Applications of Nano

There have been some interesting developments in the application of nanotechnology and related Micro/Nano Electro-Mechanical Systems.  Diabetes has been a growing medical issue/problem for a number of years.  In many cases, the disease becomes fairly advanced before there is any detection of it.  The typical means of detecting the disease is a glucose test, which has required small samples of blood.  Researchers at the University of Houston have developed an interesting twist.  They have developed a non-invasive means of testing by employing a specially designed contact lens that can sample chemicals in tears.

According to their publication [Ref. 1], glucose can be sensed optically though surface-enhanced Raman scattering spectroscopy.  This latest development is created by multiple layers of gold nanowires built on a gold film using solvent-assisted nanotransfer printing.  The device structure is optimized to use the Raman scattering to detect small molecular samples.  The device improves the sensing properties by creating narrow gaps with the nanostructure that intensifies the Raman signal.  At this time there is one caution.  While glucose is present in tears, work needs to be done to develop a correlation with blood glucose levels.

A key element in this work is that being able to monitor chemicals in tears can be the start of creating a device that can monitor various trace chemicals that are linked to a number of physical markers identified and correlated with conditions that require medical treatment or intervention.

There are a number of companies that are developing various medical devices that use micro-channels to sample fluids and provide an analysis of the materials found in almost real-time.  This improved sampling is providing better information for medical personnel at a much more rapid pace that conventional tests.  There is also work being done at various universities that is focusing on novel sensors to provide improved information.

Nanotechnology for cancer treatment has been in the news for years with some significant successes.  The creation of other medical applications could result in significant breakthroughs for many other areas of medicine.

Costs of devices: Nanotechnology is still in the early stages of development.  As the technology matures, there will be a focus on how to reduce costs.  In many cases, this will be the equivalent of comparing apples and oranges.  In the 1980s, the nuclear industry developed a tool for evaluating the representative cost of different approaches to various elements required for power plants.  This technique, Cost of Ownership, was refined by the semiconductor industry in the 1990s in order to evaluate totally different technologies that could be employed.  This is mentioned because it appears that the nanotechnology industry is starting to evaluate some of the manufacturing options.  The evidence for this is the increase in the number of citations of work done in this area in the late 1990s and early 2000s.

A closing note: While the “registration” for this blog site is active, the large number of false registrations has prevented us from approving people for active comments.

References:

  1. http://www.uh.edu/news-events/stories/2016/September/09272016-Researchers-Create-Glucose-Sensing-Contact-Lens.php

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Manufacturing with “Nano”

There are stages to the development of employing nanotechnology to various devices/products.  It has been an evolution in application and not a revolution. Among the earliest applications that reached the consumer market was the application of Carbon Nano Tubes (CNTs).  From the automotive application, Toyota employed CNTs in epoxies to create light weight and stronger bumpers for vehicles.  The advantage was an increase in strength while providing reduced weight, which translated into better vehicle mileage.  About the same time, Zyvex was instrumental in applying CNTs to sports products like tennis racquets and baseball bats.  Again, the advantage was strength with reduced weight and the ability to withstand greater forces as compared with the traditional products.  This could be considered Stage One in the application of nanotechnology.

There are numerous advances in the medical community.  Gold nanoparticles and CNTs are being developed for the treatment of certain types of cancer.  Researchers in Germany have employed iron-oxide nanoparticles for treatment of brain cancers.  These nanomaterials have been “grafted” on to viruses or similar biological entities that cancer cells consume.  The application of external sources of power to destroy the cancerous cells.  This is a Stage Two effort that incorporates the nanomaterial properties, but is “nano” only because the carrier mechanism is in the nano realm.

Graphene and similar two-dimensional materials have been shown to provide a promising basis for electronics.  CNT transistors have been demonstrated.  There have been two questions on applying these materials.  The first one is the purity or quality of the material.  Graphene tends to have voids in larger sheets, although new research indicates that it might be possible to post-cure the voids that exist.  The question for Stage Three, which is the application of nanomaterials that employ unique properties of the materials in the nano realm, is how does the mass production of these unique structures occur?

