Wearable heater made by modifying Kevlar fabric with nanowires
Sometimes
nothing feels better on stiff, aching joints than a little heat. But many
heating pads and wraps are rigid and provide uneven warmth, especially when the
person is moving around. Researchers have now made a wearable heater by
modifying woven Kevlar fabric with nanowires that conduct and retain heat.
Even at rest, the human body produces a lot of heat,
but most of this warmth dissipates to the air and is wasted. Coldweather
clothing is often made from materials that keep heat close to the body, offering
thermal insulation. For even more warmth, scientists have tried coating
textiles with metallic nanowires that can be heated with a small battery.
However, researchers are still searching for a material that provides good
thermal conductivity and insulation while being safe, inexpensive, durable and
flexible. Hyung Wook Park and colleagues wondered if they could make a wearable
heating device by incorporating metallic nanowires into Kevlar, the famous
bullet-proof fibre used in many types of body armour.
To make their wearable heater, the team grew
copper-nickel nanowires bet-ween two Kevlar sheets. They filled in the spaces
between the nanowires with a resin containing reduced graphene oxide to
encourage uniform heating. Applying a low voltage (1.5 volts) to the composite
material caused a rapid and uniform increase in surface temperature to 70°C – a
typical “high” setting on a heating pad.
In another experiment, the team showed that the
material acted as a thermal insulator by reflecting infrared radiation emitted
from a hot plate set at human body temperature. The fabric was strong,
flexible, breathable and washable, while still absorbing impacts similar to
regular Kevlar. In addition to wearable heat therapy, the new material could be
used to make heated body armour for police and military personnel in cold
climates, the researchers say.
[Nano Lett.; DOI: 10.1021/acs.nanolett.8b02408]
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