Impact of Improved Design on Knudsen Force for Micro Gas Sensor

Abstract

<jats:p>Knudsen force generated by thermally driven gas flow in a microscale structure has been used for gas detection and has shown immeasurable potential in the field of microelectromechanical system (MEMS) gas sensors due to its novel sensing characteristics. In this article, the performances of three kinds of Knudsen force gas sensors with improved isosceles triangular shuttle arm structures were studied. In the first design, the top side and right side lengths were equal; in the second, the top side and bottom side lengths were equal; and for the third, the bottom side and right side lengths were equal. A detailed investigation including gas flow, thermal characteristics, Knudsen force, and coupling effects between the shuttle-heater pairs was conducted using the direct simulation Monte Carlo (DSMC) method and the main mechanisms for gas flow presented were almost the same in this work. However, the second design returned the highest Knudsen force performance. The value increased by 42.9% (P = 387 Pa) compared to the Knudsen force of the original square shuttle arm. The results also demonstrate that the coupling effects become weak toward the right with an increase in the number of shuttle-heater pairs.</jats:p>

Hollow Nanostructures of Ternary Ce1–xCuxO2 for Volatile Organic Compound Sensing

“…Finally, Ce is a very important material for oxygen storage and is largely used in the automotive industry as a catalyst because of its ability to easily adsorb and release oxygen. Herein, as hollow morphology provides increased surface area for adsorption of oxygen, large numbers of the oxygen are trapped on the surface of the hollow structure in the conduction band, which influences the higher response. As a result, more active sites are created on the surface of the hollow structure for the reaction between oxygen ions and low concentrations of formaldehyde.…”

Numerical Investigation into the Flow Characteristics of Gas Mixtures in Knudsen Pump with Variable Soft Sphere Model

“…Equation ( 10) can be transformed into Equation ( 4) for the gas molecular diameter of the VHS model if α = 1. And if α = 1 and ω = 0.5, the representation of the HS model is obtained, see Equation (3). Moreover, for the HS, VHS, and VSS models, the post-collision relative velocities of molecules can be represented by [40]:…”

“…Gas flows induced by temperature gradients are peculiar to rarefied gases and are an interesting research subject in rarefied gas dynamics [ 1 , 2 , 3 , 4 ]. Thermal creep flow is a well-known phenomenon which occurs due to tangential temperature gradients along the channel walls, making gases flow from a low temperature side to a high temperature side without any initial pressure gradient.…”

Thermally Induced Knudsen Forces for Contactless Manipulation of a Micro-Object

“…Therefore, the configuration can be manipulated with a desired application in mind, such as two beams of different temperatures placed close to each other to be used for gas sensor mechanism [ 5 , 6 , 7 , 9 ] and a heated object placed eccentrically inside a closed system to be used for rotational mechanism [ 12 , 13 ]. Furthermore, simple geometrical modifications in the actuator mechanism have shown better performance than conventional ones [ 19 ].…”

“…The above studies [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] proved that thermally induced Knudsen forces can displace an object without physical contact and any moving parts. This displacement is usually repulsive, such as a heated cantilever being deflected away from a colder flat substrate [ 1 , 2 , 8 ].…”