Nanomaterials have shown promise, but the applications are still being developed.  The observable exception is the red coloring in the stained glass windows from the Middle Ages and before, which coloring is caused by the inclusion of gold nanoparticles in the glass.

When the need is to use actual nanomaterial structures, the ability to manufacture them is more problematic.  The initial thought is “What about semiconductors?”  Their structures are on the nanometer scale.  That is absolutely correct, but the product is much larger than nanometer-sized devices.  The question is how to we measure, test, and handle nano-scale products/devices?  As an example of this question, consider the following.  If I manufacture 30 nm gold particles, how do I know the distribution of the size?  What is the half-width of the distribution?  Can I use the same method for a gram? a Kilogram? and a ton?  How accurate will the measurements be?  There is still a large amount of significant development that is required before there will be true nanomaterial products.  It is coming, but it is not ready yet.

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Lithium, Graphene, and batteries

With the reliance of potable electronics on battery power, researchers are exploring various approached to increase the power density of materials for batteries.  The majority of batteries for applications, like cell phones, computers, other portable devices, are based on incorporating Lithium.  More information of the construction of batteries is available in Reference 1 along with other sources available on the web.  The issue is that battery life is too short for most applications and requires frequent recharging during the course of one day.  It was not too many years ago that a trip through an airport had every available outlet being used to recharge some device.  Technology has improved and battery life has lengthened, but the goal is to keep pushing the limits until devices can continue to work for much more than a day without recharging.  There has been a significant amount of research in applying forms of nanocarbon to improve the energy efficiency of batteries.

Over a year ago, there were reports of a graphene technology that will double the life of the Samsung phone batteries. [Ref. 2]  The design is considering replacing the graphite anode with graphene-coated silicon resulting in almost doubling the energy density.  It is expected that it will be several years before the technology finds its way into mainstream products.

Work has been done in improving the efficiency of lithium based batteries to extend the life of devices that rely on portable power.  [Ref. 3] Lithium ion storage is dependent on the structure of the composite materials.  Graphene enters into the picture based on its good conductivity and mechanical strength.  Using carbon nanotubes with the graphene as spacers between layers, resulting in a superior environment for formation of Fe3O4 microshpheres but also maintaining a proper ration and not allowing an overproduction of the microspheres.  Work in China has involved composites that could provide improved performance for lithium-ion batteries.

A recent article is suggesting that a single graphene monolayer could be developed as a support for the electrodes reducing the thickness of the material needed to create the battery. [Ref. 4] The details of the article indicate that anode and cathode are created by electro deposition of zinc and copper on the graphene and are packaged in a graphene based cell. [Ref. 5] This method of generating electrical power, albeit not on the nano scale, goes back at least hundreds of years.

There are other developments that are underway to improve energy storage.  Work is being done on Lithium-sulfur batteries that could have superior energy density to the current lithium-ion batteries. [Ref. 6]  The comparison indicated that the energy density of Lithium-ion batteries is in the range of 130 to 220 Watt-hours per kilogram.  In theory, the Lithium-surfer batteries could be a great as 2,600, which is an order of magnitude greater.

There are continuing developments on the application of graphene to improve the power density of batteries.  A search on “graphene batteries” will turn up links to a number of developments that are currently in process.  This effort is another example of nanotechnology working to improve every day life.

References:

  1. http://www.graphene-info.com/graphene-batteries
  2. http://www.techtimes.com/articles/64353/20150629/samsungs-new-graphene-technology-will-double-life-of-your-lithium-ion-battery.htm
  3. http://nanotechweb.org/cws/article/lab/56969
  4. http://nanotechweb.org/cws/article/lab/65531
  5. http://iopscience.iop.org/article/10.1088/0957-4484/27/29/29LT01
  6. http://cleantechnica.com/2014/12/29/graphene-kill-lithium-ion-batteries/

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Polymorphism and nano-toxicology

