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Every injection, biopsy, and infusion relies on a deceptively complex component: the medical needle. More than a simple conduit, small details about how needles are designed directly impact device performance. For OEMs, recognizing the hidden complexities of needle design is critical to avoiding costly rework, improving patient outcomes, and giving their products the best chance to succeed in the market.

Design Decision: Gluing vs. Molding

No matter what type of device you’re designing – infusion set, implantable port access, or continuous monitor – one of the earliest and most important decisions is how to affix the needle: glued or molded?

While gluing needles onto or into your device might seem like the cheapest and easiest option, it comes with significant risks:

• Messy, inconsistent application
• Needle misplacement
• Needle blockage

That’s why gluing is generally reserved for standard, off-the-shelf applications such as syringes, and even then, only when you need high volumes that justify fully automated assembly lines. These systems require expensive, specialized equipment, making them cost-prohibitive for many medical devices.

Molding is typically a better solution for more complex or custom devices. Compared to gluing, molding offers:

• Clean, consistent reliability
• Greater placement accuracy
• Reduced risk of blockage

For example, molding is a more accurate method for manufacturing subcutaneous infusion sets that require precise cannula placement. It’s also preferred for:

• Non-coring Huber needles used to access implanted ports
• IV devices where reliability and safety are paramount
• Diabetic applications such as continuous glucose monitoring, where the needle deploys a sensor instead of injecting medicine
• Specialty designs, such as bent or U-shaped needles for intensive care units or needles with protective sleeves

However, molding needles still introduces key challenges, especially when dealing with miniature applications. For example, if you mold a 0.5-in.-long .016-in. diameter needle onto plastic, the plastic shrinks and the needle is too small to apply compressive force, making it difficult to form a hermetic seal. Proper flow can also be an overlooked challenge: teams naturally focus on flow at the bevel, but it’s just as critical to prevent occlusion at the blunt end.

Whether gluing or molding, designers must carefully address each challenge to ensure reliable, consistent, and accurate manufacturing – and to avoid costly redesigns or patient safety risks later.

Design for Clinical and Patient Outcomes

It’s imperative to understand how needle design impacts clinical and patient outcomes, as a poor design can lead to pain, unreliable performance, and even device failure. Critical design considerations include:

• Orientation: For assemblies requiring directional alignment, needles must be oriented within ±2° to prevent misalignment and ensure reliable fluid transfer
• Shape: The wrong shape can lead to blocked openings that risk patient safety and reliability. For example, non-coring needles should prevent tissue from occluding the opening, but a poor design could cause tissue to block it
• Diameter: Large diameters could cause unnecessary patient pain, while smaller diameters could restrict flow or be prone to blockages. The right gauge balances comfort and performance
• Length: If the needle is too short, medication or sensors might not reach their intended destinations. If it’s too long, there’s a risk of puncturing the wrong tissues. The needle length must match the application and take the entire device into account

All of this means you can’t design needles in a vacuum. Rather, you must adopt a holistic approach to understand not only how the needle affixes to the device, but also how its design impacts clinical and patient outcomes. If your needle doesn’t perform and isn’t comfortable, someone will design a better one.

Design for Manufacturing

Traditionally, OEM engineers design and prototype needles and devices before submitting drawings to their contract development manufacturing organizations (CDMOs). These initial designs often feature innovative concepts that address market needs, but they’re not always optimized for manufacturing. That’s where partnering with a CDMO earlier in the process can accelerate time to market.

An experienced CDMO can work with OEM engineers to ensure designs are scalable and cost-effective to manufacture – potentially saving as many as eight weeks of redesign work plus additional testing. This type of early collaboration is part of a Design for Manufacturing (DFM) approach that dramatically increases the chance of commercial success.

DFM considerations include:

• Hidden complexities: For example, if a needle features a protective sleeve, it requires a manufacturing process that can retract the sleeve, mold the housing, then reapply the sleeve without damaging the needle
• Sharp ends: Needle tips must never touch or bend throughout the production process. Any bend, nick, or dulling of the point increases insertion force, causes discomfort, risks damaging surrounding tissue, and could lead to blockages. Manufacturing processes must be developed to protect the sharp end
• Manual vs. automated processes: Automation eliminates human error and reduces costs, but it’s critical to understand how to load the needle for accurate placement. It’s typically best to automate all takeouts for needles, as manual labor is cost-prohibitive for this task. Vision inspection can be employed to confirm orientation and placement while checking for errors
• Reliability: To produce a reliable product at scale, engineers must understand how to mold parts around the needle, locate the needle, and ensure the opening is free of plastic – while also creating a hermetic seal around it
• Vertical integration: Needles often need stamped or a two-pass grind to create the point. They might require passivation or chemical deburring. However, it’s difficult or impossible to find one company that can do all these things under one roof, which complicates the process by forcing OEMs to juggle multiple suppliers. One solution is to work with a vertically integrated partner who can coordinate every phase of needle manufacturing on their behalf. Doing so eliminates OEM touchpoints, reduces costs, and accelerates time to market
• End-to-End Production: Successful needle manufacturing requires more than insert molding expertise. It involves sourcing, handling, molding, assembly, packaging, and delivery. These details are often overlooked, so when comparing CDMOs, it’s important to ensure they’re quoting identical deliverables. The DFM approach means creating a plan to address each stage of production early in the process, which can easily accelerate time to market by eight weeks or more

Despite appearances, needles aren’t simple to manufacture – and decisions made early in the process often dictate market success. Engineers are talented designers, not medical manufacturers, and they often don’t know what they don’t know about the manufacturing process. That underscores the value of partnering with a CDMO early, as these organizations can offer guidance that helps OEMs design needles that can be manufactured reliably, cost-effectively, and at scale, accelerating time to market and vastly increasing the chance of product success.

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