What will nanotechnology mean to you?

2 04 2014

A hot topic in the media right now is the toxicity of chemical flame retardants that are in our furniture and are migrating out into our environment.  Tests have shown that Americans carry much higher levels of these chemicals in their bodies than anyone else in the world, with children in California containing some of the highest levels ever tested.   According to Ronald Hites of Indiana University, these concentrations have been “exponentially increasing, with a doubling time of 4 to 5 years.”[1]  These toxic chemicals are present in nearly every home – packed into couches, chairs and many baby products including (but not limited to) mattresses, nursing pillows, carriers and changing table pads (scary!).  Recent studies have found that most couches in America have over 1 pound of the toxic chemical Chlorinated Tris inside them[2], even though it was banned in children’s pajamas over cancer concerns over a generation ago.[3]

Why the concern?  Fire retardant chemicals, called PBDE’s (polybrominated diphenyl ethers) have been linked to cancer, reproductive problems and impaired fetal brain development, as well as decreased fertility.  And even though they’ve been banned in the U.S. and European Union, they persist in the environment and accumulate in your body – and they’re still being used today.

So its probably no surprise that there is a mad scramble on to produce a fire retardant that does not impact our health or the environment.   The current front runners, touted as being “exceptionally” effective yet safer and more environmentally friendly than the current fire retardants, use nanotechnology – specifically “nanocoatings” and “nanocomposites”[4] .  These composites and coatings are based on what are called “multiwalled carbon nanotubes” or MWCNTs.

Based on a final report published by the U.S. EPA in September 2013 about the assessment of the risks of using these  MWCNTs, the EPA found that there will be releases of these MWCNTs into the environment throughout the life cycle of textiles – to our air and water during production,  in the form of abraded particles of the textiles falling into the dust in our homes, and in the disposal of furniture in municipal landfills or incineration facilities.[5]

While it is reasonable to propose that substituting nanomaterials for polybrominated diphenyl ether (PBDEs)  or chlorinated triss  and calling it “sustainable”, the fact is that no quantitative study has ever been done to support this assertion . [6]

Please don’t misunderstand me – I am all for finding safer alternatives to the current crop of chemical fire retardants (assuming I buy into the argument that we actually need them).  However, I don’t want us to jump from the frying pan into the fire by rushing to use a technology which is still controversial.  But the race is on:  the US patent office published some 4000 patents under “977 – nanotechnology” in 2012, a new record.

patents nanotech

Here’s an interesting video which helps to explain how nano works – and why we will need extensive study to absorb the many implications of this emerging science.

Consider these science fiction type scenarios of how nano can be used to profoundly change our lives:

  • “nanomedicine” offers the promise of diagnosis and treatment of a disease – before you even have the symptoms.  Or it promises to rebuild neurons for people with Alzheimers or Parkinson’s disease – and stem cells for whatever ails you!   Bone regeneration.  [7]
  • Surfaces can be modified to be scratchproof, unwettable, clean or sterile, depending on the application.[8]
  • Quantum computing.
  • Solar cells capturing the sun’s visible spectrum – as well as infrared photons –  doubling the solar energy available to us.  How about zero net carbon emissions.
  • Nanoscale bits of metals can detoxify hazardous wastes.
  • Clothing that recharges your cell phone as you stroll, or an implant that measures blood pressure powered by your own heartbeat.

And yet.  The unknowns are great, and as Eric Drexler has said, the story involves a tangle of science and fiction linked with money, press coverage, Washington politics and sheer confusion.  Scientists and governments agree that the application of nanotechnology to commerce poses important potential risks to human health and the environment, and those risks are unknown. Examples of high level respected reports that express this concern include:

  • Swiss Federation (Precautionary Matrix 2008)[9]
  • Commission on Environmental Pollution (UK 2008)[10];
  • German Governmental Science Commission (“SRU”)[11];
  • Public testimony sought by USA National Institute for Occupational Safety and Health (NIOSH, Feb 2011)[12] ;
  • OECD working group (since 2007)[13];
  • World Trade Organization (WTO)[14]
  • as well as several industrial groups and various non-governmental organizations.

Nanotechnology is already transforming many products – water treatment, pesticides, food packaging and cosmetics to name a few – so the cat is already out of the bag.  Consider this small example of the nano particle  argument:  When ingested the nanoparticles pass into the blood and lymph system, circulate throughout the body and reach potentially sensitive sites such as the spleen, brain, liver and heart.[15]   The ability of nanoparticles to cross the blood brain barrier makes them extremely useful as a way to deliver drugs directly to the brain.  On the other hand, these nanoparticles may be toxic to the brain.  We simply don’t know enough about the size and surface charge of nanoparticles to draw conclusions.[16]  In textiles, silver nano particles are used as antibacterial/antifungal agents to prevent odors.

But there are almost no publications on the effects of engineered nanoparticles on animals and plants in the environment.

So it’s still not clear what nanoscience will grow up to be – if it doesn’t kill us, it might just save us.

[2] Stapleton HM, et al. Detection of organophosphate flame retardants in furniture foam and U.S. house dust. Environ Sci Technol 43(19):7490–7495. (2009); http://dx.doi.org/10.1021/es9014019.

