Table 2.

Summary of structural color actuators based on CNCs

Material	Stimuli	Mechanism	Actuation	Structural color	Sensitivity	Response time	Ref.
CNCs/PEGDA and PA-6 sandwiched structure	Humidity	Asymmetric pitch expansion between two layers	Flat to bending/twisting	Green to red (515–735 nm)	80% RH, 25 °C	5 s	75
CNCs/PEGDMA	Humidity	Asymmetric expansion between two sides	Flat to bending	Red to green with bending angle increase	Moisture 20 µL s−1	4 s	76
Bilayer PF resin using CNCs as templates	Water	Asymmetric expansion between two layers	Curling to uncurling	Double reflection 390/560 nm–685/970 nm	Dip in water or water vapor	10 s	48
PF resin doped with GO using CNCs as templates	Water	Asymmetric expansion; selective aldehyde treatment to program initial shape	Bending to unbending; 3D shapes to uncurling	600–800 nm	Dip in water	6–180 s	47
CNC/PU with AgNPs	Humidity and NIR light	Asymmetric expansion when exposed to humidity and NIR light	Flat to bending	Blue to red	RH 30% - 70%	Humidity: 9 s; NIR light: 16 s	78