Fluidic Dispensing Device Multiple Stir Bars
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Solution Overview
Problem
Microfluidic dispensing devices with compact designs, incorporating both a fluid reservoir and an on-board fluid ejection chip, face challenges in remixing fluids due to settling particulate, which can lead to clogging near the ejection chip, and existing solutions for bulk mixing are insufficient to address this issue.
Innovation Solution
A fluidic dispensing device featuring multiple stir bars with rotating paddles, where at least one stir bar has a rotational axis and paddles that rotate to define a rotational area, interacting with an external magnetic field to create a chaotic rotation, effectively remixing both bulk and ejection chip fluids by generating shear stress and ensuring uniform fluid distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact microfluidic dispensing device with on-board ejection chip is used, then device size is reduced, but fluid remixing capability near the ejection chip is insufficient
Solution Approach 1:
The fluid reservoir is divided into a bulk region and an ejection chip region, with separate stir bars assigned to each region. The first stir bar rotates in the bulk region while the second stir bar rotates near the ejection chip, allowing targeted remixing in each zone without requiring a large overall device volume.
Solution Approach 2:
The patent introduces a vertical dimension to the mixing strategy by positioning stir bars at different heights and locations within the reservoir. The second stir bar is specifically positioned to reach into the ejection chip region, creating a multi-level mixing approach that addresses both bulk and localized fluid remixing needs within a compact footprint.
2Device complexity
If a single bulk mixing mechanism is used, then device complexity is reduced, but localized fluid remixing near the ejection chip is insufficient
Solution Approach 1:
The mixing function is segmented into two independent stir bars with different rotation characteristics. The first stir bar provides bulk mixing while the second stir bar with its smaller radius and different rotation speed provides localized mixing near the ejection chip, ensuring both regions receive appropriate remixing without excessive complexity.
Solution Approach 2:
Different mixing characteristics are applied to different regions of the fluid reservoir. The second stir bar is specifically designed with a smaller radius and positioned to create high-shear mixing zones near the ejection chip where particulate removal is most critical, while the first stir bar handles bulk fluid motion.
3Productivity
If stir bar paddles rotate continuously, then mixing effectiveness is improved, but risk of clogging from settled particulate increases
Solution Approach 1:
The stir bars are designed to rotate intermittently rather than continuously, with rotation activated periodically to remix settled particulate. This periodic action disrupts sedimentation patterns and prevents clogging by regularly redistributing particles throughout the fluid without requiring constant rotation that would increase clogging risk.
Solution Approach 2:
The rotation of stir bars with multiple paddles creates turbulent flow patterns and mechanical disturbance that effectively resuspend settled particulate. The chaotic motion generated by the paddles breaking up particle aggregates reduces clogging risk by keeping particles in suspension rather than allowing them to settle and block ejection nozzles.
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 ensures effective remixing of fluids within the reservoir and near the ejection chip, preventing clogging and maintaining fluid quality by creating a uniform mixture through the rotational action of stir bars, addressing the limitations of previous bulk mixing methods.
Implementation Method 1
effectively remixing both bulk and ejection chip fluids by generating shear stress
Implementation Method 2
interacting with an external magnetic field to create a chaotic rotation
Data Source
AI summary
A fluidic dispensing device includes a housing having an exterior wall and a fluid reservoir. The exterior wall has a chip mounting surface defining a first plane, and has an opening in fluid communication with the fluid reservoir. An ejection chip is mounted to the chip mounting surface of the housing and is in fluid communication with the opening. The ejection chip has a plurality of ejection nozzles oriented such that a fluid ejection direction is substantially orthogonal to the first plane. A plurality of stir bars are moveably confined within the fluid reservoir. Each of the plurality of stir bars has a respective plurality of paddles, each having a free end tip. The free end tip of the respective plurality of paddles of at least one stir bar intermittently faces toward the opening as the plurality of stir bars rotate.