As the fields of bionanotechnologies develop, it will become possible one day to use biological nanodevices such as nanorobots for in situ and real-time in vivo diagnosis and therapeutic intervention of specific targets. A prerequisite for designing and constructing wireless biological nanorobots is the availability of an electrical source which can be made continuously available in the operational biological environment (i.e. the human body).
Several possible sources – temperature displacement, kinetic energy derived from blood flow, and chemical energy released from biological motors inside the body – have been designed to provide the electrical sources that can reliably operate in body (read: "Nanopiezotronics – a pathway to self-powering nanodevices").
Recently, the conversion of mechanical energy to electricity on the nanoscale has been successfully demonstrated by using acoustically actuated nanogenerators based on piezoelectric zinc oxide nanowires by Zhong Lin Wang's group (see: "Nanoscale power plants"). These nanogenerators can be used to drive many kinds of nanodevices, but their output powers needs to be further improved to meet the power requirement (at least 1 µW) of biological nanorobots.
Light-harvesting by photovoltaic cells has been conclusively demonstrated as an efficient way to create electricity, and many kinds of solar cells have been developed.
Unfortunately, these traditional solar cells cannot be used directly to power in vivo nanodevices because they mainly absorb visible and/or ultraviolet light – which is difficult to penetrate into biological tissues. On the other hand, light that can easily penetrate body tissue such as near infrared light in the wavelength range from 700 to 1000nm cannot be efficiently absorbed by conventional solar cells.
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