the equipment is up and running it will need to be calibrated. Since it has been months since its last operation, the equipment calibration should be the more thorough version to ensure the equipment is functioning properly.

While one normally does not think too much about the material purity or liquid contamination, these could be issues do to the long storage without usage. In previous blogs I have mentioned things like changing characteristics during shipment due to exposure to air. Liquids have the potential for dilution or contamination, which would change their characteristics when used in various processes. This requires some additional time to ensure the material you think you have is the material you actually have.

The last of these major points is the need to validate the research that was being done at the time of the Great Shutdown. Research that was not complete when the event happened needs to be redone from the very beginning. Research that had been completed shortly before the Great Shutdown needs to be replicated to ensure that the new experiments produces the same results as prior to the shutdown. The purpose of this extra effort is to ensure that something else in the workplace environment did not change and create an impact on the results that were obtained.

So, the real challenge is do everything at once and to do it is accurately as possible. In many cases the items will be done sequentially which will extend out the time for the completion of the research. Another portion of this time duration of lost research time is that it probably has a serious impact on the funds that were available for the research. This is one of the times in an organizations history that leading the way provide significant benefits. Being among the first, there are opportunities to pick up seasoned employees with skill levels that are greatly needed. Those organizations that start later may not have as wide a selection of skilled workers to choose from.

There are many more details that could be added to the startup of the research along with the actual startup of business. This could be a time to look at information flow, equipment priorities, hierarchical structure, equipment needs, and other items that would enable more accurate and faster research results. There will be strong competition within organizations for additional funding, so those who are prepared and move quickly will have an advantage. Good luck and God’s speed.

I do not provide an explicit email address due to that email address becoming overloaded with spam and advertising.  I can be reached via email: “ideas at nano-blog dot com”.  Replace the “at” and “dot” with the appropriate symbols. 

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Scientific Integrity and COVID-19

I’ve written about validating scientific findings previously.  With the current COVID-19 (coronavirus) situation, there have been numerous published claims of various “facts”, which are based on models.  It was only a couple of months ago that the news carried projections of 8 billion people being infected and 80 million people dying.  That later number was reduced to 40 million.  In the US, there were projections of up to 3 million people in the United States dying, which number has been continuously reduced to possibly a maximum of 200,000, but with a possibility of the number being much lower.  The current number of reported deaths is just over 60,000 as I write this blog.

The “facts” two months ago were 80 million worldwide would die, and now that number is currently at 226,882 world-wide who have died (updated April 30, 2020) with a projected total to be in the mid to upper 100,000s.  This current trend indicates that the total number will be less than 1% of the original projection!  What happened?  There are a lot of questions that need to be answered, but that needs to be done by the developers of the model. 

The issue that will be addressed below is why models and the subsequent results need to be understood in order to correctly explain what the “facts” presented actually mean.

First, the information provided as “facts” were not “facts” but projections based on someone’s model of the situation.  A comment years ago by a friend, Professor Bob Shannon of Texas A&M explained it well.  “All models are WRONG, some are useful!”   A strong statement, which we will explore.  

Why are all models wrong?  The answer is that models are based on assumption.  (I have spent considerable time working in modeling.) The model is only as correct as the mathematical description of the object being evaluated, the accuracy of the assumptions being made, the inclusion of all the key variables, and an estimate of the probably of the variables occurring.  Usually models are built, tested, modified, tested again, and finally run multiple times over a set of probabilities.  The resultant answers yield a possible projection with a probability range.  There are usually results that provide the extremes as well as the most probable.  Therefore, the ANSWER is not a single number but a variable with a probability range based on certain assumptions.  Notice the word “assumptions”, it is plural.  The results of the model are only as good as the assumptions.  If you do not know the assumptions, you are unable to evaluate the results from the model.  In addition, models need to be improved as the analysis continues.  This is why it is called modeling.  There are some suggestions that the basic virus impact model has not changed. [Ref. #1]  That in itself is unusual.  Models need to be continually updated to reflect learning from earlier versions.

A commentary by Holman W. Jenkins, Jr. [Ref. #2] provides thoughts about the media not being able to understand multivariate.  This is the fact that things are not simple “if A, then B”.  A short version of this is: “When it rains, Jack always wears a hat”.  Does this imply that Jack wearing a hat causes it to rain?  Of course not.  But there are other variables.  Does Jack need to keep his head covered due to a skin problem?  Does Jack always wear a hat rain or shine?  This is simple example.  But, when reporting reduces a story to a single number, it loses the contributing factors.  A better understanding of how models work is required to be able to accurately report on it.

