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Publication Number
US-10610843-B2
Publication Date
2020-04-07
Expiration Date
Abstract
This disclosure relates to a magnetic mixing apparatus that mixes a sample contained in a mixing chamber using a stir bar, while minimizing the amount of contact between the stir bar and walls of the mixing chamber. In one aspect, the apparatus comprises a ferromagnetic stir bar contained in the mixing chamber, and a driving magnet and a driven magnet located on opposite sides of the mixing chamber. The driving magnet, the driven magnet, and the ferromagnetic stir bar are each capable of rotating about a respective axis. The driving magnet, the driven magnet, and the ferromagnetic stir bar are magnetically coupled such that rotation of the driving magnet induces rotation of the driven magnet and rotation of the driving magnet and the driven magnet induce rotation of the ferromagnetic stir bar. In some embodiments, rotation of the ferromagnetic stir bar within the mixing chamber mixes the sample contained within the mixing chamber.
Core Innovation
The invention relates to a magnetic mixing apparatus configured to mix biological samples and/or lyse cells using magnetic coupling rather than direct mechanical contact. The apparatus includes a driving magnet system and a driven magnet system separated by a gap, where each system rotates about its own rotational axis, and the driven and driving magnet systems are arranged to effectuate magnetic coupling such that rotation of the driving magnet system induces rotation of the driven magnet system.
A stationary mixing assembly is disposed within the gap, and the mixing assembly comprises a mixing chamber with a bounding surface surrounding a mixing chamber volume. The mixing chamber includes a sample transfer channel and a sample exit channel in fluid communication with the mixing chamber volume, and a stir bar contained within the mixing chamber volume includes a ferromagnetic material and induces a magnetic dipole such that the magnetic dipole creates a low-reluctance magnetic circuit.
Disposition of the stir bar between the driving magnet system and the driven magnet system effectuates magnetic coupling between the stir bar, at least one driving magnet, and at least one driven magnet. As a result, rotation of the driving magnet system about the driving magnet rotational axis and rotation of the driven magnet system about the driven magnet rotational axis induce rotation of the stir bar about a stir bar rotational axis. The document further describes options including field focusers, bead-based support within the mixing assembly, and an acoustic mechanism for detecting magnetic decoupling by sensing vibration changes.
Claims Coverage
The document provides one independent claim covering the magnetic mixing apparatus with an integrated magnet-coupled stir bar inside a stationary mixing chamber, plus dependent claims that refine magnetic performance constraints, geometry/material selections, optional field focusers, bead-support features, and an acoustic detection mechanism for magnetic decoupling.
Dual rotating driving and driven magnet coupling across a gap
A driving magnet system and a driven magnet system rotate about respective axes with a gap between them, arranged to effectuates magnetic coupling between each driving magnet and a corresponding driven magnet such that rotation of the driving magnet system induces rotation of the driven magnet system.
Low-reluctance magnetic circuit using a ferromagnetic stir bar disposed between magnet systems
A stationary mixing assembly in the gap contains a stir bar comprising a ferromagnetic material, where disposition of the stir bar between the driving magnet system and the driven magnet system induces a magnetic dipole across the stir bar, creating a low-reluctance magnetic circuit and effectuating magnetic coupling between the stir bar, at least one driving magnet, and at least one driven magnet.
Induced stir bar rotation via coupled rotation of driving and driven magnet systems
Rotation of the driving magnet system about the driving magnet rotational axis and rotation of the driven magnet system about the driven magnet rotational axis induces rotation of the stir bar about a stir bar rotational axis.
Quantified residual flux density constraints for driving and driven magnets
The residual flux density of each of the driving magnet system and the driven magnet system is each between 5000 and 40000 Gauss.
Quantified relative magnetic permeability for the stir bar
The stir bar comprises a relative magnetic permeability between 500 and 1,000,000.
Quantified gap size between rotating magnet systems
The gap separating the driving magnet system and the driven magnet system has a size between 10 mm and 30 mm.
Neodymium magnets as driving and driven magnets
The one or more driving magnets and the one or more driven magnets comprise neodymium magnets.
Acoustic detection mechanism for magnetic decoupling
An acoustic detection mechanism detects magnetic decoupling of the stir bar by sensing changes in the amplitude and/or frequency of vibrations produced by the stir bar during rotation of the driving magnet system.
Across the independent claim, the core coverage is magnetic coupling through a dual rotating driving/driven magnet arrangement across a gap, together with a ferromagnetic stir bar disposed between the magnet systems so its magnetic dipole forms a low-reluctance magnetic circuit that couples the stir bar to the driving and driven magnets and induces stir bar rotation. Dependent features refine magnetic constraints (residual flux density, permeability, gap size), specify neodymium magnets, and add an acoustic mechanism to detect magnetic decoupling via vibration changes.
Stated Advantages
Enables rotation of the stir bar induced by magnetic coupling while using a stationary mixing assembly disposed within the gap.
Creates a low-reluctance magnetic circuit that effectuates magnetic coupling between the stir bar and the driving and driven magnets.
Provides an acoustic mechanism to detect magnetic decoupling of the stir bar.
Documented Applications
Mixing and cell lysis for yeast cells using lysis buffer and, in an example, measuring RT-qPCR Cq values comparable to bench vortex mixing with beads.
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