# US 2014/0154816 A1 · Devices, systems, and methods for conducting assays with improved sensitivity using sedimentation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0154816 A1 - Document ID: US20140154816A1 - Status: Published application - Kind: A1 - Application number: 13/423,050 - Filed: 2012-03-16 - Published: 2014-06-05 - Earliest claimed: 2010-07-08 - Assignees: Sandia Corporation - Inventors: Ulrich Y. SCHAFF; Chung-Yan Koh; Gregory J. Sommer - Web page: https://patentgrep.com/patent/US20140154816A1 ## CPC - G01N 33/54313: {the carrier being characterised by its particulate form} - B01L 3/50215: {using a float to separate phases} - B01L 3/502753: {characterised by bulk separation arrangements on lab-on-a-chip devices, e.g. for filtration or centrifugation} - G01N 21/6428: {Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" (in vivo A61B5/00; immunoassay G01N33/53)} - B01L 2200/0668: Trapping microscopic beads - B01L 2200/0673: Handling of plugs of fluid surrounded by immiscible fluid - B01L 2400/0409: centrifugal forces - B82Y 15/00: Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors - G01N 15/04: Investigating sedimentation of particle suspensions - 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) - B01L: CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES ## Abstract Embodiments of the present invention are directed toward devices, systems, and method for conducting assays using sedimentation. In one example, a method includes layering a mixture on a density medium, subjecting sedimentation particles in the mixture to sedimentation forces to cause the sedimentation particles to move to a detection area through a density medium, and detecting a target analyte in a detection region of the sedimentation channel. In some examples, the sedimentation particles and labeling agent may have like charges to reduce non-specific binding of labeling agent and sedimentation particles. In some examples, the density medium is provided with a separation layer for stabilizing the assay during storage and operation. In some examples, the sedimentation channel may be provided with a generally flat sedimentation chamber for dispersing the particle pellet over a larger surface area. ## Claims ### Claim 1 A method for conducting an assay comprising: layering a mixture on a density medium in an assay area, wherein the mixture includes a sample and sedimentation particles, wherein the sedimentation particles have a density greater than the density medium, and wherein the assay area is further provided with a separation layer; subjecting the mixture to sedimentation forces such that the sedimentation particles, if formed, travel through the separation layer and the density medium to a detection area; and detecting a presence of an analyte of interest in the detection area. ### Claim 2 (depends on 1) The method according to claim 1, wherein the separation layer comprises providing a material which is denser than the density medium but less dense than the coated particles and positioning the material near the detection area. ### Claim 3 (depends on 1) The method of claim 1, wherein the separation layer and density medium are isolated by hydrophobic interaction. ### Claim 4 (depends on 1) The method of claim 1, Wherein the separation layer and density medium are isolated by high viscosity ### Claim 5 (depends on 1) The method of claim 1, wherein the separation layer and density medium are isolated by charged or water ordering polymer and/or salt interaction. ### Claim 6 (depends on 1) The method according to claim 1, wherein the separation layer comprises providing a material which is denser than the sample but less dense than the density medium and positioning the material between the density medium and the sample. ### Claim 7 (depends on 6) The method of claim 6, wherein said subjecting the mixture further comprises preventing at least a portion of free labeling agent provided in the sample from being transported through the density medium. ### Claim 8 (depends on 1) The method of claim 1, wherein the sedimentation particles include particles having a negatively charged surface. ### Claim 9 (depends on 1) The method of claim 1, wherein said subjecting the mixture to sedimentation forces comprises spinning a substrate, wherein the substrate at least partially supports the mixture. ### Claim 10 (depends on 1) The method of claim 1, wherein the detection area has a first thickness smaller than a thickness of a microfluidic channel containing the density medium. ### Claim 11 (depends on 1) The method of claim 1, further comprising: collecting the sedimentation particles at an end portion of a microfluidic channel, the end portion being narrower than a main portion of the microfiuidic channel, containing the density medium. ### Claim 12 A microfluidic device for conducting an assay, the device comprising: a channel; a sample, contained in the channel, wherein the sample includes sedimentation particles configured to cause an analyte of interest, if present, to bind to the sedimentation particles; a density medium contained in the channel, the density medium having a density greater than a density of the sedimentation particles; a separation layer adjacent to the density medium; and a detection area arranged at an end portion of the channel, wherein the device is configured such that the sedimentation particles move to the detection area through the density medium and the separation layer responsive to sedimentation forces. ### Claim 13 (depends on 12) The device of claim 12, wherein the separation layer comprises a hydrophobic material. ### Claim 14 (depends on 12) The device of claim 12, wherein the separation layer comprises a mineral or organic oil. ### Claim 15 (depends on 12) The device of claim 12, wherein the separation layer comprises a perfluoroalkane fluid. ### Claim 16 (depends on 12) The device of claim 12, wherein the mixture further comprises a labeling agent including quantum dots. ### Claim 17 (depends on 12) The device of claim 12, wherein the sedimentation particles comprise at least one of polystyrene beads, polymethylmethacrylate beads, silica beads, or silica microparticles. ### Claim 18 A device comprising: a microfluidic channel having a main portion with a first width and a first depth and an end portion with a second width and a second depth, wherein the first width is greater than the second width and the first depth is greater than the second depth; a density medium disposed in the microfluidic channel; a sample disposed in the microfluidic channel, wherein the sample includes sedimentation particles configured to be transported to the end portion of the microfluidic channel responsive to sedimentation forces to form a pellet in the end portion. ### Claim 19 (depends on 18) The device of claim 18, wherein the first depth is up to about 10 times greater than the second depth. ### Claim 20 (depends on 18) The device of claim 18, wherein the detection region has a substantially rectangular profile in plan view. ### Claim 21 (depends on 18) The device of claim 18, wherein the detection region has a top depth substantially equal to a bottom depth of the detection region.