Name: merging ion concentration polarization between juxtaposed ion exchange membranes to block the propagation of the polarization zone
Uploaded: 2017-02-23T14:00:00
Description: Watch this Scientific Journal Video about Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone at JoVE.com

This work was supported by the internal fund of the Korea Institute of Science and Technology (2E26180) and by the Next Generation Biomedical Device Platform program, funded by the National Research Foundation of Korea (NRF-2015M3A9E202888).

1. Fabrication of Cation Exchange Membrane-integrated Microfluidic Chips
<ol>
	<li>Preparation of silicon masters
	<ol>
		<li>Design two kinds of silicon masters: one for patterning a cation exchange resin and the other for building a microchannel with polydimethylsiloxane (PDMS). 
		NOTE: The detail geometry will be described in the steps 1.3.1 and 1.4.1.</li>
		<li>Fabricate the silicon masters by using either conventional photolithography or deep reactive ion etching27.<...

<ol>
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We have described the fabrication protocol and the performance of a spatiotemporally defined preconcentrator in a range of the applied voltage (0.5-100 V), ionic strength (1-100 mM), and pH (3.7-10.3), achieving a 10,000-fold preconcentration of dyes and protein within 10 min. As like previous ICP devices, the preconcentration performance becomes better at higher voltage and at lower ionic strength. One additional parameter we can consider here is the distance between two cation exchange membranes. If we increase the int...

Ion concentration polarization (ICP) refers to a phenomenon that occurs during ion enrichment and ion depletion on a permselective membrane, resulting in an additional potential drop with ion concentration gradients1,2. This concentration gradient is linear, and it becomes steeper as a higher voltage is applied (Ohmic regime) until the ion concentration on the membrane approaches zero (limiting regime). At this diffusion-limited condition, the gradient (and corresponding ion flux) has been known to be maximized/saturated1. Beyond this conventional understanding, when the voltage (or current) is increased further, an overlimiting current is observed, with flat depletion zones and very sharp concentration gradients at the zone boundary1,3. The flat zone has a very low ion concentration, but surface conduction, electro-osmotic flow (EOF), and/or electro-osmotic instability promote ion flux and induce an overlimiting current3,4,5. Interestingly, the flat depletion zone serves as an electrostatic barrier, which filters out6,7,8,9 and/or preconcentrates targets10,11. Since there is an insufficient amount of ions to screen the surface charges of charged particles (for satisfying electroneutrality), the particles cannot pass through this depletion zone and therefore line up at its boundary. This nonlinear ICP effect is a generic phenomenon in various types of membranes10,11,12,13,14 and geometries6,15,16,17,18,19,20,21; this is why researchers have been able to develop various types of filtration6,7,8,9 and preconcentration10,11 devices using the nonlinear ICP.
Even with such high flexibility and robustness, it is still a practical challenge to clarify the operating conditions for the nonlinear ICP devices. The nonlinear regime of the ICP quickly removes cations through a cation exchange membrane, which causes the displacement of anions moving towards the anode. As a result, the flat depletion zone propagates quickly, which is reminiscent of shock propagation22. Mani et al. called this dynamic the deionization (or depletion) shock23. To preconcentrate targets at a designated sensing position, preventing the expansion of the ion depletion zone is necessary, for example, by applying EOF or pressure-driven flow against the zone expansion24. Zangle et al.22 clarified the criteria for ICP propagation in a one-dimensional model, and it highly depends on electrophoretic mobility17, ionic strength18, pH25, and so on. This indicates that proper operating conditions will be altered according to the sample conditions.
Here, we present detailed design and experimental protocols for a novel ICP platform that preconcentrates targets within a spatiotemporally defined position26. The expansion of the ion depletion zone is blocked by the ion enrichment zone, leaving a stationary preconcentration plug at an assigned position, regardless of the operating time, applied voltage, ionic strength, and pH. This detailed video protocol is intended to show the simplest method to integrate cation exchange membranes into microfluidic devices and to demonstrate the preconcentration performance of the new ICP platform compared to the conventional one.

<table border="0" cellpadding="0" cellspacing="0" width="720">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:239px;">Sylgard 184 Silicone Elastomer kit</td>
			<td style="width:195px;">Dow Corning</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:239px;">Trichlorosilane</td>
			<td style="width:195px;">Sigma Aldrich</td>
			<td style="width:119px;">175552</td>
			<td>Highly toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nafion perfluorinated resin, 20 wt%</td>
			<td>Sigma Aldrich</td>
			<td style="width:119px;">527122</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium chloride</td>
			<td>Sigma Aldrich</td>
			<td style="width:119px;">71394</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Potassium chloride</td>
			<td>Sigma Aldrich</td>
			<td style="width:119px;">60121</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Alexa Fluor 488 carboxylic acid, succinimidyl ester</td>
			<td>Invitrogen</td>
			<td style="width:119px;">A20000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Isothiocyanate-conjugated albumin</td>
			<td>Sigma Aldrich</td>
			<td style="width:119px;">A9771</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phosphate buffer saline, 1X</td>
			<td>Wengene</td>
			<td style="width:119px;">LB004-02</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tween 20&#160;</td>
			<td>Sigma Aldrich</td>
			<td style="width:119px;">P1379</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Epifluorescence microscope</td>
			<td>Olympus</td>
			<td style="width:119px;">IX-71</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Charged-coupled device camera</td>
			<td>Hamamtsu Co.</td>
			<td style="width:119px;">ImageEM X2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Source measurement unit</td>
			<td>Keithley Instruments</td>
			<td style="width:119px;">2635A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:239px;">Covance-MP</td>
			<td style="width:195px;">Femto Science</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

