Americans make mobile screens with transparent wood

Researchers at the University of Maryland have made interesting advances in the production of transparent wood, which can be used to produce mobile screens and other devices.

Wood is a key resource for construction, fuel and furniture production, particularly valued for its adaptability, renewability and visual appeal. Nevertheless, new applications for wood are emerging as new methods are developed to fine-tune the optical, thermal, mechanical, and ionic transport properties of materials through chemical and physical changes in the inherently porous structure and chemical composition.

To achieve this goal, researchers have developed innovative strategies to modify wood structure in recent years and integrate it with new capabilities. Such advances pave the way for the potential replacement of conventional, non-renewable, petroleum-based materials in various industries, including automotive, energy storage, construction, and environmental remediation.

This is a change of direction from the traditional areas of construction and paper industries to wood. Now transparent wood can be used to make mobile screens as well as flexible and bright devices. In addition, it can be used in structural elements such as windows that have the ability to change color.

Advances in the production of transparent types of wood

By removing pigments from plant cells, Zingfried Frink succeeded in creating transparent wood; A process that he has described in a specialized magazine related to wood. For more than a decade, Fink's discovery was the only definitive way to produce transparent wood until another scientist at Sweden's KTH Royal Institute of Technology came up with a new method, Ars Technica reports.

Simultaneously, another group of researchers led by Liang Binghu from the University of Maryland was actively involved in advancing the project of making transparent wood through direct engineering of natural wood.

The wood consists of numerous small vertical channels that look like a bundle of straw tightly fastened with glue. These tubular cells play a role in transporting water and nutrients inside the tree. After the tree is harvested, the moisture evaporates and air holes remain.

According to Ars Technica, to produce transparent wood, scientists must first change or remove the glue called “lignin”. This glue connects the bundles of cells and transfers the earthy brown color to the trunks and branches. After the lignin is removed, a milky white framework of hollow cells remains.

At this point the resulting framework remains opaque because the cell walls refract light differently than the air inside the cells, a characteristic known as the refractive index. To achieve clear wood, the air chambers are filled with a material such as epoxy resin that bends light to the same degree as the cell walls, making the wood transparent.

Various properties and other applications

Research teams working on the Transparent Wood project developed an energy-efficient, light-harvesting building material. They follow two main steps to make it, removing the light-absorbing lignin and then filling the wood with an epoxy-like polymer that matches the refractive index.

This clear wood has about 80% light haze, allowing more than 85% light to pass through. This wood can let in sunlight without causing glare, which leads to energy savings and easy lighting of closed spaces. This type of wood also has strong mechanical integrity (about 100 MPa), absorbs impact energy effectively, and is highly flexible, addressing safety concerns associated with glass materials.

Additionally, clear wood is a better insulator than glass, potentially helping buildings retain or dissipate heat. During this process, Ho and his team used polyvinyl alcohol (PVA), a polymer commonly found in adhesives and food packaging, to inject wooden skeletons. This resulted in transparent wood with a heat conduction rate five times lower than that of glass.

Berglund and his team also discovered a way to advance smart window technology, capable of transitioning between transparency and tinted modes to control views or block sunlight. According to ARS Technica, their method involved layering an electrochromic polymer (with the ability to change color through electricity) between layers of transparent wood coated with an electrode polymer to conduct electricity. Scientists now aim to increase the environmental compatibility of clear wood to minimize the use of harmful chemicals and fossil-based polymers in its production.