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40 TECHNOLOGY JUL/AUG 2025 FDM ASIA | www.fdmasia.com

multi-directional failure risks, improving structural safety and
durability.
This performance breakthrough extends its applications
beyond traditional longitudinal load-bearing structures to

scenarios requiring transverse and complex mechanical
properties. To explore the full potential of the self-densified
wood, we fabricated it into a nail for demonstration.
Due to the high strength and sharpness of the densified
wooden nails, they can easily penetrate the 3-layer wood
without requiring pre-drilling. The load-carrying test shows
that it can withstand >300 N and the failure of the sample
Fig. 4. Transverse section properties of self-densified wood. (a) Schematic is caused by the rupture of the wood board, which is even
diagram and transverse tensile strength of natural wood, mechanically
compressed wood, and self-densified wood. (b) Tensile strength of self- stronger than the steel nail.
densified wood at different angles in the transverse section. Transverse This result indicates that wood nail has better nail-holding
flexural stress-strain curves of natural wood, mechanical-compressed
wood, and self-densified wood in (c) X-axis and (d) Y-axis. (e) Transverse ability and causes less damage to the wood block during
flexural strength and (f) impact toughness of natural wood, mechanical- nailing process, which is a promising eco-friendly alternative
compressed wood, and self-densified wood in X-axis and Y-axis directions. to steel nail for many commercial applications.
(g) Digital images of wood block nailed with the self-densified wood nail.
(h) Force-displacement curves of uniaxial tensile test of self-densified In this work, we demonstrate a self-densified, super-
wood nail compared to steel nail.
strong wood via the microstructural regulation strategy. Our
approach involves releasing cellulose fibrils from the lignin

significantly improved, while the transverse tensile strength confinement through partial delignification, then the cellulose
parallel to the compression direction is greatly reduced. fibrils moving inward and filling the cell lumen via LiCl/DMAc
Specifically, the tensile strength of compressed wood swelling process, and concluding with air-drying.
increases from 9.0 to 34.0 MPa along the Y-axis but dramatically This unique self-densification process endows the resulting
decreases from 8.7 to 4.4 MPa along the X-axis. wood with a uniform microstructure, and compared to natural
In contrast, the self-densified wood is achieved by a uniform wood, its mechanical properties are significantly and uniformly
shrinkage in the transverse section. This active shrinkage gives enhanced in all directions.
the self-densified wood a uniform microstructure. The improvement in mechanical properties not only
The transverse tensile strength increases by an order of compensates for the performance heterogeneity caused

magnitude, reaching 62.5 MPa, nearly seven times that of by compression in conventional densified wood but also
natural wood, while maintaining high consistency in both overcomes its limitation of being suitable only for longitudinal
the tangential and radial directions across the cross-section. load-bearing scenarios.
Additionally, the flexural strength and impact toughness The newly developed self-densified super-strong wood
of self-densified wood also show similar trends. The flexural makes it highly attractive for many engineering and structural
strength is increased by 7.5 and 7.9 times than that of the applications including complex mechanical scenarios. This
original wood in the X-axis and Y-axis directions, respectively. versatility is demonstrated in our study through the fabrication

In summary, the balanced mechanical enhancement of of a wood nail. FDM
self-densified wood in all directions significantly mitigates ENQUIRY NO. 4101