SU-8 microfluidic device for scintillating particle detection

Several applications of X-ray and gamma ray imaging detectors, e.g. in medical diagnostics, require millimeter or sub-millimeter spatial resolution and good energy resolution. In order to achieve such features we have proposed a new type of camera, which takes advantage of micromachining technology. It consists of an array of scintillator crystals encapsulated in silicon wells with photodiodes at the bottom. Several parameters of the photodiode need to be optimised: uniformity and e$ciency of the light detection, gain, electronic noise and breakdown voltage. In order to evaluate these parameters we have processed 3;3 arrays of 1.8 mm, &10 m thick photodiodes using (1 0 0) wafers etched in a KOH solution. Their optical response at 675 nm wavelength is comparable to that of a 500 m thick silicon PIN diode. Their low light detection e$ciency is compensated by internal ampli"cation. Several scintillator materials have been positioned in the wells on top of the thin photodiodes, i.e. a 200 m thick "lm of structured CsI(Tl), single crystals of CsI(Tl) and Lu S (Ce>). First experiments of -ray detection have been performed.

Chemistry (Weinheim an der Bergstrasse, Germany), 2018

A miniaturized radio-HPLC detector has been developed comprising a microfluidic device fabricated from plastic scintillator in combination with a silicon photomultiplier light sensor, and tested with samples containing a positron-emitting radionuclide [¹⁸F]fluoride. This cost-effective, small footprint analytical tool is ideal for incorporation into integrated quality control systems for the testing of positron emission tomography (PET) radiopharmaceuticals to good manufacturing practice (GMP) standards.

Sensors and Actuators a-Physical, 2004

We present a design and process to fabricate an integrated microfluidic/microoptical device-the microfluidic optical waveguide sensor ("FlOWs"). Optical waveguides and fluidic microchannels have been defined using only a single photolithographic masking step. This integration has been demonstrated with three device types: (A) a hybrid structure with embedded SU-8 waveguides and polydimethylsiloxane (PDMS) channels; (B) a structure using only SU-8 for both the waveguides and microchannel walls and (C) a structure as a modification to the all-SU-8 structure. Testing has demonstrated the ability of the waveguides to transmit light to and receive light from the microchannels, which contain a fluorescent dye that emits upon laser excitation. This type of strategy can find effective use in a variety of bio-assay experiments.

Analytical Chemistry, 2014

Conventional flow injection systems for aquatic environmental analysis typically comprise large laboratory benchscale equipment, which place considerable constraints for portable field use. Here, we demonstrate the use of an integrated acoustically driven microfluidic mixing scheme to enhance detection of a chemiluminescent species tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydratea common chemiluminescent reagent widely used for the analysis of a wide range of compounds such as illicit drugs, pharmaceuticals, and pesticidessuch that rapid in-line quantification can be carried out with sufficient on-chip sensitivity. Specifically, we employ surface acoustic waves (SAWs) to drive intense chaotic streaming within a 100 μL chamber cast in polydimethoxylsiloxane (PDMS) atop a microfluidic chip consisting of a single crystal piezoelectric material. By optimizing the power, duration, and orientation of the SAW input, we show that the mixing intensity of the sample and reagent fed into the chamber can be increased by one to two orders of magnitude, leading to a similar enhancement in the detection sensitivity of the chemiluminescent species and thus achieving a theoretical limit of detection of 0.02 ppb (0.2 nM) of L-prolinea decade improvement over the industry gold-standard and two orders of magnitude more sensitive than that achievable with conventional systemssimply using a portable photodetector and without requiring sample preconcentration. This on-chip microfluidic mixing strategy, together with the integrated miniature photodetector and the possibility for chip-scale microfluidic actuation, then alludes to the attractive possibility of a completely miniaturized platform for portable field-use microanalytical systems.

A passive microfluidic device using SU-8 photoresist has been developed for detection and analysis of viruses. Due to its high aspect ratio with almost vertical sidewalls and its chemical stability, SU-8 offers a wide variety of applications in the fabrication of microfluidic systems. This photoresist is transparent allowing optical detection and thus, identification of biomolecules. Additionally, SU-8 shows a good biocompatibility offering the possibility to develop assay on the surface that allows the specific binding of biomolecules for analytical applications. In this work, the performance of the microfluidic device has been successfully demonstrated by detection of specific contaminants in test solutions. The microfluidic chip is composed of SU-8 microstructures which have been fabricated by means of photolithography, using glass and silicon as substrate materials. Beside the fabrication of microchannels by means of SU-8, we have also used SU-8 as adhesive layer.

Physics in Medicine and Biology, 2009

It has been observed that microfluidic chips used for synthesizing 18 F-labeled compounds demonstrate visible light emission without nearby scintillators or fluorescent materials. The origin of the light was investigated and found to be consistent with the emission characteristics from Cerenkov radiation. Since 18 F decays through the emission of high-energy positrons, the energy threshold for beta particles, i.e., electrons or positrons, to generate Cerenkov radiation was calculated for water and polydimethylsiloxane (PDMS), the most commonly used polymer-based material for microfluidic chips. Beta particles emitted from 18 F have a continuous energy spectrum, with a maximum energy that exceeds this energy threshold for both water and PDMS. In addition, the spectral characteristics of the emitted light from 18 F in distilled water were also measured, yielding a broad distribution from 300 nm to 700 nm, with higher intensity at shorter wavelengths. A photograph of the 18 F solution showed a bluish-white light emitted from the solution, further suggesting Cerenkov radiation. In this study, the feasibility of using this Cerenkov light emission as a method for quantitative measurements of the radioactivity within the microfluidic chip in situ was evaluated. A detector previously developed for imaging microfluidic platforms was used. The detector consisted of a charge coupled device (CCD) optically coupled to a lens. The system spatial resolution, minimum detectable activity and dynamic range were evaluated. In addition, a calibration of Cerenkov signal versus activity concentration in the microfluidic chip was determined. This novel method of Cerenkov radiation measurements will provide researchers with a simple yet robust quantitative imaging tool for microfluidic applications utilizing beta particles. Microfluidic chips have been designed for a multitude of applications, such as chemical synthesis, cell manipulation, DNA analysis, protein analysis, etc. (Andersson and van den Berg 2003, Sia and Whitesides 2003). One of the research interests is the development of a versatile,