What is polymorphism?  In the Oxford Dictionary, polymorph is an organism or inorganic object or material that takes various forms.  Polymorphism is defined, in material science, as the ability of a material to exist in more than one form of crystal structure. [Ref. 1] A recent publication from Brookhaven National Laboratories that was published in Nature Communications [Ref. 2] reports findings on Gold nanoclusters with 144 atoms.  They were able to find the theoretically predicted icosahedral-cored cluster (left image below) but also found samples with truncated decahedral cores (right image).  The pictures are from R&D Magazine. [Ref. 3]

rd1606_nanoparticle_gold

The researcher, Simon Billinge and his lab, pioneered a method which they call atomic Pair Distribution Function (PDF) to analyze the results of high energy x-ray scattering from the material.  The resulting polymorph provided an explanation of why other researchers have had difficulty in identifying the structure of the material.  The researchers anticipate being able to find additional materials with the polymorphism.

On a different front, there is work being done on impact of environmental exposure to nanomaterials.  Work being done at the Swiss Federal Laboratories for Materials Science and Technology examines an issue of the difference between materials produced for applications and those released in the environment. [Ref. 4]  One example that is described is titanium dioxide.  Adding the nanoparticles to paint a) enhances the self-cleaning capabilities of the paint and b) blocks UV rays thus preventing or diminishing paint degradation. One of the issues is that finding sufficient testable quantities of samples of nanoparticles that have degraded over time is difficult.  This fact makes evaluations of nano-toxicity difficult if not impossible.

Work has been done [Ref. 5] on silver nanoparticles that are added to textiles as biocides to prevent the growth/spread of microorganisms.  There is a release of some of the nanoparticles into the environment.  However, if the released silver ions compline with other ions, like sulphides, they create silver sulphide, which is not an active biocide.  This is part of an over effort to evaluate the life cycle of nanomaterials and will be available in 2017.  More information is available in Reference 6.

An interesting finding is that silver nanoparticle shape affects its toxicity. [Ref. 7]  Research was done on the impact of silver nanoparticles shape (spheres, rods, and plates) on rainbow trout cells and zebrafish embryos.  The researchers concluded that the silver nanoplates induced oxidative stress in the cells through the production of superoxides, which are toxic.  There were conditions that they placed on the experiments and will require further and expanded testing.

This brings us back to the title of this blog.  If nanomaterials can have different shapes/configuration, then the potential results of toxicological investigations will depend on the shape of the material.  If the material has the ability to shape-shift, how do we develop testing methodologies that account for the possible difference impact of the material shapes.  If you think that the shape does not make a difference, I will give you two pounds of graphite (carbon) for one pound of diamond (carbon).

The evaluation of the environmental/human impact of any nanomaterial must incorporate the fact that these materials have properties based on the shape under test and not an overall classification of material size.

References:

  1. https://en.wikipedia.org/wiki/Polymorphism_(materials_science)
  2. http://www.nature.com/ncomms/2016/160614/ncomms11859/pdf/ncomms11859.pdf
  3. http://www.rdmag.com/news/2016/06/gold-nanocluster-discovery-hints-other-shape-changing-particles?et_cid=5351098&et_rid=658352741&type=headline&et_cid=5351098&et_rid=658352741&linkid=http%3a%2f%2fwww.rdmag.com%2fnews%2f2016%2f06%2fgold-nanocluster-discovery-hints-other-shape-changing-particles%3fet_cid%3d5351098%26et_rid%3d%%subscriberid%%%26type%3dheadline
  4. http://nanotechweb.org/cws/article/tech/65333
  5. http://www.ncbi.nlm.nih.gov/pubmed/24941455
  6. http://iopscience.iop.org/journal/0957-4484/page/Focus-Lifecycle-of-nanomaterials
  7. http://nanotechweb.org/cws/article/tech/49574

 

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Is it Time for 3D Printed Food?

Why would you consider 3D printed food to be in the realm of nanotechnology?  Nanotechnology involves the usage of particles that are well below what we would consider required for food.  This is true.  In a previous blog, the work done on developing current food types are very large.  Most 3D printers are hard pressed to be accurate within a few microns, much less nanometers.

