Dry Film Resist Laminated Microfluidic System for Electrical Impedance Measurements

Yuan, C. L.; Floehr, Julia; Ingebrandt, Sven; Schnakenberg, Uwe

doi:10.3390/mi12060632

Cited by 14 publications

(14 citation statements)

References 42 publications

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“…The fabrication process of the microfluidic chip was recently published [ 23 , 24 , 27 ] and is briefly summarized here. Three 25 µm thick SUEX ® dry film resist layers were laminated, patterned by standard UV lithography, and in the case of forming the 35–36 µm in diameter microholes, structured by a dry etching process in an inductively coupled plasma reactive ion etching tool (SI 500, SENTECH Instrument GmbH, Berlin, Germany) by applying 60 sccm O 2 , 3 sccm SF 6 , 0.5 Pa, 100 W power, and −150 V DC-bias voltage.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, we developed a microfluidic approach in which the optical method is replaced with an observer-independent electrical detection method [ 23 , 24 ]. The schematic drawing of the setup is shown in Figure 1 a.…”

Section: Introductionmentioning

confidence: 99%

“…Two ring-shaped electrodes were vertically arranged around the microhole, as depicted schematically by the cross-section in Figure 1 b. Trapped spheres or cells were characterized by electrical impedance spectroscopy (EIS) [ 23 , 24 ]. EIS is a non-invasive technique that applies a frequency-dependent voltage between the electrodes and measures the corresponding current response to calculate the electrical impedance.…”

Section: Introductionmentioning

confidence: 99%

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Viscoelastic Properties of Zona Pellucida of Oocytes Characterized by Transient Electrical Impedance Spectroscopy

et al. 2023

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The success rate in vitro fertilization is significantly linked to the quality of the oocytes. The oocyte’s membrane is encapsulated by a shell of gelatinous extracellular matrix, called zona pellucida, which undergoes dynamic changes throughout the reproduction cycle. During the window of highest fertility, the zona pellucida exhibits a softening phase, while it remains rigid during oocyte maturation and again after fertilization. These variations in mechanical properties facilitate or inhibit sperm penetration. Since successful fertilization considerably depends on the state of the zona pellucida, monitoring of the hardening process of the zona pellucida is vital. In this study, we scrutinized two distinct genetic mouse models, namely, fetuin-B wild-type and fetuin-B/ovastacin double deficient with normal and super-soft zona pellucida, respectively. We evaluated the hardening with the help of a microfluidic aspiration-assisted electrical impedance spectroscopy system. An oocyte was trapped by a microhole connected to a microfluidic channel by applying suction pressure. Transient electrical impedance spectra were taken by microelectrodes surrounding the microhole. The time-depending recovery of zona pellucida deflections to equilibrium was used to calculate the Young’s modulus and, for the first time, absolute viscosity values. The values were obtained by fitting the curves with an equivalent mechanical circuit consisting of a network of dashpots and springs. The observer-independent electrical readout in combination with a fitting algorithm for the calculation of the viscoelastic properties demonstrates a step toward a more user-friendly and easy-to-use tool for the characterizing and better understanding of the rheological properties of oocytes.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Viscoelastic Properties of Zona Pellucida of Oocytes Characterized by Transient Electrical Impedance Spectroscopy

et al. 2023

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“…Therefore, a balanced, which means a radially symmetrical, flow profile at the aperture is vital. In addition, for the electrical characterization of single cells with electrical impedance spectroscopy [11][12][13][14][15][16][17][18] or DOI: 10.1002/pssa.202200862…”

Section: Introductionmentioning

confidence: 99%

Balancing of Flow at Microfluidic Apertures

Yuan

Yılmaz

Schnakenberg

2023

Physica Status Solidi (a)

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Computational fluid dynamics simulations are used to obtain a radially symmetrical flow profile at an aperture of a microfluidic channel by manually arranging flow‐directing obstacles around the aperture. For the first time, the flow profile is improved by calculating the coefficient of variation (CoV), which is applied to the flow velocity magnitude along coaxially arranged circles below the aperture in the microfluidic channel. A minimum CoV of 0.03 is obtained at the circle with the same diameter as the aperture. Channels with the optimized design are fabricated by lamination of two layers of dry film resist and patterned with UV‐lithography. The aperture is formed by using an inductively coupled plasma reactive ion etching process. Video recording of the flow behavior confirmed the simulation results experimentally. The proposed channel design and the optimization method can favorably be used for a balanced hydrodynamic trapping of particles or cells at apertures.

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“…Lamination onto patterned dry film resist is more challenging, however, risking damage to the underlying features and poor layer-to-layer adhesion. Lamination onto patterned layers may be possible if only a small percentage of the underlying resist layer is removed during development, such as when microfluidic devices are directly constructed out of dry film resist [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. However, microfluidic molds typically require most of each resist layer to be removed during development.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Multilayer Molds by Dry Film Photoresist

Koucherian

Hui

2022

Micromachines

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Dry film photoresists are widely employed to fabricate high-aspect-ratio microstructures, such as molds for microfluidic devices. Unlike liquid resists, such as SU-8, dry films do not require a cleanroom facility, and it is straightforward to prepare uniform and reproducible films as thick as 500 µm. Multilayer patterning, however, can be problematic with dry film resists even though it is critical for a number of microfluidic devices. Layer-to-layer mask alignment typically requires the first layer to be fully developed, making the pattern visible, before applying and patterning the second layer. While a liquid resist can flow over the topography of previous layers, this is not the case with dry film lamination. We found that post-exposure baking of dry film photoresists can preserve a flat topography while revealing an image of the patterned features that is suitable for alignment to the next layer. We demonstrate the use of this technique with two different types of dry film resist to fabricate master molds for a hydrophoresis size-sorting device and a cell chemotaxis device.

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Dry Film Resist Laminated Microfluidic System for Electrical Impedance Measurements

Cited by 14 publications

References 42 publications

Viscoelastic Properties of Zona Pellucida of Oocytes Characterized by Transient Electrical Impedance Spectroscopy

Viscoelastic Properties of Zona Pellucida of Oocytes Characterized by Transient Electrical Impedance Spectroscopy

Balancing of Flow at Microfluidic Apertures

Fabrication of Multilayer Molds by Dry Film Photoresist

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