Research

Bipolar ionic diode, Raman spectroscopy, and Memristor based on Micro-nano fluidic device

I designed and experimented with bipolar ionic diode fabricated by self-assembly of nanoparticles and soft lithography process. I achieved high-performance ion concentration rectification (ICR) value by optimizing salt concentration, nanopores size (nanoparticles size), and microchannel geometry. In addition, I conducted experiment to detect heavy metal ions (mercury ions) which are combined fluorescence probe at the junction (L.O.D. ~ 10pM) by using bipolar ion diode characterization that ions are accumulated at junction. [2017-2022] Furthermore, using the working principle of the bipolar ionic diode, I am trying to detect material as label-free which are rarely detected typical Raman spectroscopy by apply electrical potential on bipolar membrane fabricated by gold nanoparticles. [2022- Present] The above experiments used DC potential. Whereas our team, in collaboration with R. van Roij’s Lab in Utrecht university, conducted a neuromorphic computing experiment based on the fact that taper shape micro-nano channel has memristive effect at A.C. potential. When input 0 (negative potential) or 1 (positive potential), ion current has different conductivity because ions were accumulated or depleted by bias direction. Following, we experimented 0000, 0001, 0010 ~ 1111 (16ea), found that each signal had different conductivity. As a result, this showed us that our fluidic device is capable of reservoir computing. I conducted optimization of memristive effect by adjusting frequency, nanoparticles size, salt concentration, geometry of micro-nano channel, and time between signals. [2022-2023]

Neuron cooling experiment and neural signal analysis for cryo-anesthesia 

I designed a cryo-neuromodulation platform consisting of a microelectrode array (MEA) system, a microfluidic device, and a high-speed precision probe-type cooling device that provides localized cooling temperature. I explored the temperature conditions that cause silencing and recovery of neuronal signaling without cell damage and found the advantages of fast and local anesthesia quantitively. Furthermore, I investigated inter-network neuron signal by connecting two networks with axons using a microfluidic chip to characterize inter-network neuron signal and discussed the neuron signal by cooling. [2017-2023]