Before covering the need for nanotechnology, a review of existing equipment is useful  3D Systems [Ref. 1] has information on their Culinary Lab where experiments are being conducted on developing food the is both tasty and beneficial.  There is a web site [Ref. 2] that has a listing with examples of various types of food printers.  There was a 3D Food Printing Conference [Ref. 3] held in April 2016 in The Netherlands that addressed many aspects of food printing.  Most of the efforts currently are on producing exotic designs in the food.  There is mention of customized cakes of personalized desserts that are being commercially produced.  But, this is not a food benefit of 3D printing but a design benefit.

In a previous blog where I mentioned the Star Trek food replicator, the work being done today for NASA is directed at being able to supply food on deep-space missions.  When one considers the amount of food that would be required to support three people on an eighteen month round trip, the room required to store the food and the space to preserve and store it are not only large, but very expensive to lift out of earth’s orbit.   A demonstration of a 3D printer for food was demonstrated at a recent South by Southwest in Austin.  The startup, BeeHex, is working on converting dehydrated food particles into food with both flavor and texture. [Ref. 4]

One advantage of 3D printing of food is that it should be possible to supply nutritious food to people in very remote parts of the world.  One of the problems that exist today is that a significant potion of the food grown spoils before it reaches its intended market.  If the constituent parts could be shipped safely with danger of spoiling and then reconstituted into nutritious food, some of the hunger problem in the world would be addressed.  The European Union has a program called PERFORMANCE (Development of Personalized food using Rapid Manufacturing for the Nutrition of elderly consumers). [Ref. 5] This approach permits the addition of various nutrients needed by the person who the food is created for.  This was demonstrated in a conference in Brussels in October 2015.

NASA has a definite interest in developing this ability.  There was an SBIR award to an Austin, Texas company to begin the development of creating unflavored macronutrients, i.e., protein, starch and fat, the sustenance part of a required diet can be quickly produced in numerous shapes and textures from a 3D printer with heating capabilities. [Ref. 7]

This technique is also being investigated by various military organizations as a means of delivering quality meals in the field.  While the “Foodini” will only produce products made of dough, paste, of high viscosity liquids, this is the start of possible home appliances. [Ref. 8] The microwave comes to mind as a once expensive piece of equipment that is now common in many homes.

So where does the nano come into this picture?  The basic concepts of both handling food and handling nanomaterials come together.  Some of the materials will probably contain nanoparticles is a predefined portion to the entire volume.  This requires method of inspection and verification that currently are not defined.   There will need to be very specific procedures developed to ensure the proper mix of ingredients.  At this time, one can only guess one the various sizes will be required, but for many of the foods, printing very thin layers rapidly will be needed to create tasty and nutritious meals.  bon appétit!

References:

  1. http://www.3dsystems.com/es/culinary
  2. http://www.3ders.org/articles/20151102-3ders-monday-warm-up-the-top-3d-food-printers-that-will-feed-the-future.html
  3. http://3dfoodprintingconference.com/
  4. Austin American Statesman, April 22, 2016 edition, Tech Extra section, Page SA2.
  5. http://3dprinting.com/food/from-puree-to-3d-the-eu-performance-project-presents-results/
  6. https://www.naturalmachines.com/
  7. http://sbir.gsfc.nasa.gov/SBIR/abstracts/12/sbir/phase1/SBIR-12-1-H12.04-9357.html?solicitationId=SBIR_12_P1
  8. http://3dprinting.com/food/us-army-might-use-food-printers-future/

 

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Interesting developments in nanotechnology

There are starting to be some interesting proposal being developed that use properties of nanomaterials.  This blog will cover three recent published reports relating to 1) food; 2) non-toxic graphene; and, 3) graphene for cooling electronics.

