Vera Faustino

Bio: Vera Faustino is an academic researcher from University of Minho. The author has contributed to research in topics: Microchannel & Video microscopy. The author has an hindex of 10, co-authored 24 publications receiving 488 citations. Previous affiliations of Vera Faustino include University of Porto & Faculdade de Engenharia da Universidade do Porto.

Deformation of Red Blood Cells, Air Bubbles, and Droplets in Microfluidic Devices: Flow Visualizations and Measurements.

Abstract: Techniques, such as micropipette aspiration and optical tweezers, are widely used to measure cell mechanical properties, but are generally labor-intensive and time-consuming, typically involving a difficult process of manipulation. In the past two decades, a large number of microfluidic devices have been developed due to the advantages they offer over other techniques, including transparency for direct optical access, lower cost, reduced space and labor, precise control, and easy manipulation of a small volume of blood samples. This review presents recent advances in the development of microfluidic devices to evaluate the mechanical response of individual red blood cells (RBCs) and microbubbles flowing in constriction microchannels. Visualizations and measurements of the deformation of RBCs flowing through hyperbolic, smooth, and sudden-contraction microchannels were evaluated and compared. In particular, we show the potential of using hyperbolic-shaped microchannels to precisely control and assess small changes in RBC deformability in both physiological and pathological situations. Moreover, deformations of air microbubbles and droplets flowing through a microfluidic constriction were also compared with RBCs deformability.

A simple microfluidic device for the deformability assessment of blood cells in a continuous flow.

Abstract: Blood flow presents several interesting phenomena in microcirculation that can be used to develop microfluidic devices capable to promote blood cells separation and analysis in continuous flow. In the last decade there have been numerous microfluidic studies focused on the deformation of red blood cells (RBCs) flowing through geometries mimicking microvessels. In contrast, studies focusing on the deformation of white blood cells (WBCs) are scarce despite this phenomenon often happens in the microcirculation. In this work, we present a novel integrative microfluidic device able to perform continuous separation of a desired amount of blood cells, without clogging or jamming, and at the same time, capable to assess the deformation index (DI) of both WBCs and RBCs. To determine the DI of both WBCs and RBCs, a hyperbolic converging microchannel was used, as well as a suitable image analysis technique to measure the DIs of these blood cells along the regions of interest. The results show that the WBCs have a much lower deformability than RBCs when subjected to the same in vitro flow conditions, which is directly related to their cytoskeleton and nucleus contents. The proposed strategy can be easily transformed into a simple and inexpensive diagnostic microfluidic system to simultaneously separate and assess blood cells deformability.

A Rapid and Low-Cost Nonlithographic Method to Fabricate Biomedical Microdevices for Blood Flow Analysis

Abstract: Microfluidic devices are electrical/mechanical systems that offer the ability to work with minimal sample volumes, short reactions times, and have the possibility to perform massive parallel operations. An important application of microfluidics is blood rheology in microdevices, which has played a key role in recent developments of lab-on-chip devices for blood sampling and analysis. The most popular and traditional method to fabricate these types of devices is the polydimethylsiloxane (PDMS) soft lithography technique, which requires molds, usually produced by photolithography. Although the research results are extremely encouraging, the high costs and time involved in the production of molds by photolithography is currently slowing down the development cycle of these types of devices. Here we present a simple, rapid, and low-cost nonlithographic technique to create microfluidic systems for biomedical applications. The results demonstrate the ability of the proposed method to perform cell free layer (CFL) measurements and the formation of microbubbles in continuous blood flow.

