Nanotechnology Will Minimize Chores, and Our Use of Chemicals. Let's get Greener.
Self-Cleaning Technology Began in the 1960s
Prior to the self-cleaning ovens, or even continuous cleaning ovens, ovens were being cleaned with either baking soda and lots of muscle, or chemicals. The inside surfaces were not designed for the high temps associated with self-cleaning, nor did they survive the chemicals and muscle power used to scrub them clean, and this ultimately led to the deterioration of the inner porcelain surfaces.
Self-cleaning ovens debuted in the early 1960s. The technology used at that time was based on one of the same principles guiding the new nanotechnology for self-cleaning and stay-clean products of today: make the dirt fall off.
The Old Fashioned oven needed lots of scrubbing.
How the Self-Cleaning Oven Works
The functional characteristic of self-cleaning ovens is called the “Pyrolytic Cleaning Method”. (http://www.howstuffworks.com/self-cleaning-ovens.htm) They use a very high temperature, usually >900°F to reduce food residues to ash. Typically, the highest temperature for cooking in a residential type oven is 500°F to 550°F. But it wasn't just the high temperature that made self-cleaning possible in ovens.
Self-cleaning ovens came to be as a result of developing porcelain enamel surfaces which were infused, or bound with, metal oxides that helped to protect and reinforce the enamel and that also catalyzed a chemical reaction in the food debris. This reaction known as oxidation, assisted in the degradation of food residues into ash. In other words, this new technology made food residues fall off the inner surfaces.
How much of your daily free time is spent doing household chores?
Leading Nanotech Design Strategies
There are 4 basic material or surface design manipulations which stand out today in the realm of self-cleaning and stay-clean applications:
Super-Hydrophobic nano-lubricated design
Titanium Oxide Infusion or binding (Antimicrobial)
Water Beads on Hydrophobic Surfaces - Droplets Evaporate and Leave "Water Spots"
Fear of Water
Oil and Water Don't Mix - Super Fear of Water
Repels Water - Super Slippery
Kills or Disables Microbes
Understanding the New Designs
1) Hydrophobic surfaces repel water and water based solutions, and when splashed on, or otherwise exposed to water, the surface does not absorb it. Instead the water beads up into droplets and eventually evaporates.
2) Super-Hydrophobic nano-lubricated surfaces, not yet associated with cookware or in use commercially, are being developed wherein the surface material is comprised of a nano-sized honeycomb matrix which holds nano-sized lubricant drops to render the material super-hydrophobic and thus super-slippery. “Unlike earlier water-repelling materials, [SLIPS] repels oil and sticky liquids like honey, and it resists ice formation and bacterial biofilms as well.” (http://www.seas.harvard.edu/news/2013/08/new-coating-turns-ordinary-glass-into-super-slippery-glass)
Water Forms Sheets on Hydrophilic Surfaces - Then They Fall Off As a Sheet Due to Gravity
3) Hydrophilic surfaces hold water. Hydrophilic means water loving, and water itself is water loving, making it “cohesive”. Cohesive means the molecules of water are strongly attracted to other molecules of water. Hydrophilic surfaces hold water (via water's adhesive property) and the water then congregates into sheets (because of it's cohesive property).
So rather than beading up into little droplets with the water evaporating, the sheets of water form and can then slide off of the object due to gravity. This design aides in removing the dust and other particles that would otherwise remain on a surface in dry spots - like when water beads up on your car and leaves "water spots".
Antimicrobial Surfaces - Forget Chemical Sanitization
4) Another key goal in the development of self-clean and stay-clean products is to design surfaces or surface coatings that will kill or disable microbes that contact or remain on the surfaces. The antibacterial movement is no longer reserved for consumable products like hand lotion and dish soap, it's now moving into the realm of non-consumable (durable) products like dishes and clothing. The future ramifications are far reaching for the medical field and the military. Imagine hospital floors and furniture that repel dirt and kill pathogens, or clothing that can be worn for weeks without washing by soldiers fighting and living in nature's raw elements.
The premier chemical being used for its antimicrobial purposes today is titanium dioxide. Commonly, it is already widely used in pigments and sunscreens because of its brightness. But in 1967 a scientist named Akira Fujishima discovered titanium dioxide has photocatalytic properties, meaning it can catalyze chemical reactions when exposed to light (http://en.wikipedia.org/wiki/Akira_Fujishima). These chemical reactions can not only break molecular bonds like those between the hydrogen and oxygen in water, but they can produce electricity, and breakdown proteins – all three of these functions are important to the self-cleaning/stay-clean industries.
The manipulation of the structure and characteristics of the materials in, or just the surfaces of products today is being done on the molecular and atomic level, in a scientific field known as “nanotechnology" (http://en.wikipedia.org/wiki/Nanotechnology), and it's targeting more than your oven. Like the “non-stick Teflon coating that was first commercially applied to cookware, also in the 1960s, new ideas have arisen for applications on clothing, glass, dishware, automobile bodies, etc.
And self-cleaning is not the only game in town either. Nano-technologists are also targeting 'stay-clean' and 'antibacterial' enhancements for durable goods. Staying clean is the preventative step before self-cleaning, and it relies on the same or similar technologies of the self-clean solutions. Antibacterial enhancements, already commonly applied to some consumable goods like hand lotion and dish-washing liquid, are targeting micro-organisms on the more permanent surfaces of durable goods, aiming to either kill, or disable them. All of these endeavors are targeted to minimize the chores of today's fast-paced lifestyle.
Since a nanometer is a billionth of a meter, it's size is unimaginably small in the mind's eye of a layperson. Cleaning as we know it occurs when we remove dirt and debris from a surface. Using nanotechnology, the surface of just about anything can now be designed and constructed to not only repel dirt, debris, and liquids, but to also kill or neutralize microbes present on those surfaces.
Titanium Dioxide is a Leading Metal Oxide for its Antimicrobial Properties
So what kind of things are on the market, or on the cusp of marketability for consumer use? Self-cleaning glass is out there already. Most brands have a hydrophilic property rather than a hydrophobic one. That's because most glass surfaces are vertically aligned, like windows, and if the water forms sheets that slide off the glass, then the sheets will carry dirt and debris off too. It's easily understood if you imagine the alternative wherein a hydrophobic surface causes water beading on a car windshield – the beads evaporate and leave a dirty spot of residue on the windshield.
Additionally, these hydrophilic glass surface coatings also contain a chemical like titanium dioxide which catalyzes the breakdown of dirt, bird feces, and dead bugs. Even if remnants stay adhered to the dry glass, future rainfalls will wash them off. And what about frost or ice on the windshield? It won't form.
The textile and clothing industries are also active in applying this new technology. The military in particular, but also everyone who suffers the chore of doing laundry, will be grateful if clean clothing will stay clean longer, or clean itself. Do you think clothing can't stay clean? Even if it looks clean, what about body odor?
Body odor occurs when micro-organisms grow on the skin. The addition of chemicals like titanium dioxide can prevent body odor by killing or disabling the organisms that cause it. And because of it's catalytic properties, it also assists in denaturing proteins and breaking down organic compounds. So that spot of ketchup on your polo shirt may disappear in a few days anyway.
Dishware and other food-contact containers are the last industry this article will mention. Imagine dishes that let the food residue slide off. Imagine using no soap on, or no scrubbing of your dishware. And if you put your food covered dishes directly into a dishwasher (maybe with a built-in garbage disposer) you can still benefit because they'll just let the food slide off, and be clean!