Yes, there is a need to evaluate situations that may cause a singularity – also called a black swan event.  At one-time, black swans were considered fiction, then people found one.  It was rare at the time.  Now they are not that rare.  Recently, the 100-foot rogue waves were first considered fiction and then black swan events.  Thanks to satellite imaging, we now know that they happen relatively often is certain part of the world with certain conditions.  The point being that looking at the results of a model, one needs to consider the possibility of such event, but not use that as the final answer.  Is it possible that 8 billion of the current 8.8 billion people could get the virus?  A 91% world infection rate?  Possibly yes, but that would not be the most probable and require a significant reevaluation of the modeling assumptions. 

What we, as the public, need to hear and understand is what the assumptions were in developing the models.  The first model is what is the total impact and how is it spread over time.  The second model is what is being proposed and what is that impact.  The concern on the current situation that required governmental interaction was the potential for a huge number of cases that would overwhelm the medical system.  By using a distancing model of 6 feet and a requirement of sheltering in place, the rate of infection is slowed and occurs over a longer period so the medial facilities would not be overwhelmed.  It is not indicating that the fatality rate is lower due to these regulations.  It has only been delayed.  If a vaccine is created, it will lower the fatality rate.  To be presenting anything otherwise is an indication of not understanding what the models are saying.  Large number projections may get people nervous and provide revenue for media, but the large number projections end up forcing the improper allocation of resources.      

The Mayo Clinic responded to the projections that the COVID-19 would require major resource allocation.  This resulted in the cessation/postponement of elective surgeries, cancer treatments, and other related medical procedures.  This large projected number of serious ill people did not happen.  The result was the Mayo Clinic is furloughing and/or giving pay cuts to about 1/3 of its 70,000 employees. [Ref. #3] This does not include the impact on related, externally contracted workers.  And, that does not even address the impact on the patients who were unable to have their procedures. 

Could all of this over allocation of resources be based on the lack of knowledge of understanding what is involved is establishing guidance based on unknowns in models?  One needs to know what is involved in the assumptions, variables, and probabilities.  After the models are run, there is a final decision.  Does the answer make sense, or could there be elements missing or misstated?  91% of the world being infected, raises a very serious question about the validity of the model with me. 

If the news media responds to analyses with single number answers, when these answers are not accurate, can there be any guaranty of developing a true understanding of the problem?  I doubt it.  The consequence of this type “factual presentation” is that the general public loses trust in any statements that are published.  With that is also a loss of confidence in leadership.  Scientific facts need to be presented accurately with the assumptions accompanying the results.   Integrity in every step of the entire process is required.

References:

  1. https://www.wsj.com/articles/curve-crushing-11587753699?cx_testId=3&cx_testVariant=cx_4&cx_artPos=1#cxrecs_s
  2. https://www.wsj.com/articles/the-media-vs-flatten-the-curve-11588113213?mod=hp_opin_pos_2
  3. https://kttc.com/2020/04/10/mayo-clinic-announces-temporary-furloughs-salary-reductions-for-some-employees/

I do not provide an explicit email address due to that email address becoming overloaded with spam and advertising.  I can be reached via email: “ideas at nano-blog dot com”.  Replace the “at” and “dot” with the appropriate symbols. 

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A Time of Turmoil and a Time of Opportunity

As this month’s blog is being written, the US has a “shelter-in-place” directive that has been extended through the end of April.  There are many reports of possible medical treatments that may mitigate the current Covid-19 virus.  Most of the results are anecdotal and have not been vigorously tested.  The scientific/medical process is long and involved requiring multiple trials to prove something works.  I mention this because, the information that I write about are usually one of a kind reports.  That is why references are provided for the reader to investigate further.

While not strictly “nano”, phytomining is a very interesting concept that works with small metal particles.  Phytomining is the process of employing “hyper-accumulating” plants to extract metals from the ground. [Ref. 1]  There are a number of plants, with over 700 known, that have roots that extract metal from the ground.  There is a story that people, who understand the specific plants that grow locally, can determine areas that have gold in the soil.  The referenced article describes an experiment on a plot of land in a rural village on the island of Borneo.  Every six month, the farmer cuts off about a foot on new growth.  The plant cutting can be either squeezed to release the metal or burned to obtain the metal.  After purification the resultant material is nickel citrate.  This leads to the term phytomining or agromining.  Is this a possible means of obtaining metals that are in short supply bur needed for modern society?

