# US 8,465,987 B2 · Apparatus, microfluidic chip and method for separating particles using isomagnetophoresis > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,465,987 B2 - Document ID: US8465987B2 - Status: Granted - Kind: B2 - Application number: 12/746,730 - Filed: 2008-11-19 - Published: 2010-10-07 - Granted: 2013-06-18 - Earliest claimed: 2007-12-07 - Assignees: Korea Advanced Institute of Science and Technology - Applicants: Je-Kyun Park; Joo-Hun Kang; Sung-Young Choi; Won-Hye Lee - Inventors: Je-Kyun Park; Joo-Hun Kang; Sung-Young Choi; Won-Hye Lee - Web page: https://patentgrep.com/patent/US8465987B2 ## CPC - B03C 1/32: acting on the medium containing the substance being separated, e.g. magneto-gravimetric-, magnetohydrostatic-, or magnetohydrodynamic separation - B03C 1/288: {disposed at the outer circumference of a recipient} - 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} - B03C 2201/18: Magnetic separation whereby the particles are suspended in a liquid - B03C 2201/26: for use in medical or biological applications - Y10T 436/25375: Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.] - B03C: MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS (separating isotopes B01D59/00; combinations of magnetic or electrostatic separation with separation of solids by other means B03B, B07B) - B01L: CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The present invention relates to a method of separating fine particles by measuring the magnetic susceptibilities thereof using isomagnetophoresis. In a system for separating fine particles using isomagnetophoresis according to the present invention, fluids having different magnetic susceptibilities and fine particles to be measured are introduced into a microfluidic channel to form a magnetic susceptibility gradient, a strong magnetic field is applied to the channel to control the behavior of the introduced fine particles, thus moving the fine particles to respective positions at which the fluids having magnetic susceptibilities identical to those thereof is present. According to the present invention, fine particles having a fine difference in magnetic susceptibility can be separated from each other by measuring the magnetic susceptibilities thereof. ## Claims ### Claim 1 A method for separating fine particles using isomagnetophoresis, which comprises the steps of: (1) introducing two or more fluids having different magnetic susceptibilities from each other into a microfluidic channel to form a magnetic susceptibility gradient therein, wherein each of said two or more fluids is introduced through respective inlets and each of said two or more fluids comprises no fine particles; (2) introducing fine particles to be measured into the microfluidic channel through an inlet different from said respective inlets for said two or more fluids; (3) applying a magnetic field to the microfluidic channel in a direction perpendicular to the microfluidic channel so as to move the fine particles to respective positions at which fluids having the same magnetic susceptibilities as those thereof are present; and (4) allowing the fine particles which have passed through the microfluidic channel to be discharged through different pathways depending on their magnetic susceptibilities, wherein the method is implemented by using a system comprising: inlets for introducing said two or more fluids, having different magnetic susceptibilities, and specific fine particles; a microfluidic channel through which the introduced fluids and fine particles move; a magnetic energy source for applying a magnetic field in a direction perpendicular to the flow direction of the fine particles in the microfluidic channel; a ferromagnetic microstructure for amplifying a magnetic flux density gradient applied by the magnetic energy source; and an outlet for discharging the fine particles which have passed through the microfluidic channel, wherein the fluids moving after being introduced flow with a magnetic susceptibility gradient in the microfluidic channel, the magnetic energy source forms a magnetic field in the microfluidic channel to magnetize the introduced fine particles, and the magnetized fine particles move to respective positions at which the fluids having magnetic susceptibilities identical to those thereof are present. ### Claim 2 (depends on 1) The method of claim 1, wherein the fluids which are introduced in step (1) and the fine particles which are introduced in step (2) are simultaneously introduced into the microfluidic channel. ### Claim 3 (depends on 1) The method of claim 1, wherein the fluids which are introduced in step (1) are aligned depending on the magnetic susceptibility gradient in the microfluidic channel and flow in the aligned state. ### Claim 4 (depends on 1) The method of claim 1, wherein the inlets include: two or more fluid inlets formed at the side of the microfluidic channel, such that the fluids are introduced through the side of the microfluidic channel; and a fine particle inlet formed between the two or more fluid inlets so as to introduce the fine particles therethrough. ### Claim 5 (depends on 1) The method of claim 1, wherein the magnetic energy source consists of an electromagnet or a permanent magnet. ### Claim 6 (depends on 1) The method of claim 1, wherein the ferromagnetic microstructure consists of repeated protrusions. ### Claim 7 (depends on 1) The method of claim 1, wherein the ferromagnetic microstructure is formed at the outside of one side of the microfluidic channel in the lengthwise direction of the microfluidic channel. ### Claim 8 (depends on 1) The method of claim 1, wherein: the inlets, the microfluidic channel and the outlet are formed as patterns in a polymer substrate; the outlet pattern contains different pathways through which the fine particles, having passed through the microfluidic channel, are discharged depending on their magnetic susceptibilities; a polymer thin film is formed under the polymer substrate; the ferromagnetic microstructure is formed under the polymer substrate, the ferromagnetic microstructure being provided laterally under the microfluidic channel; and a glass substrate provided under the polymer thin film and the ferromagnetic microstructure. ### Claim 9 (depends on 8) The method of claim 8, wherein the polymer substrate is made of at least one polymer selected from the group consisting of polydimethylsiloxane (PDMS), polymethylmethacrylate (PMMA), polyacrylate, polycarbonate, polycyclic olefin, polyimide and polyurethane.