Technology overcomes surface tension

Edited by the Engineeringtalk editorial team May 2, 2007

After surface discharge treatment, tiny catheter tubing in hospital wards will continue to flow with medicines and glued surfaces will remain secure.

Surface tension keeps pond-skating insects from sinking and soap bubbles from popping.

However, in other areas of life it can cause adhesive contact surfaces to fail, medical tubing to block - and worse.

Danish company Tantec provides the perfect solution with its plasma surface discharge technology.

Untreated catheter tubing delivering liquid medicines to the human body may behave as if completely blocked, with possibly fatal consequences.

Untreated glued surfaces may later break apart.

The solution is to pre-treat surfaces to reduce the surface tension of the liquids with which they come into contact.

After surface discharge treatment, tiny catheter tubing in hospital wards will continue to flow with medicines and glued surfaces will remain secure.

Tantec focuses on the treatment of three-dimensional surfaces, particularly plastics.

The treatment process can also be used to prepare surfaces before painting.

This improves the adhesion of the paint to the material's surface.

Tantec's Vacuum Plasma treatment, VacuTEC is a widely used technique for surface modification in the medical device and automotive industry.

It can be used to clean surfaces and remove organic residues, or to promote adhesion before painting, lacquering, printing, electroplating or adhesive bonding.

Materials can be modified or "surface engineered" to change the surface properties without affecting the bulk material.

VacuTEC Plasma treatment is a low-temperature process ranging between 40-120C, thus avoiding any thermal damage.

The process can induce nonthermally activated surface reactions, causing surface changes that would not normally occur with molecular chemistries at atmospheric pressure.

These properties open up new opportunities for materials and products.

VacuTEC Plasma treatment is conducted in a controlled environment inside a sealed chamber, which is maintained at a medium vacuum, usually 2-10mbar.

The gas is energised by an electrical high frequency field, typically 20-30khz.

The components to be treated are usually electrically conductive or isolated.

The volatile plasma by-products are evacuated from the chamber by a vacuum pump, and, if necessary, can be neutralised in an exhaust scrubber.

The VacuTEC Plasma process avoids damage to materials, as it is a controlled, low-temperature process with low energy densities.

Plasma energy is highly efficient because the vacuum pressure reduces the occurrence of recombination, and increases the mean free path length of the particles resulting in higher ionic kinetic energies.

In the controlled environment of a vacuum, high adhesion effects can be achieved with the careful selection of the plasma process parameters.

When the product that requires treatment has been applied to the holding fixture, the VacuTEC is activated.

The fixture is then drawn into the chamber, the chamber door slides down automatically and the process starts.

The air is evacuated from the chamber through a vacuum valve.

The plasma is then discharged and is active for about 30 seconds, after which air is blown into the chamber, the door opens and the fixture slides out again.

The whole process lasts for about 120 seconds.

To ensure the best possible wetting and adhesion results, the coating, adhesive or paint has to be applied soon after the plasma treatment process.

VacuTEC comes in three standard sizes but can also be customised.

VacuTEC is normally used as a batch process, but it is also possible to integrate the system into an inline process.

The machine's life span is approximately 15-20 years.

Operation of the system is intuitive, and very little maintenance is necessary during its lifetime.