[3] Callahan, P and Hawthorne, M; “Chemicals in the Crib”, Chicago Tribune, December 28, 2012, http://articles.chicagotribune.com/2012-12-28/news/ct-met-flames-test-mattress-20121228_1_tdcpp-heather-stapleton-chlorinated-tris

[5] Comprehensive Environmental Assessment Applied to Multiwalled Carbon Nanotube Flame-Retardant Coatings in Upholstery Textiles: A Case Study Presenting Priority Research Gaps for Future Risk Assessments (Final Report), Environmental Protection Agency, http://cfpub.epa.gov/ncea/nano/recordisplay.cfm?deid=253010

[6] Gilman,  Jeffrey W., “Sustainable Flame Retardant Nanocomposites”; National Institute of Standards and Technology

[7] Hunziker, Patrick,  “Nanomedicine: The Use of Nano-Scale Science for the Benefit of the Patient” European Foundation for Clinical Nanomedicine (CLINAM) Basel, Switzerland 2010.

[9] Swiss National Science Foundation, Opportunities and Risks of Nanomaterials Implementation Plan of the National Research Programme NRP 64 Berne, 6 October 2009; see also Swiss Precautionary Matrix, and documents explaining and justifying its use, available in English from the Federal Office of Public Health.

[10] Chairman: Sir John Lawton CBE, FRS Royal Commission on Environmental Pollution, Twenty-seventh report: Novel Materials in the Environment: The case of nanotechnology. Presented to Parliament by Command of Her Majesty November 2008.

[11] SRU, German Advisory Council on Environment, Special Report “Precautionary strategies for managing nanomaterials” Sept 2011. The German Advisory Council on the Environment (SRU) is empowered by the German government to make “recommendations for a responsible and precautionary development of this new technology”.

[12] See: Legal basis and justification: Niosh recommendations preventing risk from carbon nanotubes and nanofibers ”post-hearing comments Niosh current intelligence bulletin: occupational exposure to carbon nanotubes and nanofibers Docket NO. NIOSH-161 Revised 18 February 2011; Testimony on behalf of ISRA (International Safety Resources Association) Before NIOSH, USA. Comments prepared by Ilise L Feitshans JD and ScM, Geneva, Switzerland. Testimony presented by Jay Feitshans, Science Policy Analyst; ISRA Draft Document for Public Review and Comment NIOSH Current Intelligence Bulletin: Occupational Exposure to Carbon Nanotubes and Nanofibers, Docket Number NIOSH-161-A.

[13] The OECD Working Party for Manufactured Nanomaterials (WPMN) “OECD Emission Assessment for Identification of Sources of release of Airborne Manufactured Nanomaterials in the Workplace: Compilation of Existing Guidance”, ENV/JM/MONO (2009)16, http://www.oecd.org/dataoecd/15/60/43289645.pdf. “OECD Preliminary Analysis of Exposure Measurement and Exposure Mitigation in Occupational Settings: Manufactured Nanomaterials” OECD ENV/JM/MONO(2009)6, 2009. http://www.oecd.org/dataoecd/36/36/42594202.pdf.
“OECD Comparison of Guidance on selection of skin protective equipment and respirators for use in the workplace: manufactured nanomaterials”, OECD ENV/JM/MONO(2009) 17, 2009. www.oecd.org/dataoecd/15/56/43289781.pdf.

[14] WHO Guidelines on “Protecting Workers from Potential Risks of Manufactured Nanomaterials” (WHO/NANOH), (Background paper) 2011

[15] Dixon, D., “Toxic nanoparticles might be entering human food supply, MU study finds”, August 22, 2013, http://munews.missouri.edu/news-releases/2013/0822-toxic-nanoparticles-might-be-entering-human-food-supply-mu-study-finds/

[16] Scientific Committee on Emerging and Newly Identified health Risks (SCENIHR), The European Commission, 2006



GMOs and nanotechnology – hope for the future

6 06 2013

I ran into some interesting ideas that seem to display why we should not immediately discredit new science – like genetic engineering or nanotechnology – because it might well provide clues to how we can continue to live on this planet.  So rather than taking a global stand against GMOs or nanotechnology perhaps we should look at how the science is used.

Carbon dioxide (CO2)  – the natural gas that allows sunlight to reach the Earth –  also prevents some of the sun’s heat from radiating back into space, thus trapping heat and warming the planet. Scientists call this warming the greenhouse effect. When t­his effect occurs naturally, it warms the Earth enough to sustain life. In fact, if we had no greenhouse effect, our planet would be an average temperature of minus 22 degrees Fahrenheit (minus 30 degrees Celsius)[1].  My kids would love the skiing, but they’d be too dead to enjoy it.  So carbon dioxide and the greenhouse effect are necessary for Earth to survive. But human inventions like power plants and cars, which burn fossil fuels, release extra CO2 into the air. Because we’ve added (and continue to add) this carbon dioxide to the atmosphere, more heat is stored on Earth, which causes the temperature of the planet to slowly rise, a phenomenon called global warming.

Carbon dioxide isn’t the only greenhouse gas (GHG) – others include water vapor, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride – but it’s the most important.  And it’s going up as a direct result of human activity.[2]  Just recently, we passed a milestone that climate scientists have warned is impressively scary – for the first time in human history, atmospheric carbon dioxide levels will surpass 400 ppm.[3]

So what to do? Traditionally, we’ve relied on natural systems to deal with this extra CO2 – like trees and other plants which soak up the stuff through photosynthesis.  But the amounts being generated exceed the capacity of natural systems to deal with it.  So we look to technological solutions, which basically consist of:  capture (i.e., trapping the gas at its emission source and then putting it someplace where it won’t escape) and geologic sequestration or storage (putting it someplace where it won’t escape.)  But I’m not a believer in these measures – after all, captured CO2 must be transported (by rail, truck or ship) to its final storage place.  And where is there a storage place that will not leak and can accommodate the 30 billion metric tons of CO2 we generate every year – without dire environmental consequences.