Nanoparticles may be successful in targeting the most dangerous of prostate tumors. [Ref. 2] Some observations have suggested that tumors with high nerve densities might grow significantly faster and spread more rapidly than tumors with low nerve densities.  Current research has challenges in identifying the different densities.  The ability to identify nerve density would provide the ability to locate the more aggressive tumors.  That is currently difficult with existing MRI techniques since tumors with dense networks can closely resemble the tumors with an undeveloped nervous system.  Researchers in China have employed combining iron oxide with a nerve binding peptide NP41.  24 hours after injection of the contrast agent material with the iron oxide particles, the high density tumors are identifiable with an MRI scan.  This work has not been advanced to the stage where it can be tested on humans.  It seems to be promising for more than prostate tumors.

I do not normally cover specific products, however, when something seems intriguing, I will provide some thoughts.  These are initial thoughts and not any recommendations for or against a product.  There is a product in the early stages of marketing that employs 60nm particles that act a capacitors (nanocapacitors).  [Ref. 3]  The explanation is that this concept was developed as part of a leading-edge antenna investigation.  Built as an appliable, bandage type device, it contains a substrate, a layer of nanocapacitors, and a carrier layer.  The carrier layer contacts the skin where there is pain.  The contention is that the nanocapacitors interfere (?) or mitigate the electrical signals the body is transmitting from the area of pain.  Does it work?  I have not tired it, so I can not issue a judgment.  The concept seems plausible.  Are there potential issues?  There could be.  It depends on what the nanomaterials are.  At the 60nm size, the properties should be very similar to the bulk material properties.  The size of the particles probably has a specific relationship to the frequency of the signal being mitigated.  The only issue that might be possible is that if the wearer employed the device to mitigate pain and performed an action that increased the severity of the source of pain.  Time will tell on this.   

These are interesting times we live in.

References:

  1. https://www.nytimes.com/2020/02/26/science/metal-plants-farm.html?utm_source=pocket-newtab
  2. https://physicsworld.com/a/nanoparticles-target-the-most-dangerous-prostate-tumours/?
  3. https://www.indiegogo.com/projects/kailo-the-future-of-pain-relief#/  Scroll down to the section that starts “your body is an electrical system” for more detail on the concept.

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Progress and Concerns

Additional information related to last month’s blog.  Single layer technology advances from the DoE’s Argonne National Laboratory have moved the Molecular Layer Etching to the atomic level. [Ref. 1] Argonne Labs have been employing Atomic Layer Etching (ALE).  Just as ALD can be employed to create single layers on a substrate, ALE can be employed to remove atomic layers.  Their work also established a relationship between the reaction temperature and the rate of material removal.  (There is a post by Karsten Arts of Eindhoven University of Technology [Ref. 2] that provides significant detail on plasma assisted ALD and thin film uniformity.)  The claim by researchers at Argonne is that this work may provide a means of creating and controlling nanomaterial geometries with the possibility of creating a means of extending Moore’s Law.  As has been stated in a number of blogs, the development of new tools or creating means to extend the usage of existing tools will provide the means of creating new materials that have properties unknown to us at this time. 

Moving to at different subject, the need for scientific integrity and reproducible results is critical for the advancement of science.  It is also true in other fields.  In a report from the University of Texas at Austin, McCombs School of Business [Ref.3], the topic of using standard algorithms to develop corporate business reports is compared to the traditional approach employed by businesses.  One key observation was that depending on the manner in which the company employed the data (or only a portion of the data), the results of the businesses could change.  Interestingly, the independent observer preferred the reports generated by the management over the algorithm approach.  The report states that the observers preferred the business developed report due to the “positive” spin on explaining the numbers. 

