Waterproof in the Spree: dichtol seals a 3D-printed sensor buoy

How a capillary-active sealant from DIAMANT Polymer GmbH makes a large-format, additively manufactured rPETG component permanently suitable for use in flowing water.

The Challenge: A Technical Component for Continuous Use in a River

The Spree River defines Berlin – yet its ecological condition remains invisible to most people. Artist, designer, and musician Jakob Kukula wanted to change that and give the Spree a voice that people could perceive. The result is a floating sensor buoy that continuously measures pH, dissolved oxygen, temperature, turbidity, and electrical conductivity. A solar-powered onboard computer transmits the data to a public platform several times a day; an integrated LED strip translates the measurements into a simple color signal – from green for healthy water to red when the river needs attention.

The buoy’s floatable outer shell is 3D-printed in large format from recycled PETG (rPETG) and encloses a CNC-milled aluminum frame as well as sensitive electronics, a rechargeable battery, and sensors. This made it clear from the start: The component must not only float but also remain reliably watertight over long periods of time.

The Challenge: Additive Manufacturing Is Not Intrinsically Airtight

As solid as an FDM print may appear, microscopic pores and channels remain between the layers and layers of a large-format print. For many applications, this is not a problem. But for a buoy that is permanently submerged in water and protects sensitive electronics, it is: Moisture intrusion jeopardizes the sensors and power supply and shortens the service life of the entire system.

The sealing requirements were therefore demanding:

• It had to reliably seal the entire, large-area printed surface – not just on the surface, but all the way into the fine channels of the wall.
• It could not alter the fit or geometry of the interlocking print modules.
• And it had to align with the project’s underlying principle of sustainability: an effective, material-efficient solution instead of a thick coating.

The Solution: dichtol – A Sealer That Gets Right to the Source of the Problem

This is exactly where dichtol from DIAMANT Polymer comes into play. dichtol is capillary-active: When applied to the printed surface, it penetrates the microscopic pores and gaps in the print on its own through capillary action and cures there into a solid, waterproof seal. The key difference from a simple topcoat: dichtol seals the leaks within the wall and forms a continuous, waterproof layer—without adding material, without clogging the fine geometry, and without adding any significant extra weight. For a floating component where every gram and every fit counts, this is an ideal approach.

The Implementation

The entire printed outer shell of the buoy was sealed with dichtol. This created the waterproof skin that allows the buoy to safely house its electronics and withstand continuous use in the river. The seal blends invisibly into the component and leaves the translucent appearance of the rPETG unaffected – a key consideration for the buoy’s design concept.

The Result

A large-format 3D print was transformed into a functional component that is ready for use and permanently waterproof. The electronics are protected, durability in water has been significantly increased—and the buoy is ready for both exhibition and practical use. It is currently on display at the Humboldt Forum in Berlin. The project exemplifies how well additive manufacturing and dichtol work together: 3D printing provides the geometry, size, and a recycled material, while dichtol makes the component watertight and field-ready. Together, they create a final product that can withstand even demanding, permanently damp environments – in a resource-efficient manner and without complex design workarounds.

Outlook

The next project phases call for larger buoys – such as those equipped with oxygen pumps for hot summers – as well as a sensor network distributed throughout the city. With each additional printed buoy, the need for a reliable sealing solution that permanently seals additively manufactured components also grows. dichtol is ready to meet this need.

Fig. 1: DIAMANT Polymer GmbH, BigRep GmbH
Fig. 2: Jakob Kukula
Figs. 3, 4: BigRep GmbH