Aurel Ymeti

Realization of a multichannel integrated Young interferometer chemical sensor

We report on the design, realization, and characterization of a four-channel integrated optical Young interferometer device that enables simultaneous and independent monitoring of three binding processes. The generated interference pattern is recorded by a CCD camera and analyzed with a fast-Fourier-transform algorithm. We present a thorough theoretical analysis of such a device. The realized device is tested by monitoring glucose solutions that induce well defined phase changes between output channels. The simultaneous measurement of three different glucose concentrations shows the multipurpose feature of such devices. The observed errors, caused by the mismatching of spatial frequencies of individual interference patterns with those determined from the CCD camera, are reduced with different reduction schemes. The phase resolution for different pairs of channels was approximately 1 x 10(-4) fringes, which corresponds to a refractive-index resolution of approximately 8.5 x 10(-8). The measured sensitivity coefficient of the phase change versus refractive-index change of approximately 1.22 x 10(3) x 2pi agrees well with the calculated coefficient of approximately 1.20 x 10(3) x 2pi.

Development of a multichannel integrated interferometer immunosensor

This report describes the design, realization and testing of a highly sensitive two-channel integrated optical (IO) Young interferometer (YI) as well as the design of a first multichannel YI. An integrated channel waveguide Y-splitter with two output parallel branches has been used as the basic optical component for building the YI. The generated interference pattern as result of the overlap of outgoing divergent beams is recorded by a CCD camera and is further analyzed by a computer program based on a Fast Fourier Transformation (FFT) algorithm. The integrated waveguide structure is fabricated in SiON technology. For testing the realized device the refractive indices of several glucose solutions have been measured. The realized sensor shows a phase resolution of 1×10−4 fringes corresponding to a refractive index resolution of 2×10−8. The long-term stability is about 1×10−3fringes×h−1 corresponding to a refractive index change of 2×10−7 h−1. The first design of the multichannel YI has four output parallel channels positioned at well-defined distances from each other, such that the phase shift between both channels of one pair can be monitored independently from the other channel pairs.

A single platform image cytometer for resource-poor settings to monitor disease progression in HIV infection

For resource‐poor countries, affordable methods are required for enumeration of CD4+ T lymphocytes of HIV‐positive patients. For infants, additional determination of CD4/CD8 ratio is needed.

CD4+ T lymphocytes enumeration by an easy-to-use single platform image cytometer for HIV monitoring in resource-constrained settings

HIV monitoring in resource‐constrained settings demands affordable and reliable CD4+ T lymphocytes enumeration methods. We developed a simple single platform image cytometer (SP ICM), which is a dedicated volumetric CD4+ T lymphocytes enumeration system that uses immunomagnetic and immunofluorescent technologies. The instrument was designed to be a low‐cost, yet reliable and robust one. In this article we test the instrument and the immunochemical procedures used on blood from HIV negative and HIV positive patients.

CD4 and CD8 Enumeration for HIV Monitoring in Resource-Constrained Settings

We developed a volumetric single platform image cytometer (SP ICM) that is dedicated to count CD4+ and CD8+ T lymphocytes for HIV monitoring in resource‐constrained settings. The instrument was designed to be low‐cost, yet reliable, easy‐to‐use, and robust.

Size-selective detection in integrated optical interferometric biosensors

We present a new size-selective detection method for integrated optical interferometric biosensors that can strongly enhance their performance. We demonstrate that by launching multiple wavelengths into a Young interferometer waveguide sensor it is feasible to derive refractive index changes from different regions above the waveguide surface, enabling one to distinguish between bound particles (e.g. proteins, viruses, bacteria) based on their differences in size and simultaneously eliminating interference from bulk refractive index changes. Therefore it is anticipated that this new method will be ideally suited for the detection of viruses in complex media. Numerical calculations are used to optimize sensor design and the detection method. Furthermore the specific case of virus detection is analyzed theoretically showing a minimum detectable virus mass coverage of 4 × 10(2) fg/mm(2) < (typically corresponding to 5 × 10(1) particles/ml).

Clinical evaluation of a simple image cytometer for CD4 enumeration on HIV‐infected patients

Affordable, easy‐to‐use, and reliable CD4+ T lymphocyte enumeration systems are needed in resource‐constrained settings to monitor HIV.

Drift correction in a multichannel integrated optical young interferometer.

We demonstrate that in a sensor based on a multichannel Young interferometer, the phase information obtained for different pairs of channels can be used to correct the long-term instability (drift) due to temperature differences between measuring and reference channels, the drift in the alignment of the setup, etc. Experiments show that the nature of a major part of the drift is such that the drift present in one of the channels can be determined by interpolation of the drift measured in the two adjacent channels. It is shown that a drift reduction of 10 times can be achieved as compared with the situation in which no correction is applied. We anticipate that these findings will permit the exploitation of the extreme sensitivity of interference-based sensors to a much greater extent.

An ultrasensitive Young interferometer handheld sensor for rapid virus detection

Future viral outbreaks are a major threat to societal and economic development throughout the world. A rapid, sensitive and easy-to-use test for viral infections is essential to prevent and control such viral pandemics. Furthermore, a compact, portable device is potentially very useful in remote or developing regions without easy access to sophisticated laboratory facilities. In this report we discuss the application of a Young interferometer sensor device for ultrasensitive and real-time detection of viruses. The essential innovation in this technique is the combination of an integrated optical interferometric sensor with antibody–antigen recognition approaches to yield very sensitive, rapid virus detection. The technology is amenable to miniaturization and mass production and, thus, has significant potential to be developed into a handheld, point-of-care device.

A Fast and Sensitive Integrated Young Interferometer Biosensor

We have developed an ultrasensitive biosensor based on an integrated optical Young interferometer. Key features of this sensor are that it is very compact, extremely sensitive, label free, and very fast. Therefore the Young interferometer has significant potential to be developed into a handheld, point-of-care device. In this chapter we review the progress that has been made on the development of integrated Young interferometer sensors. The sensor developed in our lab is discussed in detail. We demonstrate various applications of the current sensor. Special attention is paid to the detection of viruses. Finally a discussion on future prospects of this sensor for diagnostics is given.