Flexible nanocellulose/poly(ethylene glycol) diacrylate hydrogels with tunable Poisson’s ratios by masking and photocuring

Flexible hydrogels with an adjustable Poisson’s ratio were prepared, offering a way to simulate the behavior of natural organisms, expressing corresponding deformation in response to external forces. Nanofibrillated cellulose (NFC) particles were blended with photo-curable resin poly(ethylene glycol) diacrylate (PEGDA), and flexible NFC/PEGDA hydrogels with positive, near zero, and negative Poisson’s ratios (0.66 ± 0.31, 0.17 ± 0.28, and -0.39 ± 0.26, respectively) and were successfully prepared using masking and photocuring. Furthermore, the effects of different curing times and mask apertures were investigated. The clarity and structural precision of the hydrogels were used to evaluate the effects of the preparation procedures. A curing time of 20 s and a mask aperture of 5 mm were the ideal conditions for preparation of NFC/PEGDA hydrogels. Further, addition of NFC resulted in excellent hydrogel flexibility and enhanced mechanical properties. The fabrication of NFC/PEGDA hydrogels with high structural precision and tunable Poisson’s ratios has the potential for application in wearable devices and intelligent monitoring equipment.