3D-printed measuring buoy monitors the water quality of the Spree

In Berlin, the Spree is omnipresent, but its ecological condition usually remains abstract. Measurement data on pollution from wastewater, sulfates, or rising water temperatures are hidden away in technical reports and hardly tangible for passersby. Artist and designer Jakob Kukula is trying to close this gap – with a 3D-printed measuring buoy that makes water quality visible while also functioning as a design object in urban space.

For the project, Kukula needed a floating body that offers large internal cavities for electronics, power supply, and sensors, and that can be precisely coupled to an internal aluminum frame. In collaboration with BigRep, the team opted for large-format FFF 3D printing with recycled PETG. The material is translucent, mechanically robust, and can be printed in large segments that interlock to form a closed floating body. The milled aluminum core stiffens the structure, carries the modules, and ensures that the buoy maintains its orientation even in choppy water.

At the center sits a sensor module that records parameters such as pH value, dissolved oxygen, temperature, turbidity, and electrical conductivity. A compact onboard computer collects the measurements, buffers them, and transmits them several times a day to the online platform spreeberlin.de. The system is powered by solar cells integrated into a 3D-printed lid made of rPETG, which charge a battery pack. To seal the microscopic pores of the printed structure, the surface was coated with a marine varnish that limits water absorption and is intended to extend the buoy’s service life in the river.

Between the housing and the solar lid runs a circumferential LED strip that translates the measurement data into color codes. Green signals stable conditions, yellow and orange indicate critical trends, and red marks pollution events. In the future, larger buoys with integrated oxygenation systems are planned, as well as a distributed sensor network along the Spree. For Berlin, this would be not only environmental monitoring, but also an example of how large-format 3D printing can connect infrastructure, design, and urban ecology.