Magnetic fluid hyperthermia (MFH) is a noninvasive treatment that destroys cancer cells by heating a ferrofluid-impregnated malignant tissue with an ac magnetic field while causing minimal damage to the surrounding healthy tissue. The strength of the magnetic field must be sufficient to induce hyperthermia but it is also limited by the human ability to safely withstand it. The ferrofluid material used for hyperthermia should be one that is readily produced and is nontoxic while providing sufficient heating. We examine six materials that have been considered as candidates for MFH use. Examining the heating produced by nanoparticles of these materials, barium-ferrite and cobalt-ferrite are unable to produce sufficient MFH heating, that from iron-cobalt occurs at a far too rapid rate to be safe, while fcc iron-platinum, magnetite, and maghemite are all capable of producing stable controlled heating. We simulate the heating of ferrofluid-loaded tumors containing nanoparticles of the latter three materials to determine their effects on tumor tissue. These materials are viable MFH candidates since they can produce significant heating at the tumor center yet maintain the surrounding healthy tissue interface at a relatively safe temperature.
Thermoelectric generation
capable of delivering reliable performance in the low-temperature
range (<150 °C) for large-scale deployment has been a challenge
mainly due to limited properties of thermoelectric materials. However,
realizing interdependence of topological insulators and thermoelectricity,
a new research dimension on tailoring and using the topological-insulator
boundary states for thermoelectric enhancement has emerged. Here,
we demonstrate a promising hybrid nanowire of topological bismuth
telluride (Bi2Te3) within the conductive poly(3,4-ethylenedioxythiophene):polystyrenesulfonate
(PEDOT:PSS) matrix using the in situ one-pot synthesis to be incorporated
into a three-dimensional network of self-assembled hybrid thermoelectric
nanofilms for the scalable thermoelectric application. Significantly,
the nanowire-incorporated film network exhibits simultaneous increase
in electrical conductivity and Seebeck coefficient as opposed to reduced
thermal conductivity, improving thermoelectric performance. Based
on comprehensive measurements for electronic transport of individual
nanowires revealing an interfacial conduction path along the Bi2Te3 core inside the encapsulating layer and that
the hybrid nanowire is n-type semiconducting, the enhanced thermoelectricity
is ascribed to increased hole mobility due to electron transfer from
Bi2Te3 to PEDOT:PSS and importantly charge transport
via the Bi2Te3–PEDOT:PSS interface. Scaling
up the nanostructured material to construct a thermoelectric generator
having the generic pipeline-insulator geometry, the device exhibits
a power factor and a figure of merit of 7.45 μW m–1 K–2 and 0.048, respectively, with an unprecedented
output power of 130 μW and 15 day operational stability at ΔT = 60 °C. Our findings not only encourage a new approach
to cost-effective thermoelectric generation, but they could also provide
a route for the enhancement of other applications based on the topological
nanowire.
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