Perfectly Aligned, Air‐Suspended Nanowire Array Heater and Its Application in an Always‐On Gas Sensor

Abstract

In spite of the excellent thermal properties of nanowires, the typical form factor of unrefined nanowires has restricted their potential use in developing ultralow power electrothermal heater and application device. In this paper, a nanowire array with a perfectly aligned geometric structure on an air-suspended beam is proposed as a novel heating element. By locally confining the generated heat and suppressing beam conduction loss to the substrate, the proposed nanowire array heater overcomes the fundamental power consumption limits of conventional film-type microheaters. As a result, only 2.51 mW of power is required to reach an average temperature of 300 °C, surpassing the performance of state-of-the-art microheaters. The developed nanowire array heater is monolithically integrated with gas sensing nanowires to demonstrate its full capability as an ultralow power gas sensor. The fabricated device successfully detects low concentration carbon monoxide gas of 1 ppm, using less than 5 mW of power. The presented technique offers a promising pathway toward realizing always-on gas sensors driven by battery-powered mobile devices, which will ensure a hazardous gas-free safe environment. In addition, the proposed strategy of employing geometrically structured nanomaterials in the electrothermal heater design enables to lead out their potential thermal capability in many other applications.

Batch Nanofabrication of Suspended Single 1D Nanoheaters for Ultralow‐Power Metal Oxide Semiconductor‐Based Gas Sensors

“…The characteristic features (e.g., material, size, and heater structure) and performance (e.g., response, working temperature, and power) of the 1D nanoheater-based gas sensor were compared with those of recently reported low-power microheater-based gas sensors, including a commercially available device, as listed in Table 1. [4][5][6][7][8][9][10][11] The heater size was defined as the dimensions of the sensor evenly heated to the highest temperature. The presented sensor (Type 2 sensor) has a smaller heater size than the other sensors because of its nanoscale heater and regioselectively grown MOS NWs.…”

“…Comparison of the heater size and efficient heating coefficient (EHC) of the presented sensor (Type 2 sensor) with other recently reported microheater-based gas sensors. [4][5][6][7][8][9][10][11] The detailed sensor information is listed in Table 1. *Ref.…”

“…In particular, electrothermal heaters are widely used to provide thermal energy for operating functional electrical devices, such as light emitters, [1] transparent wearable electronic devices, [2] smart windows, [3] and gas sensors. [4] The application-driven development of electrothermal heaters requires high performance, low power consumption through miniaturization, and cost-effective manufacturing. To this end, the conventional approach is to build a micrometer-sized heater in the form of a suspended plate [4][5][6][7] or bridge.…”

“…[4] The application-driven development of electrothermal heaters requires high performance, low power consumption through miniaturization, and cost-effective manufacturing. To this end, the conventional approach is to build a micrometer-sized heater in the form of a suspended plate [4][5][6][7] or bridge. [8][9][10][11] However, future electrothermal heaters require enhancement in power efficiency by further reducing the size of the heater.…”

Semiconductor Gas Sensors: Materials, Technology, Design, and Application

“…Screen and inkjet printing or drop casting is usually used for thick film deposition, while sputtering is most often used for creating thin films [ 42 , 150 ]. Surface micromachining has been applied aiming to produce uniform and reliable metal oxide (SnO 2 ) gas sensors [ 159 ], while nanofabrication technology has been applied to achieve a nanowire heater with ultralow power consumption [ 160 ]. Figure 7 shows the model of a chemiresistive MOx gas sensor.…”