•A rapid prototyping method for the fabrication of whole-thermoplastic chips with embedded pneumatic micro-actuators was developed.•The fabrication consisting of only laser machining, thermal ...bonding, and surface cleaning is compatible with laboratory chip fabrication.•Whole-thermoplastic membrane-based micro check-valve and check-valve micropump for lab-on-a-chip applications were implemented.
There is a critical need to develop fabrication methods for rapid and cost-effective prototyping of thermoplastics-based microfluidics in academic research laboratories. This paper presents a method for the fabrication of whole-thermoplastic microfluidic functional elements, including a pneumatic (gas-actuated) normally closed microvalve, a micro-check valve, and a pneumatic dual-phase micropump. All devices were made from thermoplastic polyurethane (TPU) and poly(methyl methacrylate) (PMMA). The fabrication process consisted of only laser micromachining and thermal fusion bonding without need to perform any particular chemical treatment or use a master mold. These features enable the widespread adaptation of this method in academic research settings. Characterizations revealed that the fabricated normally closed microvalve could stop liquid flows at pressures lower than 2 psi in its passive operation mode where no pressure was used for valve actuation. The check valve could block liquid flows with liquid pressures of up to 30 psi in its reverse mode of operation while it could allow liquid to pass through in its forward mode. In addition, the micropump, which consisted of two check valves and a pneumatic uni-diaphragm displacement chamber, could pump liquid at an average flow rate of 87.6 ± 5.0 μL/min using an actuation frequency and pressure of 1 Hz and ±5 psi, respectively. Taken together, the developed low-cost whole-thermoplastic microfluidic functional elements could be employed for the fabrication of various lab-on-a-chip applications.
In order to offer the ability of smaller volumes and high throughput in Lab-On-a-Chip and micro Total Analysis Systems devices, more miniaturized components are needed. Due to a low Reynolds number ...on the microscale, the mixing process can be particularly troublesome. This problem is compounded by the fact that more miniaturization can be challenging in a microfluidic system. In such a case, electroosmotic (EO) force is an efficient force to perturb low Reynolds number fluid. In this paper, a novel Micro-Electro-Mechanical-Systems (MEMS) based fabrication for microfluidic devices, and a more miniaturized micromixer are presented. The proposed technology process requires the covering of excited electrode patterns by a thin Silicon-Nitride (Si₃N₄) insulator layer. Fabrication parameters such as Low Pressure Chemical Vapor Deposition (LPCVD) Si₃N₄ deposition effect, and height of the Phosphor Silicate Glass (PSG) sacrificial layer were investigated for the electroosmotically-driven mixer. Particle tracing for fluid flow was illustrated, the particles were stretched and folded for a long time, which was a proof of chaotic regime. Finite Element Analysis (FEA) revealed that the mixer with covered electrodes provides the high mixing efficiency of above 90% for a 96 μm long microchannel. Using a silicon nitride insulator layer reduces high electric field gradient at sharp corners and edges of the electrodes, leading to the elimination of unwanted electrolyte effects. Thus, the excitation and geometrical parameters were optimized for the micromixer.
Organ-on-a-chip systems are miniaturized microfluidic 3D human tissue and organ models designed to recapitulate the important biological and physiological parameters of their in vivo counterparts. ...They have recently emerged as a viable platform for personalized medicine and drug screening. These in vitro models, featuring biomimetic compositions, architectures, and functions, are expected to replace the conventional planar, static cell cultures and bridge the gap between the currently used preclinical animal models and the human body. Multiple organoid models may be further connected together through the microfluidics in a similar manner in which they are arranged in vivo, providing the capability to analyze multiorgan interactions. Although a wide variety of human organ-on-a-chip models have been created, there are limited efforts on the integration of multisensor systems. However, in situ continual measuring is critical in precise assessment of the microenvironment parameters and the dynamic responses of the organs to pharmaceutical compounds over extended periods of time. In addition, automated and noninvasive capability is strongly desired for long-term monitoring. Here, we report a fully integrated modular physical, biochemical, and optical sensing platform through a fluidics-routing breadboard, which operates organ-on-a-chip units in a continual, dynamic, and automated manner. We believe that this platform technology has paved a potential avenue to promote the performance of current organ-on-a-chip models in drug screening by integrating a multitude of real-time sensors to achieve automated in situ monitoring of biophysical and biochemical parameters.
