Hojjat Madadi

Microfluidic point-of-care blood panel based on a novel technique: Reversible electroosmotic flow

A wide range of diseases and conditions are monitored or diagnosed from blood plasma, but the ability to analyze a whole blood sample with the requirements for a point-of-care device, such as robustness, user-friendliness, and simple handling, remains unmet. Microfluidics technology offers the possibility not only to work fresh thumb-pricked whole blood but also to maximize the amount of the obtained plasma from the initial sample and therefore the possibility to implement multiple tests in a single cartridge. The microfluidic design presented in this paper is a combination of cross-flow filtration with a reversible electroosmotic flow that prevents clogging at the filter entrance and maximizes the amount of separated plasma. The main advantage of this design is its efficiency, since from a small amount of sample (a single droplet [Formula: see text]10 μl) almost 10% of this (approx 1 μl) is extracted and collected with high purity (more than 99%) in a reasonable time (5-8 min). To validate the quality and quantity of the separated plasma and to show its potential as a clinical tool, the microfluidic chip has been combined with lateral flow immunochromatography technology to perform a qualitative detection of the thyroid-stimulating hormone and a blood panel for measuring cardiac Troponin and Creatine Kinase MB. The results from the microfluidic system are comparable to previous commercial lateral flow assays that required more sample for implementing fewer tests.

A novel fabrication technique to minimize poly(dimethylsiloxane)-microchannels deformation under high-pressure operation.

PDMS is one of the most common materials used for the flow delivery in the microfluidics chips, since it is clear, inert, nontoxic, and nonflammable. Its inexpensiveness, straightforward fabrication, and biological compatibility have made it a favorite material in the exploratory stages of the bio‐microfluidic devices. If small footprint assays want to be performed while keeping the throughput, high pressure‐rated channels should be used, but PDMS flexibility causes an important issue since it can generate a large variation of microchannel geometry. In this work, a novel fabrication technique based on the prevention of PDMS deformation is developed. A photo‐sensible thiolene resin (Norland Optical Adhesive 63, NOA 63) is used to create a rigid coating layer over the stiff PDMS micropillar array, which significantly reduces the pressure‐induced shape changes. This method uses the exact same soft lithography manufacturing equipment. The verification of the presented technique was investigated experimentally and numerically and the manufactured samples showed a deformation 70% lower than PDMS conventional samples.

An efficient planar accordion-shaped micromixer: from biochemical mixing to biological application

Micromixers are the key component that allow lab-on-a-chip and micro total analysis systems to reach the correct level of mixing for any given process. This paper proposes a novel, simple, passive micromixer design characterized by a planar accordion-shape geometry. The geometrical characteristics of the presented design were analyzed numerically in the range of 0.01 < Re < 100 based on the micromixer performance. The performance of the most efficient design was experimentally investigated by means of fluorescence microscopy for a range of low diffusion coefficients, 10−12 < D < 10−11 m2/s. The micromixer structure was fabricated in a simple single-step process using maskless lithography and soft lithography. The experimental results showed a very good agreement with the predicted numerical results. This micromixer design including a single serpentine unit (1-SERP) displayed an efficiency higher than 90% (mixing length = 6.4 mm) creating a pressure drop of about 500 Pa at Re = 0.1 and 60 kPa at Re = 10. A mixing efficiency of almost 100% was readily reached when three serpentine units were included (3-SERP). Finally, the potential diagnostic value of the presented microdevice was validated experimentally for Red Blood Cell (RBC) lysis.

Study the effects of different surfactants on hydrophilicity of polydimethylsiloxane (PDMS)

The outstanding characteristics of polydimethylsiloxane (PDMS) caused its extensive use as base material to manufacture microfluidic devices. PDMS has numerous advantages coming from instinct properties such as its low cost, simple fabrication procedure, and robust nature that make it a compatible material in many applications such as biological and biomedical engineering. In spite of favorable physical and chemical properties, hydrophobic surface of PDMS is sometimes debatable. Because of PDMS is highly hydrophobic, pumping aqueous solution through microchannels using only capillary forces might be difficult. Although many surface treatments methods have been proposed to modify and increase the hydrophilicity of PDMS [Oxygen plasma [1], UV-radiation [2], Silanization and Chemical vapour deposition [3],…], the use of surfactants is the most effective and easiest method to overcome the hydrophobicity compared to more complex protocols which require expensive facilities [4,5]. The hydrophilic behavior of surfactant-added PDMS and especially its biocompatibility has allowed many microfluidic bio-applications such as separation of biomolecules [6,7], blood cell separation [8] and cell-based assay [9,10]. This paper discusses about the efficiency of adding different surfactants on the wettability of PDMS.Copyright