Abstract:An optofluidic maskless photopolymerization process was developed for in situ negatively charged nanoporous hydrogel ͓poly-AMPS ͑2-acrylamido-2-methyl-1-propanesulfonic acid͔͒ fabrication. The optofluidic maskless lithography system, which combines a high power UV source and digital mirror device, enables fast polymerization of arbitrary shaped hydrogels in a microfluidic device. The poly-AMPS hydrogel structures were positioned near the intersections of two microchannels, and were used as a cation-selective f… Show more
“…Ionic hydrogel has extensively utilized as a perm-selective material for ICP operation in various literature. [33][34][35][36][37][38][39][40] Using this system, the capillary force (or capillarity) of the perm-selective nanoporous hydrogel instead of an electric bias drove the fluid into the hydrogel matrix, while its co-ions in the fluid were rejected to enter the hydrogel. This new kind of ICP was named as Capillarity ICP (CICP).…”
Ionic hydrogel-based ion concentration polarization devices have been demonstrated as platforms to study nanoscale ion transport and to develop engineering applications, such as protein preconcentration and ionic diodes/transistors. Using a microfluidic system composed of a perm-selective hydrogel, we demonstrated a micro/nanofluidic device for the preconcentration of biological samples using a new class of ion concentration polarization mechanism called "capillarity ion concentration polarization" (CICP). Instead of an external electrical voltage source, the capillary force of the perm-selective hydrogel spontaneously generated an ion depletion zone in a microfluidic channel by selectively absorbing counter-ions in a sample solution. We demonstrated a reasonable preconcentration factor ($100-fold/min) using the CICP device. Although the efficiency was lower than that of conventional electrokinetic ICP operation due to the absence of a drift ion migration, this mechanism was free from the undesirable instability caused by a local amplified electric field inside the ion depletion zone so that the mechanism should be suitable especially for an application where the contents were electrically sensitive. Therefore, this simple system would provide a point-of-care diagnostic device for which the sample volume is limited and a simplified sample handling is demanded. V C 2016 AIP Publishing LLC. [http://dx
“…Ionic hydrogel has extensively utilized as a perm-selective material for ICP operation in various literature. [33][34][35][36][37][38][39][40] Using this system, the capillary force (or capillarity) of the perm-selective nanoporous hydrogel instead of an electric bias drove the fluid into the hydrogel matrix, while its co-ions in the fluid were rejected to enter the hydrogel. This new kind of ICP was named as Capillarity ICP (CICP).…”
Ionic hydrogel-based ion concentration polarization devices have been demonstrated as platforms to study nanoscale ion transport and to develop engineering applications, such as protein preconcentration and ionic diodes/transistors. Using a microfluidic system composed of a perm-selective hydrogel, we demonstrated a micro/nanofluidic device for the preconcentration of biological samples using a new class of ion concentration polarization mechanism called "capillarity ion concentration polarization" (CICP). Instead of an external electrical voltage source, the capillary force of the perm-selective hydrogel spontaneously generated an ion depletion zone in a microfluidic channel by selectively absorbing counter-ions in a sample solution. We demonstrated a reasonable preconcentration factor ($100-fold/min) using the CICP device. Although the efficiency was lower than that of conventional electrokinetic ICP operation due to the absence of a drift ion migration, this mechanism was free from the undesirable instability caused by a local amplified electric field inside the ion depletion zone so that the mechanism should be suitable especially for an application where the contents were electrically sensitive. Therefore, this simple system would provide a point-of-care diagnostic device for which the sample volume is limited and a simplified sample handling is demanded. V C 2016 AIP Publishing LLC. [http://dx
“…A number of researchers demonstrated on-chip DNA trapping by constructing charged membranes such as poly-AMPS 2-acrylamido-2-methyl-1-propanesulfonic acid, 12 1932-1058/2015/9(5)/054115/11/$30.00 V C 2015 AIP Publishing LLC 9, 054115-1 membranes, 13 polyimide, 14 and Nafion 15 in microchannels. However, the drawback of charged membrane is the change of the ionic charges in the surrounding buffer solutions, and such kind of device is not applicable for mass production.…”
Electrodeless dielectrophoresis is the best choice to achieve preconcentration of nanoparticles and biomolecules due to its simple, robust, and easy implementation. We designed a simple chip with microchannels and nano-slits in between and then studied the trapping of DNA in high conductive medium and low conductive medium, corresponding to positive and negative dielectrophoresis (DEP), respectively. It is very important to investigate the trapping in media with different conductivities since one always has to deal with the sample solutions with different conductivities. The trapping process was analyzed by the fluorescent intensity changes. The results showed that DNA could be trapped at the nano-slit in both high and low conductive media in a lower electric field strength (10 V/cm) compared to the existing methods. This is a significant improvement to suppress the Joule heating effect in DEP related experiments. Our work may give insight to researchers for DNA trapping by a simple and low cost device in the Lab-on-a-Chip system. V C 2015 AIP Publishing LLC. [http://dx
“…In contrast, simple nanoporous structures such as microchannel–nanochannel junctions or nanoporous polymeric elements allow sample preconcentration based on a combination of target size and charge, without sequence specificity, and with no requirement for a biotinylated strand (which typically implies generation of the product by PCR). Impressive concentration factors have been reported for preconcentration of DNA and other macromolecules at nanoporous structures including prefabricated membranes , valve structures , in situ patterned gel plugs or membranes , and nanochannels , as well as at patterned electrode structures . Nonspecific preconcentration may be preferred where there is not a conserved internal sequence for capture, or when the intended target is not directly generated by PCR.…”
Rapid separation of nucleic acids by microchip electrophoresis could streamline many biological applications, but conventional chip injection strategies offer limited sample stacking, and thus limited sensitivity of detection. We demonstrate the use of photopatterned polyacrylamide membranes in a glass microfluidic device, with or without fixed negative charges, for preconcentration of double-stranded DNA prior to electrophoretic separation to enhance detection limits. We compared performance of the two membrane formulations (neutral or negatively charged) as a function of DNA fragment size, preconcentration time, and preconcentration field strength, with the intent of optimizing preconcentration performance without degrading the subsequent electrophoretic separation. Little size-dependent bias was observed for either membrane formulation when concentrating dsDNA > 100 bp in length, while the negatively charged membrane more effectively blocks passage of single-stranded oligonucleotide DNA (20-mer ssDNA). Baseline resolution of a six-band dye-labeled ladder with fragments 100-2000 bp in size was obtained in <120 s of separation time, with peak efficiencies in the range of 2000-15,000 plates/cm, and detection limits as low as 1 pM per single dye-labeled fragment. The degree of preconcentration is tunable by at least 49-fold, although the efficiency of preconcentration was found to have diminishing returns at high field and/or long times. The neutral membrane was found to be more robust than the negatively charged membrane, with approximately 2.5-fold larger peak area during the subsequent separation, and less decrease in resolution upon increasing the preconcentration field strength.
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