Design and fabrication of a microsystem to handle biological objects

Biological particle microhandling is a common operation in medicine and microbiology, and a lot of research work has been addressed to develop faster, cheaper and more efficient manipulation techniques. In this way, microsystem technologies play an important role because they can be used to fabricate microparticle manipulators. This paper describes the design and fabrication of a microsystem to handle biological objects, based on the dielectrophoretic effects. The development of the right technological option among the possibilities at disposal is also discussed. The proposed design, a whole microsystem including electrical, optical and fluidic interfaces, was developed employing gold and platinum metals, silicon micromachining, and photoresin patterning techniques. Furthermore, the structure of the utilized microelectrode arrays, as well as the resulting microchip are also reported

From electrophoresis to dielectrophoresis: designing, fabricating, and evaluating an electroformed ratchet type microfluidic dielectrophoresis device

Dielectrophoresis (DEP) is a separation method in which a non-uniform electric field is used to induce a dipole moment in a suspended particle. If the polarization of the particle is greater than that of the suspending medium, the particle will move towards the region of higher field strength (positive DEP); while if the particle is polarized less than the suspending medium, the particle will be moved towards the low potential area (negative DEP). In recent years DEP has been gaining popularity through the construction of microscale devices, and this is due largely to the decrease in electrode spacing which allows for higher effective field strengths. Presented is the design, fabrication, and evaluation of a novel dielectrophoretic based ratchet device. The electrodes required to produce the asymmetrical field were constructed of electroformed nickel features grown on the surface of a resist patterned seedlayer coated glass slide, and this is the first time electroforming has been used to produce electrodes in the field of DEP. The electrodes were then made stand alone features located on the glass slide by wet etch removal of the unplated portions of the seedlayers located on the surface of the glass substrate. The fluidic component of this device was constructed using replica molding of poly(dimethylsiloxane), which contained a fluidic reservoir located over the ratchet electrode features. Particle selection was conducted using an a priori approach for particles of known dielectric properties. The frequency responses of perspective test particles to an asymmetrical electric field were determined through calculation of the real component of the Clausius-Mossotti factor (Re[K(ω)]). From these calculations, magnetite and polystyrene spheres were selected as test particles. The device was then evaluated using the test particles selected to determine if particle collection occurred in the regions dictated by Re[K(ω)]. Suspensions consisting of single particle types and a mixture were then evaluated, and it was found that the particles collected in the regions specified by the theoretical calculations. These results showed that the device is capable of collecting particles based on the dielectric properties of the magnetite particles and polystyrene spheres

Diseño y fabricacion de un microsistema para la manipulacion de objetos biologicos

La micromanipulación de partículas biológicas es una operación frecuente en medicina y microbiología, y se ha dedicado una gran cantidad de trabajo para desarrollar técnicas de manipulación mas rápidas, baratas y eficientes. En este sentido, la tecnología de microsistemas juega un papel importante ya que se puede utilizar para fabricar manipuladores de micropartículas. En este artículo se describe el diseño y fabricación de un microsistema para la manipulación de objetos biológicos, basado en el efecto dielectroforetico. También se discute la selección de la alternativa tecnológica mas adecuada dentro de las disponibles. El diseño propuesto, es un microsistema completo que incluye interfases eléctrica, óptica y fluidica, y se desarrolló empleando oro y platino como metales para los electrodos, micro mecanizado del silicio y técnicas de fotocurado de resinas fotosensibles. De la misma forma se describe la estructura de los microelectrodos desarrollados al igual que el circuito integrado resultante

LTCC packaging for Lab-on-a-chip application

LTCC -pakkaus Lab-on-a-chip -sovellukseen. Tiivistelmä. Tässä työssä suunniteltiin, valmistettiin ja testattiin uusi pakkaustekniikka ”Lab-on-a-chip” (LOC) -sovellukseen. Pakkaus tehtiin pii-mikrosirulle, jolla voidaan mitata solujen kiinnittymistä sirun pintaan solujen elinkelpoisuuden indikaattorina. Luotettavuustestaukset tehtiin daisy-chain -resistanssimittauksilla solunkasvatusolosuhteissa. Lisäksi työssä selvitettiin LTCC- ja ”Lab-on-a-chip” -teknologioiden perusteet teoreettiselta pohjalta. Mikrosirun pakkauksessa käytettiin joustavaa LTCC-teknologiaa. Sähköisiin kontakteihin ja niiden suojauksiin käytettiin sekä johtavia että eristäviä epoksi-liimoja. LOC-sovelluksiin on tärkeää kehittää uusia pakkausmenetelmiä jotta näiden laitteiden kaikki ominaisuudet saadaan toimimaan luotettavasti. Pakkaus testattiin samoissa olosuhteissa missä sitä tullaan käyttämään ja pakkaus kesti kaikki nämä haasteet. Lisäksi esitetty valmistusprosessi on sellainen, että sitä voidaan käyttää myös muihin ”Lab-on-a-chip” -sovelluksiin.Abstract. This work presents design, manufacturing and testing of new packaging method for Lab-on-a-chip (LOC) application. Packaging was made for silicon microchip which can measure cell adhesion on chips surface as indication of cell viability. Reliability testing was done with daisy-chain resistance measurement in real conditions. Moreover basic theory of LTCC and Lab-on-a-chip technology is presented. Resilient LTCC technology was used for packaging material and conductive/insulating epoxies were applied for electrical contacts and barriers against the environment. It is fundamentally important to develop new packaging methods for LOC applications, so all the properties can be utilized reliably. Packaging was tested under the cell growth conditions and the package showed to withstand all these challenges. Moreover the presented packaging method is possible to use also in other Lab-on-a-chip applications