We have to look outside the box.  There have been many such ideas, from the more outlandish (i.e., create man-made volcanoes to pump sulfur dioxide into the atmosphere to block sunlight and cool the planet[4]) to several I’ve outlined below that just might help.  But they depend  on the use of GMO and nano science.

As Technology.org describes it:  “It is not widely appreciated that the most substantial process of carbon sequestration on the planet is accomplished by myriad marine organisms making their exoskeletons, or shells.   Shells are produced biologically from calcium and magnesium ions in sea water and carbon dioxide from the air, as it is absorbed by sea water. When the organisms die, their shells disintegrate and form carbonate sediments, such as limestone, which are permanent, safe carbon sinks.”[5]

from ecoco: sustainable design

from ecoco: sustainable design

By studying how sea urchins grow their own shells, scientists at Newcastle University in the UK have discovered a way to trap CO2 in solid calcium carbonate using nickle nanoparticles.  “It is a simple system,” said Dr Lidija Siller from Newcastle University. “You bubble CO2 through the water in which you have nickel nanoparticles and you are trapping much more carbon than you would normally—and then you can easily turn it into calcium carbonate.”[6]  Most carbon capture and storage programs must first trap the CO2 and then pump it into holes deep under ground, which is both expensive and has a high environmental risk.    Lead author, PhD student Gaurav Bhaduri, is quoted: “ [the nickel catalyst]  is very cheap, a thousand times cheaper than carbon anhydrase”.  The two researchers have patented the process and are looking for investors.

Meanwhile, MIT professor Angela Belcher, who had done her thesis on the abalone,   and graduate students Roberto Barbero and Elizabeth Wood are also looking into this.  They have  created a process that can convert carbon dioxide into carbonates that could be used as building materials. Their process, which has been tested in the lab, can produce about two pounds of carbonate for every pound of carbon dioxide captured.

Their process requires using genetically modified yeast.

Yeast don’t normally do any of those reactions on their own, so Belcher and her students had to engineer them to express genes found in organisms such as the abalone. Those genes code for enzymes and other proteins that help move carbon dioxide through the mineralization process.

The MIT team’s biological system captures carbon dioxide at a higher rate than other systems being investigated. Another advantage of the biological system is that it requires no heating or cooling, and no toxic chemicals.

Dr. Belcher has also used genetically modified viruses so they would have a binding affinity with carbon nanotubes – which allowed them to build a high-powered lithium ion battery cathode that could power a green LED.  Dr. Belcher thinks that she might one day drive a virus-powered car.

I think these two examples demonstrate that we should always keep an open mind.  And remember that it’s not always the science that’s causing a problem, but rather how we use it.  The idea that GMO seeds are intellectual property (owned largely by Monsanto) for example, is one of the wrong ways to use this technology.  But let’s not throw the baby out with the bath water.

Nanotechnology in the textile industry

1 08 2012

We did a post on the use of nanotechnology in the textile industry about two years ago, and new research has just settled the long-standing controversy over the mechanism by which  silver nanoparticles (the most widely used nanomaterial in the world) kills bacteria.    You know, all those new textiles that advertise that they’re bacteria  and odor free – they  are  even claimed to prevent colds and flu and never need washing![1]  Not to keep you in suspense:  the  research comes with a warning:  use enough.  If you don’t kill the bacteria, you make them stronger. In honor of this new study (summarized below) we’re re-posting our previous posts on nanomaterials:

Recently, I have been noticing various products claiming to have some kind of nanotechnology-based credential. Turns out that’s because the nanotech tsunami is just gaining steam – one tally says that over 10,000 products using nanotechnology are already on the market. In the food industry, the FDA says there are no nano-containing foods on the market in the U.S., yet DK Matai, Chairman of the Asymmetric Threats Contingency Alliance, says that the USA is the world leader in nano foods, followed by Japan, Europe and China[1]. The Environmental Working Group has done it’s own count of lotions, creams, sprays, washes, cosmetics and nutritional supplements on the market in the U.S. and has found close to 10,000 that contain nanoparticles. And there’s an app for that: The Project on Emerging Nanotechnologies has an iPhone app called findNano, which urges users to photograph and submit information on a possible nanotech product for inclusion in its inventory.

Turns out that there are many who think the next Industrial Revolution is right around the corner – because of nanotechnology. They think that nanotechnology will radically transform the world, and the people, of the early 21st century. It has the capacity to change the nature of almost every human-made object. Whether that transformation will be peaceful and beneficial or horrendously destructive is unknown. So naturally it’s become very controversial. More about that later.

It seems the better term is really nanoscience.  Nanoscience is the study of things that are really really small: A nanometer is one billionth of a meter (10-9 m). This is roughly ten times the size of an individual atom. For comparison, 10 NM is 1000 times smaller than the diameter of a human hair. How small is that? “If a centimeter is represented by a football field, a nanometer would be the width of a human hair lying on the field,” offers William Hofmeister of the University of Tennessee Space Institute’s Center for Laser Applications.

From National Nanotechnology Initiative

Nanoparticles are bits of a material in which all three dimensions of the particle are within the nanoscale: nanotubes have a diameter that’s nanosize, but can be several hundred nanometers (nm) long or even longer.   A cubic centimeter of material, about the size of a sugar cube, has the same surface area of a half a stick of gum. But if you fill that cube with particles that are 1 nanometer in size, the surface area of all those particles is an astonishing 6,000 square meters, nearly the surface area of 3 football fields.Nanofilms or nanoplates have a thickness that’s nanosize, but their other two dimensions can be quite large. These nanoparticles can be designed into structures of a specific size, shape, chemical composition and surface design to create whatever is needed to do the job at hand. They can be suspended in liquid, ground into a powder, embedded into a composite or even added to a gas.

