Microfluidic devices and associated methods
Inventors
Han, Arum • Wippold, Jose A. • Guzman, Adrian R. • Huang, Can • Stratis-Cullum, Dimitra
Assignees
Texas A&M University • United States Department of the Army
Publication Number
US-12215023-B2
Publication Date
2025-02-04
Expiration Date
2040-10-07
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Abstract
A microfluidic device includes a microfluidic channel formed in the microfluidic device and defined by a floor and a ceiling positioned vertically above the floor, wherein the microfluidic channel includes at least one fluid inlet configured to receive a fluid flow and at least one fluid outlet, and wherein at least one of the ceiling and the floor of the microfluidic channel is sloped relative to a horizontal plane.
Core Innovation
The invention describes microfluidic devices featuring microfluidic channels with at least one fluid inlet and outlet, where at least one of the ceiling or floor of the channel is sloped relative to a horizontal plane. These sloped or curved microfluidic channels enable vertical variation in height along the length of the channel, allowing gradual transitions rather than abrupt step changes.
The problem addressed arises from conventional photolithography-based fabrication processes that typically produce microfluidic channels with fixed vertical heights or stepwise height changes. Abrupt height changes can induce dead volume and impose high shear forces on droplets within channels, causing droplet breakage. Additionally, conventional microfluidic systems struggle with the presence of air bubbles that disrupt fluid flow. Existing macroscale air bubble traps are positioned externally and do not effectively capture air bubbles forming within microfluidic channels themselves.
The innovation includes microfluidic devices with integrated air bubble traps using sloped chambers. The buoyant air bubbles travel upward along the sloped ceiling, accumulate, and can be removed via vacuum chambers defined by gas-permeable membranes positioned vertically above the sloped channels. The use of three-dimensional laser fabrication, particularly two-photon polymerization (2PP), enables the construction of such variable-height and sloped microfluidic channels in a more efficient manner compared to multi-layer photolithography. This sloped design facilitates gradual height transitions useful not only for removing air bubbles but also for manipulating droplets without rupturing or merging them, enabling smoother droplet transitions between layers, devices, or from tubing into devices.
Claims Coverage
The patent contains several independent claims focusing on microfluidic devices with sloped microfluidic channels and vacuum chambers for air bubble removal and fluid manipulation.
Microfluidic channel with sloped ceiling configured to direct air bubbles
A microfluidic device comprising a microfluidic channel defined by a floor and a sloped ceiling relative to a horizontal plane and the floor, with at least one fluid inlet and outlet, coupled to a vacuum chamber having a gas permeable membrane, the sloped ceiling directing air bubbles suspended in the fluid flow towards the membrane to form an air bubble trap.
Microfluidic channel with variable height increasing from inlet to outlet for air bubble trapping
A microfluidic device where the ceiling of the microfluidic channel is sloped such that the vertical height increases gradually from fluid inlet to outlet, exploiting buoyancy to urge air bubbles vertically upwards along the sloped ceiling to form an air bubble trap.
Combined vacuum chamber and sloped microfluidic channel for air bubble removal
A microfluidic device including a vacuum chamber defined by a gas permeable membrane located vertically above the sloped ceiling of the microfluidic channel, forming an air bubble trap, optionally including a vacuum pump to apply negative pressure to transport air bubbles through the membrane into the vacuum chamber.
The independent claims cover microfluidic devices featuring sloped ceilings or floors in microfluidic channels to capture and direct air bubbles towards vacuum chambers with gas permeable membranes, along with configurations to manipulate droplets via gradual height transitions within microfluidic channels.
Stated Advantages
Reduced sample and reagent volumes and reduced time required for laboratory operations due to the high throughput enabled by the device.
Improved stability and reduced droplet breakage or merging by employing gradual height transitions using sloped ceilings or floors rather than abrupt step changes.
Integrated air bubble traps within microfluidic devices allow capture and removal of air bubbles forming in channels, minimizing interference with fluid flow without relying on external macroscale bubble traps.
Fabrication using three-dimensional laser processes such as two-photon polymerization allows efficient production of variable-height and sloped microfluidic channels, overcoming limitations of photolithography.
Documented Applications
Manipulation of droplets in droplet microfluidics for bioassays including merging and compressing droplets without rupture.
Air bubble trapping and removal directly within microfluidic devices to improve fluid flow and device operation.
Vertical droplet transitions between microfluidic layers, devices, or tubing to achieve smoother flow and droplet integrity.
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