Cell Culture on MEMS Platforms: A Review

Microfabricated systems provide an excellent platform for the culture of cells, and are an extremely useful tool for the investigation of cellular responses to various stimuli. Advantages offered over traditional methods include cost-effectiveness, controllability, low volume, high resolution, and sensitivity. Both biocompatible and bioincompatible materials have been developed for use in these applications. Biocompatible materials such as PMMA or PLGA can be used directly for cell culture. However, for bioincompatible materials such as silicon or PDMS, additional steps need to be taken to render these materials more suitable for cell adhesion and maintenance. This review describes multiple surface modification strategies to improve the biocompatibility of MEMS materials. Basic concepts of cell-biomaterial interactions, such as protein adsorption and cell adhesion are covered. Finally, the applications of these MEMS materials in Tissue Engineering are presented.Institute of Bioengineering and Nanotechnology (Singapore)Singapore. Biomedical Research CouncilSingapore. Agency for Science, Technology and ResearchSingapore. Agency for Science, Technology and Research (R-185-001-045-305)Singapore. Ministry of EducationSingapore. Ministry of Education (Grant R-185- 000-135-112)Singapore. National Medical Research CouncilSingapore. National Medical Research Council (Grant R-185-000-099-213)Jassen Cilag (Firm)Singapore-MIT Alliance (Computational and Systems Biology Flagship Project)Global Enterprise for Micro-Mechanics and Molecular Medicin

Microfluidic devices for cell cultivation and proliferation

Microfluidic technology provides precise, controlled-environment, cost-effective, compact, integrated, and high-throughput microsystems that are promising substitutes for conventional biological laboratory methods. In recent years, microfluidic cell culture devices have been used for applications such as tissue engineering, diagnostics, drug screening, immunology, cancer studies, stem cell proliferation and differentiation, and neurite guidance. Microfluidic technology allows dynamic cell culture in microperfusion systems to deliver continuous nutrient supplies for long term cell culture. It offers many opportunities to mimic the cell-cell and cell-extracellular matrix interactions of tissues by creating gradient concentrations of biochemical signals such as growth factors, chemokines, and hormones. Other applications of cell cultivation in microfluidic systems include high resolution cell patterning on a modified substrate with adhesive patterns and the reconstruction of complicated tissue architectures. In this review, recent advances in microfluidic platforms for cell culturing and proliferation, for both simple monolayer (2D) cell seeding processes and 3D configurations as accurate models of in vivo conditions, are examined

Micro/Nano-Chip Electrokinetics

Micro/nanofluidic chips have found increasing applications in the analysis of chemical and biological samples over the past two decades. Electrokinetics has become the method of choice in these micro/nano-chips for transporting, manipulating and sensing ions, (bio)molecules, fluids and (bio)particles, etc., due to the high maneuverability, scalability, sensitivity, and integrability. The involved phenomena, which cover electroosmosis, electrophoresis, dielectrophoresis, electrohydrodynamics, electrothermal flow, diffusioosmosis, diffusiophoresis, streaming potential, current, etc., arise from either the inherent or the induced surface charge on the solid-liquid interface under DC and/or AC electric fields. To review the state-of-the-art of micro/nanochip electrokinetics, we welcome, in this Special Issue of Micromachines, all original research or review articles on the fundamentals and applications of the variety of electrokinetic phenomena in both microfluidic and nanofluidic devices

Quantitative Macro- and Microscale Methods for Characterizing Cell Viability

The goal of this study is to combine molecular and microdevice methods to characterize and quantify viability of single mammalian cells. Fluorescent-based assays were optimized for adherent HeLa and suspension Jurkat cells and were used as a tool for validation of a microfabricated diagnostic device. Cell and substrate/surface interactions were considered for designing a microfluidic device that can be used to characterize cell viability for quantitative biomedical and cell biology applications, which require label-free, real-time monitoring of cells. Several interdisciplinary methods are employed to evaluate electrical impedance differences between live and dead Jurkat cells in a microfluidic device. Biological Micro-Electro-Mechanical Systems (BioMEMS) offer many advantages over the conventional macroscale approaches to biomedical diagnostics, such as reduced reagents, costs, and power consumption; shorter reaction time; portability; versatility; and potential for parallel, integrated operations, thus having the potential to revolutionize how many current cell-based biomolecular assays are performed. A microchip device to detect cell viability at the single-cell level in real-time has much potential for pharmacological drug screening or point-of-care diagnostics. Optimal cell media conditions such as pH and osmolarity are evaluated to ensure cell viability and adequate sensitivity for detecting cell events via electrical impedance measurements. A fluorescent cell assay using Calcein was optimized for optical validation of Jurkat cell viability studies for cells flowing through a microchannel. Fluorescence microscopy was combined with acquired electrical impedance (at 2 MHz) to validate the presence and viability of each cell at the detection electrodes. The microchip design parameters such as substrate material and geometry of microchannel and electrodes were based of the average 12 um-diameter of Jurkat cells tested. Here, we demonstrate the design of a polymer-based chip device that is able to differentiate between live and dead Jurkat cells on the basis of electrical impedance magnitude and phase signals, which could be related to inherent dielectric differences of live and dead cells. The overall outcome of this study provides groundwork for quantifying cell viability of single cells on-chip, in real-time, in a flow-through system, without the use of expensive fluorescent labels