Tiny little devices traveling in our bloodstream while performing complete blood analysis and monitoring our well-being is the future of implantable biosensors. However, these nanorobots will need to be self-powered and there are two ways for achieving it – either to use a battery or to harvest energy from the environment.
Generating electricity “on-board” is a very attractive option for in vivo medical application because biological systems provide a great medium for converting chemical, thermal, or mechanical energy to electricity ensuring a lifetime operation.
Zhong Lin Wang and colleagues have developed a DC (direct-current) nanogenerator that converts mechanical energy into electricity. The basic principle is to use piezoelectric and semiconducting coupled nanowires (NWs), such as zinc oxide (ZnO). The nanogenerator used in the experiments was 2 mm2 and had a million of nanowires.
This nanogenerator has the potential of directly convert hydraulic energy in the human body, such as flow of body fluid, blood flow, heart beat, and contraction of blood vessels, into electric energy. But for now, a prototype of the nanogenerator is driven by ultrasonic waves through a metal frame suspended in air and creates a 25-35 nA current while submerged in 0.9% NaCl – a normal saline solution.
Reference: “Integrated Nanogenerators in Biofluid”, Nano Letters doi: 10.1021/nl0712567 S1530-6984(07)01256-8