This brings us back to scientific research where the results are promising but there is insufficient information about the original hypothesis, or the experiment procedure developed to prove/disprove the hypothesis.  A few years ago, I covered the study that found of just over 100 published reports of scientific discovery, over 80% of the results were not able to be duplicated – even by the original researcher.  Granted, that many cases, the research area is so new, that expertise of independent researchers for the review may not fully comprehend what is being done without the ability to observe the experiment.  This becomes more of an issue as the nanoscale development moves to smaller and smaller dimensions.  The equipment is normally expensive and scarce.  Time to use the equipment is strictly allocated.  Consequently, the researcher must provide details of the testing and detailed results that are comprehensive.  Removing some results need to be explained whether due to instrumentation irregularities or equipment malfunction or bad sample preparation.  Without details the integrity of the results must be suspect.  A single instance is insufficient.  If one looks at the range of probabilities for an occurrence of a sample size of one, and there is an “n-1” in the denominator, the answer is meaningless.

As the development of materials starts to incorporate more and more single atomic layer materials, the critical nature of reproducible results is necessary.  Scientific integrity has to exist.

References:

  1. https://www.anl.gov/article/new-argonne-etching-technique-could-advance-the-way-semiconductor-devices-are-made
  2. https://www.atomiclimits.com/2020/02/08/basic-insights-into-ald-conformality-a-closer-look-at-ald-and-thin-film-conformality/
  3. https://medium.com/texas-mccombs/to-remove-corporate-bias-let-algorithms-summarize-earnings-47a8055b8d53

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Is that all there is?

With apologies for using the title of a Peggy Lee song from the 70s, this reference is to nanotechnology.  There are continually more interesting findings as researchers move into smaller and smaller particle sizes.  The question really is what happens when the ability to work at sizes as single digit nanometer particles and smaller becomes practical.  To some extent, research is already at this point.  What new properties will become known?

There has been concern that the absorption of heave metals can have a detrimental effect on the human body by becoming a cumulative toxic.  Gold nanoparticles have been employed in various cancer cure Efforts since the early 2000s.  A recent report [Ref. 1] indicates that gold, chemically inert, does not remain intact within cellular structures.  In work done by researchers at the University of Paris, Sorbonne University, and the University of Strasbourg has revealed that gold nanoparticles ranging from 4nm to 22nm indicates these particles do not remain unchanged.    They observed a transformation of the nanoparticles into leaf shaped structures.  These finding may provide additional avenues of investigation for determining the means which the human body metabolizes the particles.  This could change the overall evaluation of potential toxicity.

As mentioned in last month’s blog, researchers have been able to strengthen the structure of silver without diminishing it conductive properties by “implanting” copper atoms at defect along the grain boundaries of the silver.  The maximum strengthening appears to occur when the grain boundaries are 7nm apart. [Ref. 2]

There has been a number of articles on two-dimensional materials, like graphene.  An article in Nature Electronics [Ref. 3] describes the development of heterostructures form by stacking layers of different two-dimensional materials that are possible due to Van der Waals forces.  This particular application create memristors with good thermal stability. 

This bring the discussion to the progress in Atomically Precise Manufacturing (APM).  From Wikipedia, “APM is the production of materials, structures, devices, and finished goods in a manner such that every atom has a specific location relative to the other atoms …” [Ref. 4]  In 2017, the American Chemical Society has a report [Ref. 5] that indicates over 100 molecules of noble metals have been created and are able to de manufactured.  The molecules demonstrate different properties that are different from the nanomaterials.  The research effort has grown to the point where there is a conference on Atomically Precise Nanochemistry. [Ref. 6]

So, Nanotechnology is not the bottom.  There is also work being on electron spin in the quantum realm.  The one consideration that needs to move forward as the APM and other atomic level research progresses in the issue of “safety”.   The development of a “white” paper on the challenges for the manufacture, storage, and handling of these even smaller particles has been initiated with the anticipated release of the recommendation late in 2020.  This effort will be a complementary effort to the existing Nano-Safety “white” paper from 2007. [Ref. 7]

References:

  1. https://physicsworld.com/a/gold-nanoparticles-inside-cells-are-not-inert-say-researchers/?utm_medium=email&utm_source=iop&utm_term=&utm_campaign=14290-45008&utm_content=Title%3A%20Gold%20nanoparticles%20inside%20cells%20are%20not%20inert%2C%20say%20researchers%20%20-%20Editors_pick&Campaign+Owner=
  2. https://www.uvm.edu/uvmnews/news/inventing-worlds-strongest-silver 
  3. https://www.nature.com/articles/s41928-018-0021-4
  4. https://en.wikipedia.org/wiki/Atomically_precise_manufacturing
  5. https://pubs.acs.org/doi/abs/10.1021/acs.chemrev.6b00769
  6. https://www.grc.org/atomically-precise-nanochemistry-conference/2020/
  7. http://www.tryb.org/a_white_paper_on_nano-safety.pdf

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Another Year of Progress (?)

