Hydrophobic coatings for diagnostic devices
Blood glucose meters, SpO2 monitors and home diagnostic devices regularly come into contact with blood, sweat, disinfecting alcohol and cleaning solutions. Hydrophobic nano coatings protect the internal circuit board from liquids, helping devices operate reliably and last longer.
Unlike traditional conformal coatings, ultra-thin nano coatings barely change the dimensions, weight or electrical contact capability of components, making them ideal for compact medical devices.
Liquid risks for diagnostic devices
Handheld devices typically have test strip slots, buttons and charging ports where liquids can easily seep in. A single drop of disinfectant can cause contact corrosion, leakage current on sensors or measurement errors. For devices used in hospitals, disinfecting wipe-downs several times a day increase this risk.
How nano coatings work
Fluoropolymer-based nano coatings are only 0.1–2 µm thick, creating a low-energy surface that causes liquids to bead up and roll off instead of spreading. The water contact angle typically exceeds 110 degrees. Because the coating is so thin, connectors and spring contacts still conduct normally without masking.
For diagnostic devices, we usually recommend nano coating the entire board rather than applying thick coating locally. This approach simplifies the process, eliminates connector masking and preserves the sensitivity of optical sensors.
Application Engineer, AMS Vietnam
Coating methods and inspection
Dipping or spraying
Solution-based nano coatings can be applied by dipping the entire board or by spraying, and dry at room temperature within a few minutes. This method suits small and medium-sized plants with low equipment investment.
Coating quality inspection
- Check coverage using a fluorescent tracer under UV light.
- Measure the water droplet contact angle on an accompanying test coupon.
- Test by dripping saline and alcohol onto a powered board.
- Perform salt spray or damp heat testing according to product requirements.
Limitations to be aware of
Nano coatings cannot replace enclosure sealing when a device needs prolonged immersion in water. They also have limited abrasion resistance, so they should be combined with gaskets and proper enclosure design to achieve the desired protection rating.
Before coating, boards must be cleaned of flux residue and grease, as thin coatings are very sensitive to surface contamination. A standard cleaning and drying step determines much of the coating's effectiveness.
AMS supplies hydrophobic nano coatings and supports trial coating on sample boards. Contact AMS Vietnam for advice on protection solutions for diagnostic devices.
