Scientific Secret of the Chemnitz Artwork "Model for Thought and Perception of the Phenomenon of Color" Revealed
Researchers from Chemnitz and Besançon have uncovered the unexpected property of Stefan Nestler's striking stele artwork on the TU Chemnitz campus square as the largest known realization of a photonic crystal
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David Röhlig, PhD student at the Professorship of Theoretical Physics - Simulation of New Materials, has dedicated himself to modeling the propagation of waves in crystal lattices since his Bachelor's thesis at TU Chemnitz. In several instances, the artwork "Model for Thought and Perception of the Phenomenon of Color" served as a source of inspiration for scientific investigations. Photo: Image Archive of the Press Office and Crossmedia Editorial Team/Lili Hofmann -
Inspired by Stefan Nestler’s artistic idea, TUC researchers of natural science and engineering collaborated on the artwork and performed both computational simulations and real measurements on the scattering of various wave phenomena. In this respect, special RF equipment (horn antenna and wide-range antenna) was employed in ordert to proof the property of the stele configuration as photonic crystal. Photo: David Röhlig -
The work of the researchers shows that through their unsual approach, inspired by an artwork, a two-fold perspective change is possible. First, a phenomenon abundant in the nano world has been proven to have a relevance in the macro world. Second, it was uncovered that an piece of art, in principle an item created without a specific purpose, has an intrinsic scientific and technical relevance. Photo: David Röhlig -
Art and Construction: the artwork „Denk- und Wahrnehmungsmodell für das Phänomen der Farbe“ (Model for Thought and Perception of the Phenomenon of Color) was created in 1998 in front of the Central Auditorium Hall of TU Chemnitz by the Dresden-based artist Stefan Nestler. Photo: Image Archive of the Press Office and Crossmedia Editorial Team/Stefan Becker
When hearing the word "crystal," one inevitably pictures precious stones that glitter impressively, sparkle, or leave lasting impressions with various color effects. Yet this common term does not merely exhaust itself in the decorative appearance of mineral treasures. A careful observation of sunlit, iridescent butterfly wings, shimmering peacock feathers, or the shifting hues of a chameleon reveals not only aesthetic beauty but also conceptual sophistication stemming from a shared physical mechanism: these surfaces are revealed to be highly complex, nanoscale-structured patterns, invisible to the naked eye yet remarkable in their optical effects.
These are known as "photonic crystals," structures that reflect certain ranges of light colors while allowing others to pass through. The interplay of scattering, absorption, and transmission creates spectral dependencies that impressively blur the lines between science and art, at least from a perceptual standpoint. Such phenomena rely on the wave nature of light, first described around 1650 by the Dutch naturalist Christian Huygens. They can be explained through the interaction of light waves with regularly structured surfaces, whose typical structural widths correspond roughly to the wavelength of visible light. This wavelength falls between 400 and 700 nanometers, about one hundredth the diameter of a human hair (approximately 0.05 millimeters, or 50 micrometers). Thus, the spectral properties of peacock feathers or other regularly patterned materials can be well-explained by the wave nature of light and by scattering and transmission effects, logically leading to their identification as photonic crystals.
A Chemnitz artwork and its unexpected significance for science
An interdisciplinary team consisting of members from the Faculty of Natural Sciences, the Faculty of Electrical Engineering and Information Technology, and the Research Center for Materials, Architectures, and Integration of Nanomembranes (MAIN) at Chemnitz University of Technology, along with researchers from the University of Marie & Louis Pasteur in Besançon (France) and the Fraunhofer Institute for Electronic Nano Systems (ENAS), have successfully identified, following in the footsteps of Huygens and Fresnel, a man-made artistic installation the largely regular arrangement and previously unknown wave-breaking properties of which qualify it as the largest realization of a photonic crystal reported hitherto in the scientific community. This installation manipulates the propagation of radio waves—electromagnetic waves in the gigahertz range—which play a crucial role in information and communication technology, including frequencies relevant to modern 4G and 5G mobile standards.
