Sub-microfluidic Dispensing Tip with Conductive Path and Helium Sparging
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Solution Overview
Problem
Conventional technologies face challenges in accurately and efficiently dispensing microfluidic or sub-microfluidic volumes of liquids, particularly in the range of nanoliters to tens of microliters, due to issues like air bubble buildup, electrostatic deflections, and geometric constraints, which affect the precision and reliability of drop release and placement.
Innovation Solution
The implementation of a dispensing system that uses a helium sparging degassing method, electrostatic fields to mitigate deflections, and a transverse dispensing tip configuration to facilitate the precise dispensing of droplets down to the picoliter range, ensuring reliable and accurate drop placement on target substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dispensing technologies are used for microfluidic volumes, then the system structure is simple, but the dispensing precision and reliability deteriorate due to air bubble buildup and electrostatic deflections
Solution Approach 1:
A conductive fluid path comprising a syringe, conduit, and dispensing tip with conductive coating is introduced as an intermediary component between the reagent reservoir and the target substrate. This conductive path mitigates electrostatic deflections of droplets during flight by providing a grounded reference, thereby improving dispensing precision without requiring complex active control systems.
Solution Approach 2:
The system employs a degassing mechanism that maintains a positive pressure inert atmosphere (e.g., nitrogen or helium) over the reagent in the reservoir and throughout the fluid path. This inert environment prevents air bubble formation and dissolution into the reagent, ensuring reliable droplet ejection and improving dispensing reliability.
2Manufacturing precision
If conventional dispensing methods are used, then the device complexity is low, but the droplet placement accuracy deteriorates in geometrically constrained areas
Solution Approach 1:
The system replaces purely mechanical droplet ejection with a hybrid mechanism combining positive displacement pumping, electrostatic actuation, and conductive field control. This allows precise control of droplet formation, ejection timing, and trajectory, enabling accurate placement in geometrically constrained areas while maintaining manageable system complexity through integrated control.
3Reliability
If air bubble buildup is not addressed, then the system remains simple, but the droplet ejection reliability deteriorates
Solution Approach 1:
The system performs preliminary degassing of the reagent before dispensing operations begin. A degassing mechanism with a positive pressure inert atmosphere is activated to remove dissolved gases and prevent air bubble formation in advance, ensuring reliable droplet ejection throughout the dispensing process without requiring complex real-time bubble detection and removal systems.
4Manufacturing precision
If electrostatic fields are not mitigated, then the system structure remains simple, but the droplet trajectory control deteriorates
Solution Approach 1:
A conductive fluid path and alignment member serve as an intermediary grounded reference that mitigates electrostatic field effects on droplet trajectories. By providing a continuous conductive path from the dispensing tip through the fluid to ground, the system reduces electrostatic deflections without requiring complex active electrostatic shielding or control mechanisms.
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 the stability and precision of dispensing small droplets, reduces air bubbles and electrostatic interference, and allows for accurate placement of droplets in geometrically constrained areas, improving the robustness and accuracy of microfluidic dispensing systems.
Implementation Method 1
pressurizing a reservoir containing a reagent to a degassing high first pressure by providing a static pressure from a helium source over the reagent to degas the reagent
Implementation Method 2
The first pressure in the reservoir is reduced to a low second pressure. The reservoir is vented to ambient conditions. A pump connected to the reservoir is operated to draw the reagent from the reservoir into the pump.
Implementation Method 3
An electric field is generated between the tip and an alignment member so that an electric field gradient is created substantially parallel to the intended droplet trajectory
Implementation Method 4
The reagent is positively displaced through the tip to dispense droplets onto or into the target with the electric field providing a bias that facilitates droplet ejection and release from the tip
Data Source
AI summary
The invention relates generally to dispensing of fluids and, in particular, to methods and systems for dispensing microfluidic or sub-microfluidic volumes of droplets of chemical, biological or other reagents or liquids. Embodiments of the invention have particular efficacy in accurately dispensing small drops having volumes from about 100 nL down into the picoliter range.