Journal of Microelectromechanical Systems, 2001

This paper presents the fabrication of a microchemical chip for the detection of fluorescence species in microfluidics. The microfluidic network is wet-etched in a Borofloat 33 (Pyrex) glass wafer and sealed by means of a second wafer. Unlike other similar chemical systems, the detection system is realized with the help of microfabrication techniques and directly deposited on both sides of the microchemical chip. The detection system is composed of the combination of refractive microlens arrays and chromium aperture arrays. The microfluidic channels are 60 m wide and 25 m deep. The utilization of elliptical microlens arrays to reduce aberration effects and the integration of an intermediate (between the two bonded wafers) aluminum aperture array are also presented. The elliptical microlenses have a major axis of 400 m and a minor axis of 350 m. The circular microlens diameters range from 280 to 300 m. The apertures deposited on the outer chip surfaces are etched in a 3000-A-thick chromium layer, whereas the intermediate aperture layer is etched in a 1000-A-thick aluminum layer. The overall thickness of this microchemical system is less than 1.6 mm. The wet-etching process and new bonding procedures are discussed. Moreover, we present the successful detection of a 10-nM Cy5 solution with a signal-to-noise ratio (SNR) of 21 dB by means of this system.

2010

In this paper, we present a simple, rapid, and low-cost procedure for fabricating micro-nozzles and micro-diffusers using in microfluidic devices to control the flow of the fluid which pass through the microchannels. This procedure uses commercially accessible and typical materials, which is used in several applications in microelectronic labs. Glass is used as main substrate to get advantages of photo transparent specifications of this material. In this method a thick layer of positive photoresist on the glass substrate for fabrication of lens is utilized. A mild BOE solution with additional HCL is employed to achieve an excellent etching quality and a smoother etched surface. The depth of the surface can be reach to 100 m without PR damage effect after 1 hour of etching process. The aluminum evaporation process produces a thin layer of aluminum across the substrate which makes it as a block against passing the light. Dispensing SU-8 on Al layer and using UV back-exposure technique the tapered structured is fabricated as a mold for PDMS which can be used in different microfluidic applications. The simulation results shows that the focal length up to 800 m with the lens curvature of 150 m is achievable.

2009

Based on the planar integrated free space optical systems approach the design and manufacturing results of a fluorescence detector are presented. The system is fabricated by micro milling on a KUGLER microgantry® 5x milling machine. The fluorescence detector is designed for the integration into the segmented flow environment for pH-sensing in fluid segments.

Vartaka ‘horse’s hoof’ rebus vartaka ‘merchant’ in Indus Script Corpora and significance of horse’s hoof in aśvamedha yajna Śatapathabrāhmaṇa (शतपथब्राह्मण) Kāṇḍa 1, Adhyāya 2, Brāhmaṇa 2 uses the synonym śapha a synonym of Meluhha logos vartaka ‘horse’s hoof’ to signify the size of the Soma to be realised in a yajna which is medhā ‘ dhana, wealth’, Naigh. ii, 10. Thus, aśvamedha yajna is a metaphor for aś ‘to master, become master of’ (RV.) + medhā ‘ dhana, wealth’; i.e., to become a master of dhana, wealth’. Round horse’s hoof is used as अश्वशफमात्रं a measure of the metal lump size realized in a yajna. Vartaka ‘horse’s hoof’ signifying such a measure becomes the metonym for traded wealth, bartering soma in maritime trade transactions. aśvaśaphamātraṃ kuryādityu haika āhuḥ | kastadveda yāvānaśvaśapho yāvantameva svayam manasā na satrā pṛthum manyetaivaṃ kuryāt 1.2.2.10. And some now say: “He should make it of the size of a horse’s hoof!” But who knows how large is a horse’s hoof? Let him make it of such a size as in his own mind he does not think would be too broad. English translation: Alternative transliteration: ashvashaphamatram, asvasaphamatram, [Devanagari/Hindi] अश्वशफमात्रं, [Bengali] অশ্বশফমাত্রং, [Gujarati] અશ્વશફમાત્રં, [Kannada] ಅಶ್ವಶಫಮಾತ್ರಂ, [Malayalam] അശ്വശഫമാത്രം, [Telugu] అశ్వశఫమాత్రం aśva—śapha m. a horse's hoof, ŚBr. xiii ; KātyŚr. (Monier-Williams) -शफ a. cloven-hoofed. (Apte) an-eka—śapha mfn. cloven-hoofed, Pāṇ. i, 2, 73 Comm. (Monier-Williams) एक eka शक a. whole-hoofed. (-फः) an animal whose hoof is not cloven (as a horse, ass &c.); अजाविकं सैकशफं न जातु विषमं भजेत् Ms.9.119. (Apte) The Horse-Sacrifice in the Taittirīya-Brāhmaṇa: The Eighth and Ninth Prapāṭhakas of the Third Kāṇḍa of the Taittirīya-Brāhmaṇa with Translation Paul-Emile Dumont Proceedings of the American Philosophical Society, Vol. 92, No. 6 (Dec. 27, 1948), pp. 447-503 (57 pages) https://www.jstor.org/stable/3143199