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TECHNOLOGY 47
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remarkably. Du and co-workers developed an optically switchable
However, both mechanical and optical features of the and mechanically resistant perovskite-coated thermochromic
resulting TW can be worsened due to shrinking phenomena, transparent wood (derived from delignified balsa wood that
which the infiltrated polymers may undergo during their was subsequently infiltrated with poly(methyl methacrylate))

polymerisation/curing: consequently, cracks or defects alongside to be employed as an effective smart window.
the interface between the bleached wood scaffold and the This latter exhibited not only enhanced mechanical behaviour
infiltrated resin may originate. (i.e., enhanced tensile and flexural strength – about 71 and
Some strategies have been proposed to overcome these 93 MPa, respectively) but also a significant solar modulation
issues. They include: i) the use of refractive index-matched capability and an optical transmittance as high as 78 percent,
resins that exhibit a low shrinkage upon curing, and ii) the suitable for the design of novel glazing materials having
modification, usually by esterification, of the hydroxyl-rich inner enhanced thermal regulation and energy-saving potential.
surfaces of the channels in the bleached wood scaffold to Zhang and co-workers designed and produced an all-
improve the compatibility between this latter and the infiltrated wood-based flexible electronic device, derived from the

resin. This way, it is possible to obtain defect-free, highly self-densification of balsa wood that was converted into
transparent materials combining lightness, toughness, and self-densification-wood-derived-paper, operating at room
outstanding mechanical properties. temperature, and exploiting the occurrence of capillary forces
simply generated by water evaporation.
Recent Advances The obtained material showed a suitable optical transmittance
The world that revolves around transparent wood is changing (beyond 40%), a very high haze (around 93% at 800 nm
very rapidly, achieving new performance targets that were wavelength), as well as an outstanding tensile strength (about

unpredictable a few years ago and envisaging new potential 230 MPa) in the fibre direction, much higher than pristine balsa
applications of this up-to-date material. wood and standard cellulose paper.
Indeed, as an innovative transparent material, transparent Besides, thanks to its high wettability, the self-densification-
wood exhibits not only outstanding optical features but also wood-derived-paper was appropriate for being written with
exceptional mechanical behaviour (in terms of strength, a conductive carbon ink (obtained from the carbonisation
toughness, and impact resistance), which plays a key role in of balsa wood) to get customised patterns: this way it was
providing the viability and safety of its uses in the building possible to produce cheap and biodegradable flexible sensors,
sector. suitable for stably monitoring finger movements.
Besides, its high optical transmittance in a wide wavelength

range and tunable haze make transparent wood an appealing
alternative to such conventional materials as glass for
architectural uses.
In addition, the structure and morphology of TW allow
for its use as a functional material, making it suitable to
replace conventional materials (i.e., fossil-derived plastics) in
advanced sectors including ultrafiltration membranes, solar

cells, superflexible electronic devices, thermal insulators, energy
storage materials, and phase-change materials, among others.