Nanogates use voltage to control the passage of molecules through small pores

The collaboration, led by researchers at Osaka University, has developed a nanogate that can be opened and closed by applying electricity. Nanogates exhibit a variety of behavior depending on the material in the solution on either side of the gate and the applied voltage, making them attractive for a variety of applications, including sensing and controlled chemical reactions.

This work is published in Nature Communications.

The nanogates consisted of a single small pore formed in a silicon nitride film. The membrane was placed in a flow cell formed on the chip, and the solution was introduced on either side of the membrane.

The researchers applied a voltage to the flow cell through an electrode on the chip, measured the resulting ion current, reflecting the transport of ions through the pore. The ion current was sensitive to ions in the solution on either side of the membrane. Therefore, the flow of ions and the resulting precipitation or dissolution of metal compounds in the pores can be precisely controlled.

Different types of ion transport occurred due to changes in pore diameter due to precipitation (closed nanogate) or dissolution (opened nanogate);

“The precipitate grows and closes the pores at a negative voltage and reduces the ionic current,” says Makusu Tsutsui, lead author of the study. “Inverting the voltage polarity caused the sediment to dissolve and the pores resumed.”

Under certain conditions, the formation of pore-blocking precipitates gave the highest rectification rate. This is a measure of the trend of ions that move only in one direction, achieved so far in nanofluidic devices.

In addition to acting as a rectifier, the system can also act as a memorizer. In other words, memory effects were observed in relation to current and voltage. This memory was generated by the continuous precipitation and dissolution of the material within the pores.

Additionally, the diving reaction can be adjusted to allow detection of biomolecules. This was demonstrated using DNA. This system showed different output signals as individual DNA molecules migrated through the pores.

“The ability to finely control pore size using applied voltages should allow for adjustment of pores to a specific analyte just before a measurement is made,” explained senior author Tomoji Kawai. I will. “We also expect to be able to use our approach to develop a reaction system to access new compounds.”

Using a single controlled pore membrane in nanofluidic electrochemical devices is a versatile approach that can be tailored to specific applications such as sensing, chemical reactions, and neural morphology computing.