Amazing New Self-Cleaning MaterialsTo be useful, most of the things in our lives need their surfaces to remain relatively clean, and many need regular repair. Typically, this involves the actions of a human agent. However, a recent goal of scientists has been to make things self-cleaning and self-repairing.
For something to be self-cleaning, there still needs to be some agent that organizes, polishes, or sanitizes it. Today, scientists are developing non-human agents that can either clean themselves or keep themselves clean under normal conditions. Meanwhile, self-repairing surfaces need an agent that knits the damaged surface back together.
These breakthroughs are proving to be great time- and money-savers, but perhaps more significantly, many of them have positive health implications, as well. Lets review several of the new technologies, starting with those that focus on saving time and money.
For example, scientists at Chinas Donghua University have developed a new cotton fabric that uses ordinary sunlight to rid itself of stains and bacteria.1 The active agent is a compound of titanium dioxide, a white material that already plays a role in many everyday commodities, such as white paint, foods, and sunscreen lotions. When exposed to certain types of light, titanium dioxide breaks down dirt and kills microbes.
Self-cleaning cotton fabrics have been created before, but they only worked when exposed to ultraviolet rays, while this new fabric is activated by ordinary sunlight. This means clothing items can be cleaned and deodorized simply by hanging them on a clothesline outside.
To further accelerate the discoloration of stains, nanoparticles composed of silver and iodine are included in the coating. One important characteristic of this coating is that even if the clothing is washed and dried in the traditional way, it will remain intact.
This self-cleaning property of titanium dioxide is also being leveraged for other applications, including patio furniture, paints for buildings, and coatings for glass surfaces.
In another important development, researchers at Eindhoven University of Technology have developed a coating with a surface designed to enable mobile phones that will remain clean from fingerprints, cars that never need to be washed, and aircraft that need less frequent repainting.2
Similar coatings have been around for years; they have on their surfaces nano-sized molecular groups that provide these specific properties. But up to now, these molecular groups have been easily and irreversibly damaged by minor contact with the surface, causing these properties to be quickly lost. This has been a big limitation to the possible applications of these coatings.
To resolve this problem, the Eindhoven team developed a surface with special "stalks" carrying the functional chemical groups at their ends. These stalks are mixed throughout the coating so that even if the outer surface layer is removed by abrasion, the "stalks" in the underlying layers re-orient to the new surface, thereby restoring the function.
A common application of this technology will be to make cars self-cleaning for long periods of time.
Like dirt and bacteria, corrosion can impair the appearance and functionality of an object. Furthermore it can actually undermine its structural integrity. Fortunately, a new coating has been created by a team at the University at Buffalo using graphene to protect metals against corrosion.3
Applied to copper, for example, it slows corrosion by seven times; on nickel, corrosion is 20 times slower. Microelectronic components and other applications where a thin coating is optimal are ideal applications for the graphene coating.
Self-cleaning materials with the ability to kill or prevent the growth of bacteria that cause infections could have a significant impact on human health. Just consider a few examples:
- First, researchers have developed chemical-free surfaces, using nanotechnology, that prevent bacteria from attaching.4 This is an improvement over conventional methods that use potentially harmful metal ions, nanoparticles, chemicals, or UV radiation. Biomedical devices will be the key beneficiaries of these new surfaces, since chemical additives can have adverse effects on them.
- Second, surfaces coated with metalloacids have been proven to kill off microbial strains, even in multidrug-resistant microorganisms.5 This is good news for hospitals in their fight against the spread of hospital-acquired infections, which are a major public health concern. Today, these infections result in approximately 99,000 deaths in the U.S. alone. It appears that these surfaces, developed by French researchers, kill microorganisms by diffusing ions through microbial cell membranes, where they inhibit metabolic activity, resulting in the destruction of the cell.
