Nano-particle trap using a microplasma

• US 7,728,253 B2
• Filed: 06/29/2006
• Issued: 06/01/2010
• Est. Priority Date: 06/29/2005
• Status: Expired due to Fees

• Current Assignee: Northeastern University
• Original Assignee: Northeastern University
• Inventors: Hopwood, Jeffrey A.
• Primary Examiner(s): Paschall; Mark H
• Application Number:
  US11/478,348
• Publication Number:
  US 20100072391A1
• Time in Patent Office: 1,433 Days
• Field of Search: 219/121.59, 219/121.41, 219/121.43, 219/121.45, 219/121.46, 216/59, 216/60, 15634524-34527, 118/723.R
• US Class Current: 219/121.46
• CPC Class Codes: G01N 15/0656 using electric, e.g. electrostatic methods or magnetic methods by investigating individual particles G01N15/1031, G01N15/12
• CPC Class Codes: G01N 15/075 by optical means
• CPC Class Codes: G01N 21/68 using high frequency electric fields
• CPC Class Codes: H01J 37/32366 Localised processing

Abstract

A system and method employing a microplasma to electrically charge nano- or micro-particles in a gas phase and, subsequently, trap the charged particles within the microplasma using the microplasma'"'"'s built-in electric fields are disclosed. Confinement of the particles allows their density to be increased over time such that very low concentrations of particles can be detected, e.g., by methods such as laser scattering and/or detection of the plasma-induced charge on the particles. Preferably, charge detection methods are employed when nano-particles are to be trapped and detected.

Claims

1. A system for detection of particles in a gas, said system comprising:

a trap comprising a microplasma generator that provides a microplasma, said microplasma configured to receive a sample of said gas so that the particles in the vicinity of said microplasma become trapped and concentrated within said microplasma; and

a particle sensor that measures at least one of the particle count and the size distribution of said particles in said gas.

2. The system of claim 1, wherein said microplasma generator is a low power generator.

3. The system of claim 1, wherein said microplasma generator is portable.

4. The system of claim 1, wherein said microplasma generator comprises a split-ring resonator.

5. The system of claim 1, wherein said microplasma generator is a miniature inductively coupled plasma generator.

6. The system of claim 5, wherein said microplasma generator is a monolithic inductively coupled plasma generator.

7. The system of claim 1, wherein said particle sensor detects collected particles by charge.

8. The system of claim 1, wherein said particle sensor is a scattering laser detector.

9. The system of claim 1, wherein said particle sensor is a differential mobility detector.

10. The system of claim 1, wherein said particle sensor detects collected particles by light emissions from said particles or from atoms and molecules eroded from said particles.

11. The system of claim 1, wherein said system traps and measures particles having a radius less than approximately 50 nm.

12. A method of trapping and detecting particles in a gas phase, said method comprising the steps of:

providing a microplasma generator;

forming a microscopic glow discharge (microplasma) with said generator;

feeding said microplasma with a sample of gas from said gas phase, wherein particles in the vicinity of said microplasma become negatively charged, trapped and concentrated within said microplasma;

detecting said particles trapped within said microplasma to determine at least one of particle count and size distribution of said particles.

13. The method of claim 12, wherein said detecting step comprises the steps of:

applying a voltage waveform to said microplasma; and

collecting charged particles emptied from said microplasma by said voltage waveform on an electrode.

14. The method of claim 13, wherein said waveform is a pulse, a ramp or a sinusoid.

15. The method of claim 12, wherein said detecting step comprises the steps of:

modulating power supplied to said microplasma generator, wherein said microplasma dissipates; and

collecting charged particles emptied from said dissipated microplasma on an electrode.

16. The method of claim 15, wherein, in said modulating step, said power is turned off.

17. The method of claim 12, wherein at least some of said trapped and detected particles have a radius that is less than approximately 50 nm.