One of the most popular methods to fabricate biomedical microfluidic devices is by using a soft-lithography technique. However, the fabrication of the moulds to produce microfluidic devices, such as SU-8 moulds, usually requires a cleanroom environment that can be quite costly. Therefore, many efforts have been made to develop low-cost alternatives for the fabrication of microstructures, avoiding the use of cleanroom facilities. Recently, low-cost techniques without cleanroom facilities that feature aspect ratios more than 20, for fabricating those SU-8 moulds have been gaining popularity among biomedical research community. In those techniques, Ultraviolet (UV) exposure equipment, commonly used in the Printed Circuit Board (PCB) industry, replaces the more expensive and less available Mask Aligner that has been used in the last 15 years for SU-8 patterning. Alternatively, non-lithographic low-cost techniques, due to their ability for large-scale production, have increased the interest of the industrial and research community to develop simple, rapid and low-cost microfluidic structures. These alternative techniques include Print and Peel methods (PAP), laserjet, solid ink, cutting plotters or micromilling, that use equipment available in almost all laboratories and offices. An example is the xurography technique that uses a cutting plotter machine and adhesive vinyl films to generate the master moulds to fabricate microfluidic channels. In this review, we present a selection of the most recent lithographic and non-lithographic low-cost techniques to fabricate microfluidic structures, focused on the features and limitations of each technique. Only microfabrication methods that do not require the use of cleanrooms are considered. Additionally, potential applications of these microfluidic devices in biomedical engineering are presented with some illustrative examples.

Polydimethylsiloxane (PDMS) is an elastomer with excellent optical, electrical and mechanical properties, which makes it well-suited for several engineering applications. Due to its biocompatibility, PDMS is widely used for biomedical purposes. This widespread use has also led to the massification of the soft-lithography technique, introduced for facilitating the rapid prototyping of micro and nanostructures using elastomeric materials, most notably PDMS. This technique has allowed advances in microfluidic, electronic and biomedical fields. In this review, an overview of the properties of PDMS and some of its commonly used treatments, aiming at the suitability to those fields’ needs, are presented. Applications such as microchips in the biomedical field, replication of cardiovascular flow and medical implants are also reviewed.

Poly(vinylidene fluoride), PVDF, thin films have been processed by spin-coating with controlled thickness, morphology and crystalline phases. The influence of the polymer/solvent mass ratio of the solution, the rotational speed of the spin-coater and the temperature of crystallization of the films on the properties of the material has been investigated. It is shown that high-quality films with controlled thicknesses from 300 nm to 4.5 μm and with a controlled amount of electroactive crystalline phases can be obtained in a single deposition step, which allows tailoring the material characteristics for specific applications.

Nanomedicine has emerged in the last few decades as a field that can significantly impact the diagnose and therapy of human diseases. [1,2] Based on the outstanding properties that materials acquired at the nanoscale, such as high surface-to-volume ratio, high physicochemical stability, high charge carrier mobility and biocompatibility, a variety of nanoformulations have been developed to be applied in medicine by tailoring their size, shape, charge, and surface functional groups. [2,3] Based on those properties, the design of multifunctional nanoparticles (NPs) for nanomedicine is one of the most promising and exciting research areas that is expected to revolutionize the medical field in the next few decades. [4] Some of these multifunctional NPs have the potentiality to combine both diagnosis and therapy, the so-called theranostics, which is one of the ultimate goals of this field to achieve personalized and precise medical care (Figure 1). Among the therapeutic techniques, nanomaterials developed for drug delivery purpose have been widely investigated as smart drug nanocarriers capable to target tumor cells, protect drugs from degradation, enhance drug solubility, improve biodistribution, extend drug life cycle, and prevent lethal side-effects to healthy tissues and organs. [2,3] The design of these smart drug delivery systems can be engineered to target a specific location by taking advantages of the host environment, using for instance antibodies, aptamers or peptides; and then react autonomously as stimuli-responsive drug release agents, triggered by endogeneous chemical reactions (e.g., enzymes, pH, hydrolysis) or exogeneous stimulisensitive mechanisms (e.g., near infrared light, temperature raise induced by an alternating magnetic field, among others). [5] Comprehensive reviews on the topic of smart nano-based drug delivery systems can be found elsewhere. [5,6] Further complex functionality is represented by smart theranostics, which hold high promise for the nanomedicine of the future. Next, recent representative examples from the research arena are described. Cai et al. [7] make use of enzyme-responsiveness to design a cathepsin B-sensitive theranostic agent. They synthesized a biodegradable conjugate composed of a Gd chelate (Gd-DOTA) as a T1-magnetic resonance imaging (MRI) contrast agent, Despite the progress achieved in nanomedicine during the last decade, the translation of new nanotechnology-based therapeutic systems into clinical applications has been slow, especially due to the lack of robust preclinical tissue culture platforms able to mimic the in vivo conditions found in the human body and to predict the performance and biotoxicity of the developed nanomaterials. Organ-on-a-chip (OoC) platforms are novel microfluidic tools that mimic complex human organ functions at the microscale level. These integrated microfluidic networks, with 3D tissue engineered models, have been shown high potential to reduce the discrepancies between the results derived from preclinical and clinical trials. However, ...

Since the first microfluidic device was developed more than three decades ago, microfluidics is seen as a technology that exhibits unique features to provide a significant change in the way that modern biology is performed. Blood and blood cells are recognized as important biomarkers of many diseases. Taken advantage of microfluidics assets, changes on blood cell physicochemical properties can be used for fast and accurate clinical diagnosis. In this review, an overview of the microfabrication techniques is given, especially for biomedical applications, as well as a synopsis of some design considerations regarding microfluidic devices. The blood cells separation and sorting techniques were also reviewed, highlighting the main achievements and breakthroughs in the last decades.