Many important functions of living organisms take place at the nanoscale. The human body uses natural nanoscale materials, such as proteins and other molecules, to control the body’s many systems and processes. A typical protein such as hemoglobin, which carries oxygen through the bloodstream, is 5 nms in diameter. Based on the definition of nanotech given above, biotech can be thought of as a subset of nanotech – “nature’s nanotechnology.”

Manipulating something so mind-bogglingly small is where the “technology” part comes in – it’s about trying to make technologies, such as computers and medical devices, out of these nanoscale structures. Nanotechnology is different from older technologies because unusual physical, chemical, and biological properties can emerge in materials at the nanoscale. Nano particles have different physical properties from their macro or life-size scale counterparts. For example, copper is an opaque mineral, but at the nano scale it is transparent. Some particles, like aluminum, are stable at macro scale but become combustible when reduced to nano-particles; a gold nanowire is twenty times stronger than a large bar of gold.

Molecular manufacturing is the name given to a specific type of “bottom-up” construction technology. As its name implies, molecular manufacturing will be achieved when we are able to build things from the molecule up, and we will be able to rearrange matter with atomic precision.

As I mentioned earlier, something so little understood is controversial, with many different points of view. These differences start with the very definition of nanotechnology, and moves on to what nanotechnology can achieve. Then there is the ethical challenge – what is the moral imperative about making technology that might help increase our lifespans available to all, for example?

Finally, the concern about possible health and environmental implications is perhaps the most controversial. The problem is that some properties of these tiny particles are unknown, and potentially harmful, and scientists are still trying to determine whether their size affects their toxicity. Scientists worry that the small particles used in nanotechnology could penetrate biological barriers designed to keep out larger particles; also we don’t have guidelines about how much we can safely ingest without harm. For more on possible harm to human health, click here.

Nanotechnology has been discovered by the textile industry – in fact, a new area has developed in the area of textile finishing called “Nanofinishing”. Making fabric with nano-sized particles creates many desirable properties in the fabrics without a significant increase in weight, thickness or stiffness, as was the case with previously used techniques. Nanofinishing techniques include: UV blocking, anti-microbial, bacterial and fungal, flame retardant, wrinkle resistant, anti-static, insect and/or water repellant and self-cleaning properties.

One of the most common ways to use nanotechnology in the textile industry is to create stain and water resistance. To do this, the fabrics are embedded with billions of tiny fibers, called “nanowhiskers” (think of the fuzz on a peach), which are waterproof and increase the density of the fabric. The Nanowhiskers can repel stains because they form a cushion of air around each cotton fiber. When something is spilled on the surface of the fabric, the miniature whiskers actually cohesively prop up the liquid drops, allowing the liquid drops to roll off. This treatment lasts, they say, for about 50 home wash cycles before its effectiveness is lost.    A corollary finish is that of using nanoparticles to provide a “lotus plant” effect which causes dirt to rinse off easily, such as in the rain.

Nanotechnology can also be used in the opposite manner to increase the ability of textiles, particularly synthetics, to absorb dyes. Until now most polypropylenes have resisted dyeing, so they were deemed unsuitable for consumer goods like clothing, table cloths, or floor and window coverings. A new technique being developed is to add nanosized particles of dye friendly clay to raw polypropylene stock before it is extruded into fibres. The resultant composite material can absorb dyes without weakening the fabric.

The other main use of nanoparticles in textiles is that of using silver nanoparticles for antimicrobial, antibacterial effects, thereby eliminating odors in fabrics. Nanoparticles of silver are the most widely used form of nanotechnology in use today, says Todd Kuiken, PhD, research associate at the Project on Emerging Nanotechnologies (PEN). “Silver’s antimicrobial property is one that suits a lot of different products, and companies pretty much run the gamut of how many consumer products they put it in.” 

PEN’s database of consumer products that contain nanoparticles lists 150 different articles of clothing, including athletic clothes, jogging outfits, camping clothing, bras, panties, socks, and gloves, that are treated with nano-silver because it kills the bacteria that cause odor.

The new research mentioned above was published in the American Chemical Society’s Nano Letters by  researchers at Rice University[2] , who found that the assumption that silver nanoparticles are toxic to bacteria is unfounded.

Scientists have long known that silver ions, which flow from nanoparticles when oxidized, are deadly to bacteria, and the assumption was made that silver nanoparticles were equally toxic. In fact, when the possibility of ionization is taken away from silver, the nanoparticles are practically benign in the presence of microbes, said Pedro Alvarez, George R. Brown Professor and chair of Rice’s Civil and Environmental Engineering Department.[3]  He said the straightforward answer to the decade-old question is that the insoluble silver nanoparticles do not kill cells by direct contact. But soluble ions, when activated via oxidation in the vicinity of bacteria, do the job nicely.

To figure that out, the researchers had to strip the particles of their powers. “Our original expectation was that the smaller a particle is, the greater the toxicity,” said Zongming Xiu, a Rice postdoctoral researcher and lead author of the paper. “We found the particles, even up to a concentration of 195 parts per million, were still not toxic to bacteria,” Xiu said. “But for the ionic silver, a concentration of about 15 parts per billion would kill all the bacteria present. That told us the particle is 7,665 times less toxic than the silver ions, indicating a negligible toxicity.”  In fact, E. coli bacteria became stimulated by silver ions when they encountered doses too small to kill them.

