Sometimes, even the best intentions can have unexpected consequences.

Consider, for example, the intent of a Northwestern University engineering team and the eventual outcome of its endeavors. Tasked with reducing the size of a dissolvable temporary pacemaker, the Northwestern engineers began thinking about the extent of a potential scaledown.

“…we figured maybe there’s some ideas to make it [pacemaker] much smaller, and in fact, make it so miniaturized that you can envision the use of multiple pacemakers at different locations across the surface of the heart,” John A. Rogers, Ph.D., explained in a podcast broadcast earlier this year. Rogers is the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering, and Neurological Surgery at Northwestern, and the director of the Querrey Simpson Institute of Bioelectronics.

“…there were a lot of reasons why miniaturization was of interest to us,” he continued, “ and we began to think about that.”

The team’s thoughts ultimately led to the creation of a pacemaker so small, it can fit inside the tip of a syringe. The pacemaker is paired with a small, soft, flexible, wireless, wearable device that mounts to a patient’s chest for pacing control. When an irregular heartbeat occurs, the wearable component automatically shines a light pulse to activate the pacemaker. The short pulses penetrate through the patient’s skin, breastbone, and muscles to control the pacing.

“There’s a crucial need for temporary pacemakers in the context of pediatric heart surgeries, and that’s a use case where size miniaturization is incredibly important,” Rogers noted. “In terms of the device load on the body— the smaller, the better.”

Indeed, smaller is better, particularly in the medtech industry, where demand for non-invasive and diagnostic solutions are prompting micromolders to produce more precise and complex tiny components that were unthinkable just a few short years ago. To dig deeper into micomolding’s growing proficiencies, MPO spoke to more than a dozen experts over the last few weeks. They included:

Sherry Bekier, account manager; Jared Cicio, molding/production manager; Patrick Haney, R&D engineer; Gary Hulecki, CEO; Kyle Kolb, tooling supervisor; Cheyenne Stack, account manager; and Jason Ward, project manager at MTD Micro Molding, a Charleton, Mass.-based micro medical manufacturer of ultra-precision molded components.

Brian Beringer, engineering director at Hoffer Plastics, a custom injection molder in South Elgin, Ill.

Donna Bibber, vice president of corporate development; and Alex Drury, engineering manager at Nissha Medical Technologies’ Isometric Micro Molding Center of Excellence in New Richmond, Wis.

Mark Finn, senior vice president, Healthcare Business Development, Enterprise Sales, and Marketing Strategy; Harald Schmidt, vice president, MHS (Mold Hotrunner Solutions Inc.); and Jörg Schmidt, director of Strategic Marketing at Westfall Technik Inc., a global network of expert plastics manufacturing companies offering end-to-end solutions across the medical, packaging, and consumer goods industries.

Scott Herbert, founder and president of Rapidwerks Inc., a Pleasanton, Calif.-based precision micromolder.

Rob Morin, vice president of Sales and Marketing at PDC (Plastic Design Company), a Scottsdale, Ariz.-based contract manufacturer specializing in micro injection molding. 

Jeff Randall, P.E., vice president and chief technology officer at MRPC, a Butler, Wis.-based fully integrated contract manufacturer of medical device assemblies and components.

Michael Barbella: Please discuss the latest advancements in micromolding technologies for medical applications. 

Brian Beringer: When we talk about advancements in micromolding for medical applications, the driving force is that parts keep getting smaller and more complex at the same time. Non-invasive technologies such as in-home monitoring, wearables, drug delivery and diagnostics are shrinking to improve patient comfort, discretion and wear time. That means designs must integrate more function into less space, often pushing components into true micro territory with thinner walls, tighter channels and functional features within just a few square millimeters. To meet these demands, highly engineered components are molded as single pieces that reduce part counts, eliminate secondary assembly steps and deliver reliable performance at scale. 

