Effect of laser processing parameters and glass type on topology of micro-channels

Traditional processes to manufacture micro-fluidic devices include standard lithography, electron beam writing and photo-patterning. These techniques are well established but most are limited to surface micro-fabrication. Laser micro-machining provides an alternative for microfabrication of devices. This paper presents Design of Experiment models for the fabrication of micro-channel structures with four different types of glass, soda-lime, fused-silica, borosilicate and quartz. A 1.5kW CO2 laser with 90 μm spot size was used to fabricate micro-channels on the surface of glass sheets. Power, P, pulse repetition frequency, PRF, and translation speed, U, were set as control parameters. The resulting geometry of the channel (depth and width) and transmission capabilities were measured and analyzed. A comparison of the results of this experimental testing with the four glass types showed that quartz and fused-silica glasses would have better channel topologies for chemical sensing applications

Spiropyran modified microfluidic chip channels for photonically controlled sensor array detection of metal ions

Microfluidic chips are particularly attractive for analytical purposes because they provide a convenient small platform for rapid analysis and detection.1 Furthermore, spiropyrans dyes can be used as photonically controlled, self-indicating molecular recognition agents for the fabrication of sensors.2 Here, we show how through integrating the beneficial characteristics of microfluidic devices and spiropyrans dyes, a simple and very innovative chip for on-line metal ion sensor array can be realised. The chip (4x3cm) consists of four independent 180m depth, polydimethylsiloxane (PDMS) channels. 1’-(3-Carboxypropyl)-3,3’-dimethyl-6-nitrospiro-[2H-1]-benzopyran-2,2’-indoline is covalently immobilised on the ozone plasma activated PDMS microchannel surfaces. Upon exposure to UV light, the transparent PDMS channels change to light purple colour because the spiropyran molecules of the surface undergo a heterocyclic ring cleavage that result in the formation of the highly conjugated merocyanine form. When stock solutions of several ion metals (Ca2+,Zn2+,Hg2+,Cu2+) are pumped independently through the four channels, different optical responses were observed for each metal. 1-L.Basabe-Desmonts et al. Anal.Bioanal.Chem.(2008)390:307–315. 2-R.J.Byrne et al. J.Mat.Chem.(2006)16:1332-1337

Spiropyran modified PDMS micro-fluidic chip device for photonically controlled sensor array detection of metal ions

Micro‐fluidic chips are particularly attractive in biological and life sciences for analytical purposes because they provide a convenient small platform for rapid analysis and detection [1]. Using micro‐fluidic devices for the determination of ions emerges as a potential solution to some of the challenges not overtaken by conventional techniques e.g. atomic absorption, inductively‐coupled plasma‐optical emission, mass spectrometry and ion‐selective electrodes [2]. For example, these devices can integrate complex sample handling processes, calibration, and detection steps into a compact, portable system. Moreover they require small sample volumes (low μl or nl), consume little power, and are easily constructed for multi‐analyte detection, either through multiple parallel fluidic architectures or by using arrays of detection elements. Organic photochromic compounds like spiropyrans are particularly interesting targets for the development of new approaches to sensing since they offer new routes to multi‐functional materials that take advantage of their photo‐reversible interconversion between two thermodynamically stable states (a spiropyran (SP) form, and a merocyanine (MC) form), which have dramatically different charge, polarity and molecular conformations. Furthermore, they can be easily incorporated into membranes for improved robustness and ease of handling [3], but from our perspective, most interesting of all, they have metal ion‐binding and molecular recognition properties which are only manifested by the MC form. Based on the coordinationinduced photochromism characteristic of the MC form, spiropyrans have been employed as molecular probes for metal ions and organic molecules [4]. In this abstract, we show how through integrating the beneficial characteristics of micro‐fluidic devices and spiropyrans photoswitches, a simple and very innovative chip configured as an on‐line metal ion sensor array can be realised (Figure 1). The micro‐fluidic device consists of five independent 94 μm depth, 150 μm width channels fabricated in polydimethylsiloxane. The spiropyran 1’‐(3‐carboxypropyl)‐3,3’‐dimethyl‐6‐nitrospiro‐1‐benzopyran‐2,2’‐indoline (SP‐COOH) is immobilised by physical adsorption directly on ozone plasma activated PDMS micro‐channel walls. When the colourless, inactive, spiropyran coating absorbs UV light it switches to the highly coloured merocyanine form (MC‐COOH), which also has an active binding site for certain metal ions. Therefore metal ion uptake can be triggered using UV light and subsequently reversed on demand by shining white light on the coloured complex, which regenerates the inactive spiropyran form, and releases the metal ion. When stock solutions of several metal ions (Ca2+, Zn2+, Hg2+, Cu2+, Co2+) are pumped independently through the five channels, different optical responses were observed for each metal (Figure 2), (i.e. complex formation with metal ions is associated with characteristic shifts in the visible spectrum), and the platform can therefore be regarded as a micro‐structured device for online multi‐component monitoring of metal cations

The use of scanning contactless conductivity detection for the characterisation of stationary phases in micro-fluidic chips

The use of scanning capacitively coupled contactless conductivity detection for the evaluation of the structural homogeneity and density of both packed and monolithic stationary phases in microfluidic chips is presented here for the first time