The Environmental Protection Agency (EPA) granted  it’s first-ever approval to use nanosilver particles in fabrics in December 2011, and is based on a conditional four year registration. . “Conditional” means that the manufacturer must provide test results (within four years) showing how the nanosilver particles interact with the environment. However, the EPA has a long history of letting such approvals linter, and has already expressed concern about nanosilver particles impacts on health, saying the approval “will likely lead to low levels of human and environmental exposure and risks.”

Last year, the Swiss Federal Laboratories for Materials Testing and Research examined what happens to silver nanoparticles in fabrics during washing – and found that these silver nanoparticles actually wash out of fabrics – so there is a high likelihood that the silver will spread into the environment. Another study found that socks treated with nanosilver lost, on average, half the nanoparticles embedded in the fabric during washing.

Among other well documented studies (see sites listed below) which have shown silver nanoparticles to be highly toxic to bacteria, fungi and other microorganisms is one by Duke University, in which it was found that silver nanoparticles negatively impacted the growth of plants – and also kills the beneficial soil microbes which sustain the plants. “Nanoparticles likely enter the environment through wastewater, where they accumulate in biosolids (sewage sludge) at wastewater treatment plants. One of the ways in which the sludge is disposed of is through land application, because it is valuable as a fertilizer. Whereas fertilizers add nutrients to the soil that are essential for plant growth, plants also depend on soil bacteria and fungi to help mine nutrients from the air and soil. Therefore, the antimicrobial effects of silver nanoparticles could have impacts at the ecosystem level—for example, affecting plants whose growth is dependent on soil-dwelling microorganisms.” Another study (Choi, Yu, Fernandez et al in Water Research 2010) found that once nanosilver is washed down the drain, it’s highly effective at killing the microorganisms used to treat sewage in wastewater treatment plants, which could lead to bigger problems with drinking-water safety.

The future for textile applications using nanotechnology is exploding due to various end uses like protective textiles for soldiers, medical textiles and smart textiles. Consider the T-shirt. Research is being done that will use nanotechnology-enhanced fabric so the T-shirt can monitor your heart rate and breathing, analyze your sweat and even cool you off on a hot summer’s day. What about a pillow that monitors your brain waves, or a solar-powered dress that can charge your ipod or MP4 player? The laboratory of Juan Hinestroza, assistant professor of Fiber Science and Apparel Design at Cornell University, has developed cotton threads that can conduct electric current as well as a metal wire can, yet remain light and comfortable enough to give a whole new meaning to multi-use garments. This technology works so well that simple knots in such specially treated thread can complete a circuit – and solar-powered dress with this technology literally woven into its fabric. Dr. Hinestroza designed the fabrics used in a Cornell Univesity fashion show by designer Olivia Ong, which guards the wearer against bacteria, repels stains, fights off allergies and oxidizes smog. And costs about $10,000 per yard to make.

And yet, there is mounting evidence that nanotechnology requires special attention. Here’s an excerpt from an interview with Andrew Maynard, science advisor to the Project on Emerging Technologies (PEN), from Technology Review:

  • “Individual experiments have indicated that if you develop materials with a nanostructure, they do behave differently in the body and in the environment.
  • We know from animal studies that very, very fine particles, particles with high surface area, lead to a greater inflammatory response than the same amount of larger particles. We also know that they can enter the lining of the lungs and get through to the blood and enter other organs. There is some evidence that nanoparticles can move into the brain along the olfactory nerve, so this is completely circumventing the blood-brain barrier.
  • There really isn’t any consensus on how you go about evaluating the risks associated with carbon nanotubes yet. In cell cultures, you have to have some idea what kind of response you’re looking for. We already know in some studies that the lungs see carbon nanotubes almost as biological materials–they don’t see it as a foreign material. But then because of that, they start building up layers of collagen and cells around these nanotubes. They almost see them as a framework for building tissue on. Now, that actually may be a good thing in parts of the body, but in the lungs you end up using up the air space. But without that information, you wouldn’t necessarily know what were the appropriate cell tests to do in the first place.
  • The thing that concerns me is, there is very much a mind-set that is based on the conventional understanding of chemicals. But nanomaterials are not chemicals. They have a structural component there as well as a chemical component.

At the recent meeting of the Society of Environmental Toxicology and Chemistry (SETAC), more than 20 studies were presented on the fate of nanoparticles once they enter the environment, and nearly all found that these materials were building up in organisms, such as earthworms, insects, and fish, and having subtle effects on their abilities to survive

The Rodale website had some suggestions for those of us who are worried about smelly clothes: Try nature and a little common sense.

  • Pretreat. Before you wash your smelly gym clothes, sprinkle some baking soda on them, leaving it on for about an hour before laundering them to remove perspiration odors as well as stains.
  • Launder with care. Because sweat can be oily, it can build up on clothing, becoming difficult to remove with regular detergents and water. Add a cup of white vinegar to the rinse cycle; vinegar helps break through oils on fabric, and it serves as a deodorizer. Or hand-wash your clothes with shampoo, which is designed to cut through body oils.
  • Line-dry. Nothing cuts through bad odors like oxygen and sunlight. Let your clothes dry outside, rather than in a machine, and you’ll save energy, make your clothes last longer, and prevent offensive odors the next time you hit the gym. Read our Nickel Pincher’s line-drying story for the ultimate in line-drying advice.

