# US 11,079,420 B2 · Surface charge measurement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,079,420 B2 - Document ID: US11079420B2 - Status: Granted - Kind: B2 - Application number: 16/397,925 - Filed: 2019-04-29 - Published: 2020-03-05 - Granted: 2021-08-03 - Earliest claimed: 2011-06-15 - Assignees: Malvern Panalytical Limited - Applicants: Malvern Panalytical Limited - Inventors: Jason Corbett; Fraser McNeil-Watson; Robert Jack - Web page: https://patentgrep.com/patent/US11079420B2 ## CPC - G01R 29/24: Arrangements for measuring quantities of charge - G01N 15/00: Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials - G01N 21/51: inside a container, e.g. in an ampoule (G01N21/53 takes precedence) - G01N 27/447: using electrophoresis - G01N 2021/513: {Cuvettes for scattering measurements} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract The invention relates to methods and apparatus for determining properties of a surface. Embodiments disclosed include an apparatus for measuring a surface charge of a sample, comprising: a sample holder having an opposed pair of electrodes and configured to hold a sample in position in a measurement volume between the electrodes such that a planar surface of the sample is aligned orthogonal to the electrode surfaces; a measurement chamber for containing a measurement liquid and having an open end configured to receive the sample holder to position the electrodes in a preset orientation; a laser light source positioned and configured to direct a laser beam through the measurement chamber between the electrodes and parallel to the planar surface of the sample when the sample holder is received in the measurement chamber; and a detector positioned and configured to detect scattered light from the measurement volume, wherein the apparatus is configured to allow for detection of the scattered light by the detector over a range of distances from the surface of the sample. ## Claims ### Claim 1 An apparatus for determining a zeta potential of a planar surface of a sample, comprising: a sample holder having an opposed pair of electrodes and configured to hold the sample in position in a measurement volume between the electrodes such that the planar surface of the sample is aligned orthogonal to the electrode surfaces; a measurement chamber for containing a liquid electrolyte and having an open end configured to receive the sample holder to position the electrodes in a preset orientation; a laser light source positioned and configured to direct a laser beam through the measurement chamber such that, when the sample holder is received in the measurement chamber, the laser beam is directed through the measurement volume between the electrodes and parallel to the planar surface of the sample; and a detector positioned and configured to detect scattered light from the measurement volume, wherein the apparatus is configured to allow for detection of the scattered light by the detector received from detection points over a range of distances from the planar surface of the sample; wherein the sample holder includes an actuation mechanism supported by a static section, the actuation mechanism configured to adjust a position of the planar surface of the sample, relative to the static section, in a direction normal to the planar surface of the sample, to allow the detector to receive light from detection points over a range of distances from the planar surface of the sample. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein the apparatus is configured to allow relative movement of the laser beam and sample holder for detection of scattered light by the detector over a range of distances between the laser beam and the planar surface of the sample. ### Claim 3 (depends on 1) The apparatus of claim 1 wherein the laser light source is configured to provide the light beam having a width extending over the range of distances from the sample surface. ### Claim 4 (depends on 1) The apparatus of claim 1 wherein the laser light source is configured to provide multiple light beams through the measurement chamber. ### Claim 5 (depends on 1) The apparatus of claim 1 wherein the sample holder comprises a first portion and a second portion, the electrode pair disposed at a distal end of the second portion. ### Claim 6 (depends on 5) The apparatus of claim 5 wherein the actuation mechanism is configured to translate the second portion relative to the first portion. ### Claim 7 (depends on 6) The apparatus of claim 6 wherein the actuation mechanism is configured to translate the second portion relative to the first portion in a direction parallel to the electrode surfaces or orthogonal to the surface of the sample. ### Claim 8 (depends on 6) The apparatus of claim 6 wherein the actuation mechanism comprises a rotatable element for linear translation of the second portion relative to the first portion. ### Claim 9 (depends on 8) The apparatus of claim 8 wherein the rotatable element is a calibrated micrometric screw. ### Claim 10 (depends on 1) The apparatus of claim 1 wherein the sample holder is configured to be located in the measurement chamber in two or more distinct orientations such that the sample is located in two or more respectively different positions relative to the measurement chamber. ### Claim 11 (depends on 10) The apparatus of claim 10 wherein the sample holder is configured such that the electrodes are rotated 180 degrees between first and second distinct orientations. ### Claim 12 (depends on 1) The apparatus of claim 1 wherein the sample holder and measurement chamber comprise correspondingly shaped stepped mating surfaces to provide the two or more distinct orientations when the stepped mating surfaces are engaged with each other. ### Claim 13 (depends on 1) The apparatus of claim 1 comprising a calibration jig configured to hold the sample holder in a predefined position such that the planar sample surface in position between the electrodes is translatable to a predetermined location, relative to the static section of the sample holder, defined by the calibration jig. ### Claim 14 (depends on 1) The apparatus of claim 1, wherein the apparatus is configured to determine a measure of movement of tracer particles suspended in the liquid electrolyte in the measurement volume between the electrodes from scattered light detected by the detector. ### Claim 15 (depends on 14) The apparatus of claim 14 wherein the measurement of particle movement is determined by Doppler analysis of the scattered light. ### Claim 16 (depends on 14) The apparatus of claim 14 configured to determine a measure of zeta potential of the planar surface of the sample by extrapolation of two or more measurements of movement of tracer particles at different relative distances between the laser light beam and the sample surface. ### Claim 17 (depends on 14) The apparatus of claim 14 wherein the apparatus is configured to allow relative movement of the laser beam and sample holder for detection of scattered light by the detector over a range of distances between the laser beam and the planar surface of the sample. ### Claim 18 (depends on 17) The apparatus of claim 17 configured to determine a measure of zeta potential of the planar surface of the sample by extrapolation of two or more measurements of movement of tracer particles at different relative distances between the laser light beam and the sample surface. ### Claim 19 (depends on 1) The apparatus of claim 1 configured to apply an alternating voltage to the opposed pair of electrodes to provide an alternating electric field between the electrodes across the planar surface of the sample during detection of the scattered light by the detector. ### Claim 20 A method of determining zeta potential of a planar surface of a sample, comprising: providing a sample holder having an opposed pair of electrodes with the sample held in position in a measurement volume between the electrodes such that the planar surface of the sample is aligned orthogonal to the electrode surfaces, the sample holder including an actuation mechanism supported by a static section, the actuation mechanism configured to adjust a position of the planar surface of the sample relative to the static section in a direction normal to the planar surface; receiving the sample holder in an open end of a measurement chamber containing a liquid electrolyte, to position the electrodes in a preset orientation; directing a light beam from a laser light source through the measurement chamber such that, with the sample holder received in the measurement chamber, the laser light beam is directed through the measurement volume between the electrodes and parallel to the planar surface of the sample; and detecting scattered light from tracer particles suspended in the liquid electrolyte in the measurement volume with a detector, wherein scattered light is detected by the detector from detection points over a range of distances from the planar surface of the sample. ### Claim 21 (depends on 20) The method of claim 20 configured to determine a measure of zeta potential of the planar surface of the sample by extrapolation of two or more measurements of movement of the tracer particles at different relative distances between the laser light beam and the sample surface.