Food: In a paper in Journal of Agricultural and Food Chemistry, Researchers from Washington University (St. Louis, Missouri) [Ref. 1] present findings on a means of improving crop production by using nanomaterials.  An article by UPI [Ref. 2] puts the finding in more general terms.  As the requirement for additional food production increases, farmers employ more fertilizers.  One of the key components in phosphorous.  There are potential problems with this. When the excess fertilizer is washed from the field, it enters the waterways.  As it concentrates, it aids the growth of oxygen depleting algae, which kill fish.  There was also a comment that if farmers continue to use the phosphorous containing fertilizers at the current rate, there is the potential of running out of readily available phosphorous. The consequences are reduction in food supply, increase in the cost of food, and an increase in hunger.  Even if it were 100 years instead of the projected 80 years, the decrease in the availability of phosphorous will have an impact on society.

The researchers created zinc oxide nanoparticles the aids plant roots increase their ability to absorb the phosphorous in the soil.  The zinc interacts with three plant enzymes and enables the enzymes to convert the phosphorous into a less complex version that is easier for the plant to absorb.  The zinc oxide is applied to the plant leaf; it enables the plant to absorb 11% more phosphorous from the soil.  The ability to more effectively use the existing phosphorous means that less will be required to increase the plan harvesting.  (This is assuming that the mechanism will work similarly with all plants, which needs to be prove.)  The interesting thing about this work is that the zinc oxide is produced by a fungus.  This means that there is not a need for a complex manufacturing process to produce the nanomaterial.

Non-toxic: An interesting announcement was released on April 16, 2016 by Directa Plus. [Ref. 3]    In the announcement, the company stated that “all of its graphene-based products have received international certification from Farcoderm Srl (a toxicity testing agency) confirming them to be safe for human contact.  The material is manufactured in Lomazzo, Italy.  The company supplies material that in incorporated into sportswear and other products.

Graphene for cooling: Researchers in Gothenburg, Sweden announced the application of functionalized graphene nanoflakes-based film. [Ref. 4] The key to the process is the addition of molecules added to the surface of the material “to encourage various chemical and physical properties.”  They are incorporating amino-silane molecules to improve the in-plane heat conduction.  There results were published in the Journal of Nature Communications, where the full article is available. [Ref. 5] They measured significantly lower temperatures at previously identified hotspots on electronic devices.  For those interested, the article contains a significant amount of detail on their understanding of the processes involved.

The impact of being able to remove heat from the circuit itself enables the more effective operation of the electronics, which should result in a longer life.  However, there is a very large “if”.  For this heat transfer to be effective, the heat that is transferred must be removed from the entire electronics assembly.  Unless this removal occurs, the heat will remain in the entire package and result in a heat buildup.  Dissipating heat from a large package is continually being worked and is an easier problem to solve than the one this concept addresses.

References:

  1. http://pubs.acs.org/doi/abs/10.1021/acs.jafc.5b05224
  2. http://www.upi.com/Science_News/2016/04/29/Nanoparticles-offer-a-boost-to-food-crop-production/9711461946901/?spt=rln&or=3
  3. http://www.directa-plus.com/Press/Directa%20Plus%20receives%20safety%20certifications%2021.04.16.pdf alternate access through http://www.directa-plus.com/
  4. http://www.upi.com/Science_News/2016/04/29/New-graphene-based-film-may-keep-your-next-laptop-cool/9781461937124/?spt=rln&or=5
  5. http://www.nature.com/ncomms/2016/160429/ncomms11281/full/ncomms11281.html

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Nanotechnology information

Currently, I am involved in writing a chapter on information reliability for a nano-safety book that should be published by early 2017.  My colleague, Evelyn Hirt, who has been leading this chapter effort, found some interesting developments in reviewing the traditional sources of nanotechnology information.  The typically recognized governmental sites are still functioning.  A number of new sites, which have connections to various government agencies around the world, have been added.  There are still a number of sites that are maintained through government funding.  Traditionally, these sites contain the latest information.  Some sites are either disappearing or have become stagnant, probably due to lack of funding.

Non-governmental organizations have, like the Royal Society of Chemistry and The American Chemical Society, have information available to both their members and the general public (although some information requires paying a fee).  These organization apply a portion of their members’ dues to creating and maintaining a database that can be very useful.

