Nanoscience Applied to Hearing Aids

(Or, how my hearing aid is more water resistant than yours!)

What is Nanoscience?                                                   

Hearing aid protected against water with nano-coating technology.

Simply defined, nanoscience is the study of unique properties of matter that occur at the nanoscale (lengths of roughly 1 to 100 nanometers – or one billionth of a meter).  The application of nanoscience is called nanotechnology.  A National Science Foundation official has more precisely defined nanotechnology as a science that deals with materials and systems that have these key properties:

1. At least one dimension is from one 1 to 100 nanometers;
2. The process of the design uses fundamental control over the physical and chemical attributes of molecular-scale structures; and
3. They can be combined to form larger structures

Nanotechnology Treatment

Various types of nanotechnology applications exist.  In general, the process comes from the high-tech semiconductor industry and can be adapted to provide a range of treatments for different applications.

Because the properties of matter depend in part on size, the physical, chemical and biological properties of matter generally differ at the nanoscale as opposed to when compared to larger quantities of the same material.  This is due, in part, to the difference in surface area per unit of volume at the nanoscale.  For a given material, increasing the number of nanoscale particles increases the proportion of atoms on a surface compared with the number of internal atoms.  Atoms at the surface often behave differently from those located in the interior since they have a higher energy state.  The result is that more chemical reactions can take place between atoms and molecules at the surface.  Essentially, nanoscale particles can act as miniature chemical reactors.  Additionally, other properties such as magnetism, hardness and electrical and heat conductivity can be changed substantially by modifying materials at the nanoscale.  These changes arise from surprising collective and quantum size effects that arise from confining electrons in nanometer-sized structures.

In essence, nanotechnology can be applied to many kinds of surfaces, whether they are used in transportation, building, leather, wood, plastic, rubber, metal, etc.  When applied as a coating, nano-coating fills a ceramic molecule into the capillary of the object’s surface, which then becomes a transparent nano-protected film as a coating on the surface.  The nano-coating technology can be applied to a wide range of products and materials without changing the look or feel.

How is it applied?

Spray-on Coating

The technology works by applying a nanometer-thin polymer layer over the entire surface of an item.  It can be applied as a spray-on coating to keep items such as an iPod™ screen from scratching, make paper products waterproof, allow an item to be easily cleaned, and perform other minor modern miracles.

Ionized Gas

P2i nano-coating ionized gas system for hearing aid moisture protection application.

Another application, and one that is better directed to hearing aids, is the use of an ionized gas (plasma), to molecularly bind this layer to the surface in such a way that it will not leach away.  The process offers superior oil and water repellency by reducing the surface energy to ultra-low levels.  This process cannot be sprayed-on and has to be applied in a stand-alone nano-coating system.

Invisible Technology, Visible Results

Nanotechnology As Applied to Hearing Aids

Hearing aids are often subjected to moisture and water penetration, build-up of cerumen and body chemistry that leads to battery contact corrosion and reduced reliability.  All of these factors contribute to “down time” and can compromise warranties and increase repair costs.

As applied to hearing aids, nanotechnology is in the form of a nano-coating of the device and/or its components to protect against moisture.  It acts as a liquid repellent.

This coating is molecularly bonded to the surface material of the hearing aid and is as durable as the material it protects.  However, if the surface of the hearing aid is removed (not normally expected unless there is excessive wear), the surface coating is removed as well in that area.  Using footwear as an example, the technology will last as long as the material it protects.

Several major hearing aid manufacturers currently use nano-coating in production of their hearing aids.  But, keep in mind that not all nanotechnology applied to hearing aids offers the same protection.  Also, some manufacturers apply nano-coating to only select products.  The amount of protection depends on the application used, and varies as the technology continues to evolve.  Additionally, some nanotechnology has been directed toward specific components of the hearing aid while others are applied to the entire device – inside and outside.

Nano-coating has the following general design characteristics:

1. Protection/reliability.  It provides an amazing level of liquid repellency to whole devices, so that on treated surfaces, liquids form beads and simply roll off.  The benefit is to prevent damage via corrosion.  This improves the reliability of electronic devices that contain delicate, expensive components at high risk of liquid damage through corrosion or electrical failure.
2. Durability.  Due to the chemical bonding with the substrates, the coatings have superior interaction with a variety of substrates.  In addition, the coating itself is durable and maintains its functionality longer because the nanoparticles do not segregate over time (which is a problem with many other moisture-protective coatings on the market).  Liquid repellent nano-coating is physically bonded at a molecular level, so it lasts as long as the material it protects.
3. Thinness.  The coating can range from a few hundred namometers to a few micrometers, depending on the thickness of the base.  Unique ultra-thin protective layer invisibly improves the performance of electronic devices without affecting the product’s look or feel.
4. Lightness.  Typical weights are 0.1 to 1.0 micrograms per square meter.  This is negligible for most applications, except if a polymer or other base is required, then the resulting weight will be essentially that of the base.
5. Variability in transparency.  Transparency can range from completely opaque to highly transparent.
6. Functionality.  Some “smart” action can be provided (changing color with level of illumination, photocatalytic activity, roughness control, thermoluminescence, etc.).
7. Economy:  The coatings typically use economical ceramic nanoparticles, straightforward manufacturing processes using specialized equipment, and produce good coverage with less coating material.

The above properties are merely a guide.  A great deal of customization is possible and the requirements of each application situation need to be examined in detail.

The nanotechnology used most recently by some manufacturers for hearing aids is primarily a coating process from P2i called Aridion™.  As applied to hearing aids, it is described under various marketing names unique to each hearing aid company.  P2i states that Aridion™ is five times more durable than the market-leading moisture coating.  Every component of the hearing aid (inside and outside) is coated with Aridion™ at a nanoscopic level, resulting in a durable liquid-repellent coating.  P2i’s technology employs a special pulsed ionized gas (plasma), which is created within a vacuum chamber at room temperature to chemically attach a nanometer-thin polymer layer over the entire surface of the hearing aid.  During the plasma process, the monomer becomes part of the material itself.  This dramatically lowers the product’s surface energy so that when liquids come into contact with it they form beads and simply run off.  The coating is molecularly bound to the product surface at a nanoscopic level, which means it becomes inseparable from it and is as durable as the material it protects.  Because the coating is one thousand times thinner than a human hair, it is invisible to sight or touch.  It does not affect the look, feel, or acoustic performance of the hearing aid.

So, look for an increased use of nano-coating on hearing aids.  But keep in mind that just because a manufacturer uses the technology for some of their hearing aids, it may not apply to all of their hearing aids.  And, not all nano-coating is created equal.

An example of how this technology works can be viewed  at: http://www.youtube.com/watch?v=v1YZF2qr0CI&feature=related