- Another self-cleaning approach being considered in the fight against hospital-acquired infections is the use of anti-microbial copper surfaces.6 Like metalloacids, this type of surface shows promise because it can quickly kill bacterial, viral, and fungal pathogens. This would be an important step in reducing mutational resistance and the spread of antibiotic-resistant organisms. Recent trials conducted in intensive care units, by researchers at the University of Southampton, demonstrated that anti-microbial copper surfaces reduced the risk of acquiring a hospital infection by 40 percent.
- A fourth example involves food spoilage, which can be both a health concern and an economic issue. To address this problem, scientists have developed a new food packaging material that is being called "killer paper" for its ability to fight bacteria that cause food to spoil.7 The paper is coated with silver nanoparticles, a powerful anti-bacterial agent. This material has the potential to offer an alternative to traditional food preservation approaches, such as radiation, heat treatment, and refrigeration.
In light of this trend, we offer the following forecasts for your consideration:
First, widespread adoption of self-cleaning materials will impact jobs both positively and negatively.
Currently, the costs of maintaining cleanliness, and the costs caused by uncleanliness, such as disease and spoilage, have the upside of providing jobs. These jobs are in various industries, including cleaning supplies and cleaning services. These are the types of jobs that will be lost as self-cleaning materials improve and are incorporated into everyday life. However, as typically happens with "creative destruction," a loss of jobs in one area is likely to be offset by jobs gained in new industries. In this case, new self-cleaning technologies will spawn work to support new products and new applications. More jobs will also be created indirectly, as people shift their spending away from the costs associated with cleaning to more discretionary areas.
Second, expect to see a decline in infections, especially in hospitals, over the next 10 years.
In the recent past, weve seen a sharp rise in infections and fatalities arising from opportunistic infections. But as surfaces become self-sanitizing, it will be much easier to protect patients from such infections.
References List :
1. ACS Applied Materials & Interfaces, December 10, 2011, Vol. 3, Iss. 12, "Realizing Visible-Light-Induced Self-Cleaning Property of Cotton through Coating N-TiO2 Film and Loading Agl Particles," by Deyong Wu and Mingce Long." ⓒ Copyright 2011 by the American Chemical Society. All rights reserved. http://pubs.acs.org 2. Advanced Materials, July 17, 2012, Vol. 24, Iss. 27, "Self-Replenishing Surfaces," by T. Dikic, W. Ming, R.A.T.M. van Benthem, A.C.C. Esteves, and G. de With. ⓒ Copyright 2012 by John Wiley & Sons, Inc. All rights reserved. http://onlinelibrary.wiley.com 3. For more information about using graphene to slow down metal corrosion, visit The State University of New York at Buffalo website at: http://www.buffalo.edu 4. Infection Control Today, December 28, 2010, "Consortium Learns from Nature to Produce New Chemical-Free, Antibacterial Plastic Skins." ⓒ Copyright 2010 by Virgo Publishing, LLC. All rights reserved. http://www.infectioncontroltoday.com 5. Antimicrobial Resistance & Infection Control, November 14, 2012, "Biocidal Activity of Metalloacid-Coated Surfaces Against Multidrug-Resistant Microorganisms," by Nathalie Tetault, Houssein Gbaguidi-Haore, Xavier Bertrand, Roland Quentin and Tathalie van der Mee-Marquet. ⓒ Copyright 2012 by BioMed Central Ltd., part of Springer Science+Business Media. All rights reserved. http://www.aricjournal.com 6. BMC Proceedings, June 29, 2011, "New Insights into the Antimicrobial Mechanisms of Copper Touch Surfaces," by B. Keevil and S. Warnes. ⓒ Copyright 2011 by BioMed Central Ltd, part of Springer Sciences+Business Media. All rights reserved. http://www.biomedcentral.com 7. Langmuir, January 18, 2011, "Sonochemical Coating of Paper by Microbiocidal Silver Nanoparticles," by Ronen Gottesman, Sourabh Shukla, Nina Perkas, Leonid A. Solovyov, Yeshayahu Nitzan, and Aharon Gedenankan. Copyright 2011 by ACS Publications. All rights reserved. http://pubs.acs.org
