Advanced Paper‐Based Three‐Dimensional Electronics Fabricated via Freeform Direct Laser Writing

ABSTRACT This study presents a borax–water‐activated cellulose nanofiber (BWCNF) material that can be readily transformed into robust three‐dimensional (3D) electronics through molding and freeform direct laser writing (FDLW). Compared with untreated cellulose nanofiber (CNF), BWCNF exhibits 135% of the tensile strength and 186% of the extensibility. Molded wavy structures also show excellent shape retention, with negligible force–strain hysteresis (<0.5%) over 1000 stretch–release cycles at 40% strain. Laser‐induced graphene (LIG) can be patterned directly on these 3D BWCNF structures, yielding a sheet resistance as low as 54 Ω sq − 1 and a D‐to‐G Raman band intensity ratio of 1.5. The resulting devices include wave‐structured piezoresistive strain sensors with gauge factors (GF) as high as 44.5 at 48% strain ( R 2 > 0.97) and low response hysteresis (6%–9%), capacitive touch sensors for directional control (approximately 300% relative capacitance change per 0.8 × 0.8 cm electrode), and light‐emitting diode (LED) arrays assembled on a 3D paper model. These results demonstrate that borax–water activation enables robust paper‐based substrates for advanced 3D electronics.