Pipetting Needle Centering via Auxiliary Cannula Guide
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Solution Overview
Problem
Existing pipetting devices face challenges in accurately piercing septa of sample vessels with small openings and maintaining precise alignment, leading to potential needle damage and inefficiencies in sample handling, especially when using thin needles and tightly packed sample vessels.
Innovation Solution
A pipetting device with a guide arm and centering device featuring conical bevels and circular segment-shaped indentations, which securely grips the sample vessel and ensures precise alignment, allowing a thicker auxiliary cannula to guide and support the thinner pipetting needle, reducing the risk of buckling and facilitating easy septum penetration and withdrawal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a thin pipetting needle is used to access small opening sample vessels, then the needle can reach through the small opening, but the needle becomes unstable and may buckle or bend during septum piercing
Solution Approach 1:
The patent implements nesting by placing the thin pipetting needle inside the thicker auxiliary cannula. The auxiliary cannula acts as an outer protective structure that guides and supports the inner needle, preventing buckling while allowing the thin needle to access small openings. This nested configuration enables the system to combine the advantages of both thin (accessibility) and thick (stability) needles.
Solution Approach 2:
The auxiliary cannula serves as an intermediary structure between the pipetting device and the sample vessel. It provides mechanical support and guidance for the thin needle during the piercing process, acting as a mediator that transfers and stabilizes the piercing action while protecting the fragile needle from lateral forces that would cause buckling.
2Extent of automation
If the pipetting device is moved in a liquid handler with mechanical movement, then sample handling can be automated, but positioning inaccuracies of +/-1 mm occur preventing precise septum centering
Solution Approach 1:
The centering device performs preliminary action by pre-positioning and centering the needle relative to the sample vessel opening before the actual septum piercing occurs. This preliminary centering step compensates for the +/-1 mm positioning inaccuracies inherent in automated liquid handlers, ensuring the needle is properly aligned with the septum center before the piercing motion is executed.
Solution Approach 2:
The centering device enables self-service by allowing the needle to automatically center itself on the sample vessel opening through the geometric design of the centering fingers and conical bevels. This self-centering mechanism eliminates the need for complex external positioning systems and compensates for mechanical positioning errors inherent in automated liquid handlers.
3Stability of the object's composition
If a thick auxiliary cannula is used to guide the thin needle, then needle stability improves, but the auxiliary cannula itself may not fit through small sample vessel openings
Solution Approach 1:
The auxiliary cannula is designed to partially enter the sample vessel opening rather than requiring complete insertion. The cannula extends beyond the opening, providing sufficient guidance and support for the needle during the piercing action without needing to fit entirely through the small opening. This partial insertion approach allows the cannula to have a larger outer diameter for stability while still being compatible with small openings.
Data Source
Figure 1a
Figure 1b
Figure 2a~2b
AI summary
A pipetting device (2) for taking sample liquid from a sample vessel (52) closed at the top with a septum (70), comprising a pipetting needle (4) and an auxiliary cannula (18) for piercing the septum, which is designed for axially guiding the pipetting needle through the auxiliary cannula, is characterized in that the pipetting device comprises a guide arm (6) at the lower end (10) of which an end plate (12) is arranged, which is axially displaceable along the guide arm against a spring resistance, that a centering device (14) is provided which can be inserted into the end plate of the guide arm, and that at least three centering fingers (26) with conical chamfers (34) are formed radially outside in the circumferential direction around the centering device, which form a holding device for the sample vessel and can grip the sample vessel from the outside at the top during operation.This makes it possible, even with a structurally simple pipetting device and very thin pipetting needles, to safely pierce the septum of a sample vessel and easily withdraw the pipetting needle from the septum.