Alex Drury: Advancements in simulation continue to improve the design and development of medical micromolded components. As simulation software continues to improve it directly impacts the customer’s ability to bring a ready for market design to final production tooling reducing the need for multiple prototype loops and extensive tooling revisions.  

Donna Bibber: For example, it’s not uncommon to incorporate simulations at the very start of a PFMEA that provides a full first article inspection for the full range of process variables. Simulation software has evolved to the point of extremely useful and accurate theoretical data matching up to full factorial empirical data that provides for a very robust clinical trial submission. 

Mark Finn, Harald Schmidt, Jörg Schmidt: Recent micromolding breakthroughs are enabling levels of precision, repeatability, and efficiency that were previously out of reach for medical applications. MHS/Westfall Technik’s M3 micro-molding platform represents a major step forward. Instead of conventional volumetric shot metering with plunger-driven injection, it leverages ISOKOR technology, a patented three-stage process that fills cavities in milliseconds via melt expansion. This allows direct gating of parts as small as a few milligrams, with zero cold-runner scrap – a crucial cost advantage for expensive resins used in healthcare. The machine is compact, modular, and scalable, designed to run millions of identical parts in fully automated cells with integrated vision and sensor systems. Supporting these hardware innovations is the MHS Micro Lab, equipped with CT scanning, TGA/DSC, and other analytics, enabling molecular-level validation of micro parts. These capabilities align perfectly with medical sector demands: regulatory compliance, biocompatibility, and total process traceability. Together, these advancements give medical device manufacturers the ability to produce ultra-tiny, complex geometries in PEEK, LCP, or bioresorbable materials, all while ensuring consistency, cleanroom compatibility, and scalability from R&D through commercial production.

Patrick Haney: In micro molding, we’re pushing beyond simply selecting a plastic material for a program and are instead working to fully capitalize on what a material can do. That means combining material science with design strategy to get the best possible performance for the specific functional goals of a device. Plastics remain widely used because of their excellent strength-to-weight ratio, but we can optimize that further by looking at the finer details of material behavior. For example, we’re paying closer attention to tacticity to promote weld strength—an approach that helps strengthen features and reduce defect modes. This evolution reflects a shift from just picking a resin to engineering around the specific material characteristics that can make a micro medical device both stronger and more reliable.

Scott Herbert: Smarter, sensor-driven molding: Modern molds use cavity-pressure and temperature sensors tied to systems for monitoring, plus automated switchover and hot-runner balancing. This enables tighter shot-to-shot control, documented quality, and fewer escapes, which is key for ISO 13485/QSR environments. 

• AI/ML in the loop: Recent research and commercial modules use ML to detect deviations in pressure curves and adapt process settings in near-real time—moving toward semi-autonomous, “self-optimizing” molding cells. 
• Conformal-cooled tooling (AM inserts): Additively manufactured, conformal cooling channels are cutting cycle times, improving temperature uniformity, and reducing warpage—especially valuable for thin-wall micro parts.
• Micron-level metrology at scale: Optical metrology validate internal features and assemblies non-destructively, supporting IQ/OQ/PQ and complaint containment. 
• Process validation rigor: Stronger emphasis on ISO 13485/QSR alignment with robust IQ/OQ/PQ, DOE, GR&R/CpK, and full lot traceability.

Rob Morin: In the past 12 to 18 months, several important advancements have reshaped micromolding for medical applications. First, closed loop process control at the micro scale is now common, using high response electric presses, micro valve gating, and in cavity pressure and temperature sensors. Unlike traditional machine signals, these sensors measure what is happening directly inside the mold cavity, showing exactly when resin fills, packs, and the gate freezes. This real time data allows processors to switch from fill to pack at the correct moment on every shot, which dramatically improves consistency in thin wall and microfluidic parts.

Second, conformal cooled inserts made with metal additive manufacturing are improving thermal management. Instead of relying on straight, drilled cooling lines, conformal channels can curve and wrap tightly around microfeatures, keeping cavity temperatures uniform. The result is shorter, more stable cycles without introducing stress or dimensional drift.

