Spermatozoa detection and counting on Chip

Semen analysis is usually one of the first tests performed for detecting the cause of infertility of a couple. Therefore the man has to collect his semen in a special container and deliver it within one hour of collection to the hospital. The parameters determined with a semen analysis are the morphology and motility of the spermatozoa in the semen, as well as the concentratio

Blood-brain barrier (BBB): an overview of the research of the blood-brain barrier using microfluidic devices

The blood-brain barrier (BBB) is a unique feature of the human body, preserving brain homeostasis and preventing toxic substances to enter the brain. However, in various neurodegenerative diseases, the function of the BBB is disturbed. Mechanisms of the breakdown of the BBB are incompletely understood and therefore a realistic model of the BBB is essential. This chapter highlights the anatomy and physiology of the BBB and gives an overview of the current available in vitro models to study the BBB in detail. Proof-of-concept work of BBB-on-Chips are described. Additionally, examples are given to optimize the present devices by engineering the microenvironment to better mimic the in vivo situation. This combination of biomedical science and micro-engineering will generate exciting new results in the field of neurovascular biology

Continuous focusing, fractionation and extraction of anionic analytes in a microfluidic chip

Electrokinetic focusing and separation methods, specifically ion concentration polarization focusing (ICPF), provide a very powerful and easy to use analytical tool for several scientific fields. Nevertheless, the concentrated and separated analytes are effectively trapped inside the chip in picoliter volumes. In this article we propose an ICPF device that allows continuous and selective extraction of the focused analytes. A theoretical background is presented to understand the dynamics of the system and a 1D model was developed that describes the general behavior of the system. We demonstrate the selective extraction of three fluorescent model anionic analytes and we report selective extraction of the analytes at a 300-fold increased concentration

Free Flow Ion Concentration Polarization Focusing (FF-ICPF)

Electrokinetic separation techniques in microfluidics are a powerful analytical chemistry tool, although an inherent limitation of microfluidics is their low sample throughput. In this article we report a free-flow variant of an electrokinetic focusing method, namely ion concentration polarization focusing (ICPF). The analytes flow continuously through the system via pressure driven flow while they separate and concentrate perpendicularly to the flow by ICPF. We demonstrate free flow ion concentration polarization focusing (FF-ICPF) in two operating modes, namely peak and plateau modes. Additionally, we showed the separation resolution could be improved by the use of an electrophoretic spacer. We report a concentration factor of 10 in human blood plasma in continuous flow at a flow rate of 15 μL min–1

Droplet encapsulation of electrokinetically-focused analytes without loss of resolution

Lab-on-chip electrokinetic focusing and separation techniques are widely used in several scientific fields. In a number of cases, these techniques have been combined with a selective analyte extraction for off-chip analysis. Nevertheless, the usability of the extracts is limited by diffusion which reduces the separation resolution. In this paper we propose the integration of a droplet generator capable of continuous or on-demand generation and extraction of electrokinetically separated and focused analytes. We demonstrate the selective droplet extraction of model analytes separated and concentrated via ion concentration polarization focusing (ICPF). We report extracted droplets with 1000-fold increased concentration. Importantly, the droplet generator does not interrupt the ICPF process making it suitable for integration with the majority of electrokinetic separation techniques

Macro valve and peristaltic pump with cleanroom-free fabrication for multiplexed organ-on-chip applications

Integrated microfluidic valves enable automated control in microfluidic systems as they can be applied for mixing, pumping, and compartmentalisation purposes. However, many organ-on-chip systems require channel dimensions in the range of hundreds of micrometres while the typical fabrication process for normally open micro valves requires a reflow photoresist which is not capable of achieving these dimensions. Here we show a mechanical macro valve, fabricated cleanroom-free by micromilling, closing and bridging a 400 μm high, 1000 μm wide channel. Furthermore, we use the valves to create an inlet switch and a peristaltic pump with a pumping rate of 2 μL/min

DNA-Origami Enabled Distance-Dependent Sensing

Localized surface plasmon resonance is a popular optical detection technique due to its ease of use. However, the main issues of this technique are its selectivity and sensitivity towards (small) single molecules. We address these challenges by introducing a distance-dependent plasmonic sensing method based on a gold nanoparticle (AuNP) tethered by a single DNA hairpin to a gold film (Au-film). The plasmonic properties of a AuNP enable us to distinguish the z-height of the particle. In the absence of a target sequence, the hairpin keeps the AuNP close to the Au-film, while hybridization with a target sequence results in an extended state of the DNA tether. We experimentally confirmed the assembly of this sensor and by simulations, predicted the plasmonic signal of the two states. Finally, we showed experimental results as proof of concept of our sensing method