merging ion concentration polarization between juxtaposed ion exchange membranes to block the propagation of the polarization zone

The ion concentration polarization (ICP) phenomenon is one of the most prevailing methods to preconcentrate low-abundance biological samples. The ICP induces a noninvasive region for charged biomolecules (i.e., the ion depletion zone), and targets can be preconcentrated on this region boundary. Despite the high preconcentration performances with ICP, it is difficult to find the operating conditions of non-propagating ion depletion zones. To overcome this narrow operating window, we recently developed a new platform for spatiotemporally fixed preconcentration. Unlike preceding methods that only use ion depletion, this platform also uses the opposite polarity of the ICP (i.e., ion enrichment) to stop the propagation of the ion depletion zone. By confronting the enrichment zone with the depletion zone, the two zones merge together and stop. In this paper, we describe a detailed experimental protocol to build this spatiotemporally defined ICP platform and characterize the preconcentration dynamics of the new platform by comparing them with those of the conventional device. Qualitative ion concentration profiles and current-time responses successfully capture the different dynamics between the merged ICP and the stand-alone ICP. In contrast to the conventional one that can fix the preconcentration location at only ~5 V, the new platform can produce a target-condensed plug at a specific location in the broad ranges of operating conditions: voltage (0.5-100 V), ionic strength (1-100 mM), and pH (3.7-10.3).

The schematic fabrication steps of a membrane-integrated microfluidic preconcentrator are shown in Figure 1. A detailed description of the fabrication is given in the Protocol. The designs and device images of the spatiotemporally defined preconcentrator26 are contrasted with those of a conventional preconcentrator11 (Figure 2). The ICP phenomenon in the spatiotemporally defined preconcentrator was investiga...

Watch this Scientific Journal Video about Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone at JoVE.com

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone

The protocol for a novel ion concentration polarization (ICP) platform that can stop the propagation of the ICP zone, regardless of the operating conditions is described. This unique ability of the platform lies in the use of merging ion depletion and enrichment, which are two polarities of the ICP phenomenon.

The ion concentration polarization (ICP) phenomenon is one of the most prevailing methods to preconcentrate low-abundance biological samples. The ICP ...

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Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Alginate Microcapsule as a 3D Platform for Propagation and Differentiation of Human Embryonic Stem Cells (hESC) to Different Lineages

Alginate Microcapsule as a 3D Platform for Propagation and Differentiation of Human Embryonic Stem Cells hESC to Different Lineages

Human embryonic stem cells (hESC) are emerging as an attractive alternative source for cell replacement therapy since they can be expanded in culture ...

Multi-analyte Biochip (MAB) Based on All-solid-state Ion-selective Electrodes (ASSISE) for Physiological Research

Multi-analyte Biochip MAB Based on All-solid-state Ion-selective Electrodes ASSISE for Physiological Research

Lab-on-a-chip (LOC) applications in environmental, biomedical, agricultural, biological, and spaceflight research require an ion-selective electrode (ISE) ...

Fluorescence Recovery after Merging a Droplet to Measure the Two-dimensional Diffusion of a Phospholipid Monolayer

We introduce a new method to measure the lateral diffusivity of a surfactant monolayer at the fluid-fluid interface, called fluorescence recovery after ...

Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and ...

Assembly and Characterization of Biomolecular Memristors Consisting of Ion Channel-doped Lipid Membranes

The ability to recreate synaptic functionalities in synthetic circuit elements is essential for neuromorphic computing systems that seek to emulate the ...

Focused Ion Beam Lithography to Etch Nano-architectures into Microelectrodes

With advances in electronics and fabrication technology, intracortical microelectrodes have undergone substantial improvements enabling the production of ...

Silicon Nanowires and Optical Stimulation for Investigations of Intra- and Intercellular Electrical Coupling

Myofibroblasts can spontaneously internalize silicon nanowires (SiNWs), making them an attractive target for bioelectronic applications. These ...

Propagation of Dental and Respiratory Cells and Organs in Microgravity

Gravity is one of the key determinants of human cell function, proliferation, cytoskeletal architecture and orientation. Rotary bioreactor systems (RCCSs) ...