A Microfluidic Deformability Assessment of Pathological Red Blood Cells Flowing in a Hyperbolic Converging Microchannel

Abstract: The loss of the red blood cells (RBCs) deformability is related with many human diseases, such as malaria, hereditary spherocytosis, sickle cell disease, or renal diseases. Hence, during the last years, a variety of technologies have been proposed to gain insights into the factors affecting the RBCs deformability and their possible direct association with several blood pathologies. In this work, we present a simple microfluidic tool that provides the assessment of motions and deformations of RBCs of end-stage kidney disease (ESKD) patients, under a well-controlled microenvironment. All of the flow studies were performed within a hyperbolic converging microchannels where single-cell deformability was assessed under a controlled homogeneous extensional flow field. By using a passive microfluidic device, RBCs passing through a hyperbolic-shaped contraction were measured by a high-speed video microscopy system, and the velocities and deformability ratios (DR) calculated. Blood samples from 27 individuals, including seven healthy controls and 20 having ESKD with or without diabetes, were analysed. The obtained data indicates that the proposed device is able to detect changes in DR of the RBCs, allowing for distinguishing the samples from the healthy controls and the patients. Overall, the deformability of ESKD patients with and without diabetes type II is lower in comparison with the RBCs from the healthy controls, with this difference being more evident for the group of ESKD patients with diabetes. RBCs from ESKD patients without diabetes elongate on average 8% less, within the hyperbolic contraction, as compared to healthy controls; whereas, RBCs from ESKD patients with diabetes elongate on average 14% less than the healthy controls. The proposed strategy can be easily transformed into a simple and inexpensive diagnostic microfluidic system to assess blood cells deformability due to the huge progress in image processing and high-speed microvisualization technology.

A Review of Current Methods in Microfluidic Device Fabrication and Future Commercialization Prospects

Abstract: Microfluidic devices currently play an important role in many biological, chemical, and engineering applications, and there are many ways to fabricate the necessary channel and feature dimensions In this review, we provide an overview of microfabrication techniques that are relevant to both research and commercial use A special emphasis on both the most practical and the recently developed methods for microfluidic device fabrication is applied, and it leads us to specifically address laminate, molding, 3D printing, and high resolution nanofabrication techniques The methods are compared for their relative costs and benefits, with special attention paid to the commercialization prospects of the various technologies

Active and passive micromixers: A comprehensive review

Abstract: The present review (with 205 refs.) addresses the need for microdevices, presents the basic microfluidic equations and describes the relevant numerical and experimental approaches. Various types and designs of passive and active micromixers are presented. In addition, the relevant effective dimensionless or dimensional parameters and the fabrication technology for different micromixer types are introduced. Different general configurations of lamination, obstacle, convergence-divergence and curved-channel are discussed for passive micromixers. The active micromixers are categorized and described as pressure field driven, acoustic field driven, magnetic field driven, electric field driven and thermal field driven.

3D printing for chemical, pharmaceutical and biological applications

Abstract: 3D printing is becoming increasingly prevalent in modern chemistry laboratories. This technology provides chemists with the ability to design, prototype and print functional devices that integrate catalytic and/or analytical functionalities and even to print common laboratory hardware and teaching aids. Although access to 3D printers has increased considerably, some design principles and material considerations need to be weighed before employing such technology in chemistry laboratories. In addition, a certain level of expertise needs to be acquired in order to use computer-aided design, printing software and the specialist hardware associated with higher-end instrumentation. Nonetheless, the recent progress in this field is encouraging, with these printing technologies offering many advantages over traditional production methods. This Review highlights some of the notable advances in this growing area over the past decade. 3D printing is becoming a mainstream technology with considerable increase in access to affordable desktop printers. However, specific design principles and material considerations need to be weighed when printing functional devices that integrate catalytic and/or analytical functionalities, as well as when printing common laboratory hardware.

Fabrication and Applications of Microfluidic Devices: A Review.

Abstract: Microfluidics is a relatively newly emerged field based on the combined principles of physics, chemistry, biology, fluid dynamics, microelectronics, and material science. Various materials can be processed into miniaturized chips containing channels and chambers in the microscale range. A diverse repertoire of methods can be chosen to manufacture such platforms of desired size, shape, and geometry. Whether they are used alone or in combination with other devices, microfluidic chips can be employed in nanoparticle preparation, drug encapsulation, delivery, and targeting, cell analysis, diagnosis, and cell culture. This paper presents microfluidic technology in terms of the available platform materials and fabrication techniques, also focusing on the biomedical applications of these remarkable devices.