SNU Professor Sung Jae Kim / Hallym University Professor Gun Yong Sung / POSTECH Professor Gunsu Yun's Team Develops World's First Technology For Direct Visualization of Selective Ion Transport

 

-Published as the latest issue of the Scientific Report

 

▲ From left SNU Professor Sung Jae Kim of the Department of Electrical and Computer Engineering, Hallym University Professor Gun Yong Sung of Materials Science & Engineering, Researcher Kim Won-seok of SNU Electrical and Computer Engineering and Professor Gunsu Yun of the Physics Department at POSTECH.

 
Korean researchers have developed a technology that records by video, the selective movement of ions passed within a nanoporous membrane based on their polarity through the movement of ions through plasma luminescence.
 
The joint research teams led by SNU Professor Sung Jae Kim of the Department of Electrical and Computer Engineering, , Hallym University Professor Gun Yong Sung of Materials Science & Engineering and and Professor Gunsu Yun of the Physics Department at POSTECH passed visible light emitted during the ion-plasma energy transfer through a nanoporous membrane, and it was announced on June 2 that they succeeded  in the selective passage of positive ions within the structure like Na+ and Li+ through the analysis of specific visible light of each ion.
 
The study was obtained after systematic analysis of interesting phenomena in microfluidic channels discovered accidentally five years ago, and is the world's first technology to combine plasma luminance characteristics with nanotropic hydroponics, so that ion transport phenomena within nano-porous membranes can be observed according to their own luminous colors.
 
The nanoporous membrane transmits only ions that are opposite to the polarity of wall charges, because the distance between the channel walls is greatly small, being below few tens of nanometers or less. In other words, nanostructures made of glass, silicon, etc. have negative charges on the surface of the material, allowing only positive ions to pass through. This selective perm-selectivity has been a key mechanism in the field of nano-electrokinetics and has been the starting point for various studies, including seawater desalination and ion concentrators. However, because direct observation of ion transport inside nano porous membrane is difficult, only research has been conducted using indirect experimental evidence such as voltage-current measurement or fluorescence imaging.
 
If this result is applied, it is expected that various outputs such as active nano-luminous devices, nano-imaging devices, and ion analysis devices will be obtained, and it will also be used in biotechnology, where only indirect fluorescence imaging methods are used.
 
 "We have persistently analyzed phenomena that have been discovered by chance and have come up with a new methods of visualization that can observe key phenomena in the field of nano-electric hydroponics," said SNU Professor Sung Jae Kim. "Currently, a joint research team is developing a lab-on-a-chip platform that can quantify ions using this technology."
 
The results of the study were published in the 'Scientific Report' on June 1. The research was conducted with support from the Ministry of Science and ICT's support project for mid-sized researchers and the Snu-Cosmax Technology Promotion Center.




 

 
By taking over a relatively low voltage of around 50 V, air bubbles were first generated within the microfluid channel (Figure. step 1) and a high voltage of 500 V was taken over to form a plasma triggered by the bubbles, resulting in the emission of visible light with an ionic color (Figure 2. step 2). Next, by the transfer of voltage to both ends of the nano porous membrane, plasma visible light produced within the microfluid channel penetrated inside the nano porous membrane, and only the visible light corresponding to the cationary ions was filmed using a high speed camera (Figure 3. step 3). It was also observed that lithium ions of higher mobility are always transported from the front end and glowed in comparison to sodium ions with lower mobility (see figure).