A universal tunable nanofluidic diode via photoresponsive host–guest interactions

Inspired by biological ion channels, scientists have fabricated various artificial nanosystems. However, nanofluidic diode systems with replaceable functional groups are rarely reported. In this work, we demonstrated a universal tunable nanofluidic diode based on a conical polyimide nanochannel. Using host–guest interactions between β-cyclodextrin and azobenzene, bidirectional nanofluidic diodes were prepared, and the degree of rectification could be adjusted with high precision by tuning the pH conditions. This work provides a novel approach to create a nanofluidic platform with replaceable surface functional groups, which has great potential in fields such as photosensitive nanofluidic devices, drug transport and release, and nanofluidic logic devices. Through combining nanochannel technique and host–guest interaction, a universal tuneable nanofluidic diode is fabricated. By changing different azobenzene derivatives, the system can achieve replaceable surface charges, and realize the light and pH dual stimuli responses. The system has potential applications in fields such as photosensitive nanofluidic devices, light-controlled drug transport, pH-activated drug release and devices for optical information storage. A nanoscale device that allows optical control of the flow of electrically charged liquids has been developed by Chinese researchers. Nanofluidics, the control of fluid flow in nanometer-wide channels, is useful for processing and analyzing small liquid samples such as blood. Many of the components required in nanofluidic circuits echo the functionality of electronic components. Diodes, for example, integral to every electronic circuit, allow flow in only one direction. Pei Liu from the Technical Institute of Physics and Chemistry, Beijing, and colleagues created a nanofluidic diode comprising a conical channel made from a polymer resin in which flow can be activated by light. Flow control is achieved by harnessing the optically induced reactions between different organic molecules embedded in the channel walls. The diode direction can be switched by altering the pH level in the device.