Scientists have just developed a novel material capable of spontaneously adapting its behavior to light, without any sensor or external control. This nanoscale device, inspired by the functioning of living systems, paves the way for "autonomous" materials for optics, energy, or sensing. These results are published in
Nature Communications.
Living systems possess a remarkable ability to adapt to their environment: the human eye adjusts its sensitivity to light, plants regulate their hydration. They constantly optimize their functions to maintain balance in the face of variations in their surroundings. Reproducing such autonomy in artificial materials is a major challenge in materials science.
a: Device of plasmonic nano-antennas integrated into a MOF matrix.
b–c: Observation of light scattering at 850 nm from the antennas, and its evolution over time under laser irradiation.
d–e: Variation of the normalized scattering intensity over time, measured for the entire array and for a single antenna.
Indeed, currently, most so-called "smart" materials require external control or a stimulus to change their behavior: for example, shape-memory polymers recover an initial shape when heated, piezoelectric materials produce an electrical voltage when subjected to mechanical stress. In contrast, self-regulation relies on an autonomous response based on feedback loops, which are still difficult to implement in artificial systems.
To overcome this limitation, scientists from the Laboratoire de Chimie de la Matière Condensée de Paris (CNRS / Sorbonne Université), the Laboratoire Charles Fabry (CNRS / Université Paris-Saclay), and the Centre de Nanosciences et de Nanotechnologies (CNRS / Université Paris-Saclay) propose a device capable of self-regulating its light absorption depending on its intensity. It is based on the combination of two complementary building blocks: a plasmonic metasurface of gold nano-antennas, capable of absorbing light and converting it into heat, and a porous film of
Metal-Organic Framework (MOF) type, which is temperature-sensitive.
In the presence of vapor, the MOF film changes its optical index when it heats up. This change shifts the resonance of the nano-antennas and reduces their absorbance. Thus, when the light intensity increases, the system automatically absorbs less light and limits its heating. This thermo-optical feedback loop gives the device a self-regulated behavior, comparable to that of a thermostat at the nanoscale.
Remarkably, this self-regulation is not static. At the scale of a single nano-antenna, researchers observed spontaneous oscillations under constant illumination. A behavior comparable to that of a steam engine powered by light, which relies on the time delay between the rapid heating of the nano-antennas and the slower response of the porous material.
These results, published in the journal
Nature Communications, open new perspectives for the development of autonomous materials capable of adapting and evolving without external control. In the long term, they could find applications in adaptive optics, thermal management, smart sensors, or even devices capable of operating according to programmed rhythms, similar to biological systems.