Low-cost, low-power, heater-free solid state gas sensors based on pulsed self-heated nanostructures

Self-heating and pulsed self-heating operation modes are applied to the use of conductometric gas sensor devices. Self-heating is proven to occur in sensing active layers formed by large arrays of randomly deposited nanostructures, in particular, drop-casted carbon nanofibers. Using this methodology, cheaper gas sensor devices without heater can be fabricated. Moreover, the device power consumption is reduced by self-heating operation by at least two orders of magnitude. A temperature calibration, needed for non-controlled deposition techniques of the active film, is proposed. Self-heating and external heater operation is also compared and found to be equivalent. Pulsed self-heating mode is applied to further reduce the power consumption. A simple processed signal is obtained from pulsed operation, achieving high stability. Gas sensing characteristics are fully studied for both modes for humidity sensing as an example of application.