The artwork in the spotlight is "Denk- und Wahrnehmungsmodell zum Phänomen der Farbe" ("Model of Thought and Perception of the Phenomenon of Color") by Dresden-based artist Stefan Nestler, adorning the forecourt of the Central Auditorium Building at TU Chemnitz since 1998. It consists of 187 vertical, regularly arranged hollow steel pillars of varying heights, square in cross-section, originally representing colors from the so-called RAL color scale, widely used in industry and architecture as a reference standard. Accompanying the pillar structure is a glass panel engraved with a quote from philosopher Ludwig Wittgenstein (1889–1951), inviting contemplation on the ideal representation of color, concluding with the words: "For do not forget that your gaze wanders, and there is no description of what you see."
As recently reported by researchers from Chemnitz and Besançon in the interdisciplinary journal "Scientific Reports," published by Springer Nature Portfolio, the artwork symbolizes not only an abstract representation of colors but also practically achieves a "color-selective" transmission of radio wave signals. Analogous to the play of colors on a butterfly's wings—though on a considerably larger scale—electromagnetic waves at certain frequencies within the so-called "bandgap" are prohibited from propagating through the material structure and are thus reflected. This is precisely the classic behavior expected from a photonic crystal.
Unexpectedly, the European Capital of Culture Chemnitz 2025 now hosts an artwork that, upon detailed scientific analysis, sets new benchmarks. Thus, Chemnitz 2025 will become not only a stage for art and culture but also the setting for an unexpected scientific discovery—highlighting, as quoted by Lichtenberg, the astonishing complexity underlying our human perception of color.
The project received funding from Chemnitz University of Technology under the TUCculture2025 initiative (projects "Chemnitz: Wood, Light, Sound" and "Wave Games"), the Free State of Saxony (Saxon State Doctoral Scholarship), and the French region of Bourgogne-Franche-Comté.
Voices from TU Chemnitz on the Scientific Discovery:
David Röhlig, PhD student at the Professorship of Theoretical Physics – Simulation of New Materials at TU Chemnitz, scholarship holder: "This work is a beautiful example of how an initially seemingly utopian idea becomes reality through interdisciplinary cooperation."
Prof. Dr. Angela Thränhardt, Professor of Theoretical Physics – Simulation of New Materials and Dean of the Faculty of Sciences at TU Chemnitz: "It is truly remarkable: Right in the middle of the Capital of Culture Chemnitz, even on the university campus, a work of art opens a real window into the world of a fundamental physical principle – that of the propagation of waves in photonic crystals."
Prof. Dr. Ralf Zichner, Professor of High Frequency Engineering and General Electrical Engineering at TU Chemnitz: "Interdisciplinary collaboration opens up new perspectives and promotes innovation. This exchange between disciplines allows us to gain new insights and overcome existing boundaries of knowledge."
Dr. Thomas Blaudeck, Managing Director of the Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN): "The work is a beautiful example of how curiosity and serendipity, i.e., the in-depth observation and description of something not previously sought and the intellectual engagement with it, can constitute science."
Original Publication: David Röhlig, Vincent Laude, Ralf Zichner, Felix Thieme, Angela Thränhardt and Thomas Blaudeck "Radio wave attenuation by a large-scale photonic crystal sculpture", Scientific Reports 15, 12317 (2025), DOI 10.1038/s41598-025-95986-9.
Event Notice: The artwork "Model for Thought and Perception of the Phenomenon of Color" by Stefan Nestler also invites visitors to participate in experiments as part of the TUCculture2025 project "Wellenspiele" (Wave Games) on TUCtag 2025 on May 10th. These experiments are intended to spark interest in studying natural sciences and engineering at TU Chemnitz and will take place from 2:00 PM to 5:45 PM at the artwork in front of the Central Auditorium Building of TU Chemnitz, Reichenhainer Str. 90.
Further information can be obtained from: Dr. Thomas Blaudeck, Phone +49 (0)371 531-35610, Email thomas.blaudeck@main.tu-chemnitz.de, and Prof. Dr. Angela Thränhardt, Phone +49 (0)371 531-37636, Email angela.thraenhardt@physik.tu-chemnitz.de.
(Author: Dr. Thomas Blaudeck, Translation: Tobias Bollig)
Mario Steinebach
05.05.2025
