Warmth stored in building walls can be converted into energy, while flexible solar modules keep interiors cool.
Yet a research team from Germany is looking to regulate room temperatures without using electricity at all. Its shade-giving system for windows is modelled on movements found in woody fruits.
Taking its cue from pine cone scales, the team developed a sheet that swells or shrinks depending on the air humidity. The material was 4D printed using cellulose fibres.
Thus, the sequence in which the three-dimensional, bilayered form was printed decisively shaped its properties. In high humidity, the material absorbs moisture and expands; in low humidity, the reverse is true. Moisture is released and the material contracts.
Not shady either: colour-changing smart windows.
