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Copper nanorods could be used to enhance body heat transfers

 

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Hollow nanotubes and their cousins nanorods (non-hollow) are two of the more versatile nanotechnologies in the toolkits of today's scientists. These technologies are less than two decades old yet they each have dozens of uses ranging from the esoteric to the purely everyday. And perhaps they can even help reduce our growing reliance upon electricity.

 

Nanotubes have been employed to make molecule-sized transistors, destroy cancer cells, permit fluids to flow 100,000 times faster and make possible visionary technologies like space elevators. Nanorods are solid structures produced by direct chemical synthesis but have applications similar to nanotubes. They are used for detection of bioweapons and in the mass production of high-efficiency solar cells. They have even been used to create metamaterials, strange-acting engineered materials making invisibility cloaks a potential in the near future.

 

Arranging nanotubes and nanorods into regular structures produces unique applications. Sheets of nanotubes have been configured to make artificial muscles. Recently, a French team has developed copper nanorods configured as an array on a flat sheet with the rods standing on end like bristles on a brush. The array functions as the positive electrode for a battery designed to charge and discharge at rates unachievable by traditional battery technologies.

 

With that electrode technology in mind this author's design group, Jet Flyer, speculated on personalized uses of such arrays including cooling the human body during summer heat waves.

 

Keeping Cool and Saving Energy

 

The greatest positive impact a consumer can make on energy conservation is to reduce home air-conditioning usage. World net electricity consumption is projected to more than double from 14,781 billion kilowatt-hours in 2003 to 21,699 billion kilowatt-hours in 2015 and 30,116 billion kilowatt-hours in 2030. One-sixth of the energy produced world-wide is consumed in the home and air-conditioning accounts for more than half of the HVAC electricity consumption in U.S households -- more than 180 billion kiloWatt hours. With recent summer heat waves taking a heavy toll across Europe, usage there and across the globe will likely increase.

 

Improving mechanical air-conditioning efficiency would be one solution, but the root problem is the inefficiency of cooling the human body. Jet Flyer's design concept employs the French team's copper nano-assembly electrode modified to serve as heat exchangers. Copper is an excellent conductor of heat as well as electricity.

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The design employs 300 nanometer copper film plaques affixed with an electrochemically assisted growth of high density copper nanorods. Each exchanger has 50 times the surface area of its base. Applied to the skin in a lotion, the top epidermal layer of the skin becomes populated with millions of nano heat exchangers. The base of the tiny heat exchangers are coated with a lipophilic polymer promoting their sticking to the surface of the skin base-side down.

 

The plaques are easily washed away with the surfactants in soaps.

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To reduce accumulation in waste water the nanorods are coated with magnetite (Fe3O4) allowing for easy magnetic removal during municipal water treatment. This keeps the nano-assemblies from building up in waste water.

 

The human body cools mostly by means of radiative heat and secondarily by evaporative cooling (perspiration). It radiates heat away by dilating capillary blood vessels below the skin's surface. Then the heat transfers to the outer skin (epidermis) and away from the body through the air. However, above 35 degrees C the body switches to almost all evaporative cooling via perspiration. This nano design attempts to improve radiative cooling by improving the efficiency of heat exchange before resorting to evaporative cooling.

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Lotions of various plaque concentrations would be made available in an RCF (Radiative Cooling Factor) scale similar to the sunscreen SPF scale. Higher RCF numbers indicate a higher cooling potential. Highest RCF rated lotions would be utilized to help quickly cool victims of hyperthermia (hyperpyrexia) and heat stroke. One half of all heat-related deaths occur in persons older than 65 years so the elderly would be a prime user of such a lotion, as would athletes, outdoor workers and members of the military.

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If cooling the body could be attained in this manner it would reduce the usage of air-conditioning and thus reduce a major source of energy consumption. The resultant reduced demand on power plants would help decrease the production of greenhouse gases since coal and natural gas are projected to be the fastest growing fuel type for electricity generation during the next twenty-five years.