Do not expect to find most of the information that will probably need.  As of 2011 there is information on the Chemical Abstract Service for under 63 million (63 x 108) chemical sequences.  Considering the known elements, the estimates are that over 10200 possible individual nanoscale particles.

Information on the web is another story.  The Internet, which was originally the ARPANet (1968 RFQ), was designed for the rapid communication of scientific data.  Peer review is typically a long process with peer reviews, comments to the authors, rebuttals, decision on publication value.  Rapid dissemination of information at that time was by air mail instead of surface mail.  There was a need to more rapidly share scientific information.  Consequently, the ARPANet was conceived to solve this problem among universities and scientific organizations.  This has evolved into today Internet with high speed communications. Today there are billions of different sites with a vast array of “information.”

While all the types of sources mentioned above normally provide good information, the information on the web is not always accurate.  The explosion of data available on the web is not always beneficial.  Information needs to be checked and verified.  There are other sites that previously had been key sources of information, and now are no longer maintained due to funding issues.  Consequently, the data provided is aged and may not be the latest available information.

Even with governmental site, there may be issues.  Occasionally, there have been conflicting announcements from different approaches issued by different agencies within one government department.  In 2008, two of the US Environmental Protection Agency programs, Office of Pesticide Programs and the Office of Pollution Preventions and Toxics, issued conflicting directives on what would be considered a new chemical based on size alone and the other indicating that this would not be the case if the material was used previously.

With the openness of the internet, anyone can post anything, accurate or not.  There is no overseeing guidance.  In addition, there is a greater degree of polarization of opinions and the lack of discourse on scientific findings.  While there always have been differences of opinion, today’s approach appears to be to attack the opposing side.  Even politics seems to be getting into the determination of scientific fact.    Senator Whitehouse (Dem, RI) is threatening to use RICO (Racketeer Influences and Corrupt Organizations Act) to silence researchers with opinions that differ from his supporters [Ref. 1].  Twenty scientists have asked the President to use the RICO to silence critics of their stance [Ref. 2].  This direction is ominous and can severely inhibit scientific research.

Consequently, the ability to obtain accurate, factual information is becoming more challenging.  This requires the individual to do more investigation to find out the truth.  One needs to check and double check.  All I can say is “Good Hunting.”

References:

  1. http://www.weeklystandard.com/senator-use-rico-laws-to-prosecute-global-warming-skeptics/article/963007
  2. http://dailycaller.com/2015/09/17/scientists-ask-obama-to-prosecute-global-warming-skeptics/

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More “Nano” Scare Tactics

This past week has seen a number of headlines about the Johnson & Johnson been awarded a jury verdict requiring them to pay $73 million to the family of a woman who died of cancer, which was claimed to be caused by the material in the Johnson & Johnson talc based Baby Powder. [Ref. 1]  The jury found Johnson & Johnson liable for fraud, negligence, and conspiracy according to the family’s lawyers.  The case has created concerns regarding the safety of using talcum powder.  Both Baby Powder and Shower to Shower products are made of talc, which are mineral rocks that contain magnesium, silicon, and oxygen, while some forms can contain asbestos. [Ref. 2]  Everyone knows asbestos is a potential carcinogen.  As pointed out in an article [Ref. 3], both talc and asbestos are categorized as silicates, containing both silicon and oxygen.  To further complicate the situation, the pictures of talc [Figure 1] and talc with asbestos [Figure 2 with the long cylindrical shaped material on the talc flakes] are available. [Ref. 4 & 5].  So, talc with asbestos has the potential to be an issue.  However, asbestos has been removed from any talc product since the 1970s.

Figure1-160229Figure2-160229

      Figure 1                                                                               Figure 2

So where does this lead to?  First, the Cancer.org site [Ref. 6] states that talc as a powder absorbs moisture and cuts down on friction making useful to help prevent rashes.  The site indicates that there is a need to differentiate between talc that contains asbestos and talc that is asbestos-free. There are conclusions from studies that indicate that asbestos-free talc is classified as “not classifiable as to carcinogenic to humans.”