Some other studies on toxicity of nanoparticles:





Digital Printing

3 02 2012

The idea of digital  printing on textiles has been around for some time.  Carpet inkjet printing machines have beenused since the early 1970s.  Digital ink jet printing of continuous rolls of textile fabrics was shown at ITMA in 1995.   Again at ITMA in  2003, several industrial inkjet printers were introduced to the marketplace which made digital printing on textiles the new industry standard.  These new generation machines had much higher outputs, higher resolution printing heads, and more sophisticated textile material handling systems allowing a wide varieof fabrics to be printed.

One reason for the comparatively slow growth of digital printing on textiles may be related to the  extreme demands of the textile applications.  Although ink-jet printing onto fabric works in fundamentally the same way as any office type ink-jet prints onto paper, fabric has always been inherently more difficult to print due to its flexible nature.  The level of flexibility varies from warp to weft and with each degree around the bias, so guiding the fabric under digital printer heads has proven to be very challenging.  Other challenges:

  • There are many  types of synthetic and natural fibers,   each with its own ink compatibility characteristics;
  • in addition to dealing with a fabric that is stretchable and flexible, it is often a highly porous and textured surface;
  • use requirements  include light fastness, water fastness (sweat, too) through finishing operations and often outdoor use, heavy wear, abrasion, and cleaning;
  • the fabric not only has to look good but to feel good too;
  • fabric has much greater absorbency, requiring many times the ink volume compared with  printing on papers.

Before any printing is carried out, the designs need to be developed in a digital format that can be read by the printers. Thus, all development has to be based on co-operation between the design software companies, the ink manufacturers and the printing machine developers.

In the face of such odds, digital textile printing is happening.  And how!  Digital inkjet printing has become one of the most important textile production printing technologies and is, in fact, transforming the industry. It has been influencing new workflows, business plans and creative processes. The opportunities for high-value digital printer applications are so large that many hardware and chemistry vendors are investing heavily in textile and textile-related products and systems. Between 2000 and 2005 digitally printed textile output rose by 300% to 70m square metres.[1]  This is still less than 1% of the global market for printed textiles, but  Gherzi Research, in a 2008 report, suggests the growth of digital printing on fabrics to be more than 20% per year.  This growth is largely driven by the display/signage sector of the market;[2] it is only recently that interior designers, seeking unique solutions for their clients, have been turning to digital printing.

Digital processes have become so advanced that it is becoming very hard to tell digitally printed fabric apart from fabric printed the traditional way – although for my money, they’ll never replicate the artisanal hand crafted quality of hand screened or hand blocked prints, where the human touch is so delightfully evident.  The lower energy, water and materials consumption means that more printers are switching to digital as it becomes competitive for shorter runs.   Although there are many advantages already to digital printing, the few downsides, such as lower production speeds compared to rotary screen printing and high ink costs are both changing rapidly.

As with traditional screen printing technologies, the variables in digital technologies are as varied as in screen printing,  with additional complexity of computer aided technologies requiring changes from the design stage onward.   Digital textile printing output is a reflection of the design and color management software (such as Raster Image Processing or  RIP) that provides the interface between the design software and the printer, the printer itself, the printing environment, the ink, the fabric, the pre-treatment, the post-treatment and last, but not least, the operator.

This print method is being heavily touted as the “greenest” option.  Let’s find out why they make these claims.

In theory, inkjet technology is simple – a printhead ejects a pattern of tiny drops of ink onto a substrate without actually touching it. Dots using different colored inks are combined together to create photo-quality images.  There are no screens, no cleanup of print paste, little or no wastage.

In practice, however, it’s a different story.  Successful implementation of the technology is very complex. The dots that are ejected are typically sub-micron size, which is much smaller than the diameter of a human hair (70 microns);  one square meter of print contains over 20 billion droplets! [3] They need to be positioned very precisely to achieve resolutions as fine as 1440 x 1440 dots per inch (dpi).  Since the inks used must be very fluid so as to not clog the printheads, nanotechnology is a huge part of the ink development.  In fact, according to Xennia, a world leader in digital printing inks, “microfluidic deposition systems are a key enabler for nanotechnology”.  This precision requires multi-disciplinary skills –  a combination of careful design, implementation and operation across physics, fluid mechanics, chemistry and engineering.

There are two general designs of ink jet printers:  continuous inkjet (CIJ)  and drop-on-demand (DOD). As the names imply, these designs differ in the frequency of generation of droplets.

In continuous ink jet printers, droplets are generated continually with an electric charge imparted to them. As shown schematically in Figure 1, the charged droplets are ejected from a nozzle. Depending upon the nature of the imposed electric field, the charged droplets are either directed to the media for printing, or they are diverted to a recirculation system. Thus, while the droplets are generated continuously, they are directed to the media only when/where a dot is desired. Historically, continuous ink jet printing has enjoyed an advantage over other inkjet technologies in its ability to use inks based on volatile solvents, allowing for rapid drying and aiding adhesion on many substrates. The disadvantages of the technology include relatively low print resolution, very high maintenance requirements and a perception that CIJ is a dirty and environmentally unfriendly technology due to the use of large volumes of volatile solvent-based fluids. Additionally, the requirement that the printed fluid be electrically chargeable limits the applicability of the technique.

FIGURE 1.Continuous ink jet (schematic). Charged droplets leaving the nozzle are directed either toward a substrate or toward an ink recirculation system, depending upon the imposed electric field.

