Asymmetric Langmuir-Blodgett and Hydrophilization Process to Realize Density-Controllable Carbon Nanotube Array on Flexible and Stretchable Substrates

Well-aligned Carbon nanotube (CNT) arrays are very promising for application in flexible and stretchable devices. In this work, an improved LB method and a new hydrophilization method are combined together to achieve CNT arrays with controllable density on various flexible and stretchable substrates like Polyethylene naphthalate (PEN), polyimide (PI) and polydimethylsiloxane (PDMS) for the first time. The LB method is featured by multiple and asymmetrical compression-expansion cycles. By varying the target surface pressure, the nanotube density on PEN substrate can be rationally controlled. Besides, a new hydrophilization method by growing a SiO ₂ thin layer is proposed. After the treatment, the water contact angle on various organic substrates can be reduced significantly. This method can improve the performance and stability of flexible and stretchable devices. The change of equivalent resistance of CNT array film on PEN substrate is within 40% after bending 2000 times with a curvature radius of 4 mm, and it is within 20% on PI substrate.