The Leidenfrost effect and superhydrophilic plasma coatings

Recently, thin-film boiling, via the Leidenfrost effect, has been demonstrated as a promising concept for converting thermal energy to mechanical motion. In this 2019 published paper, the authors address two key challenges users face when working with Leidenfrost heat engine levitating rotors and their sustained rotation. Their aim, “to provide new opportunities for novel approaches for heat to motion conversion in extreme environments”.

The initial challenge facing researchers was the replenishment of liquid to achieve continuous operation of the device and the second, to broaden the temperature range and subsequently the stability of the rotor. Their intention was to produce superhydrophilic coatings to the substrate in order to contest the negative effects. The coatings were achieved in part by using Henniker’s HPT-100 system.

Results and further information can be found in our brief summary below;

Leidenfrost heat engine: Sustained rotation of levitating rotors on turbine-inspired substrates.


A Leidenfrost rotor is where a solid component is coupled to a rotating liquid volume using surface tension, and levitated in continuous operation over a turbine-inspired substrate.

The Leidenfrost rotor in this paper consists of a volume of water levitating over a heated turbine-inspired substrate and supporting a thin circular solid glass plate (diagram below).


(image courtesy of


They used two methods to clean a glass plate; rinsing with IPA / DI water and a Henniker HPT-100 plasma system.

“The glass plates were cleaned using two different methods: (1) rinsing with isopropyl alcohol (IPA) and de-ionized (DI) water and then dried using compressed air; (2) plasma-cleaning for 30 s at 100% power (Henniker Plasma HPT-100). The latter method was used to make the glass plate superhydrophilic and, therefore, to enhance its coupling with the liquid.”



(image courtesy of

In the diagram above (b) Is the plasma treated glass plate and only exhibits a faint vapor bubble whereas the others have a more prominent vapor bubble. The formation of a vapor bubble in the motor in this process is unfavourable as it causes liquid redistribution and leads to an unstable plate rotation.

“Although a vapor bubble is still faintly visible under the plasma treated glass plate in Fig. 4(b) (above) , the plate rotation is relatively more stable compared to the untreated glass plate under the same operating conditions. With plasma cleaning, the plate rotation demonstrated no measurable radial or vertical displacement at terminal angular speed. The terminal speed and torque also show a slight increase relative to the IPA and DI water rinsed glass plates (Fig. 5 below)”


(image courtesy of

Fig. 5. Variation of (a) terminal angular speed , (b) torque with temperature for plasma cleaned glass plate compared to a glass plate rinsed with Isopropyl alcohol (IPA) and de-ionized (DI) water. The variation in temperature is ±5 °C.

In conclusion

Stability and temperature were sufficiently altered through the use of plasma cleaning.

“The size of these vapor bubbles affects the stability of the rotation of the plate and the obtained torque. The use of a glass plate allows us to monitor the liquid distribution over the substrate and, therefore, assess methods to ensure a stable rotation. We find that by making the glass plate hydrophilic or superhydrophilic and using substrates with deeper grooves, the formation of the vapor bubble at the centre of the substrate is reduced. This leads to a better coupling between the solid and liquid components and a stable rotation of the Leidenfrost rotor.”



(All information courtesy of

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Cirrus Plasma System – The effect of surface treatments on interfacial bonding

Researchers from the School of Engineering at the University of Edinburgh have recently published an article which included surface treatments on interfacial bonding using  the Henniker Cirrus Atmospheric Plasma System.

The results displayed a significant improvement in the alloys surface wettability and hydrophilic properties.

The work and results are summarised below.
(cited from the Materials and Design publication. [1])

Henniker's Cirrus and Nimbus Atmospheric Plasma Treatment Equipment Range

Novel thermoplastic fibre-metal laminates manufactured by vacuum resin infusion: The effect of surface treatments on interfacial bonding.



In the paper, Resin-infused thermoplastic fibre-metal laminates (TP-FML) have been manufactured and the bond strength between the metal and composite was tested. The wettability, topography and chemical composition of the treated Al alloy sheets were studied by employing contact-angle goniometry, coherence scanning interferometry, profilometry and X-ray photoelectron spectroscopy.


Prior to surface treatments, the Al alloy sheets were acetone-wiped with lint-free tissues to degrease the surface and afterwards they were subjected to four different surface treatments; alkaline etching, acid treatment, electrochemical etching and an atmospheric plasma treatment using a Henniker Cirrus system.


Surface wettability:

One pass of the atmospheric plasma nozzle at 1mm/s decreased the contact angle from 82 ± 1° to 32 ± 2.5°. This also increased the surface energy from 34.3mJ/m2 to 63.5mJ/m2. The atmospheric plasma treatment showed the most improved contact angle and surface energy measurements out of all four treatments used, with the next best being the acid etching decreasing contact angle to 37 ± 3°  and increasing surface energy 61.05mJ/m2.

“The plasma treated Al alloy surface exhibited a significant improvement in the surface wettability due to increased surface polarity. The oxidation of the surface and the removal of the carbonaceous components made the Al surface more hydrophilic.”  [2]

Chemical Composition:

The X-ray photoelectron spectroscopy (XPS) method was adopted to determine the chemical composition on the surface of the treated Al alloy samples. The atomic fraction of carbon on the surface of the degreased-only Al alloy sample was ~72%, which was reduced to 48% after atmospheric plasma treatment.

