Existing nanosensor technologies depend on an external power source (typically a battery) to operate. Chemical and biological sensors based on nanowire or nanotube technologies exhibit observable ultrasensitive detection limits due to their unusually large surface-to-volume architecture. This suggests that nanosensors can provide a distinct advantage over conventional designs. This advantage is further enhanced when the nanosensor can harvest its meager power requirements from the surrounding environment.
Self-powering sensors have been developed that harvest environmental energy supplies using one-dimensional semiconducting nanowire arrays. The self-powering or “batteryless” device can be made small enough to serve in unique situations ranging from military to medical applications. Two prototype platforms were fabricated for batteryless chemical detectors using one-dimensional semiconductor nanowires.
The best currently available nanogenerators can capture, convert, store, and use the energy inherent in piezoelectrics (mechanical/vibration energy), thermo-electrics (heat energy), and photovoltaics (solar and other light energy). Matrix-assisted energy conversion is the next step in eliminating the need for batteries and other external power sources. In this system, polar organic molecules interact with partially exposed nanowires to form a nanoconverter.
This self-powered platform relies on the response of a polymeric film to drive the piezoelectric effect in a nanowire array. The hybrid organic/inorganic platform begins with a nanowire array embedded in an environmentally responsive organic polymer (PVC). This matrix sits atop a support substrate. Both ZnO and boron-doped Si nanowires have proved to be excellent sensor materials. Two sensing platforms were therefore created, based on these two materials. The working principle of the nanosensor on each platform relies on the partial exposure of semiconducting nanowires to target chemical species, and a non-ohmic contact that is necessary for the nanosensors to function.
The sensor converts chemical energy into electrical energy, eliminating an external power source and reducing bulk and weight. The nanosensor responds selectively to a variety of organic molecules such as ethanol, etc. Heat from the surrounding environment can be harvested to power the detector.