•A rapid prototyping method for the fabrication of whole-thermoplastic chips with embedded microvalves was developed.•Unfocused laser machining was used for fabrication of semi-circular microchannels ...with polyurethane as actuation membrane.•A chemical treatment method was optimized for smoothening the surface of the laser-machined microchannels.•A low-temperature thermal fusion bonding strategy was developed for the bonding of PMMA to polyurethane.
Recently, there has been an increasing effort in developing new fabrication methods for rapid prototyping of microfluidic chips using thermoplastic materials. This is mainly due to the excellent properties of thermoplastics including inherent robustness to mechanical deformation and resistance to chemicals. In this paper, we report on the development of a novel rapid prototyping method to fabricate microfluidic chips from thermoplastic materials with embedded pneumatic controls. A CO2 laser micromachining method was employed to engrave and cut poly(methyl methacrylate) (PMMA) sheets, which together with a thermoplastic polyurethane (TPU) film, enabled fabrication of various functional microfluidic elements including microvalves, micropumps, and bioreactors. To generate the gas-actuated microvalve, unfocused CO2 laser beam was used to fabricate semi-circular fluid channels in PMMA. An optimized chemical surface treatment procedure was subsequently applied to smoothen the surface of the microchannels. TPU film serving as a flexible membrane was attached above the semi-circular channel sandwiched by another piece of PMMA containing a gas channel to achieve the architecture of the microvalve. A thermal fusion bonding method was developed to bond TPU film to the PMMA components in a single step. A peristaltic micropump was also fabricated consisting of sequential interconnected gas-actuated microvalves. In addition, results from cell cultures in fabricated whole-thermoplastic bioreactors demonstrated biocompatibility of the whole-thermoplastic microchips. Taken together, the developed fabrication process in conjunction with proposed thermoplastic materials provide an inexpensive and versatile method for rapid prototyping of various microfluidic devices.
Abstract
In this study, a planar printed circuit board (PCB) coil with FR4 substrate was designed and simulated using the finite element method, and the results were analyzed in the frequency domain. ...This coil can be used in wireless power transfer (WPT) as a transmitter or receiver, eliminating wires. It can also be used as the receiver in radio frequency energy‐harvesting (RF‐EH) systems by optimizing the planar PCB coil to convert radio‐wave energy into electricity, and it can be employed as an excitation (transmitter) or receiver coil in nuclear magnetic resonance (NMR) spectroscopy. This PCB coil can replace the conventional coil, yielding a reduced occupied volume, a fine‐tuned design, reduced weight, and increased efficiency. Based on the calculated gain, power, and electromagnetic and electric field results, this planar PCB coil can be implemented in WPT, NMR spectroscopy, and RF‐EH devices with minor changes. In applications such as NMR spectroscopy, it can be used as a transceiver planar PCB coil. In this design, at frequencies of 915 MHz and 40 MHz with 5 mm between coils, we received powers of 287.3
W and 480
W, respectively, which are suitable for an NMR coil or RF‐EH system.
In this work a novel electrode structure is proposed to separate viable and non-viable yeast cells by travelling-wave dielectrophoresis (twDEP). The electrodes are chevron-shaped which the sharp ...angle at the center of the electrodes is replaced by a curvature. We employed finite element method to simulate and observe the electric fields related to conventional dielectrophoresis (cDEP) and twDEP and correspondingly to estimate the cell trajectories under the applied electric field. Furthermore, we discuss different physical and geometrical parameters to design our twDEP microseparator to get the most accurate operation and higher separation efficiency. First, we study the adequate frequency and medium conductivity. Then, we explore the optimized electrode dimensions for target cells. From the simulations, we discovered that by the proposed electrode structure and applying phase shifted AC electric potential with amplitude of 2 V
p
-
p
and frequency of 70 kHz viable yeast cells discriminate from non-viable ones and get focused on a band at the center of the channel, simultaneously. The simulation results reveal that here the maximum twDEP force is applied to yeast cells when electrode width is about 12 μm. Finally, we propose possible different electrode forms that can be derived from our proposed electrode shape to manipulate different cells/particles.
