transfer | nano sciences | technology

Joining technique without welding or adhesion

Kiel University and a partner company showcase new metal and plastic connections at the Hannover Messe



Welding and gluing techniques are still the main methods for permanently joining metals together. But this elaborate procedure at high temperatures pushes plastics and sensitive metals to their limits. A research team from Kiel University (CAU) and Phi-Stone AG is working on a gentle joining technique. They have used a special etching process to permanently join aluminium and plastic together, among others. Combinations with steel, light alloys such as magnesium or light composites from fibreglass reinforced or carbon-fibre reinforced plastics are now also possible. At the CAU booth at the Hannover Messe (Hall 2, booth C07), they are presenting the portable application of the process as well as how it can be integrated into existing plant technology. Potential areas of application include the automobile industry, ship-building, aviation or trade/craft.

Not all metals can be welded together or glued to a plastic. Thin materials often cannot withstand the high temperatures, coatings are destroyed or other materials close to the welded seam are damaged. The method, which Professor Rainer Adelung’s CAU working group developed together with the university’s start-up Phi-Stone, can be used to permanently join both metals to metals as well as metals to plastics, at room temperature and in just a few minutes via micro-inter-locking.

“There are masses of rivets in an aeroplane’s window frames, for example. Altogether they are quite heavy. But the materials used in the plane’s body cannot be joined by welding. Using our technique, you could join the metals and plastics together without needing rivets - saving up weight and also fuel,” emphasised Professor Rainer Adelung, head of the Functional Nanomaterials working group to describe the method’s potential. 

Interlocking structured surface

With so-called “nanoscale sculpturing”, the surface of a metal is precisely roughened using an electro-chemical etching process, so that a fine, rectangular hook structure is created at the micrometre level. When two of these treated surfaces are inter-locked, a strong bond is created which is very difficult to break. Whereas the glue needs to be applied to quite a large area with adhesive techniques, the sculpturing process only requires a comparably small area for a firm hold.

The process is particularly suitable for adding parts to existing constructions or in hard to reach places, such as bodywork in the car, ship or plane building industry. The etching process can also be used to remove surface coatings.

Expanding the applications

The potential applications should in future be expanded to include additional materials and shapes. Examples from fundamental research into ultra-lightweight materials with record densities of less than 1 mg/cm³ enable functional applications in aeronautics and space. Processing wires, curved surfaces and pipes are also conceivable. “This type of surface treatment acts like corrosion protection. The fine network of hooks doesn’t let any water through. Screws treated in this way, for example, wouldn’t rust solid,” explained Hartmut Schmidt-Niepenberg, from the Board of Directors at the cooperating partner, Phi-Stone AG. They are currently also conducting tests with galvanised steel sheets, like the ones used in roofing. The high temperatures cause the galvanised coating to vaporise if you weld the sheets to other metals. This is why it normally has to be removed first and then re-coated again afterwards. The Kiel research team’s etching process could significantly speed this job up.

Mobile use or integrated into plants

The prototype of a mobile joining unit developed by Phi-Stone AG makes the process flexible to use, too. Its modular structure also enables it to be integrated into existing plant technology and it can be individually adapted to meet industrial needs. Using etching cells produced via 3D printing, metal surfaces can be precisely processed. Together with their first customers, they want to incorporate customer requirements and develop the prototype to market-readiness. Two patents have already been registered in this regard.

Key facts:
What?  Presentation: “Light made easy. Innovative Composites for quick joining between metals, fiber composites and functional carbon materials”

Who?   Prof. Dr Rainer Adelung, Functional Nanomaterials working group

When? The lecture will be held in English on Monday 3 April at 11.30am and 1.30pm. In addition, demonstrators of the mobile joining unit and metal and plastic connections will be shown throughout the week.

Where? CAU booth C07 in Hall 2 “Research & Technology”, exhibition grounds (Nord 2 entrance), 30521 Hanover

For more information about the "Nanoscale Sculpturing" etching process:
M. Baytekin‐Gerngross, M.D. Gerngross, J. Carstensen and R. Adelung: Making metal surfaces strong, resistant, and multifunctional by nanoscale‐sculpturing. Nanoscale Horizons. DOI: 10.1039/C6NH00140H!divAbstract

Video of the joining process:

Foto: Siekmann, CAU

Der Flansch aus Aluminium hält fest an der Aluminiumwand.

Foto: Mark-Daniel Gerngroß

Unter dem Mikroskop wird die feine Widerhakenstruktur der aufgerauten Metalloberfläche sichtbar. Verschiedene Materialien lassen sich so miteinander „verhaken“ und dauerhaft verbinden.


Foto: Siekmann, CAU

Auf der Hannover Messe präsentiert die Forschungsgruppe der CAU zusammen mit der Kieler Firma Phi-Stone AG ihre mobile Fügestation.


Kiel University
Professor Rainer Adelung
Functional Nanomaterials Working Group
Tel.: +49 (0)431/880 6116

Phi-Stone AG
Hartmut Schmidt-Niepenberg,
Chairman of the Board
Scientific Head 
Tel.: +49-431-7054186

Julia Siekmann
Science communication
Priority research area Kiel Nano, Surface and Interface Science (KiNSIS)