In DOD ink jet printers, droplets are generated only when they are needed. There are two subcategories in DOD jet printers:

  • The droplets can be generated by heating the ink to boil off a droplet,  called thermal ink jet.  Thermal inkjet technology (TIJ) is most used in consumer desktop printers but is also making some inroads into industrial inkjet applications. In this technology, drops are formed by rapidly heating a resistive element in a small chamber containing the ink. The temperature of the resistive element rises to 350-400ºC, causing a thin film of ink above the heater to vaporise into a rapidly expanding bubble, causing a pressure pulse that forces a drop of ink through the nozzle. Ejection of the drop leaves a void in the chamber, which is then filled by replacement fluid in preparation for creation of the next drop.  The advantages of thermal inkjet technology include the potential for very small drop sizes and high nozzle density. High nozzle density leads to compact devices, lower printhead costs and the potential for high native print resolution. The disadvantages of the technology are primarily related to limitations of the fluids which can be used. Not only does the fluid have to contain a material that can be vaporised (usually meaning an aqueous or part-aqueous solution) but must withstand the effects of ultra high temperatures. With a poorly designed fluid, these high temperatures can cause a hard coating to form on the resistive element (kogation) which then reduces its efficiency and ultimately the life of the printhead. Also, the high temperature can damage the functionality of the fluid due to the high temperatures reached (as is the case with certain biological fluids and polymers).
    • Alternatively, the droplets can be ejected mechanically through the application of an  electric stimulation of a piezoelectric crystal (usually lead zirconium titanate)  to elicit a deformation.  This distortion is used to create a pressure pulse in the ink chamber, which causes a drop to be ejected from the nozzle.   This method is shown in Figure 2. Piezo  drop-on-demand inkjet technology is currently used for most existing and emerging industrial inkjet applications. In this technology, a piezoelectric crystal (usually lead zirconium titanate) undergoes distortion when an electric field is applied. This distortion is used to create a pressure pulse in the ink chamber, which causes a drop to be ejected from the nozzle. There are many variations of piezo inkjet architectures including tube, edge, face, moving wall and piston, which use different configurations of the piezo crystal and the nozzle. The advantages of piezo inkjet technology include the ability to jet a very wide variety of fluids in a highly controllable manner and the good reliability and long life of the printheads. The main disadvantage is the relatively high cost for the printheads, which limits the applicability of this technology in low cost applications.
    • FIGURE 2.Piezoelectric drop on demand ink jet (schematic). In a DOD ink jet printer, upon application of a mechanical pulse, the ink chamber is deformed. This results in the ejection of a droplet toward the substrate.

As with screen printing, there are steps other than printing which are often overlooked:   the first step in digital printing is the pretreatment of the fabric.  Because many chemicals and/or auxiliaries cannot be incorporated into the printing ink, they must be applied to the fabric during the pretreatment. The entire process has to be designed to control bleeding, but also to achieve the hand, color, and fastness required in  the finished textile. For basic fabric pretreatment, the elements of this solution can include:

  • Antimigrants – To prevent migration of ink and prevent “bleeding.”
  • Acids/Alkalis – To support reactions of acid and reactive inks, respectively.
  • Urea/Glycols – To increase moisture content of the fabric, giving high, even fixation of the inks.
  • “Effects” Chemicals – Vary widely in purpose. Although there are too many effects to mention here, they can include chemicals to improve the brightness of the prints, water and stain repellants, UV absorbers to improve the fabric’s resistance to sunlight, fabric softeners/stiffeners, even antimicrobials to provide resistance to mildew and germs.

Many patented and proprietary formulations for pre treatment exist, ranging from simple formulations of soda ash, alginate and urea to more sophisticated combinations of cationic agents, softeners, polymers and inorganic particulates such as fumed silica. Many of these have been aimed at fashion fabrics such as cotton, silk, nylon and wool. The processing of the fabric during pretreatment is also an important factor in producing a superior finished printed fabric. Fabrics must be crease-free and even in width. Some producers provide fabrics that are backed with removable paper to allow companies with graphic printers that have been retrofitted with textile inks to print fabrics. This paper, and the adhesive that holds it to the fabric, must be properly applied so that the paper can be removed easily from the fabric.

Inks used in digital printing are thinner than those used for traditional printing, so the fabric also needs to be prepared by soaking it in a thickening agent.  This agent reacts to moisture by swelling.  As soon as a drop of dye touches the pre treated fabric, the thickener will swell up, keeping the dye in its place.  Without this agent, the dye would run and bleed on the fabric.

Inkjet inks must be formulated with precise viscosities, consistent surface tension, specific electrical conductivity and temperature response characteristics, and long shelf life without settling or mould-growth. The inks, made up  of pigments or dyestuffs of high purity,  must be milled to very fine particle size and distributed evenly in solution.  In addition, further properties such as adequate wash-, light- and rub-fastness are necessary.

Inkjet inks contain dyes or pigments but like screen printing inks they contain other things too:

  • Surfactants
  • Liquid carriers (water or other solvents)
  • Binders
  • Rheology modifiers
  • Functional materials
  • Adhesion promoters
  • Other additives
  • Colorants (dyes or pigments)[4]

The inks used in digital printing today have comparable color performance and fastness as compared to traditional screen printing inks.  They fall into four general categories:

  1. Water based – can contain glycol plus pigments or dyes.  These inks are designed to run specifically in printers with thermal and piezo-electric print-heads.  Dyes used include:

                  Reactive dyes, particularly suited to cotton, viscose and other cellulosic materia

                 Acid dyes, used for wool, silk and nylon.

                 Disperse dyes are used for synthetics like polyester and nylon.