Finally, hybrid toolmaking methods that combine micro EDM, femtosecond laser texturing, and precision hard-milling deliver sharper edges and burr free micro features. Together, these innovations are enabling cleaner knit lines, more reliable ultra-thin walls, and consistent lumen geometries. These capabilities directly improve the performance of drug delivery devices, microfluidic cartridges, and minimally invasive surgical tools.

Jeff Randall: Micromolding has benefitted from several technological improvements including processing controls, process monitoring, smaller in-mold sensors, faster reacting sensors and controls, improvements in thermal management, mold treatments and coatings, moldmaking/machining capabilities, laser machining, and additive manufacturing.

Barbella: What are customers demanding/desiring from their micromolded parts?

Sherry Bekier: Developing micro molded medical devices is a complex process with inherently long lead times. By the time customers reach us, they’ve usually completed prototyping and are moving into production development. At this stage, they expect most design features to remain unchanged, since design iterations would require redoing costly and time-consuming testing steps. To help minimize delays and ensure a smoother path to market, we strongly encourage companies to begin feasibility discussions with MTD as early as possible in their development process.

Drury: Customers continue to push the limits of component design with long thin-walled features, with the added challenge of scaling tooling and process solutions to high volume production at an affordable cost target.

Bibber: Not only do customers demand this as micromolding becomes the enabling component of the device, micromolding suppliers must demand extreme precision of all parts of the DfM process. Generally speaking, this includes mitigating risks in material lot to lot variation; mold building shut offs and automation fixtures to tolerances of one resolution beyond that of the micromolded part or assembly tolerance; processing equipment variation; gage R&R variation <10% of the overall tolerances; and designing and monitoring environmental factors to be < 10% of tolerance.

Finn, Harald Schmidt, Jörg Schmidt: Medical device manufacturers today are raising the bar for micromolded components. Above all, they expect consistency at the micron scale—parts with tolerances below 10 µm (8th the diameter of a human hair) that can be reproduced millions of times without dimensional drift. Customers demand clean, flush gate vestiges and runner-free molding, since any excess material or surface blemish can compromise function in a high-precision device. Material integrity is also non-negotiable. Sensitive, high-performance polymers like PEEK, LCP, POM or PEI must not undergo shear or thermal degradation during processing, as even small molecular changes can impact biocompatibility or mechanical performance. A breakthrough in micro-molding that solves the inherent problem with melt residence time can be found in the patented technology of the M3. (A technical white paper is available at the MHS website.) Customers also emphasize scalability: they want a smooth, validated transition from prototype to high-volume production without starting over on process parameters or tooling. Quality assurance is another key expectation—medical customers increasingly require digital traceability of every cycle, with in-line metrology and vision systems verifying critical dimensions. Finally, sustainability and cost control are part of the equation. With no room for material waste in expensive resins, customers look for processes to cut cold-runner scrap and improve yield. In essence, customers are asking for perfection at scale: every part identical, every cycle controlled, every material property preserved—all delivered through an efficient, cleanroom-ready system.

Herbert: Ultra-tight tolerances and stability (micron-scale features, repeatable DoE-proven windows). 

Zero-flash, clean edges, burr-free gates, and robust knit lines for fluidics and drug-delivery mechanisms.

Cleanroom production (ISO 7/8), material/device traceability, and complete validation packages with cavity-pressure signatures attached to lots.

Sterilization compatibility (EtO, gamma, e-beam, steam) and biocompatibility documentation for contact/implant use.

Shorter lead times and supply-assurance, ideally via automation and lights-out inspection.

Morin: Medical device customers are raising their expectations for micro molded parts in three key areas. First, they require repeatable dimensional capability down to the single digit micron level. This level of precision is critical for functional fits, controlled fluid flow, and optical performance. Second, customers demand high quality surfaces with low particulate levels, controlled roughness, and tailored wettability to improve fluid handling. Third, there is a strong push for integration. By combining multiple functions into a single part through the overmolding of metals or radiopaque elements, incorporating living hinges, or embedding alignment features, manufacturers can simplify assemblies and reduce costs.

