Huseyin Uvet

Vision-Based Automated Single-Cell Loading and Supply System

Automated continuous individual cell transfer is a critical step in single-cell applications using microfluidic devices. Cells must be aspirated gently from a buffer before transferring to operation zone so as not to artificially perturb their biostructures. Vision-based manipulation is a key technique for allowing nondestructive cell transportation. In this paper, we presented a design for an automated single-cell loading and supply system that can be integrated with complex microfluidic applications for examining or processing one cell at a time such as the current nuclear transplantation method. The aim of the system is to automatically transfer mammalian donor (~ 15 ¿m) or oocyte (~ 100 ¿ m) cells one by one from a container to a polydimethylsiloxane (PDMS) microchannel and then transport them to other modules. The system consists of two main parts: a single-cell suction module, and a PDMS-based microfluidic chip controlled by an external pump. The desired number of vacuumed cells can be directed into the microfluidic chip and stored in a docking area. From the batch, they can be moved to next module by activating pneumatic pressure valves located on two sides of the chip. The entire mechanism is combined with monitoring systems that perform detection/tracking and control.

On-chip single particle loading and dispensing

In this paper, on-chip particle loading and dispensing modules are presented with their results for the automation of a single particle retrieving from a microfluidic channel. Our proposed microfluidic chip has several modules. Each one of them has important functions as (a) loading micro-particles singly to main microfluidic flow by the aid of magnetically driven microtools (MMT); (b) finding particle position in a microfluidic channel by micro-capacitance sensors; (c) adjusting micro-channel height locally by pneumatic pressure valve; (d) dispensing particles out from the microfluidic chip to incubation environment. Novelty of this paper is summarized as follows: (1) Multi-photoresist combination technique for the pneumatic pressure valve; (2) Automatic on-chip particle dispensing with micro-capacitance sensors. We showed feasibility of automatic dispensing of a single polystyrene bead (about 100 µm) from the chip to atmosphere. The performances of each module (hybrid structure, sensor and dispensing parts) were evaluated individually. We succeeded in determination of the movement of micro-particles (about 50–100 µm) with the velocity of over 6 mm/sec. by the micro-capacitance sensors. The advantages of the proposed system are that composed of the reusable drive system such as xy motorized stage, pumps and a disposable microfluidic chip.

Miniaturized Vision System for Microfluidic Devices

One of the biggest obstacles for lab-on-chip (LOC) devices is the miniaturization of large-scale devices and its methodologies. Miniaturization of the current microscopic technologies combined with image processing may bring significant advantages for LOC devices in the dynamic processes of sizing, positioning, flow control and cell manipulation at different time scales. Here, we propose a vision system boarded on a polydimethylsiloxane (PDMS) polymer-based chip, which can be utilized in a complex microfluidic network for continuous monitoring of mammalian egg and donor cells of sizes in the range of 10–100 μm. The developed prototype system has sufficient resolution and is accompanied with a robust detection method for cell-based microfluidic applications. To assess its performance, an image processing algorithm was applied, and the capability of the detection method was evaluated using 11- and 26-μm particles. The results show that the proposed optical system of monitoring and illumination can be effectively incorporated into PDMS structures aiming at LOC devices.

Multi-view fast object detection by using extended haar filters in uncontrolled environments

In this paper, we propose multi-view object detection methodology by using specific extended class of haar-like filters, which apparently detects the object with high accuracy in the unconstraint environments. There are several object detection techniques, which work well in restricted environments, where illumination is constant and the view angle of the object is restricted. The proposed object detection methodology successfully detects faces, cars, logo objects at any size and pose with high accuracy in real world conditions. To cope with angle variation, we propose a multiple trained cascades by using the proposed filters, which performs even better detection by spanning a different range of orientation in each cascade. We tested the proposed approach by still images by using image databases and conducted some evaluations by using video images from an IP camera placed in outdoor. We tested the method for detecting face, logo, and vehicle in different environments. The experimental results show that the proposed method yields higher classification performance than Viola and Joness detector, which uses a single feature for each weak classifier. Given the less number of features, our detector detects any face, object, or vehicle in 15fps when using 4 megapixel images with 95% accuracy on an Intel i7 2.8GHz machine.

High-speed delivery of microbeads in microchannel using magnetically driven microtool

This paper presents on-demand microbeads delivery system in a microfluidic chip by magnetically driven microtool (MMT). The four of horizontally arranged permanent magnets and the piezoelectric vibrator are used to actuate the Ni based microtool precisely in the chip. The MMT injects the beads mechanically to flow and then into ejection operation part. We succeeded in transferring microbeads one by one with the required pace to the next process in order to achieve stable dispensing microbeads out from the microfluidic chip to incubation environment. We succeeded in demonstration of the delivery and ejection of polystyrene beads (100 µm) with the flow velocity of from 0.02 ml/h to 0.04 ml/h and MMT frequency from 1 Hz to 6 Hz to adjust the pitch of each micro-bead. The spacing interval of microbeads could be mainly adjusted by changing of MMT frequency and the flow velocity of output stream. The proposed system shows advantages of high-speed, high success ratio and disposable of microfluidic chip having MMT.