As always when reflecting over a year that is ending, there is good news and there is bad news.  We’ll start with the good.  A lot of technology is being created.  As mentioned last month, new material properties are being created.  The one that I find the most fascinating is the creation of transparent wood!  This material was developed at the KTH Royal Institute of Technology in Stockholm. [Ref. 1] The wood is capable of both storing heat and being transparent, although the transparency becomes translucent as the heat is released.  The figure shows the fully transparent wood on the left and the translucent heat release wood on the right. 

In order to manufacture the wood, the researchers took balsa wood and removed its lignin (provides strength and color) and added acrylic into the remaining tissues filling the empty space remaining from the removal of the lignin and hollow spaces that carry water within the tree.  This produced the structure that restored the strength lost by the removal of the lignin and provided the optical properties.

Another report [Ref 2] describes increasing the strength of silver conductor by introducing very sight amounts of copper.   Their 42% increase in strength is due to their discovery of a new mechanism that works at the nanoscale.  They started with the premise that all metals have defects, which leads to undesirable qualities.  To compensate for these changes, many have solved that issue by creating alloys to make materials stronger, which tends to reduce electrical conductivity.   The team, including researchers from the University of Vermont, Lawrence Livermore National Lab, Ames lab, Los Alamos Nations Lab, and UCLA, began with the fact that as a material size is reduced to the size of a crystal, the material gets stronger. (Hall-Petch relation).  This relation no longer holds when the material is in the 10s of nanometers.  The boundaries between grains becomes unstable and can move.  (Significantly more detail is in the referenced article.)  Introduction of copper atoms, which are slightly smaller than silver atoms, allows the copper atoms to move into defect areas in the grain boundaries.  The team reported the maximum strength is achieved with boundaries that are 7 nanometers apart. 

The future of semiconductors is continuing down the path of continual size reduction.  The next release of the Roadmap will provide the requirements for individual structures that will be measured in tenths of nanometers.  While that is still years away, the fact that such structures are being contemplated implies the development of equipment that will be able to increase our ability to evaluate phenomena in the single digit nanometer and and below.

There appears to great things happening, so what is the bad news.  Unfortunately, the bad news is that the true application of the scientific method is being compromised occasionally.  I am not going to pick one specific study.  There have been retractions from researchers when others in the field have pointed out that their investigations have produced data that was removed in the final determination of the findings.  This is nothing new, but the increase in retractions has been growing since the mid 1990s. [Ref. 3] While the referenced article points out that retractions are not all bad, the increase in fabricated results or falsification has risen along with the rise in retractions.  We must have trust in research that is reported.

References:

  1. https://www.theguardian.com/environment/2019/apr/03/scientists-invent-transparent-wood-in-search-for-eco-friendly-building-material
  2. https://www.uvm.edu/uvmnews/news/inventing-worlds-strongest-silver  
  3. https://alumni.berkeley.edu/california-magazine/just-in/2016-03-16/retraction-action-science-fraud-more-retractions-could-be

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Mitigating Radioactive Waste with Nanomaterials

As the tools available become more precise and develop new capabilities, discoveries arise that are surprising.  Sometimes, this occurs by accident as happened by scientists in Germany, Russia, and Sweden.  The report [Ref. #1] indicate the scientists found a chemically stable compound containing plutonium.  Specifically, the team led by Kristina Kvashnina at the Helmholtz Center Dresden-Rossendorf found that a compound containing plutonium in its fifth oxidations state can remain stable for “long” periods of time.  The team created nanoparticles of plutonium-oxide atoms in different oxidation states. 

 “One of the most fundamental properties of the chemical behavior of plutonium is the variety of its oxidation states.  The oxidation state is defined by the number of electrons that are removed from the valence orbitals of a neutral atom.  In the pentavalent oxidation state, plutonium has three electr4ons in the 5f shell, leaving the 6d orbitals empty. The oxidation state of plutonium determines its chemical behavior and its reactivity.” [Ref. 2]

The team observed the resultant particle structure using X-ray equipment at the European Synchrotron Radiation Facility in Grenoble, France.  They found that the theory agreed with the rapid formation of the plutonium-oxide nanoparticles in its third, fourth, and fifth states.  The sixth oxidation state proved to be different and appeared to have a two-step process that took some time to complete.

