Functionalization—the scientific term for the addition of new functions to an existing material—is a common technique in materials science, chemistry, and nanotechnology. In architecture, function is often considered at an assembly, system, or spatial level. Although functionalization research commonly involves polymers, glass, and metal oxides, some researchers and designers are adding new functions to wood. In this case, function is added to the wood itself by surface manipulations. The approach is used to modify characteristics like color, hydrophobicity, magnetism, and antimicrobial properties, often transforming the material.
The most striking functionalizations are unexpected, running counter to a material’s familiar characteristics. One example is electrification—a surprising function given wood’s low conductivity. Wood.e is a composite material for furniture fabrication designed to conduct electricity. As a composite, it is not a functionalized material per se—the term typically refers to the modification of the surface of an individual material—but the concept is similar.
Designed by Bjorn Blisse, Folker Konigbauer, and Reinhard Zetsche from Transalpin with German furniture manufacturer Becker, Wood.e comprises three layers of plywood of different thicknesses. Conductive metal plates are sandwiched between the plies, providing 12 volts of electricity, and the materials can be molded into bent shapes for seating, tables, and shelving. By delivering a current internally, Wood.e allows users to activate various devices—such as light fixtures, fans, or speakers—by attaching them to the surface, eliminating the need for wires or cables.
A team of researchers including scientists from the Swiss Federal Laboratories for Materials Science and Technology in Dübendorf, Switzerland, and Swiss Federal Institute of Technology (ETH Zürich) has created another kind of energy-conveying wood composite. In this case, the composite is a flooring material that generates power from footfalls. The invention, published in Matter, harnesses the phenomenon of triboelectricity to transfer electrons. The triboelectric effect is a process in which the friction between objects in contact—seen in the static cling of laundry garments or packing peanuts—produces an electrical charge. To make wood triboelectric, the researchers modified two layers of spruce to acquire and lose electrons—a tendency atypical for wood. They applied a polydimethylsiloxane silicone coating on one layer and functionalized the other by growing ZIF-8 nanocrystals on its surface. Footsteps on the material result in the periodic contact and release of the layers, passing electrons from the nanocrystals to the silicone. The resulting flooring generates 80 times more electricity than unmodified wood and can power LED light bulbs and small electronic devices.
Scientists at the University of Maryland and Johns Hopkins University became interested in using wood for electromagnetic shielding. The function requires conductivity, typically through metals, and blocks the propagation of electromagnetic fields, isolating electronic components from their surroundings. To create conductive wood for this purpose, the researchers first modified wood by dissolving the lignin, ridding structural polymer within the material. They then injected polypyrrole, a conductive polymer, inside the newly opened cellular channels. The transformed 1.4-inch-thick material has a structural electromagnetic interference shielding effectiveness of 58 decibel. (By comparison, the SE of steel fiber–filled polymers is typically 36 to 42 decibels.) Furthermore, the modified wood retains some of its original compressive and tensile strength as well as its low density, making it appropriate for lightweight load-bearing applications.
Converting wood into an electrically conductive material might seem counterintuitive as it undermines the notion of utilizing a material for its intrinsic qualities and sends current through an inherently flammable substance. Nevertheless, wood’s superior environmental performance compared to many materials has motivated researchers to experiment with wood’s attributes and applications in wide-ranging ways. In the future, a few varieties of multipurpose, functionalized wood might comprise the bulk of a building—including its operational systems as well as its structure, cladding, and finishes.
The inventors of the triboelectric wood floor imagine the built environment as the fundamental place of application for this research. According to lead author Guido Panzarasa, “the ultimate goal is to understand the potentialities of wood beyond those already known and to enable wood with new properties for future sustainable smart buildings."