The final resolution of this and other similar cases will take years to play out.  There will be a number of articles and news reports indicating the “problems” with talc.  At the same time, additional screening studies will be developed, conducted, and the outcomes evaluated.

The point of this blog is that we live in a world where sensational headlines make the news.  The fact that talc has a mineral composition that also occurs in asbestos provides a topic for reporting that talc is the same, which it is not.  The availability of pictures showing the asbestos with talc powder implies that the powder is dangerous.  There was even a report that indicated talc has shapes like asbestos.  Obviously, some looked at a picture of talc with asbestos and thought it was all talc.  Instant self-publishing becomes an issue when a person sees something and makes an incorrect association which is then published.

The caution that the article on the talc verdict brings is twofold.  First, the jury award is not final, and even if it is settled without any contesting, there was no proof that the talc was responsible for the woman’s death from cancer.  There are a number of explanations in the references below that indicate there might be a link, the probability is very low.  Second, the rapid reporting of an announcement like this will stay on the web regardless of the final outcome.  This fact implies that as more and more articles, blogs, etc., are developed, it will be harder and harder to find out accurate information.

 

References:

  1. http://www.reuters.com/article/us-johnson-johnson-verdict-idUSKCN0VW20A
  2. http://www.independent.co.uk/life-style/health-and-families/health-news/does-talcum-powder-cause-cancer-johnson-johnson-baby-powder-shower-to-shower-a6894926.html
  3. http://www.thedailybeast.com/articles/2016/02/24/can-baby-powder-really-cause-cancer.html
  4. http://www.nanoshel.com/product/talc-nanoparticles/ talc nanopowder
  5. http://usgsprobe.cr.usgs.gov/picts2.html Anthophyllite asbestos altering to talc, upstate NY
  6. http://www.cancer.org/cancer/cancercauses/othercarcinogens/athome/talcum-powder-and-cancer
  7. http://www.safetyandcarecommitment.com/ingredient-info/other/talc?&utm_source=google&utm_medium=cpc&utm_campaign=J%26J+-+Talc+Powder&utm_term=talcum%20powder%20cancer&utm_content=J%26J+Talc+Safety+-+E|mkwid|s9MN8PMFz_dc|pcrid|85363851134 Johnson & Johnson’s statement on their talc products.

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Vacuum Tubes

This might seem like an unusual topic for nanotechnology.  The vacuum tube was the centerpiece of electronic advancement prior to solid state devices.  Their application was incorporated into most electronics through the mid 1960s.  Even today, audiophiles will tell you that the sound produced by equipment that uses vacuum tubes is superior to anything else that is currently available.  Very high power devices also incorporate vacuum tubes.  The fundamental concept of a vacuum tube consists of a cathode, a grid(s), and an anode in a glass tube, which had the internal gases exhausted to a hard vacuum level (less than 10-6 Torr).  One Torr is equal to 0.00132 standard atmospherics (One atmosphere of pressure is that experienced at sea level).

The principle of operation for the vacuum tube is to heat the cathode material to generate a stream of electrons that are captured by the anode.  This current flow can be amplified by applying voltages to the grid(s).  What started with one grid evolved into multi-grid tubes.  There are issues with the vacuum tubes.  The heat generated by the vacuum tubes impacts the lifetime of the cathode’s emission of electrons.  There is also a wait time until the tubes in a circuit have warmed up in order to function properly.  Average lifetime of the tubes was roughly 1,500 hours.  The impact of this short lifetime was a continual need to replace vacuum tubes.  (More information can be found in Ref. 1)

The advantage of semiconductors were much more than extended lifetimes.  Semiconductor are much smaller, don’t require a vacuum, which makes them more rugged.  There is a consistency and reliability of semiconductors that vacuum tubes were unable to match.  One negative of semiconductors is that the state changes are either on or off (digital signals).  Vacuum tubes can provide an analogue change in signal.  The semiconductor industry worked around this issue by creating digital to analogue and analogue to digital converters.

