Moveable Stir Bar for Microfluidic Fluid Remixing
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Solution Overview
Problem
Microfluidic dispensing devices with compact designs, incorporating both a fluid reservoir and an on-board ejection chip, face challenges in remixing fluids due to settling particulate, which can lead to clogging near the ejection chip, and existing solutions do not effectively address both bulk and localized remixing within the device.
Innovation Solution
A microfluidic dispensing device featuring a moveable stir bar with paddles, confined within a fluid reservoir, that rotates to create shear stress and remix fluids both in the bulk region and near the ejection chip, utilizing an external magnetic field to drive the stir bar's rotation and facilitate fluid mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact microfluidic dispensing device with integrated fluid reservoir and ejection chip is used, then device size is reduced, but fluid remixing capability deteriorates due to settling particulate
Solution Approach 1:
The stir bar is designed to be moveable rather than fixed, allowing it to dynamically adjust its position and orientation within the fluid reservoir. This enables the stir bar to effectively reach and remix fluid in both the bulk region and the ejection chip region, resolving the contradiction between compact device size and fluid remixing capability by creating a dynamic mixing system that adapts to different fluid zones
Solution Approach 2:
The stir bar acts as an intermediary mixing element that bridges the gap between the bulk fluid reservoir and the ejection chip region. By positioning and orienting the stir bar to intermittently face toward the first opening in fluid communication with the ejection chip, it mediates the transfer of mixing action from the bulk region to the ejection chip region, ensuring particulates are redistributed before reaching the nozzles
2Quantity of substance
If fluid mixing is provided only in the bulk region of the fluid reservoir, then bulk fluid remixing is achieved, but localized remixing near the ejection chip is insufficient leading to clogging
Solution Approach 1:
The stir bar is designed with asymmetric paddle configuration and moveable positioning to create different mixing intensities in different regions. The paddles are arranged such that when the stir bar rotates, they create enhanced localized mixing near the ejection chip opening while also maintaining bulk region mixing, thereby addressing both bulk and localized remixing needs simultaneously
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
The device effectively remixes fluids within the reservoir and near the ejection chip, preventing clogging and ensuring consistent fluid delivery by distributing particulates and maintaining fluid uniformity through the creation of a shear stress greater than the critical value.
Implementation Method 1
utilizing an external magnetic field to drive the stir bar's rotation
Implementation Method 2
rotates to create shear stress and remix fluids
Data Source
AI summary
A fluidic dispensing device includes a housing having an exterior wall and a chamber. The exterior wall has a first opening. The chamber has an interior space and has a port coupled in fluid communication with the first opening. A stir bar is located in the chamber. The stir bar has a rotational axis. A guide portion is located in the chamber. The guide portion includes a confining member having a guide opening that defines an interior radial confining surface that engages the stir bar, wherein the guide opening facilitates a radial movement of the stir bar in a direction substantially perpendicular to the rotational axis.