Beyond the part itself, customers also expect robust documentation and quality systems. This includes lot traceability, complete OQ and PQ data packages, and cleanroom discipline that supports rapid design history file and device master record build out. Meeting these requirements helps accelerate regulatory approvals and reduces the risk of costly redesigns later in the program.

Randall: One of the most misunderstood issues with micromolded parts is tolerancing. When micro features enter the picture, there generally is not much allowance for manufacturing tolerances. There are many contributors to dimensional variation including material properties, lot-to-lot variation of the material, process variation, cavity-to-cavity variation, and machining tolerances. Designers need to work closely with their micro-molders to understand the sources of variation BEFORE the design is finalized—maybe there is a way to achieve the same function by using features that are less vulnerable to these variations.

Cheyenne Stack: It’s not just about what customers want from their micromolded parts—it’s about the entire process. From the start, our customers appreciate open feedback on DFM and thoughtful material recommendations that set the stage for success with complex micro designs. They count on MTD not only for the exceptional product quality that comes from our advanced tooling capabilities, but also for the clear, transparent communication that guides them through every step of the project. We’re relentless about getting the part right, no matter how challenging it is. With strong problem-solving skills and a dedicated team, MTD ensures each product makes it across the finish line—through validation and into production. 

Jason Ward: Customers have been chasing the technical limits of plastic with part designs, ranging from dead sharp features for ideal tissue fixation, complete optical clarity, and completely flashless molding. As features have become smaller and more complex, we’ve needed to iterate and develop new methods to both manufacture and inspect these parts, pushing the boundaries of what’s possible with fabrication and inspection.

Barbella: What are the most critical design considerations for medical device micromolding?

Beringer: One of the most critical considerations is simple, but important: making sure your part design and expectations are suited for micromolded parts rather than conventional injection molding. Part designs that work well at conventional scale can’t just be “shrunk down” and expected to perform the same way. Factors like wall thickness, tolerances and material flow behave differently in micro applications.

Material choice comes first. The most critical design decisions in medical micromolding start with the resin. It must retain performance at micro scale and in the intended environment. That means confirming drying, melt stability and shrink behavior at the required wall thickness, and aligning biocompatibility and sterilization with what the resin can truly handle. If the material cannot fill thin sections or hold features over time, everything downstream will struggle against physics.

Part design comes next. Design for Manufacturability (DFM) should be a front-end activity, not a late-stage checkbox. Our goal is to engage with our customers early to ensure the tolerances are achievable at production scale and if they can be maintained repeatably. Control wall thickness because tiny changes swing flow, cooling and warp. Simplify complex geometries where possible or add features that guide flow and cooling. Plan handling, inspection and assembly strategies so delicate surfaces survive the full process.

Important consideration must be given to tooling for consistent micromolded components Investing upfront in accurate, comprehensive tooling sets the stage for smoother scale-up and long-term performance. Balancing filling across cavities minimizes variation, while gate and vent strategies protect delicate features from shear. Careful cooling design keeps cycles stable, and the right steels, coatings and ejection methods prevent marks on intricate details. 

Aligning material selection, part design and mold design through DFM from the start lowers risk, shortens validation and allows programs to scale without redesign. The payoff is micromolded parts that meet tolerances with confidence, perform reliably and achieve lower total cost over the product lifecycle.

Drury: Traditional molding guidelines still apply to micromolded components generally and we suggest customers still adhere to them when designing components.  Typically design advice for customers is to start aggressively with feature sizes and wall sections as it pertains to device performance, which in turn, allows them to stand out in the market.  Historically, we have had to encourage customers to push the envelope and be open minded on what they feel is possible in a molded part to differentiate their devices.  There are often occasions where a parallel path, more complex design option leads to large commercial gain for customers. 

