Graphene-based magnetic hall sensor for fluid flow analysis at nanoscale level

Patent metadata

Field	Value
Publication number	US-9891084-B2
Application number	US-201715467084-A
Country	US
Kind code	B2
Filing date	Mar 23, 2017
Priority date	Oct 14, 2015
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A method of detecting a particle comprises magnetizing a particle using an AC magnetic field; generating an AC voltage in a sensing device having a conductive substantially 2-dimensional lattice structure from the magnetized particle; superimposing a DC magnetic field on the generated AC voltage in the sensing device; and measuring an AC Hall voltage at the sensing device.

First claim

What is claimed is:

1. A method of determining a flow velocity field, comprising:
magnetizing a particle in a fluid flowing in a channel by applying an AC magnetic field to the particle;
measuring a first AC Hall voltage at a first sensing device in the channel, the first sensing device comprising a first graphene element biased with a voltage;
measuring a second AC Hall voltage at a second sensing device in the channel, the second sensing device comprising a second graphene element biased with a voltage;
determining a time-shift between the first measured AC Hall voltage and the second measured AC Hall voltage; and
determining a fluid flow velocity in the channel based on the determined time-shift and a spatial distance between the first sensing device and the second sensing device.

2. The method of claim 1 , wherein measuring a first AC Hall voltage at a first sensing device in the channel comprises,
generating an AC voltage, from the magnetized particle, in a conductive substantially 2-dimensional lattice structure of the first sensing device, and
superimposing a DC magnetic field on the generated AC voltage in the conductive substantially 2-dimensional lattice structure of the first sensing device.

3. The method of claim 1 , wherein determining a time-shift between the first measured AC Hall voltage and the second measured AC Hall voltage comprises cross-correlating the first measured AC Hall voltage and the second measured AC Hall voltage using the equation:
V corr ( Δt )= ∫dt′V 1 ( t′ )· V 2 ( t′+Δt )

where V corr is the correlated voltage, V 1 is a first Hall voltage signal, V 2 is a second Hall voltage signal, and t is time.

4. The method of claim 3 , wherein an average flow speed of the fluid flowing in the channel is indicated by:
UΔY/Δt

where U is speed, Y is distance along the channel, and t is time.

5. The method of claim 1 , further comprising providing a reference voltage to the first sensing device and the second sensing device external to the channel.

6. The method of claim 1 , further comprising measuring a third AC Hall voltage at a third sensing device in the channel, the third sensing device comprising a third graphene element biased with a voltage and being arranged with the first sensing device and the second sensing device to form an array of equally spaced sensors.

7. The method of claim 1 , further comprising determining two-dimensional information related to the particle, the two-dimensional information being determined based on measuring the first AC Hall voltage, measuring the second AC Hall voltage, and measuring a third AC Hall voltage to determine a position of the particle with X and Y resolution.

8. The method of claim 7 , further comprising allying the determined two-dimensional information related to the particle with at least two time-shifted signals from at least two different positions along the channel.

9. The method of claim 1 , further comprising determining three-dimensional information related to the particle, the three-dimensional information being determined based on an inferred vertical position of the particle.

10. The method of claim 9 , wherein the inferred vertical position of the particle is based on a strength of a Hall voltage modulated by a vertical distance between the particle and at least one of the first graphene element and the second graphene element.

11. A method of determining a velocity field, the method comprising:
providing a matrix of cross-shaped graphene sensors in a fluid flow path;
magnetizing a particle in the fluid flow path by applying an AC magnetic field to the particle;
measuring a first AC Hall voltage at a first cross-shaped graphene sensor in the matrix of cross-shaped graphene sensors;
measuring a second AC Hall voltage at a second cross-shaped graphene sensor in the matrix of cross-shaped graphene sensors;
determining a fluid flow velocity in the fluid flow path based on a change in position of the particle in a direction across the fluid flow path and in a streamwise direction with the fluid flow path.

12. The method of claim 11 , wherein determining a fluid flow velocity comprises measuring a time-shift between the first measured AC Hall voltage and the second measured AC Hall voltage.

13. The method of claim 12 , wherein measuring a time-shift between the first measured AC Hall voltage and the second measured AC Hall voltage comprises cross-correlating the first measured AC Hall voltage and the second measured AC Hall voltage using the equation:
V corr ( Δt )= ∫dt′V 1 ( t′ )· V 2 ( t′+Δt )

where V corr is the correlated voltage, V 1 is a first Hall voltage signal, V 2 is a second Hall voltage signal, and t is time.

14. The method of claim 11 , further comprising locating a portion of each cross-shaped graphene sensor of the matrix of cross-shaped graphene sensors external to the flow of the particle in the fluid flow path.

15. The method of claim 14 , further comprising providing a reference voltage signal to each externally-located portion.

16. The method of claim 11 , further comprising inferring a vertical position of the particle to determine three-dimensional information related to the particle.

17. The method of claim 16 , wherein the inferred vertical position of the particle is based on a strength of a Hall voltage modulated by a vertical distance between the particle and at least one of the first cross-shaped graphene sensor in the matrix of cross-shaped graphene sensors and the second cross-shaped graphene sensor in the matrix of cross-shaped graphene sensors.

Assignees

• IBM

Inventors

• Engel Michael
• Neumann Barros Ferreira Rodrigo
• Steiner Mathias

Classifications

• G01R33/072 Primary

  Constructional adaptation of the sensor to specific applications · CPC title

• G01F1/708

  Measuring the time taken to traverse a fixed distance · CPC title

• G01N27/745

  for detecting magnetic beads used in biochemical assays (concerning the assays G01N33/54326; sensors therefor G01R33/1269; automatic analysers therefor G01N35/0098) · CPC title

• G01R33/1269

  of molecules labeled with magnetic beads (magnetic particles for bio assay G01N33/54326) · CPC title

• G01R33/07

  Hall effect devices · CPC title