Aerosol Ionizer with Pulsed UV Charging and MEMS Electrometer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microelectromechanical systems (MEMS) face challenges in efficiently detecting charged particles due to their large surface area to volume ratio, which affects electrostatic and wetting phenomena, and existing technologies struggle to effectively measure and separate aerosol particles based on electrical mobility and size.
Innovation Solution
A MEMS-based charged particle detection system utilizing an ion production chamber with a UV energy source, helium gas, and a scanning electrical mobility sizer, coupled with a capacitive MEMS electrometer and signal processing electronics, which introduces samples perpendicular to the gas flow and uses multiple jets for mixing efficiency, and employs a vibrating reed electrometer with parallel plate capacitors to measure charge and reduce feed-through interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional MEMS are used for charged particle detection, then device miniaturization is achieved, but detection sensitivity and measurement precision deteriorate due to large surface area to volume ratio affecting electrostatic phenomena
Solution Approach 1:
The patent changes the operating parameters of the MEMS electrometer, specifically operating in a high-impedance mode with carefully controlled leakage currents. By adjusting the bias voltages and optimizing the capacitive coupling parameters, the system achieves adequate detection sensitivity despite the small device size. The electrometer operates with input impedances exceeding 10^12 ohms, allowing sufficient charge accumulation from aerosol particles to produce measurable voltage signals.
Solution Approach 2:
The patent uses a capacitive coupling approach where the charge from aerosol particles is transferred to a larger capacitance structure (the electrometer input capacitance) that can be more effectively measured. The MEMS device captures the charge, and this charge is then read out through a optimized capacitive divider network that amplifies the signal for measurement, effectively creating a measurement copy of the tiny charge signal.
2Productivity
If UV ionization is used to charge aerosol particles, then particle charging efficiency is improved, but background ion contamination and measurement noise increase
Solution Approach 1:
The patent extracts only the necessary UV irradiation time required for adequate particle charging, then removes the UV source before measurement begins. The system uses a pulsed UV charging approach where particles are charged for a controlled duration, then the UV source is turned off completely during the measurement phase. This separation of charging and measurement phases eliminates background ion contamination while maintaining charging efficiency.
Solution Approach 2:
The patent performs particle charging as a preliminary action before the actual measurement process. The aerosol stream is charged by UV irradiation in a charging region, then this pre-charged stream is transported to the measurement region where no UV radiation is present. This preliminary charging action ensures particles have sufficient charge for detection without introducing background ions during the sensitive measurement phase.
3Productivity
If multiple jets are used to introduce sample perpendicular to gas flow, then mixing efficiency is improved, but device complexity increases
Solution Approach 1:
The patent introduces the sample aerosol stream perpendicular to the main gas flow direction, creating a cross-flow mixing geometry. Instead of mixing in the same dimension as the flow, the sample is injected from a orthogonal direction, allowing rapid mixing through turbulent diffusion and shear forces. This dimensional approach to mixing achieves efficient homogenization with simpler jet structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enhances the detection of charged particles by correlating particle concentrations with measured charge, improving sensitivity and noise filtering, and effectively separates aerosol particles based on electrical mobility and size, providing accurate particle number size distribution measurements.
Implementation Method 1
an ion production chamber with a UV energy source disposed towards the chamber
Implementation Method 2
light may be used to force electrons from the surface of a solid. This process is generally referred to as the photoelectric effect (or photoelectric emission or photoemission)
Implementation Method 3
a capacitive MEMS electrometer
Data Source
AI summary
A system and method comprising an ion production chamber having an ultra-violet light source disposed towards said chamber, a coated quartz plate between the chamber and the UV source whose coating absorbs incident UV light and ejects electrons into the chamber through the photoelectric effect, a harvest gas disposed to flow through the chamber from an inlet to an outlet, and a jet operable to introduce a sample into the harvest gas flow. In some embodiments the system includes using helium as the harvest gas. Certain embodiments include introducing a sample perpendicular to the harvest gas flow and using multiple sample introduction jets to increase mixing efficiency. In some embodiments the harvest gas and particle sample jet are one and the same. The charge sample may be coupled to a MEMS-based electrometer.