Finn, Harald Schmidt, Jörg Schmidt: Designing for medical micromolding requires an awareness of both material behavior and process realities at the microscale. The first priority is direct gating: ensuring the part can be filled without cold runners or secondary operations that might leave contamination or burrs. Gate placement must support rapid and uniform cavity filling and avoid stress points (isotropic conditions). Designers must also consider parting line integrity, since even the faintest mismatch or flash can render a device unusable in high-precision medical assemblies. Wall thickness is another critical factor—micro features may not fill properly if the melt freezes off or shrinks. High-speed, high-velocity injection solves this. Material selection is tied closely to design. High-performance polymers like PEEK or bioresorbables require geometries that minimize sharp corners and allow even flow under delicate processing conditions, whereas LCP is ideal for thin-wall part features. Tolerances must be realistic: while machines like the M3 achieve micron-level accuracy, designs should allow for slight shrinkage, controlled by proper cooling layouts. Though it must be noted that the high-speed, high-pressure ISOKOR process found in M3 micro-molding machines guarantees virtually no shrinkage. Designers must also plan for automation compatibility, since parts are typically handled by robotic systems and verified through automated vision inspection. Finally, regulatory considerations loom large—design documentation must support validation, traceability, and risk management under standards such as ISO 13485. A thoughtful upfront design dramatically reduces downstream risks in medical micromolding projects.

Herbert: Material-led DfM: Choose resins for sterilization route, lubricity, and creep/fatigue (e.g., PEEK vs. PLLA/PLGA). Validate moisture sensitivity and thermal history limits for bioresorbables.

• Gating and flow: Sub-gates/valve gates placed to minimize knit lines across functional features; extremely fine vents (on the order of a few ?m) to avoid burn/shorts.
• Thin-wall stability: Use conformal-cooled inserts to flatten temperature gradients; simulate shear/temperature to preserve molecular weight (especially resorbables). 
• Ejection/handling:Gentle ejection (vacuum, stripper plates, air assist); plan for automated micro-part handling and packaging—human handling often isn’t viable.
• Metrology plan: Upfront micro-CT strategy for “impossible-to-touch” dimensions; align with IQ/OQ/PQ evidence and control charts.
• Traceability & cleanliness: ISO 13485 UDI/lot control, material certificates, and documented cavity-pressure bands.

Haney: When developing micro molded components, it’s natural for customers to focus first on the device’s application requirements—that’s what the part ultimately needs to achieve. At the same time, considering manufacturing requirements early on is just as important, because a design that’s extremely difficult to mold may not be scalable in production.

Micromolding brings unique challenges, so the best results come when both application and manufacturing needs are addressed together from the start. If mating components are already fixed and the micro part has to fit into very tight constraints, it can create a more complex DFM situation. We’re experienced in tackling those situations, but outcomes are even better when there’s room for flexibility, open discussion, and collaboration on options.By weighing design functionality alongside manufacturability, we can work together to create parts that not only meet the device’s performance goals but can also be reliably produced at scale.

Gary Hulecki: At MTD Micro Molding, we’re frequently challenged with producing highly complex geometries within extremely tight tolerances. For inspecting internal or encapsulated features, CT scanning has long been essential, providing critical insight where conventional tools fall short. However, CT scanning is often time-intensive, requiring lengthy data acquisition and reconstruction processes, along with significant manual preparation, especially when high resolution is needed. To address these limitations and accelerate our inspection workflows, MTD has invested in a state-of-the-art 5-axis optical metrology system capable of ultra-precise surface-level measurements, including both shape and surface roughness analysis. This advanced system enables comprehensive measurement planning, simulation, and automated execution, eliminating the need for deep metrology expertise or even the need for physical part availability in the early stages.

By significantly reducing the complexity of fixture design and setup, the focus shifts from how a feature can be measured to how quickly can we complete the measurements. This reduces the cost and time associated with inspecting challenging geometries, reinforcing MTD’s commitment to precision, efficiency, and innovation in micro manufacturing.