The conclusion was that the time lengthening could be due to a stable form of the fifth state.  This had not been observed experimentally before.  Theoretically, if this is correct, it would be possible for the particles could remain stable over months, which would be a major change in our understanding of the chemical properties of nuclear material, particularly nuclear waste.  The team did additional experimentation using high-energy resolution fluorescence and confirmed that a stable form of the fifth oxidation state has actually be observed.  They further confirmed the compound’s stability by drying it our of liquid suspension and measuring the absorption spectrum over time. 

 So, what is the significance of a stable state of plutonium-oxide? 

One of the most significant issues facing the nuclear power industry is the disposal of “spent” radioactive material for reactors.  Plutonium plays a prominent role in nuclear energy production as well as nuclear weapons.  The development of storage methods for nuclear waste is challenging to say the least.  With various materials capable of remaining radioactive for tens of thousands of years, the design of containment that will safeguard the material is difficult.  There are ongoing studies on ways to mitigate the long-term effects of the radioactive material.  This research may provide researchers a methodology to create nanomaterials that mitigate the effects of the radioactive materials by converting them into stable compounds.  This work provides a new method of evaluating was to handle long-term storage of radioactive waste.

References:

  1. https://physicsworld.com/a/surprisingly-stable-plutonium-compound-could-affect-nuclear-waste-storage/
2.      “A Novel Metastable Pentavalent Plutonium Solid Phase on the Pathway from Aqueous Plutonium(VI) to PuO2 Nanoparticles ” https://onlinelibrary.wiley.com/doi/10.1002/anie.201911637

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New nanomaterials and implications

With all the publications touting new materials or the creation of new properties of materials, it is often difficult to identify disparate findings into something that could combine into very useful devices.  We will consider two findings.

 A team of scientists from the University of Vermont. Lawrence Livermore National Labs and other Labs developed a form of silver with enhanced strength.  [Ref. 1] They found a new nanoscale mechanism that enable improving metal strength without reducing electrical conductivity.  Currently, in order to improve strength related properties like reducing brittleness or softening, various alloys are employed to make the materials stronger.  This improvement has led to a decrease in electrical conductivity.

Starting with the fact that as grains of material get smaller, they get stronger.  When the size becomes less than tens of nanometers wide, the boundaries between grains become unstable and can move.  One approach to improving the strength in metals like silver is to create a special type of grain boundaries known as coherent twin boundaries.  These boundaries are very strong but deteriorates when the size is less than a few nanometers due to imperfections in the lattice. 

The researchers have developed an approach to create a “nanocrystalline-nanotwinned metal.  Employing a small amount of copper atoms, which are slighter smaller than silver atoms, to move into defects in both grain and twin boundaries.  This has created a super strong form on sliver with the conductivity of silver retained.  It appears that the copper atoms move into the interface and not into the main part of the silver structure. 

This effort overcomes softening previous observed as the grains get to small, which is called the Hall-Petch breakdown.  The researchers a confident that their findings can be applied to other materials.

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Researchers at the University of Porto (Portugal) found a negative thermal expansion (NTE) effect in Gd5Si1.3Ge2.7 magnetic nano granules. [Ref. 2] Most material expand (Positive Thermal Expansion – PTE) when heated and contract when cooled.  This material is part of a family of materials that has important implications in the development of future devices.

Work in materials like glass has been developing glass that has Low Expansion Coefficients for more than 50 years.  This type of precision in glass is required to manufacture the very high-resolution optical telescopes. 

The ability to create materials that combine both positive expansion and negative expansion to electronics would enable the development of more robust material inter-connections (contacts) that can withstand the rigors of wide temperature extremes. 

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Why are these findings important?  Currently, efforts are being made to create longer lasting electronics.  Material fatigue and power consumption are two major concerns.  What electronics are available that will be functioning 100 years from today?  Excluding the obsolescence factor, there is nothing that will be working as designed.  The current exploration conversations are about considering project to both the Moon and Mars.  There are space probes that have been functioning for tens of years.  Other probes stop functioning “mysteriously”.  Multiple redundancy provides a partial work-around.  But, how much redundancy is allowable when the “mission” is weight limited.  There are no manufacturing facilities on places that are being considered for human exploration.  The ability to manufacture devices are better able to withstand temperature extremes, use power more efficiently, and remain operations for longer periods of time are needed.  The research mentioned above is not the answer, but may be the first steps to a solution.