Keywords; Fibre-metal laminates, Thermoplastic matrix, Surface treatments, Interface bonding, Mechanical properties

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Henniker Plasma sponsor 14th International Adhesion Conference

Adhesion ’19

The 14th International Triennial Conference on the Science and Technology of Adhesion and Adhesives.


Following the success of the Adhesion conferences, held on a triennial basis since 1980, the 14th in the series of international conferences, Adhesion ’19 will take place in Bristol.

Henniker Plasma are a headline sponsor at the upcoming event and they will be attending with a small tabletop exhibit showcasing their latest products and technology. If you would like to discuss your requirements to improve adhesion then please visit their stand.


The scientific committee, which is drawn from specialists well-known to the international adhesion community and is chaired by Steve Millington, has requested papers on all aspects of the science and technology of adhesion and adhesives, including:

• Adhesion in the marine environment
• Adhesives for electronic applications
• Advances in adhesive materials: structural and pressure-sensitive adhesives
• Bio-adhesion and biomedical adhesion
• Engineering aspects of adhesion and engineering applications
• Environmental and ecological aspects
• Fundamental aspects of adhesion
• Industrial aspects
• Innovative designs and applications
• Mechanical properties of bonded joints including joint design and durability
• Nanotechnology as applied to adhesives
• New crosslinking chemistries and novel polymer structures used in adhesives
• Quality procedures, testing and standardisation
• Science, technology and properties of surfaces

The conference runs from 3rd -5th of September for more details please visit the official conference site here

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New North American Distribution


Princeton Scientific Corporation.

Henniker Plasma announces new North American distribution partners, Princeton Scientific Corp., a supplier of material science & research products.

Princeton Scientific have supplied high purity materials & semiconductor instrumentation for over 25 years. In recent years they have branched out into UHV equipment for research and industrial institutes. Consequently, they have an excellent and long-standing reputation within the U.S. scientific community.

Princeton Scientific will distribute and provide technical support for Henniker’s full product range, and in addition, will help to develop the future presence of Henniker’s plasma treatment systems and service in the region.



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Application Highlight: plasma cleaning of optics & lenses

Plasma cleaning of optics & lenses: reliable and repeatable plasma surface treatment without the eye watering price tag!

Plasma treatment of IOLs and many other devices produces easy to wet, hyper-clean surfaces by activation and by the removal of trace organic contamination that is present on almost all surfaces.

Long lasting treatments are performed within a few minutes and with no chemical waste or residue. Henniker Plasma designs and manufactures laboratory and process scale plasma systems that are easy to operate & maintain and don’t cost the earth.

  • Plasma cleaning improves wettability of gas permeable contact lenses
  • Increases patient comfort
  • Plasma cleaning removes trace organic contamination from other optics
  • Surfaces are rendered more hydrophilic
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Application Highlight: plasma treatment to improve paint/print adhesion

Plasma Treatment Prior to Printing/Painting

Plasma treatment of polymer and composite materials, which are widely used in automotive and aerospace industries, produce superior paint finishes and significant improvement in paint adhesion.

Available treatments can be applied in both batch-plasma and atmospheric in-line plasma cases and often remove the need for tedious mechanical abrasion and other preparations. We have delivered many plasma solutions to improve paint adhesion from small bench-top units to very fast cycle industrial scale paint plant solutions. We also offer a wide range of surface test methods for comparison of pre- and post-plasma treated parts.

Grid cut test

These two examples of Grid test cut methods below; (DIN EN ISO 2409) clearly demonstrate the enhanced bonding of paint (right image) on plasma activated surfaces after treatment.

                                  Untreated surface                                                                    Plasma treated surface

Grid cut test of a plastic spray painted sample prior to plasma treatmentGrid cut test of a plastic spray painted sample after plasma treatment - displaying improved paint adhesion


  • Atmospheric Plasma Treatment to improve ink adhesion
  • Effective treatment of a wide range of engineering plastics
  • Treatment of complex 3D objects
  • Typically 2-fold to 10-fold improvement in peel-strength
  • Localised plasma treatment without masking replaces surface abrasion pre-treatments

For more information regarding plasma technology contact us today.

contact us

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Happy Birthday to…..US!

Celebrating 10 Years: 2009-2019.

2019 marks our 10th Anniversary and it’s amazing how quickly the years have flown by, from humble beginnings to becoming one of the most respected and trusted suppliers of Plasma and Surface Science equipment both in the UK and internationally.


In the past ten years we have outgrown our business premises no fewer than three times and are now settled within the Manor Park Science and Technology hub, close to Sci Tech Daresbury, a national science and innovation campus.

After forming at the beginning of a recession we have been able to achieve year on year growth for every year in which we have been in business. We now export to every continent and last year we supplied and installed some of the most advanced Surface Science and Materials Growth research systems to several of the UK’s most prestigious Universities.

We continue to invest more in research and development than ever before. This, along with our exceptionally talented and dedicated staff, has been key in our continued success story and one of the reasons that our customers continue to place their trust in us, something for which we are always grateful.

“We would like to thank our friends, customers, colleagues and everyone that we have worked with for helping us to achieve our goals over the past decade. We never take anyone or anything for granted and we appreciate each and every organisation and individual who chooses to work with us. We look forward to continuing to serve you all for the next ten years!”

Terry Whitmore, MD


Categorised in: News & Events