Illumination Normalization for Outdoor Face Recognition by Using Ayofa-Filters

Abstract In this paper, we propose an illumination normalization app roach, which apparently improves the face recognition accuracy in outdoor environments. The pro posed approach computes the frequency variability and reflection direction on local face regions w here the direction of the light source is unknown. It effectively recovers the illumination on a face su rface. Majority of conventional approaches needs constant albedo coefficients as well as known illumina tio source direction to recover the illumination. Our novel approach computes unknown reflection d rections by using spatial frequency components on salient regions of a face. The method requires only one single image taken under any arbitrary illumination condition where we do not know the li ght source direction, strength, or light sources. The method relies on the spatial frequencies and do es not need to use any precompiled face model database. It references the nose tip to evaluate the re flection model that contains six different reflection vectors. We tested the proposed approach by still images from major face databases and conducted testing by using video images from an IP camera pla ced in outdoor. The efficiency of the Ayofa-filter was tested by both holistic-based approach es and feature-based methods. We used principal component analysis (PCA) and linear discriminan t analysis (LDA) as holistic methods and used Gabor-wavelets and active appearance model (AAM) as fe ature-based methods. The error rates obtained after the illumination-normalization show that o ur novel method significantly improves the recognition ratio with these recognition methods.

Micro-UFO (Untethered Floating Object): A Highly Accurate Microrobot Manipulation Technique

A new microrobot manipulation technique with high precision (nano level) positional accuracy to move in a liquid environment with diamagnetic levitation is presented. Untethered manipulation of microrobots by means of externally applied magnetic forces has been emerging as a promising field of research, particularly due to its potential for medical and biological applications. The purpose of the presented method is to eliminate friction force between the surface of the substrate and microrobot. In an effort to achieve high accuracy motion, required magnetic force for the levitation of the microrobot was determined by finite element method (FEM) simulations in COMSOL (version 5.3, COMSOL Inc., Stockholm, Sweden) and verified by experimental results. According to position of the lifter magnet, the levitation height of the microrobot in the liquid was found analytically, and compared with the experimental results head-to-head. The stable working range of the microrobot is between 30 µm to 330 µm, and it was confirmed in both simulations and experimental results. It can follow the given trajectory with high accuracy (<1 µm error avg.) at varied speeds and levitation heights. Due to the nano-level positioning accuracy, desired locomotion can be achieved in pre-specified trajectories (sinusoidal or circular). During its locomotion, phase difference between lifter magnet and carrier magnet has been observed, and relation with drag force effect has been discussed. Without using strong electromagnets or bulky permanent magnets, our manipulation approach can move the microrobot in three dimensions in a liquid environment.

High-speed single cell dispensing system

In this paper, we discuss the single cell dispensing system to increase both the speed and the success rate of single cell dispensing. Two pairs of capacitance sensors are placed in a biochip to detect the flow velocity of cells, and the air pressure is applied to eject cells by synchronizing the timing. Then, the system theoretically has a capability to eject 3 cells/sec with maximum flow velocity is 10 mm/sec. Finally, we succeeded in automatic dispensing of a single polystyrene bead (=100 µm) from a biochip to culture well atmosphere using developed cell ejection system with the success rate of 50 %. Furthermore, we also succeeded in single swine oocyte dispensing by developed system.

Micro valve system for individual cell transportation in microfluidic chip

Recently, micro valves to control some kinds of fluids in channels in a microchip have been developed. Now we pay attention to in-chip somatic cell cloning with microfluidic technology. There are some steps, cell supply, cutting, sorting, coupling, fusion and so on, for this work. And we focused on a cell supply system spending cells one by one in microfluidic chip, and attempt to transport an individual cell to objective course by the control of pressure valves. Here, we made three kinds valves, a) open channel 2-layer valve, b) open channel 3-layer valve, and c) close channel 2-layer valve. We compare these valves about interception condition of micro channel flow and time to take for open/close. And then we evaluated them with suitable for the smooth cell transportation by these comparisons.

Stabilization of Microrobot Motion Characteristics in Liquid Media

Magnetically actuated microrobot in a liquid media is faced with the problem of head-tilting reaction caused by its hydrodynamic structure and its speed while moving horizontally. When the instance microrobot starts a lateral motion, the drag force acting on it increases. Thus, the microrobot is unable to move parallel to the surface due to the existence of drag force that cannot be neglected, particularly at high speeds such as >5 mm/s. The effect of it scales exponentially at different speeds and the head-tilting angle of the microrobot changes relative to the reference surface. To the best of our knowledge, there is no prior study on this problem, and no solution has been proposed so far. In this study, we developed and experimented with 3 control models to stabilize microrobot motion characteristics in liquid media to achieve accurate lateral locomotion. The microrobot moves in an untethered manner, and its localization is carried out by a neodymium magnet (grade N48) placed inside its polymer body. This permanent magnet is called a carrier-magnet. The fabricated microrobot is levitated diamagnetically using a pyrolytic graphite placed under it and an external permanent magnet, called a lifter-magnet (grade N48), aligned above it. The lifter-magnet is attached to a servo motor mechanism which can control carrier-magnet orientation along with roll and pitch axes. Controlling the angle of this servo motor, together with the lifter-magnet, allowed us to cope with the head-tilting reaction instantly. Based on the finite element method (FEM), analyses that were designed according to this experimental setup, the equations giving the relation of microrobot speed with servo motor angle along with the microrobot head-tilting angle with servo motor angle, were derived. The control inputs were obtained by COMSOL® (version 5.3, COMSOL Inc., Stockholm, Sweden). Using these derived equations, the rule-based model, laser model, and hybrid model techniques were proposed in this study to decrease the head-tilting angle. Motion control algorithms were applied in di-ionized water medium. According to the results for these 3 control strategies, at higher speeds (>5 mm/s) and 5 mm horizontal motion trajectory, the average head-tilting angle was reduced to 2.7° with the ruled-based model, 1.1° with the laser model, and 0.7° with the hybrid model.