References:

  1. https://www.uvm.edu/uvmnews/news/inventing-worlds-strongest-silver
  2. https://physicsworld.com/a/giant-negative-thermal-expansion-seen-in-nanomagnet/?utm_medium=email&utm_source=iop&utm_term=&utm_campaign=14290-44232&utm_content=Title%3A%20Giant%20negative%20thermal%20expansion%20seen%20in%20nanomagnet%20-%20Editors_pick

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Nanotechnology is getting interesting

In our June 30 blog, we covered Part 2 of an upcoming technology disruption.  This blog is covering material from the IEEE Spectrum magazine [Ref. 1] on a Carbon Nanotube microprocessor.  A more detailed article is available from Nature [Ref. 2].  CNT transistors have been around for more than 10 years.  There have even been some processors assembled into extremely simple “computers”.  This device contains nearly 15,000 transistors.  It has the ability to say “Hello”, which is the traditional test of a functioning computer.  Current microprocessors contain billions of transistors, so there is still a long way to go, but it is a start. 

Key facts of the development created by a team from MIT and Analog Devices include it is a fully programmable 16-bit carbon nanotube microprocessor.  It is based on the RISC-V instruction set and can work with both 16-bit and 32-bit instructions.  In order to accomplish this, there were three problems that needed to be overcome. 

In our opinion, the most challenging was the fact that there is no process that will create only semiconducting CNTs.  There is always a mix of metallic with the semiconducting CNTs.  There are indications that today’s best processes for semiconducting CNTs can produce four 9s semiconducting purity but not the eight or nine 9s required for a robust manufacturing process.  The issue with the impurity is an increase in signal noise. 

As with many breakthroughs, the solution is different from developing additional ways of increasing the semiconducting CNT purity.  The researchers worked with various circuit designs to analyze the capabilities of the designs.  What was found is that there is a pattern of results that suggested certain combinations of logic gates were better in significantly reducing the noise.  The power waste issue turned out to be minor compared to the noise issue.  With this information, they developed a set of design rules that permits large scale integration of CNTs with readily available purity.

The issue how to create the circuitry was the first one solved to get to the important development above.  Typically, CNT transistors are created by spreading a solution with CNTs uniformly across the surface of a wafer.  The issue they had is that there are aggregates or clumps of CNTs bundled on the surface.  Obviously, this is unacceptable due to the clumps being unable to form transistors.  The solution was to use the fact that single CNTs are held to the surface by van de Waals forces and bundles of CNTs are not; so, it is possible to remove the bundles. 

The third challenge is that for CMOS logic, both NMOS and PMOS transistors are required.   It is not practical to try to dope individual structures to provide the desired N or P characteristic.  The researchers employed a dielectric oxide to either add or subtract electrons.  Using atomic layer deposition (ALD), they were able to deposit an oxide with the desired properties one atomic layer at a time.  By selecting the proper materials, the researchers were able to reliably create PMOS and NMOS devices together.  This process is a low temperature process that permits building layers of transistors between levels of interconnects.

The interesting concept provided in developing the CNT microprocessor is that the processes employed are currently employed in semiconductor manufacturing.  The development of this type of concept into a full, high volume device does not require the development of a new industry with new tooling requirements.  It is possible that as the techniques evolve, current semiconductor manufacturing companies could evolve the processes and not have a major retooling effort.  This fact could encourage the hastening of acceptance of CNT transistors.  It will be interesting to observe the progress over the next few years.

References:

  1. https://spectrum.ieee.org/nanoclast/semiconductors/processors/modern-microprocessor-built-using-carbon-nanotubes?utm_source=circuitsandsensors&utm_medium=email&utm_campaign=circuitsandsensors-09-03-19&mkt_tok=eyJpIjoiTWpSa01HVTNZemN4TXpnNCIsInQiOiJhQTkxMkYyNTF5SVFyZzY0eXhHZmVUMlJhZ2hzeml2TE94KzVEdkR6cHIzMHFkUmhOZ0ZJYzBEMlRrUEZHaDNWRFhjcWdZRUlUUkdmeHc0Z3NNZmFoUEUycTFNWjFHSmhcL3NKNSt6VllYYVVCUDRLWm9qTURrcWtKSElxcVA3UmMifQ%3D%3D
  2. https://www.nature.com/articles/s41586-019-1493-8

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