Magnetic conduits for localized bead extraction in digital microfluidics
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Solution Overview
Problem
In digital microfluidics, existing systems face challenges in efficiently removing and re-suspending magnetically responsive beads from droplets due to reduced magnetic forces and gradients caused by thick PCBs and the need for careful magnet alignment, leading to inefficient bead retention and fluid removal.
Innovation Solution
Integration of magnetic conduits into the PCB allows for stronger and more localized magnetic forces and gradients, enabling precise positioning of beads without requiring careful magnet alignment, using backing magnets to direct magnetic fields through these conduits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If large magnets are placed underneath the PCB to generate strong magnetic fields, then magnetic force on beads is improved, but magnetic gradient becomes more diffuse and location of bead extraction is ill-defined
Solution Approach 1:
The patent applies local quality by replacing a single large magnet with multiple small magnets positioned at specific locations underneath the PCB. Each small magnet creates a localized magnetic field with a defined gradient, concentrating the magnetic force at precise locations rather than diffusing it across a large area. This allows bead extraction to occur at well-defined locations while maintaining strong magnetic forces.
2Adaptability or versatility
If a thick PCB is used to incorporate multiple layers including embedded heaters, then device functionality is improved, but distance between magnet and droplets increases reducing effective magnetic force
Solution Approach 1:
The patent applies preliminary action by pre-calculating and optimizing the positions of multiple small magnets underneath the thick PCB to compensate for the increased distance. The magnetic field gradients are engineered in advance to achieve the required magnetic force at the droplet location, accounting for the PCB thickness and other incorporated layers.
3Manufacturing precision
If magnets are carefully aligned with the PCB to ensure compatible bead extraction location, then bead extraction precision is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing a single large magnet into multiple smaller magnets arranged in a specific pattern underneath the PCB. This segmentation allows each small magnet to be independently positioned at optimized locations, creating well-defined magnetic gradients without requiring complex alignment procedures. The modular arrangement simplifies the overall device complexity while maintaining high precision for bead extraction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances bead-based extractions and purifications by concentrating magnetically responsive beads on the surface, improving retention and fluid removal efficiency while simplifying the alignment process.
Implementation Method 1
a backing magnet with a magnetic field and where the magnetic conduit is configured for directing the magnetic field through the magnetic conduit to the first hydrophobic surface
Implementation Method 2
magnetically responsive beads
Implementation Method 3
By applying a defined voltage to electrodes of the electrode array, a change of the surface tension of the liquid droplet, which is present on the addressed electrodes, is induced. This results in a remarkable change of the contact angle of the droplet on the addressed electrode, hence in a movement of the droplet.
Data Source
AI summary
A digital microfluidics system with electrodes attached to a substrate and covered by a hydrophobic surface and a control unit for manipulating liquid droplets by electrowetting, providing in close proximity to electrodes a magnetic conduit for directing a magnetic field of a backing magnet to the first hydrophobic surface, providing on the hydrophobic surface a liquid droplet that has magnetically responsive beads moving by electrowetting the liquid droplet with the magnetically responsive beads until a part of which is placed atop of the magnetic conduit, actuating the backing magnet of the magnetic conduit and attracting/concentrating magnetically responsive beads while actuating the backing magnet, moving by electrowetting the liquid droplet with decreased number of magnetically responsive beads away from the specific magnetic conduit. Also disclosed are a method for suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics and a disposable cartridge to carry out the methods.