There has been research on the development of “Vacuum transistors”.  [Ref. 2]  By reducing the dimensions of the solid state device to the nano realm, the distance from the cathode to the anode becomes shorter than the mean free path of a gas molecules.  The result is that the device can be operated in atmosphere and does not need a vacuum.  The low current levels also required for the device to operate, works in preventing damage to the cathode that would typically occur at atmospheric pressure.  There are more details available from NASA [Ref. 3] and other sources [Ref. 4].

Where does this effort stand today?  NASA Ames has demonstrated it in the lab.  Some parallel work is being done at CalTech.  The demonstration of a functioning circuit that is manufactured using mass production techniques has not been shown.  However, this is a “nano” technology that is promising.  Keep watching for future developments.

 

References:

  1. http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm
  2. http://spectrum.ieee.org/semiconductors/devices/introducing-the-vacuum-transistor-a-device-made-of-nothing
  3. https://www.nasa.gov/ames-partnerships/technology/technology-opportunity-nanostructure-based-vacuum-channel-transistor
  4. http://www.extremetech.com/extreme/185027-the-vacuum-tube-strikes-back-nasas-tiny-460ghz-vacuum-transistor-that-could-one-day-replace-silicon-fets

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A Name Change?

The usage of the term “nano” appears to be decreasing. There is an increase in the usage of “Advanced Materials” and “Emerging Technology.” Is this a sign of a maturing technology?

There have been a number of recurring cycles where a particular technology description gets all the headlines in various publications. The 1990s were a time of buckeyballs and carbon nanotubes (CNTs). The CNTs developed the fastest with applications that employed the properties of lightweight and high strength. The Toyota application of replacing the bumpers on vehicles with a composite that included CNTs provided increases in fuel mileage and higher impact resistance. CNTs were applied to increase the performance of tennis rackets and baseball bats. There were many attempts to create business niches in the manufacture of the materials. There were two problems, the resultant material is expensive to produce and has not been scaled up to very large production quantities.

There were concerns about CNTs and their impact on both people and the environment. CNTs typically are less than 5 µm long. Unfortunately, their shape is a needle-like structure, which is similar to 5 of the 6 types of asbestos, which is much longer than 20 µm. Experiments have been run that demonstrate a large quantity of bundles of extra-long CNTs will produce lesions in rat tissue that is similar to those produced by asbestos.

The medical profession has been working toward a number of solutions that incorporate nanomaterials with virus-type organisms. Nano-gold is being employed in therapeutics and diagnostics due to its energy transfer capability. Illuminated with infrared light, the gold heats quickly. It the gold is attached to a molecule that cancer cells try to capture, heating the nano-gold after the molecule is captured by the cancer will destroy the cancer cells. In a similar fashion, CNTs are extremely efficient at turning microwaves into heat. This is similar to the effect of gold-nanoparticles except the source is microwaves instead of infrared light. There has been work done with nano-iron particles to treat certain types of brain cancer.

So there are advantages and disadvantages that can be proven. Work in continuing, but there is less claims to incorporating “nanomaterials” in advertisements/publications. Researchers are working on solutions and not only material properties.

The discovery of the 2 dimensional carbon material, which is called graphene, has led to a number of research applications. There are variations of graphene based on the addition of other elements has produce very interesting materials. Current research is looking at applications in electronics where the existing semiconductor technology seems to be slowing down. This is a material that has a significant amount of current interest. Looking back at this year’s blogs, graphene has been addressed a few times. But, the publications are presenting it as a 2-D material, because there are similar 2-D materials with some better characteristics than graphene. Graphene was the starting point for the exploration of materials with properties that were not considered before. The use of the term “graphene” will diminish in the titles of articles over the next few years and applications are being announced.

What is being experienced is that research is identifying a class of materials with properties of interest and others are joining in the research creating new materials. If a material is one atom think, like the thinnest graphene, but a meter one each of the two sides, it is a nanomaterial? Or is it an advanced material using emerging technologies?

Yes, there will be new materials that will capture headlines, for a while. I think that the emphasis is becoming the applications of technologies and not the individual materials. If this happens, the terms “Emerging Technologies” and “Advanced Materials” will see greater usage in publications and advertising.

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