Dual-channel microcantilever heaters for volatile organic compound detection and mixture analysis

Abstract

We report on novel microcantilever heater sensors with separate AlGaN/GaN heterostructure based heater and sensor channels to perform advanced volatile organic compound (VOC) detection and mixture analysis. Operating without any surface functionalization or treatment, these microcantilevers utilize the strong surface polarization of AlGaN, as well as the unique heater and sensor channel geometries, to perform selective detection of analytes based on their latent heat of evaporation and molecular dipole moment over a wide concentration range with sub-ppm detection limit. The dual-channel microcantilevers have demonstrated much superior sensing behavior compared to the single-channel ones, with the capability to not only identify individual VOCs with much higher specificity, but also uniquely detect them in a generic multi-component mixture of VOCs. In addition, utilizing two different dual channel configurations and sensing modalities, we have been able to quantitatively determine individual analyte concentration in a VOC mixture. An algorithm for complete mixture analysis, with unique identification of components and accurate determination of their concentration, has been presented based on simultaneous operation of an array of these microcantilever heaters in multiple sensing modalities.

High Temperature AlGaN/GaN Membrane Based Pressure Sensors

“…The corrosion resistance of silicon is also limited at high temperatures. This moved the researcher’s interest to higher bang-gap materials like SiC, AlN, Gallium Nitride (GaN) and so forth [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Due to their higher band gap, these materials have excellent thermal stability at higher temperatures.…”

“…The sensitivity for the applied strain for AlGaN/GaN transducers will have higher values than those of silicon, where only the carrier mobility gets modulated with the applied strain. These characteristics of AlGaN/GaN interface make them better suitable material for the sensing applications over silicon [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Silicon carbide based piezo resistive pressure sensors at temperatures up to 600 °C have been studied, however these devices have low output signals and low pressure sensitivity values [ 16 , 17 , 18 ].…”

An AlGaN/GaN Dual Channel Triangular Microcantilever Based UV Detector

“…The achieved responsivity, detectivity, and EQE are comparable to other 2DEG-IDT devices reported earlier. , We attribute this to various factors, such as the lack of a substrate and a suspended MEMS geometry, which lead to a low dark current, as the possibility for substrate conduction is eliminated. The suspended geometry also helps to concentrate the electric field, , leading to a higher photocurrent, which obviates the need for a wide bandgap UV transparent substrate like sapphire for backside illumination and helps with multimodal sensing applications. − Additionally, the tapered channel geometry of the device leads to the concentration of excess carriers generated elsewhere in the high field region near the apex, which can lead to higher photocurrent.…”

“…The demonstrated UV PD employed a mesa structure design, with meander geometry, on a SiC substrate. III-Nitride based microcantilever structures have been demonstrated to be extremely sensitive and versatile. , They have been used to develop various types of sensors to detect ultralow deflection, photoacoustic waves, trace quantities of chemicals, and volatile organic compounds …”

“…III-Nitride based microcantilever structures have been demonstrated to be extremely sensitive and versatile. 42,43 They have been used to develop various types of sensors to detect ultralow deflection, photoacoustic waves, 44 trace quantities of chemicals, 45 and volatile organic compounds. 46 In this work, we report a novel UV PD structure utilizing dual AlGaN/GaN heterostructure based 2DEG channels separated by a semi-insulating GaN layer, shaped in the form of a triangular microcantilever.…”