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50 TECHNOLOGY SEP/OCT 2024 FDM ASIA | www.fdmasia.com

In this context, Zhang and co-workers produced a highly
transparent wood composite (optical transmittance beyond
83%) derived from delignified balsa wood.
This latter was infiltrated with refractive-index-matched

partially polymerised acrylamide, in the presence of very small
amounts of nanofiller, namely: Ag nanowires (0.1 wt%), carbon
nanotubes (0.1 wt%), and reduced graphene oxide (0.1 wt%).
The resulting TW composite exhibited a very low
thermal conductivity (around 0.45 W/(mK)) and a remarkable
electromagnetic absorption performance. In particular, for
2.0 mm thick samples, the effective absorption bandwidth
achieved 9.5 GHz, almost seizing the whole X (8.2–12.4 GHz)
and Ku (12.4–18 GHz) bands.

Perspectives
Zhou et al. thoroughly investigated the performance of a The idea of creating transparent wood was born to study the
fully biobased, biodegradable, and flexible transparent wood, anatomical characteristics of the wood itself. However, the
suitable for replacing traditional plastics in flexible electronics, growing awareness of energy saving, the need to create a
anti-counterfeiting, and UV protection applications. virtuous system based on the recyclability of materials and the
To this aim, gelatine was grafted onto delignified balsa circular economy, and the urgent demand for limiting global

wood and subsequently crosslinked with tannic acid: the so- warming have recently proposed TW as one of the possible
obtained films (thickness of about 100 μm) combined high answers to these problems.
tensile strength (around 155 MPa) and optical transmittance The possibility of creating windows that would allow light
(86.2% at 600 nm), low haze and UV blocking effectiveness, to pass through but which, at the same time, would act as a
as well as remarkable stability in water. thermal barrier, immediately appeared as an obvious but essential
Liu and co-workers succeeded in preparing transparent application of TW. In addition, the advantage represented
wood (from balsa wood) with soft-/hard-switchable and shape by the enhanced impact resistance properties compared to
recovery capabilities by infiltrating an epoxy-based polymer traditional glass has made it a potential replacement for both
(whose Tg – glass transition temperature – was around 0°C) practical and commercial interest.

into the delignified wood template. The resulting material On the other hand, even the material obtained when the
showed high optical transparency and haze (70 and 95%, internal structure of the wood remains visible soon aroused the
respectively, for TW samples 2.0 mm thick), tunable stiffness, economic interest of furniture manufacturers, who immediately
and shape-recovery capability. appreciated its aesthetic characteristics.
One very recent application of transparent wood refers At present, the growing interest in this material is beginning
to the design of effective electromagnetic wave absorption to involve more advanced sectors, in particular electronics:
materials characterised by small thickness and wide effective indeed, TW is proving to be an appealing material in the

absorption bandwidth, which may contribute to alleviating fields of solar cells, luminescent devices, photonics, and
electromagnetic pollution. LEDs, among others.