Chen Jinyan, Tran Van-Thai, Du Hejun, Wang Junshan, Chen Chao
State Key Lab of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Micromachines (Basel). 2021 Apr 30;12(5):504. doi: 10.3390/mi12050504.
Airflow sensor is a crucial component for monitoring environmental airflow conditions in many engineering fields, especially in the field of aerospace engineering. However, conventional airflow sensors have been suffering from issues such as complexity and bulk in structures, high cost in fabrication and maintenance, and low stability and durability. In this work, we developed a facile direct-writing method for fabricating a low-cost piezoresistive element aiming at high-performance airflow sensing, in which a commercial pen was utilized to drop solutions of single-walled carbon nanotubes onto tissue paper to form a piezoresistive sensing element. The encapsulated piezoresistive element was tested for electromechanical properties under two loading modes: one loading mode is the so-called pressure mode in which the piezoresistive element is pressed by a normal pressure, and another mode is the so-called bending mode in which the piezoresistive element is bended as a cantilever beam. Unlike many other developed airflow sensors among which the sensing elements are normally employed as cantilever beams for facing winds, we designed a fin structure to be incorporated with the piezoresistive element for airflow sensing; the main function of the fin is to face winds instead of the piezoresistive element, and subsequently transfer and enlarge the airflow pressure to the piezoresistive element for the normal pressure loading mode. With this design, the piezoresistive element can also be protected by avoiding experiencing large strains and direct contact with external airflows so that the stability and durability of the sensor can be maintained. Moreover, we experimentally found that the performance parameters of the airflow sensor could be effectively tuned by varying the size of the fin structure. When the fin sizes of the airflow sensors were 20 mm, 30 mm, and 40 mm, the detection limits and sensitivities of the fabricated airflow sensors were measured as 8.2 m/s, 6.2 m/s, 3.2 m/s, 0.0121 (m/s), 0.01657 (m/s), and 0.02264 (m/s), respectively. Therefore, the design of the fin structure could pave an easy way for adjusting the sensor performance without changing the sensor itself toward different application scenarios.
气流传感器是许多工程领域中监测环境气流状况的关键部件，尤其是在航空航天工程领域。然而，传统的气流传感器一直存在结构复杂、体积庞大、制造和维护成本高以及稳定性和耐久性低等问题。在这项工作中，我们开发了一种简便的直写方法来制造低成本的压阻元件，旨在实现高性能气流传感，其中使用商用笔将单壁碳纳米管溶液滴到薄纸上以形成压阻传感元件。对封装后的压阻元件在两种加载模式下进行了机电性能测试：一种加载模式是所谓的压力模式，即压阻元件受到常压挤压；另一种模式是所谓的弯曲模式，即压阻元件作为悬臂梁弯曲。与许多其他已开发的气流传感器不同，在这些传感器中传感元件通常用作面对风的悬臂梁，我们设计了一种鳍片结构与压阻元件结合用于气流传感；鳍片的主要功能是面对风而不是压阻元件，随后将气流压力传递并放大到压阻元件以实现常压加载模式。通过这种设计，压阻元件还可以通过避免承受大应变和直接与外部气流接触来得到保护，从而可以保持传感器的稳定性和耐久性。此外，我们通过实验发现，通过改变鳍片结构的尺寸可以有效地调整气流传感器的性能参数。当气流传感器的鳍片尺寸分别为20毫米、30毫米和40毫米时，所制造的气流传感器的检测限和灵敏度分别测量为8.2米/秒、6.2米/秒、3.2米/秒、0.0121（米/秒）、0.01657（米/秒）和0.02264（米/秒）。因此，鳍片结构的设计可以为在不改变传感器本身的情况下针对不同应用场景调整传感器性能铺平一条简便的道路。
