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The hydrophilic lubricating coating on the surface of medical catheters is usually only a few micrometers thick. If the coating is too thin, the lubrication effect will be greatly reduced; Too thick, the coating is prone to peeling off, increasing the sensation of foreign objects. Therefore, the thickness control of the surface coating on medical catheters is particularly important. But the catheter is usually a cylindrical curved surface, and the light spot of a regular film thickness gauge cannot be focused. The reflected signal is scattered, and the measured data and signal are also fluctuating.
For this particular situation, we use the Filmetrics F40 optical film thickness gauge. The method of F40 is very simple: connect it to a microscope and shrink the measurement spot to the micrometer level. The advantage of doing this is that although the catheter appears curved in macro view, as long as the light spot is small enough and the relative measurement point is a flat plane, accurate thickness measurement data can be obtained. Optical principle, no need to damage the sample, no need to prepare the sample, just align, click on the measurement case, and the result will be displayed in a few seconds.
We tested four commonly used clinical catheters: super smooth endotracheal tube, nasobiliary drainage tube, sterile catheter, and disposable gastric tube. Below are the test records and pictures organized for your reference.
When using a regular film thickness gauge to measure the coating of a catheter, these problems are often encountered:
Surface scattering:The light spot is too large, and the cylindrical surface reflects the light everywhere, resulting in chaotic signals and poor repeatability.
Contact damage:Using a probe or micrometer to press, the coating is soft and will deform when pressed, resulting in thinner measured data than the actual thickness.
Destruction sampling:Slicing to see the cross-section is accurate, but one tube is destroyed and the efficiency is low.
Difficulty in evaluating uniformitySingle point data cannot represent the entire catheter, but multi-point measurement is time-consuming and laborious.
| project | specification |
|---|---|
| Measuring principle | Spectral reflectance method (non-contact, non-destructive) |
| thickness range | 10 nm to 250 μ m (depending on the material) |
| spot size | Can be as small as a few micrometers (connected to a microscope) |
| repetitiveness | <0.01 μ m (typical value) |
| measure time | <1 second/point |
| Applicable scenarios | Curved surface coating, small areas, soft thin film of the catheter |
If your requirements are single point sampling, R&D verification, and incoming material re inspection, F40 is sufficient and can be manually positioned with a microscope.
If your production line requires batch full inspection, or if you want to see the coating thickness distribution along the entire catheter axis, we recommend F54. It integrates the scanning platform of F50 automatic mapping film thickness gauge, which can preset paths, automatically complete multi-point mapping, generate thickness distribution maps, and make uniformity clear at a glance.
The catheter is round, can F40 measure accurately?
Can. The key is that the light spot should be small enough. After connecting the F40 to the microscope, the light spot can be reduced to a few micrometers, and the measurement area on the surface of the catheter is almost flat, with reflected signals not affected by curvature interference. This is the core reason why we chose the F40 measurement catheter coating.
The coating is transparent, how to measure the thickness?
The spectral reflectance method measures transparent or semi transparent films. When light hits the coating, some of it reflects off the surface, while the other penetrates the coating and reflects off the bottom interface, forming interference fringes between the two beams of light. F40 calculates the physical thickness by analyzing the interference spectrum and combining it with the optical constants (n, k values) of the material.
What is the difference between F40 and F54?
F40 is a manually positioned micro area film thickness gauge, suitable for sampling and research and development; F54 integrates an automatic XY platform on the basis of F40, which can preset multi-point measurement paths and automatically complete batch scanning, suitable for full inspection and uniformity analysis of production lines.
Do measurements require sample preparation or catheter destruction?
No need. F40 is a non-contact optical measurement, where light is applied to the coating surface without contact or damage, and the measured catheter can be used normally. Put it on, test it, and take it away, the whole process takes less than a minute.
If you have the same application requirements, please feel free to contact us for free sample measurement!
We will produce a report, please take a look at the data.
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