Microneedle Injection Molding for Real-Time Potassium Monitoring
- 21 hours ago
- 3 min read
Metyos, a Paris-based deeptech medical company, is developing a smart biowearable designed to transform how potassium levels are monitored in patients at risk of dyskalemia — a clinical term describing abnormal potassium levels in the blood.
Dyskalemia encompasses both hyperkalemia (elevated serum potassium) and hypokalemia (reduced serum potassium), two clinically significant electrolyte disturbances frequently observed in patients with renal and cardiovascular conditions. Accurate potassium monitoring remains critical in at-risk populations. However, potassium monitoring in clinical practice remains largely dependent on periodic laboratory blood tests.
Metyos set out to change that.
Their solution is a painless, reusable skin patch that continuously tracks potassium levels and sends real-time data directly to a smartphone and healthcare professionals. By enabling continuous monitoring, the device allows patients to make informed daily decisions while providing doctors with richer, longitudinal data for improved care.
At a Glance
Challenge
Develop a manufacturable microneedle-based polymer component for a smart medical biowearable capable of continuous potassium monitoring.
Solution
Micromolds supported the project with a Design for Manufacturability (DFM) evaluation and precision micro injection molding feasibility trials to validate replication of highly miniaturized microneedle geometries.
Outcome
Demonstrated that micro injection molding can reliably replicate the required microneedle structures, providing increased confidence in scalability for future development phases.
From Concept to Manufacturable Component
At the heart of the Metyos device is a polymer microneedle structure engineered to interact with the skin in a minimally invasive manner. These structures must meet strict dimensional and functional requirements while remaining comfortable and safe for continuous wear.
However, microneedle geometries present significant manufacturing challenges. High-aspect-ratio micro features (as close as 5:1), delicate tip geometries, and extreme sensitivity to material flow make replication particularly demanding. The needles have 0.130mm diameter through holes, meaning mold shut-offs happening at extreme precision.
To evaluate production feasibility, Metyos partnered with Micromolds to explore how micro injection molding of microneedle arrays could support the design and enable scalable manufacturing.
“We were happy to collaborate with the Micromolds team. Without their support and willingness to push the boundaries of what is feasible in the world of injection molding, we could not have launched our ambitious project. Innovation stems from collaboration between like-minded companies, and Micromolds proved to be a strong and highly capable partner in our challenge.”
Engineering the Tooling Strategy
To evaluate production feasibility, Micromolds conducted a comprehensive Design for Manufacturability (DFM) assessment focused on micro-scale process behaviour and structural integrity.
The review addressed:
Polymer flow dynamics within micro-scale cavities
Transition zones between needle base and tip
Feature density and spacing within the array
Demolding forces acting on fragile high-aspect-ratio structures
Complex venting solutions to overcome air traps at the needle tips
Based on this analysis, a precision steel injection mold incorporating a glass insert was developed to support micro-feature replication under controlled molding conditions.
Silica insert was machined with selective laser etching technology. This technology was creatively chosen to enable innovative venting solutions which is not possible with traditional manufacturing methods. The venting channel was made of just a few micrometers at the very tip of the needle which allowed us to mold as sharp as possible needle tips.
The core side of the mold was machined with precision micro milling technology. The most challenging part was not to crash the glass at the shutoff intersections of steel and glass which required us a lot of iterative testing and CNC facing 1 by 1 micron to achieve precision we need. Quite a few glass inserts were smashed and sacrificed for this stage.
A range of materials were selected, as the needles must be rigid and tough and high flow is needed for high aspect micro features, also biocompatibility is a must.
Validating Microneedle Array Replication with Micro Injection Molding
Initial molding trials focused on validating:
Accurate replication of high-aspect-ratio microneedle features
Tip sharpness and structural consistency
Stable cavity filling behavior
Controlled and repeatable demolding
Through iterative refinement of process parameters and tooling configuration, consistent replication of the microneedle array was achieved.
The validation phase confirmed that the geometry could be reliably molded using a steel tool with integrated glass insert and medical-grade polymer, establishing confidence in manufacturability and future scale-up potential.
Supporting the Future of Continuous Health Monitoring
The manufacturability evaluation confirmed that precision micro injection molding can replicate the microneedle geometries required for continuous potassium monitoring applications.
By validating manufacturability early in the development cycle, Metyos gained increased confidence in scalability and a clearer pathway toward future production.
As connected health technologies continue to advance, solutions like the Metyos smart biowearable highlight how innovative device concepts can move from laboratory development toward real-world impact — when supported by the right manufacturing expertise.
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