Harvey Kasdan

Deterministic lateral displacement MEMS device for continuous blood cell separation

This work presents a new MEMS device which uses deterministic lateral displacement for the continuous separation of leukocytes (white blood cells) and erythrocytes (red blood cells). By running blood cells in laminar flow through an array of columnar obstacles, deterministic lateral displacement asserts that the path a cell follows is determined by its size. The system consists of PDMS channels with posts on glass slides. An effective separation region of 7 mm by 1.8 mm is achieved on a 1 cm by 1 cm chip. A 420 /spl mu/m lateral separation was achieved for 5 /spl mu/m and 10 /spl mu/m beads. The critical particle size for separation was found experimentally to be 8 /spl mu/m, concluded from our results using 5 /spl mu/m, 7 /spl mu/m, 8 /spl mu/m and 10 /spl mu/m polystyrene beads. Diluted whole blood and blood fraction of concentrated leukocytes were also tested with the devices in agreement with blood count results. Problem of blood cell stiction to device surfaces was investigated.

Robust image recognition by fusion of contextual information

Abstract This paper studies the fusion of contextual information in pattern recognition, with applications to biomedical image identification. In the real world there are cases where the identity of an object is ambiguous if the classification is based only on its own features. It is helpful to reduce the ambiguity by utilizing extra information, referred to as context, provided by accompanying objects. We investigate two techniques that incorporate context. The first approach, based on compound Bayesian theory, incorporates context by fusing the measurements of all objects under consideration. It is an optimal strategy in terms of achieving minimum set-by-set error probability. The second approach fuses the measurements of an object with explicitly extracted context. Its linear computational complexity makes it more tractable than the first approach, which requires exponential computation. These two techniques are applied to two medical applications: white blood cell image classification and microscopic urinalysis. It is demonstrated that superior classification performances are achieved by using context. In our particular applications, it reduces overall classification error, as well as false positive and false negative diagnosis rates.

A Micro Device for Separation of Erythrocytes and Leukocytes in Human Blood

We report a MEMS device for continuous and binary separation of leukocytes (white blood cells, WBCs) and erythrocytes (red blood cells, RBCs) by their sizes. The system consists of PDMS cylindrical pillars inside fluidic chamber on glass slides. A 420 mum lateral separation was achieved for 5 mum and 10 mum beads. The critical particle size for separation was successful predicted by simulation and experimentally determined by calibration with polystyrene beads. The separation function (lateral displacement versus particle size) was also measured experimentally. Diluted whole blood and blood fraction of concentrated leukocytes were tested with the devices with erythrocyte to leukocyte ratio in agreement with blood count results. Experiments with fluorescent labeled leukocytes confirm the separation of leukocytes from erythrocytes and measured the separation efficiency

Four-part differential leukocyte count using μflow cytometer

This paper reports the four-part differential leukocyte count (DLC) of human blood using a MEMS microflow (μflow) cytometer. It is achieved with a two-color laser-induced fluorescence (LIF) detection scheme. Four types of leukocytes including neutrophils, eosinophils, lymphocytes and monocytes are identified in blood samples, which are stained by fluorescein isothiocyanate (FITC) and propidium iodide (PI). The DLC results show good correlation with the count from a commercial hematology analyzer. The whole system is also implemented into a portable instrument for space application.

Fluorescent Labeling, Sensing and Differentiation of Leukocytes from Undiluted Whole Blood Samples

In this paper, we demonstrated leukocyte labeling, sensing and differentiation from undiluted human whole blood samples with microfabricated devices. A challenging issue in leukocyte sensing from blood samples is the required high dilution level, which is used mainly to prevent interference from the overwhelmingly outnumbered erythrocytes. Dilution is undesirable for micro hemacytometers. It not only increases sample volume and processing time, but also requires mixing and buffer storage for on- chip implementation. Unlike commercial bulk instruments and previous efforts by other groups, we completely eliminated the requirement for dilution by staining leukocytes specifically with fluorescent dye acridine orange (AO) in undiluted human whole blood and then sensing them in microfluidic devices. Green fluorescent signal centered at 525 nm was used for leukocyte count and red fluorescent signal centered at 650 nm was used for leukocyte differentiation. Throughput of one hundred leukocytes per second was achieved, which means operation time for one sample only requires several seconds.

Platinum Black Electroplated Impedance Particle Sensor

The paper presents a micro electrical impedance particle sensor. To solve the problem of large electrode electrolyte interface impedance, we electroplated the electrodes with platinum black. Devices are fabricated with integrated parylene technology. An electrical model for the system is proposed and analytic solutions are obtained. Impedance spectra measurement of the device filled with various media are in excellent agreement with model analysis. Signals from individual 10 mum polystyrene beads passing the sensing electrodes are successfully obtained