Portable capillary-based (non-chip) capillary electrophoresis

Miniaturized, portable instrumentation has been gaining popularity in all areas of analytical chemistry. Capillary electrophoresis (CE), due to its main strengths of high separation efficiency, relatively short analysis time and low consumption of chemicals, is a particularly suitable technique for use in portable analytical instrumentation. In line with the general trend in miniaturization in chemistry utilizing microfluidic chips, the main thrust of portable CE (P—CE) systems development is towards chip-based miniaturized CE. Despite this, capillary-based (non-chip) P—CE systems have certain unmatched advantages, especially in the relative simplicity of the regular cylindrical geometry of the CE capillary, maximal volume-to-surface ratio, no need to design and to fabricate a chip, the low costs of capillary compared to chip, and better performance with some detection techniques. This review presents an overview of the state of the art of P—CE and literature relevant to futuredevelopments. We pay particular attention to the development and the potential of miniaturization of functional parts for P—CE. These include components related to sample introduction, separation and detection, which are the key elements in P—CE design. The future of P—CE may be in relatively simple, rugged designs (e.g., using a short piece of capillary fixed to a chip-sized platform on which injection and detection parts can be mounted). Electrochemical detection is well suited for miniaturization, so is probably the most suitable detection technique for P—CE, but optical detection is gaining interest, especially due to miniaturized light sources (e.g., light-emitting diodes)

Numerical model for light propagation and light intensity distribution inside coated fused silica capillaries

Numerical simulations of light propagation through capillaries have been reported to a limited extent in the literature for uses such as flow-cell design. These have been restricted to prediction of light path for very specific cases to date. In this paper, a new numerical model of light propagation through multi-walled cylindrical systems, to represent coated and uncoated capillaries is presented. This model allows for light ray paths and light intensity distribution within the capillary to be predicted. Macro-scale (using PMMA and PC cylinders) and micro-scale (using PTFE coated fused silica capillaries) experiments were conducted to validate the model's accuracy. These experimental validations have shown encouragingly good agreement between theoretical predictions and measured results, which could allow for optimisation of associated regions for monolith synthesis and use in fluidic chromatography, optical detection systems and flow cells for capillary electrophoresis and flow injection analysis

Mechanical barrier project

V první části této bakalářské práce je vypracován rozbor různých koncepcí řešení mechanických závor pro hlídaná parkoviště osobních automobilů. V druhé části je vybráno vhodné konstrukční řešení odpovídající zadání. K tomu jsou provedeny důležité výpočty a z nich vycházející konstrukční návrh splňující parametry zadání. Tento návrh je podložen sestavnými výkresy.In the first part of this thesis is developed analysis of mechanical barriers conceptions for guarded parking. In the second part is chosen construction solution which corresponds to specified conditions. There are also done important calculations and mechanical design based on them. This design is supported by assembly drawings.

Control stress analysis of LVS 511 gear

Diplomová práce se zabývá analýzou skříně kyvné převodovky lesní vyvážečky LVS 511. Téma je navrženo firmou Strojírna Novotný s.r.o. Cílem práce je provést pevnostní propočet skříně převodovky a hlavního přenosového hřídele. Stěžejní část práce je zaměřena na vytvoření konečnoprvkového výpočetního modelu a vyhodnocení v softwaru NX I-Deas.This master’s thesis deals with analysis of the gearbox housing of forwarder LVS 511. Theme is designed by Strojírna Novotný s.r.o. Objective of the work is to perform strain stress analysis of gear housing and main transmission shaft. The main part of the thesis is focused on creating of finite element model and evaluation in NX I-Deas software.

Fibre coupled micro-light emitting diode array light source with integrated band-pass filter for fluorescence detection in miniaturised analytical systems

In this work, a new type of miniaturized fibre-coupled solid-state light source is demonstrated as an excitation source for fluorescence detection in capillary electrophoresis. It is based on a parabolically shaped micro- light emitting diode (µ-LED) array with a custom band-pass optical interference filter (IF) deposited at the back of the LED substrate. The GaN µ-LED array consisted of 270 individual µ-LED elements with peak emission at 470nm, each about 14µm in diameter and operated as a single unit. Light was extracted through the transparent substrate material, and coupled to an optical fibre (400µm in diameter, numerical aperture NA = 0.37), to form an integrated µ-LED-IF-OF light source component. This packaged µ-LED-IFOF light source emitted approximately 225µW of optical power at a bias current of 20mA. The bandpass IF filter was designed to reduce undesirable LED light emissions in the wavelength range above 490 nm . Devices with and without IF were compared in terms of optical power output, spectral characteristics as well as LOD values. While the IF consisted of only 7.5 pairs (15 layers) of SiO2/HfO2 layers it resulted in an improvement of the baseline noise as well as the detection limit measured using fluorescein as test analyte, both by approximately one order of magnitude, with a LOD of 1×10-8 mol/L obtained under optimised conditions. The µ-LED-IF-OF light source was then demonstrated for use in capillary electrophoresis with fluorimetric detection. Limits of detection obtained by this device were compared to those obtained with a commercial fibre coupled LED device