There is a growing interest to develop microfluidic bioreactors and organ-on-chip platforms with integrated sensors to monitor their physicochemical properties and to maintain a well-controlled ...microenvironment for cultured organoids. Conventional sensing devices cannot be easily integrated with microfluidic organ-on-chip systems with low-volume bioreactors for continual monitoring. This paper reports on the development of a multi-analyte optical sensing module for dynamic measurements of pH and dissolved oxygen levels in the culture medium. The sensing system was constructed using low-cost electro-optics including light-emitting diodes and silicon photodiodes. The sensing module includes an optically transparent window for measuring light intensity, and the module could be connected directly to a perfusion bioreactor without any specific modifications to the microfluidic device design. A compact, user-friendly, and low-cost electronic interface was developed to control the optical transducer and signal acquisition from photodiodes. The platform enabled convenient integration of the optical sensing module with a microfluidic bioreactor. Human dermal fibroblasts were cultivated in the bioreactor, and the values of pH and dissolved oxygen levels in the flowing culture medium were measured continuously for up to 3 days. Our integrated microfluidic system provides a new analytical platform with ease of fabrication and operation, which can be adapted for applications in various microfluidic cell culture and organ-on-chip devices.
This paper describes the design and fabrication of an optical glucose sensing system in a microfluidic chip on a PDMS substrate. We studied the potential of the near infrared wavelength, 940 nm as ...glucose sensor based on Beer lambert's law. This sensor consists of a 940nm IR-LED as a light source and a PIN photodiode that is sensitive to that wavelength. The detection of glucose was performed by aqueous glucose solutions in the clinical concentration range in a PDMS-based microfluidic chip. The relationship between system output voltage and glucose concentration was studied in transmission spectroscopy. For glucose solutions ranging from 60 to 300 mg/dL the output voltages were approximately changed linearly from 1211 to 1129 mv. Based on the promising results obtained from the experiments, this sensor has the potential for glucose detection in complex physiological environments.
Separation of micron-sized particles is a challenge by highly miniaturized channel systems. In order to offer the ability of smaller volumes and high throughput in Lab-on-a-chip devices more ...miniaturized components are needed. Due to very low Reynolds number of buffer fluid, microseparators based on travelling wave dielectrophoresis effect have a good efficiency in such applications. In the present paper, a microchannel technique based on surface micromachining is modified to a microseparator. The proposed device is a miniaturized 4-phase travelling wave microseparator with the height of 5 urn, which can be used for separation of biological particles such as cells and some types of viruses. According to numerical simulations, the device can separate and sort different species, as well as different sized cells of the same species. Due to fabrication process, the electrodes made of highly doped poly-silicon are covered by a thin silicon-nitride layer. Additional advantage of the silicon-nitride layer over electrode arrays is the prevention of high electric field gradient. The effect of this thin insulating layer on functionality of the microseparator has been investigated. The simulation results show that a good separation occurs in the frequency range of 1MHz, when electrical conductivity of buffer fluid is near lus/m. The fabrication process is presented and influences of other parameters such as permittivity of fluid and fluid conductivity on the operation of the separator are discussed.
This work presents utilizing of electric field to separate viable and nonviable yeast cells in a droplet. The separator consists of two parallel plates with deposited electrodes and a droplet is ...placed between them. Bottom electrodes are boomerang-shaped and are used for cell separation by travelling-wave dielectrophoresis. The upper electrodes are square-shaped and are utilized for cutting the droplet, after the cell separation. Bottom microelectrodes are excited with 90 degrees' phase shifted electric potentials with amplitude of 4 V p-p and frequency of 70 kHz. In this situation, nonviable yeast cells are not significantly affected by travelling-wave dielectrophoresis while viable ones are focused at the center of the curvature of the electrodes. This is a significant advantage of our proposed in-droplet separator, because ensures the accumulation of viable yeast cells at the rightest corner of the droplet and guarantees that they remain at the right daughter droplet through the droplet cutting process. The design process and simulations are explained. Simulations have been done in a commercially available finite element software to simulate electric field and predict the cell trajectories. Then the results are validated by comparing them with previous works in the literature.
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