Rapid and sensitive colorimetric ELISA using silver nanoparticles, microwaves and split ring resonator structures

We report a new approach to colorimetric Enzyme-Linked Immunosorbent Assay (ELISA) that reduces the total assay time to < 2 min and the lower-detection-limit by 100-fold based on absorbance readout. The new approach combines the use of silver nanoparticles, microwaves and split ring resonators (SRR). The SRR structure is comprised of a square frame of copper thin film (30 μm thick, 1 mm wide, overall length of ~9.4 mm on each side) with a single split on one side, which was deposited onto a circuit board (2×2 cm 2). A single micro-cuvette (10 μl volume capacity) was placed in the split of the SRR structures. Theoretical simulations predict that electric fields are focused in and above the micro-cuvette without the accumulation of electrical charge that breaks down the copper film. Subsequently, the walls and the bottom of the micro-cuvette were coated with silver nanoparticles using a modified Tollen's reaction scheme. The silver nanoparticles served as a mediator for the creation of thermal gradient between the bioassay medium and the silver surface, where the bioassay is constructed. Upon exposure to low power microwave heating, the bioassay medium in the micro-cuvette was rapidly and uniformly heated by the focused electric fields. In addition, the creation of thermal gradient resulted in the rapid assembly of the proteins on the surface of silver nanoparticles without denaturing the proteins. The proof-of-principle of the new approach to ELISA was demonstrated for the detection of a model protein (biotinylated-bovine serum albumin, b-BSA). In this regard, the detection of b-BSA with bulk concentrations (1 μM to 1 pM) was carried out on commercially available 96-well high throughput screening (HTS) plates and silver nanoparticle-deposited SRR structures at room temperature and with microwave heating, respectively. While the room temperature bioassay (without microwave heating) took 70 min to complete, the identical bioassay took < 2 min to complete using the SRR structures (with microwave heating). A lower detection limit of 0.01 nM for b-BSA (100-fold lower than room temperature ELISA) was observed using the SRR structures. © 2010 S.A. Addae et al

Length Sensing and Control in the Virgo Gravitational Wave Interferometer

The gravitational wave detector Virgo is presently being commissioned. A significant part of last year was spent in setting up the cavity length control system. This work was carried out with steps of increasing complexity: locking a simple Fabry-Perot cavity, then a Michelson interferometer with Fabry-Perot cavities in both arms, and finally recycling the light beam into the interferometer. The applied strategy and the main results obtained are describe

The Virgo interferometric gravitational antenna

Submitted to: Class. Quantum Grav.The interferometric gravitational wave detectors represent the ultimate evolution of the classical Michelson interferometer. In order to measure the signal produced by the passage of a gravitational wave, they aim to reach unprecedent sensitivities in measuring the relative displacements of the mirrors. One of them , the 3-km-long Virgo gravitational wave antenna, which will be particularly sensitive in the low frequency range (10-100 Hz), is presently in its commissioning phase. In this paper the various techniques developed in order to reach its target extreme performance are outlined

The status of VIRGO

In this paper the main characteristics of the interferometric gravitational waves detector Virgo are presented as well as its present status and perspectives

Interferometric detectors of gravitational waves on Earth: the next generations

International audienceThe interferometric detectors of gravitational waves of first generation are now taking data. A first detection might be possible with these instruments, but more sensitive detectors will be needed to start the gravitational wave astronomy. The interferometers of second generation will improve the sensitivity by a factor ten, allowing to explore a universe volume 1000 times larger. The technology is almost ready and the construction will start at the beginning of next decade. The community of the physicists involved in the field has also started to make plans for third generation detectors, for which a long term technology development will be required. The plans for the upgrades of the existing detectors and the scenario for the evolution of the field will be reviewed in this paper

Noise budget and noise hunting in VIRGO

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Data Acquisition System of the Virgo Gravitational Waves Interferometric Detector

International audienceVirgo is an experiment aiming at the detection of gravitational waves emitted by astrophysical sources. Its detector, based on a 3km arms interferometer, is a complex setup which requires several digital control loops running up to 10kHz, an accurate and reliable central timing system and an efficient data acquisition, all of them being distributed over 3km. We overview here the main hardware and software components developed for the data acquisition system (DAQ) and its current architecture. Then, we briefly discuss its connections with interferometer's controls, especially through the automation of the interferometer's startup procedure. Then, we describe the tools used to monitor the DAQ and the performances we measured with them. Finally, are described also the tools developped for the online detector monitoring, mandatory complement of the DAQ for the commissioning of the Virgo detector

LIGO and VIRGO: large interferometers searching for gravitational waves

International audienceThe largest interferometric detectors for gravitational waves, LIGO and Virgo, have reached (or are close to) the design sensitivity and have started taking science data. The operation of such detectors is reviewed and the expected sources and detection rates are discussed. LIGO and Virgo might make the first detection, but more advanced detectors will be needed to truly open the field of gravitational wave astronomy: the current ideas and plans for the upgrades of the existing interferometers are presented

GRB 050915a & the Virgo detector

GravitationalWaves (GWs) are expected to be emitted in association with Gamma-Ray Bursts (GRBs). In this context, we are analyzing data collected by the Virgo interferometer during 2005 to develop a method aimed to search for coincidences between GW bursts and GRBs. Our analysis is currently focused on Virgo C7 run and the long GRB 050915a, observed by the Swift satellite. The goal of such analysis is either to identify significant events around the GRB trigger time or, in the absence of such events, to set a limit on the strength of the associated GW emission. This study is a prototype for evaluating Virgo capability in constraining the GW output associated with a typical long GRB. Here we give an overview of the procedure we are following in our analysis