Rafał Walczak

Inkjet 3D printing of microfluidic structures—on the selection of the printer towards printing your own microfluidic chips

This article reports, for the first time, the results of detailed research on the application of inkjet 3D printing for the fabrication of microfluidic structures. CAD designed test structures were printed with four different printers. Dimensional fidelity, shape conformity, and surface roughness were studied for each printout. It was found that the minimum dimension (width or depth) for a properly printed microfluidic channel was approximately 200 μm. Although the nominal resolution of the printers was one order of magnitude better, smaller structures were significantly deformed or not printed at all. It was also found that a crucial step in one-step fabrication of embedded microchannels is the removal of the support material. We also discuss the source of print error and present a way to evaluate other printers. The printouts obtained from the four different printers were compared, and the optimal printing technique and printer were used to fabricate a microfluidic structure for the spectrophotometric characterisation of beverages. UV/VIS absorbance characteristics were collected using this microfluidic structure, demonstrating that the fabricated spectrophotometric chip operated properly. Thus, a proof-of-concept for using inkjet 3D printing for the fabrication of microfluidic structures was obtained.

Microsensors for Microreaction and Lab-on-a-Chip Applications

Since the first successful applications of the microfluidical devices, measurement of physical, chemical and biochemical parameters of performed reactions and analysis became next challenge and millstone towards successful application of developed instrumentation in many field of science and industry, as well as, deeper understating of microand nanoworld of fluidics (Ehrfeld at al., 2005). Although, methodology of these measurements was well known from many years, the main problems that occurred were dimensional incompatibility of available macroscopic solutions and sensing problems caused by significant reduction of managed and analyzed volumes. Therefore, microsensors became important part of the microfluidical device enabling real-time and on-chip measurement of measurable parameters like pressure, temperature, conductivity, absorbance or fluorescence. In this chapter miniature on-chip integrated pressure sensors, discreet corrosion resistant pressure sensor and conductometric flow-through detector will be described in details. Nevertheless, optical microrensors like absorbance NIR and VIS detector, as well as fluorometric detector will be shown. Technology of the sensors utilizes microengineering techniques where silicon and glass play main role as constructional materials. Threedimensional formation and assembling techniques of silicon and glass allow to fabricate miniature sensors. For each presented microsensor, the fabrication techniques will be described in details. Great attention is also paid for development of the complete measurement system consisting of the microsensors itself but also specialized electronics and information environment for full data management and measurement or analyse result presentation.

A miniaturised image based fluorescence detection system for point-of-care-testing of cocaine abuse

In this paper, we describe a miniaturised image-based fluorescence detection system and demonstrate its viability as a highly sensitive tool for point-of-care-analysis of drugs of abuse in human sweat with a focus on monitor individuals for drugs of abuse. Investigations of miniaturised and low power optoelectronic configurations and methodologies for real-time image analysis were successfully carried out. The miniaturised fluorescence detection system was validated against a reference detection system under controlled laboratory conditions by analysing spiked sweat samples in dip stick and then strip with sample pad. As a result of the validation studies, a 1 ng mL−1 limit of detection of cocaine in sweat and full agreement of test results with the reference detection system can be reported. Results of the investigations open the way towards a detection system that integrates a hand-held fluorescence reader and a wearable skinpatch, and which can collect and in situ analyse sweat for the presence of cocaine at any point for up to tenths hours.

A Trip from a Tube to a Chip Applied Micro and Nanotechnology in Biotechnology, Veterinary and Life Sciences

More than 200 known diseases are transmitted via foods or food products. In the United States, food-borne diseases are responsible for 76 million cases of illness, 32,500 cases of hospitalisation and 5000 cases of death yearly. The ongoing increase in worldwide trade in livestock, food, and food products in combination with increase in human mobility (business- and leisure travel, emigration etc.) will increase the risk of emergence and spreading of such pathogens. There is therefore an urgent need for development of rapid, efficient and reliable methods for detection and identification of such pathogens.

Algorithms and approaches for processing an output signal from lab-on-a-chip devices in bioanalysis

Algorithms and approaches used for implementing software for processing an image output signal from microfluidic devices are presented in this paper. Such microdevices (often called a lab-on-a-chip) are utilized in analysis of biological cells; their behaviors are investigated under different sets of conditions. We present here algorithms for cell detecting, processing and automatic recognition of shape and size of cells in lab-chips for bioanalysis.

Microfluidic method of pig oocyte quality assessment in relation to different follicular size based on lab-on-chip technology.

Since microfollicular environment and the size of the follicle are important markers influencing oocyte quality, the aim of this study is to present the spectral characterization of oocytes isolated from follicles of various sizes using lab-on-chip (LOC) technology and to demonstrate how follicle size may affect oocyte quality. Porcine oocytes (each, n = 100) recovered from follicles of different sizes, for example, from large (>5 mm), medium (3–5 mm), and small (<3 mm), were analyzed after preceding in vitro maturation (IVM). The LOC analysis was performed using a silicon-glass sandwich with two glass optical fibers positioned “face-to-face.” Oocytes collected from follicles of different size classes revealed specific and distinguishable spectral characteristics. The absorbance spectra (microspectrometric specificity) for oocytes isolated from large, medium, and small follicles differ significantly (P < 0.05) and the absorbance wavelengths were between 626 and 628 nm, between 618 and 620 nm, and less than 618 nm, respectively. The present study offers a parametric and objective method of porcine oocyte assessment. However, up to now this study has been used to evidence spectral markers associated with follicular size in pigs, only. Further investigations with functional-biological assays and comparing LOC analyses with fertilization and pregnancy success and the outcome of healthy offspring must be performed.

LABONFOIL: investigations regarding microfluidic skin patches for drug detection using flexible OLEDs

This contribution describes first results concerning the overall and especially optical system design of microfluidic skin patches for drug detection based on fluorescence analysis of sweat samples. This work has been carried out within the European project LABONFOIL which aims to develop low-cost lab-on-chip systems for four different applications, one of them for the detection of cocaine abuse by professional drivers. To date work has focused on the integrated design of the skin patch itself including methods for sweat collection as well as studies concerning the feasibility of OLEDs for optical excitation of the fluorescence signal.

Optical microlenses for MOEMS

A new concept of the fabrication process for glass microlenses (external diameter ED<1 mm, focal length a few millimeters), based on the silicon master mask-less anisotropic wet etching in KOH, vacuum anodic bonding and re-flow of borosilicate glass, followed by the precise wafer-scale polishing and DRIE has been presented. A single spherical microlens as well as an array of spherical microlenses with focal length between 44.8 and 8.6 mm and external diameter 0.35 to 0.985 mm have been repeatable manufactured.

The model of a light transmittance through translucent objects in lens-free imaging setups

In this paper the model of a light transmittance through translucent object inside lens-free imaging setup is presented.

Comparison of algorithms for detection and real-time tracking of living microorganisms in lab-on-a-chip devices

This paper is devoted to present technique of the use of image processing for lab-on-a-chip techniques. Algorithms and methods for cell detecting, obtaining their parameters and multiparametric cell tracking in lab-on-a-chip were presented and discussed from the point of real-time detection.