Dielectrophoresis is a force applied to microparticles in non-uniform electric field. The presented study discusses the fabrication of the glassy carbon interdigitated microelectrode arrays using lithography process based on lithographic patterning and subsequent pyrolysis of negative SU-8 photoresist. Resulting high resistance electrodes would have the regions of high electric field at the ends of microarray as demonstrated by simulation. The study demonstrates that combining the AC applied bias with the DC offset allows the user to separate sub-populations of microparticulates and control the propulsion of microparticles to the high field areas such as the ends of the electrode array. The direction of the movement of the particles can be switched by changing the offset. The demonstrated novel integrated DEP separation and propulsion can be applied to various fields including in-vitro diagnostics as well as to microassembly technologies.
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Electrokinetic Propulsion of Polymer Microparticulates Along Glassy Carbon Electrode Array
Abstract Dielectrophoresis (DEP) is a force applied to microparticles in nonuniform electric field. This study discusses the fabrication of the glassy carbon interdigitated microelectrode arrays using lithography process based on lithographic patterning and subsequent pyrolysis of negative SU-8 photoresist. Resulting high-resistance electrodes would have the regions of high electric field at the ends of microarray as demonstrated by simulation. The study demonstrates that combining the alternating current (AC) applied bias with the direct current (DC) offset allows the user to separate subpopulations of microparticulates and control the propulsion of microparticles to the high field areas such as the ends of the electrode array. The direction of the movement of the particles can be switched by changing the offset. The demonstrated novel integrated DEP separation and propulsion can be applied to various fields including in vitro diagnostics as well as to microassembly technologies.
more »
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- Award ID(s):
- 1661877
- NSF-PAR ID:
- 10313493
- Date Published:
- Journal Name:
- Journal of Micro and Nano-Manufacturing
- Volume:
- 8
- Issue:
- 2
- ISSN:
- 2166-0468
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Chinese hamster ovary (CHO) cell is the most widely used mammalian cell line for commercial production of therapeutic protein. Any presence of non-viable cells in culture medium may adversely affect subsequent functionality of these proteins. Therefore, separation of non-viable cells from suspending medium is critical in biopharmaceutical and biomedical sectors. One such method termed Deterministic Lateral Displacement has already shown promising capabilities in separating cells based on the cell size difference by taking advantage of the predictable flow laminae. However, in cases where size overlaps between viable and non-viable cells are present, separation based solely on size suffers and high-resolution separation techniques are required. Dielectrophoresis, one of the most widely used nonlinear electro-kinetic mechanism, has the potential to manipulate the same size cells depending on the dielectric properties of individual cells. In this work, we demonstrated that a DLD device can be combined with a frequency-based AC electric field to perform high resolution continuous separation of non-viable CHO cells from the viable or productive cells. The behavior of the coupled DLD-DEP device is further investigated by employing numerical simulation to check the effect of geometrical parameters of the DLD arrays, velocities of the flow field and required applied voltages. A moderate row shift fraction with velocity 700μm/s provided a good separation behavior without any trapping. The cell viability was also ensured by maintaining proper electric field which otherwise may cause cell loss due to ion leakage. Our developed numerical model and presented results lay the groundwork for design and fabrication of high resolution DLD-DEP microchips for enhanced separation of viable and nonviable cells.
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We present a plasmonic-enhanced dielectrophoretic (DEP) phenomenon to improve optical DEP performance of a floating electrode optoelectronic tweezers (FEOET) device, where aqueous droplets can be effectively manipulated on a light-patterned photoconductive surface immersed in an oil medium. To offer device simplicity and cost-effectiveness, recent studies have utilized a polymer-based photoconductive material such as titanium oxide phthalocyanine (TiOPc). However, the TiOPc has much poorer photoconductivity than that of semiconductors like amorphous silicon (a-Si), significantly limiting optical DEP applications. The study herein focuses on the FEOET device for which optical DEP performance can be greatly enhanced by utilizing plasmonic nanoparticles as light scattering elements to improve light absorption of the low-quality TiOPc. Numerical simulation studies of both plasmonic light scattering and electric field enhancement were conducted to verify wide-angle scattering light rays and an approximately twofold increase in electric field gradient with the presence of nanoparticles. Similarly, a spectrophotometric study conducted on the absorption spectrum of the TiOPc has shown light absorption improvement (nearly twofold) of the TiOPc layer. Additionally, droplet dynamics study experimentally demonstrated a light-actuated droplet speed of 1.90 mm/s, a more than 11-fold improvement due to plasmonic light scattering. This plasmonic-enhanced FEOET technology can considerably improve optical DEP capability even with poor-quality photoconductive materials, thus providing low-cost, easy-fabrication solutions for various droplet-based microfluidic applications.more » « less
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In this study, we investigated hierarchical microarchitecture formation of magnetic barium hexaferrite (BF) platelets inside the polydimethylsiloxane (PDMS) matrix using electric and magnetic field colloidal assembly technique. First, external fields were applied to the colloidal solution to form the microstructure before curing the composites. After microstructure formation the composites were cured to freeze the microstructure by the application of heat. We investigated two different cases in this study-(1) magnetic field processed composites and (2) multi-field processed composites which were processed under both magnetic and electric field. We observed that macro-chains formed due to the electric and magnetic field had much higher length compared to the macro-chains formed due to the just magnetic field. For both cases individuals BHF are found to be oriented in the direction of external field. The analysis of SEM microstructures using ImageJ and MATLAB showed that at least two different level of hierarchies are present in the microstructure for both cases which can be named as BHF stacks and micro-chains. From the microstructure analysis, we found that compared to just magnetic field processed composites, the orientation of individual particles, BHF stacks and micro-chains in relation to the external field were found to be higher for the multi-field processed composites. Magneto-electro-hydrodynamics modeling of the polymer-particulate mixture predicted similar behavior. Computational simulations were performed wherein particulates, subjected to both DEP forces and additional magnetic dipole interactions, were allowed to form quasi-equilibrium structures before locking in a final structure to represent curing. Results show that dielectrophoretic (DEP) force produced from the local non-uniform electric field facilitates the translation of the platelets towards formation of chain-like structure, while external magnetic field augmented the rotation of particles inside the chain-like structure. Analysis of the simulation of microstructures confirms that multiple level of hierarchies are present in the composites microstructure for both cases, while the case with both electric and magnetic fields produced longer chains. The understanding of the hierarchical microstructure formation using the multi-field processing technique will help in the future to fabricate more complex microarchitectures with resulting multi-material properties.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4046561
