Vacuum Coating Technology: The Core Process of Biosensor Electrode Manufacturing

Principles of Magnetron Sputtering Technology

Magnetron sputtering is a physical vapor deposition (PVD) technique carried out in a high-vacuum environment, and it is the mainstream manufacturing process for high-end precious-metal biosensor electrodes. The basic principle is as follows: high-purity argon is introduced into a vacuum chamber and ionized by an electric field to form a plasma; the high-energy argon ions are accelerated by the field and bombard the precious-metal target (such as gold, platinum, or silver), ejecting atoms from the target surface layer by layer, which then deposit uniformly onto substrates such as PET or PI to form a dense nanoscale metal film.

Compared with DC sputtering, magnetron sputtering introduces a magnetic field near the target, confining electrons in spiral trajectories close to the target surface. This greatly increases the ionization efficiency of argon, allowing deposition to proceed at lower pressure and lower temperature. This is critical for biosensor electrodes — high-quality metal films can be deposited on heat-sensitive polymer substrates without damaging them. Huili Biotech's vacuum coating lines control film thickness within tens to hundreds of nanometers, with ±5% accuracy.

Process Advantages over Electroplating and Screen Printing

There are three main manufacturing routes for biosensor electrodes: electroplating, screen printing, and vacuum coating. Magnetron sputtering has become the preferred choice for high-performance precious-metal bioelectrodes thanks to its comprehensive advantages:

• Dense and uniform films: Sputtered atoms deposit with high kinetic energy, forming dense films with low porosity, avoiding the pinholes and internal stress common in electroplated layers, resulting in more stable electrode impedance.
• Strong adhesion: Sputtered particles bond with the substrate at the atomic level; combined with titanium or chromium adhesion layers, the film adhesion significantly exceeds that of electroplating and screen printing, resisting delamination under repeated bending and long-term immersion.
• Uniform thickness: With masks and planetary fixtures, film-thickness uniformity across an entire panel can be controlled within a very small deviation — the physical foundation of batch-to-batch consistency.
• Environmentally friendly: The entire process takes place in vacuum, uses no plating chemicals, and produces no waste liquid, in line with green manufacturing.
• High material purity: High-purity targets (e.g., Au ≥ 99.99%) are used directly as raw material, giving the film a controllable composition with extremely low impurities, ensuring the catalytic activity and chemical stability of precious-metal electrodes.

How Key Process Parameters Affect Electrode Performance

Magnetron sputtering is not a one-touch process. The final electrochemical performance of an electrode is jointly determined by a series of process parameters, including:

• Base vacuum and working pressure: Insufficient vacuum introduces impurities such as oxygen and water vapor, causing film oxidation and increased resistance; the working pressure affects the mean free path of deposited particles and thus the film density.
• Sputtering power and deposition rate: Power determines the deposition rate and particle energy. An excessively fast rate tends to produce columnar-grain defects, while an overly slow rate reduces throughput; a balance must be struck between film quality and production efficiency.
• Substrate temperature and bias: Appropriate substrate heating and bias voltage improve film adhesion and crystalline quality, but the temperature ceiling must be strictly controlled for polymer substrates.
• Film thickness design: Film thickness directly affects conductivity, catalytic surface area, and flexibility. Too thin a film raises sheet resistance and signal noise; too thick a film increases cost and degrades bending performance.

The coordinated optimization of these parameters is the core know-how of precious-metal electrode manufacturing.

Mass-Production Practice for Gold and Platinum Electrodes

Since its founding in August 2023, Huili Biotech (Changzhou) Co., Ltd. has focused on the R&D and manufacturing of precious-metal biosensor electrodes based on magnetron sputtering vacuum coating. Located in Changzhou's Science & Education Town, the company operates sputtered gold, platinum, and silver electrode lines covering blood glucose, ketone, blood gas, CGM, and uric acid/lactate testing.

In mass production, Huili Biotech controls the CV of key electrode performance indicators to ≤5% through target pre-sputter cleaning, in-line film-thickness monitoring, and parameter locking. With an annual capacity exceeding one million pieces, an MOQ of 1,000 pieces, sample lead times of 1–2 weeks, and mass-production delivery in 2–4 weeks, the company provides flexible OEM/ODM services for in vitro diagnostic test-strip manufacturers and sensor developers.

Conclusion

Vacuum coating technology — magnetron sputtering in particular — is redefining the performance ceiling of biosensor electrodes. From film density and adhesion to batch consistency, process accumulation at every step ultimately translates into end-product accuracy and reliability. Huili Biotech provides high-precision precious-metal electrode R&D and mass-production services for blood glucose, ketone, blood gas, CGM, and other testing fields. Partners with custom electrode requirements are welcome to get in touch.