# US 11,077,440 B2 · Methods and apparatus to facilitate gravitational cell extraction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,077,440 B2 - Document ID: US11077440B2 - Status: Granted - Kind: B2 - Application number: 16/460,551 - Filed: 2019-07-02 - Published: 2020-01-23 - Granted: 2021-08-03 - Earliest claimed: 2018-07-17 - Assignees: Agilent Technologies, Inc. - Applicants: Agilent Technologies, Inc. - Inventors: Curt A. Flory; Dustin Chang; Pallevi Srivastva; Rolfe Anderson - Web page: https://patentgrep.com/patent/US11077440B2 ## CPC - B01L 3/502761: {specially adapted for handling suspended solids or molecules independently from the bulk fluid flow, e.g. for trapping or sorting beads or physically stretching molecules} - B01L 3/50273: {characterised by the means or forces applied to move the fluids} - B01L 3/502746: {characterised by the means for controlling flow resistance, e.g. flow controllers, baffles or throttle valves} - B01L 2200/027: for microfluidic devices - B01L 2200/0668: Trapping microscopic beads - B01L 2200/143: Quality control, feedback systems - B01L 2300/0645: Electrodes - B01L 2300/0663: Whole sensors - B01L 2300/14: Means for pressure control - B01L 2400/0457: passive flow or gravitation - B01L 2400/0487: fluid pressure, pneumatics - B01L: CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE ## Abstract The invention relates generally to methods and apparatus that gravitationally transfer cells from a first medium to a second medium. More specifically, the invention relates to a novel microfluidic device. The microfluidic device includes a cell transfer region, a cell settling channel, a waste channel, a cell output channel, and an input medium channel. The cell settling channel, the waste channel, and the cell output channel extend from, are in fluid communication with, and are smaller in cross section than the cell transfer region. The cell output channel is substantially perpendicular to the cell settling channel and to the waste channel. The input medium channel extends from and is in fluid communication with the cell output channel. ## Claims ### Claim 1 A microfluidic device for gravimetrically transferring cells from a first medium to an input medium, the microfluidic device comprising: a cell transfer region; a cell settling channel extending from and in fluid communication with the cell transfer region, the cell settling channel being smaller in cross section than the cell transfer region; a waste channel extending from and in fluid communication with the cell transfer region, the waste channel being smaller in cross section than the cell transfer region; a cell output channel extending downwardly from and in fluid communication with the cell transfer region such that cells in the cell transfer region fall into the cell output channel via gravity, the cell output channel being smaller in cross section than the cell transfer region and substantially perpendicular to the cell settling channel and to the waste channel; an input medium channel extending from and in fluid communication with the cell output channel. ### Claim 2 (depends on 1) The microfluidic device of claim 1, wherein the input medium channel is a first input medium channel and further comprising a second input medium channel extending from and in fluid communication with the cell output channel. ### Claim 3 (depends on 2) The microfluidic device of claim 2, wherein the first and second input medium channels are opposite one another. ### Claim 4 (depends on 1) The microfluidic device of claim 1, wherein the input medium channel comprises an entry portion, the entry portion being nonperpendicular relative to the cell output channel. ### Claim 5 (depends on 1) The microfluidic device of claim 1, wherein the cell settling channel and the waste channel are opposite one another. ### Claim 6 (depends on 1) The microfluidic device of claim 1, wherein the cell settling channel and the waste channel are offset relative to the cell transfer region and to one another. ### Claim 7 (depends on 1) The microfluidic device of claim 1, wherein the cell settling channel extends for at least a cell settling length. ### Claim 8 (depends on 1) The microfluidic device of claim 1, wherein the cell transfer region is configured to divert lower flow laminae of the first medium from the cell settling channel to the cell output channel; and divert upper flow laminae of the first medium from the cell settling channel to the waste channel. ### Claim 9 (depends on 8) The microfluidic device of claim 8, wherein the cell settling channel is configured to allow cells to fall from the upper flow laminae to the lower flow laminae before arriving in the cell transfer region. ### Claim 10 (depends on 1) The microfluidic device of claim 1, wherein: a sensor is in fluid communication with the cell output channel, the sensor being configured to generate an electrical conductivity value of a second medium in the cell output channel, the second medium being a mixture of the first medium and the input medium; a regulator is in fluid communication with the waste channel, the regulator being configured to adjust back pressure of the first medium in the waste channel; and a controller is in communication with the sensor and with the regulator, the controller being configured to control the regulator based on the electrical conductivity value. ### Claim 11 (depends on 10) The microfluidic device of claim 10, wherein the controller is configured to: receive the electrical conductivity value from the sensor; determine a ratio value of the first medium to the input medium in the cell output channel based on the electrical conductivity; and determine whether the ratio value is within a predetermined range. ### Claim 12 (depends on 11) The microfluidic device of claim 11, wherein the predetermined range has an upper limit and a lower limit and the controller is configured to: if the ratio value exceeds the upper limit, open the regulator; and if the ratio value is below the lower limit, constrict the regulator. ### Claim 13 (depends on 10) The microfluidic device of claim 10, wherein: a first pump is in fluid communication with the cell settling channel and a cell culture container, the cell culture container being configured to store cells suspended in the first medium and the first pump being configured to pump the cells and the first medium from the cell culture container to the cell settling channel; a second pump is in fluid communication with the input medium channel and a reservoir, the reservoir being configured to store the input medium and the second pump being configured to pump the input medium from the reservoir to the microfluidic device. ### Claim 14 (depends on 13) The microfluidic device of claim 13, wherein the controller is in communication with the first and second pumps and is configured to control the first and second pumps. ### Claim 15 (depends on 13) The microfluidic device of claim 13, wherein the regulator is in fluid communication with the cell culture container to return first medium from the waste channel to the cell culture container. ### Claim 16 (depends on 10) The microfluidic device of claim 10, wherein the cell transfer region is configured to: divert lower flow laminae of the first medium from the cell settling channel to the cell output channel; and divert upper flow laminae of the first medium from the cell settling channel to the waste channel. ### Claim 17 (depends on 16) The microfluidic device of claim 16, wherein the cell settling channel is configured to allow cells to fall from the upper flow laminae to the lower flow laminae before arriving in the cell transfer region. ### Claim 18 A method for gravimetrically transferring cells from a first medium to a second medium, the method comprising the steps of: pumping, with a first pump, a suspension of cells suspended in a first medium into a cell settling channel of a microfluidic device; pumping, with a second pump, an input medium into an input medium channel of the microfluidic device; sensing, with a sensor, an electrical conductivity of the second medium in a cell output channel of the microfluidic device, the second medium being a mixture of the first medium and the input medium; determining, with a processor, a ratio of the first medium to the input medium in the cell output channel based on the electrical conductivity; adjusting, with a regulator, a back pressure of the first medium in a waste channel of the microfluidic device based on the ratio. ### Claim 19 (depends on 18) The method of claim 18, wherein adjusting the back pressure of the first medium in the waste channel comprises determining, with the processor, whether the ratio is within a predetermined range. ### Claim 20 (depends on 19) The method of claim 19, wherein the predetermined range has an upper limit and a lower limit and adjusting the back pressure of the first medium in the waste channel comprises opening the regulator if the ratio value exceeds the upper limit; and constricting the regulator if the ratio value is below the lower limit.