  1.   Pigments (as well as disperse dyes)  present a more difficult set of problems for ink makers. Both exist in    water as a dispersion of small particles. These inks must be prepared with a high degree of expertise so that the particles will not settle or agglomerate (flocculate) and clog the printheads. The particle size must have an average of 0.5 micrometer and the particle size distribution must be very narrow with more than 99% of the particles smaller than 1 micrometer in order to avoid clogging of the nozzles. The major outstanding problem with the use of pigments in inkjet systems is how best to formulate and apply the resins which are required to bond the pigment particles to the fabric surface. Several different approaches, from coating pigment particles with advanced surfactants, to spraying resin through a separate jet head to screen printing binder over an inkjet  printed color have been suggested.
  2. Solvent based – Solvent-based inks are relatively inexpensive and have the advantage of being able to produce good vivid colors. However, their main ingredients are volatile organic compounds (VOCs) which produce harmful emissions. These inks need to be employed in machines which have ducting to extract the solvents to atmosphere. It is possible to remove the VOC’s using activated carbon filters without ducting to outside the building however you still have to dispose of the solvent laden graphite. Fabrics produced using solvent-based inks have a strong odor. The higher the level of the solvent, the greater the keying, or bonding, with the material’s surface to give a durable finish. Types of solvent range from eco-solvent, low and mild solvent through to hard or full solvent. The term eco-solvent does not necessarily mean less environmentally damaging than conventional solvent, as discussed in the post entitled “Textile Printing and the Environment”.
  3. Oil based – requires the use of a printer which is compatible; otherwise similar to water and solvent based inks.  Oil-based inks are less commonly used, but offer very reliable jetting since the ink does not evaporate.
  4. UV curable – generally made of synthetic resins which have colored pigments mixed in.  Curing is a chemical reaction that includes polymerization and absorption by the fabric. UV inks consist of oligomers, pigments, various additives and photoinitiators (which transfer the liquid oligomers and monomers into solid polymers).
  5. Phase change –  ink begins as a solid and is heated to convert it to a liquid state. While it is in a liquid state, the ink drops are propelled onto the substrate from the impulses of a piezoelectric crystal. Once the ink droplets reach the substrate, another phase change occurs as the ink is cooled and returns to a solid form instantly.

Once you have digitally printed the fabric, you must perform some process to fix the ink. What process this is depends on the type of ink you used.  Each dye type needs a specific finishing agent.

Finally, the fabric needs to be washed to remove the excess dye and thickening agents.  Fabrics are washed in a number of wash cycles at different temperatures to make the print washfast.

So at the end of this process, you can see that there is no real difference in the amount – or kinds –  of chemicals used, except perhaps those lost through wastage.  So what exactly are the green claims based on?

The traditional printing industry produces large amounts of waste – both dyes/pastes and water, and it has high energy useage.  There are also large space reqirements to operate presses, which produce a lot of noise.  In a project sponsored by the European Union’s LIFE Program, an Italian printing company,  Stamperia di Lipomo, transferred from conventional printing to digital.[5]  They found that these new digital presses lowered water, energy and materials consumption significantly.  The following reductions were achieved:

  • Production space required by 60%
  • Noise by 60%
  • Thermal energy usage by 80%
  • Wastewater by 60%
  • Electricity consumption by 30%
  • By-production of waste dyes = eliminated entirely

Digital printing has other advantages, which include:

  • Minimal set up costs – short runs and samples are economical – so traditional mill minimums can be avoided.  Costs per print are the same for 1 or 1000000.
  • There is no down time for set up – the printer is always printing – so there is also increased productivity.
  • Faster turnaround time – and very fast design changes.  Turnaround time for samples can be reduced from 6 to 8 weeks to a few days.
  • Print on demand, dramatically reducing time to market.
  • Just-in-time customization or personalization
  • Theoretically no limit on number of colors.
  • Decreases industrial waste and print loss.

The disadvantages most often cited, that of high cost of inks and shorter printing speeds, are quickly being overcome by the manufacturers.

One concern I have is that of the use of nanotechnology, which seems to be an inextricable part of the equation.  Already nanotechnology is enabling manufacturers to offer functional finishes in post processing, such as stain and water repellants, fire retardants, and UV blocking .  It is also being used in smart clothing:  To harness the energy of the sun, flexible thin film modules are sewn onto clothes. However, since they show clearly when sewn,  digital textile printing makes these modules inconspicuous.[6]

The traditional industry still looks at digital textile printing parameters from the context of what it “can’t do,” compared to conventional printing (much of which is already history).  For a much smaller group of designers, textile artists, fine artists, costumers, wide-format printers and the like, this technology is much more about what it “can do” to provide to provide products and services the market has never before seen. For these people, textile printing offers parameters not available with conventional printing:  unlimited repeat size, tonal graphics, engineered designs that cross several seam lines, quicker samples, customization and short-run production.  And the use of the technology is beginning to catch the imagination of more and more textile designers, as they realize that their old reaction to computer generated graphics (dismissive to say the least)  is truly outdated.  Claire Lui, Print magazine associate editor, points out that in  ultra-custom milieus, design and printing become more like art than common manufacturing.

The traditional textile industry needs to understand that, in the same way the Internet is not going to replace the television as a form of entertainment or information, this new digital technology isn’t about replacing existing processes , but rather about leveraging the expanded parameters to offer new niche products and services.  And we must remember too that digital printing is not the panacea it’s touted to be for the environment, though it seems to have less of a pollution footprint than traditional screen or rotary printing.

[3] Xennia

[4] Yeong, Kay, “Inkjet Printing: Microfluidics for the Nanoscale”; http://www.xennia.com/Xennia/uploads/ppp-InkjetPrintingMicrofluidicsfortheNanoscale-Jun2010.pdf