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This paper reports an ultra-fast manipulation on micro-scale objects in a microfluidic channel. The objects are manipulated in simple harmonic motions and the manipulation speed has been achieved up to 3000 Hz. While the maximum speed was only about 130 Hz in previous works, the speed is advanced with an additional order in this work. Based on the experimental results, we find that the gain decreases...
This paper discusses an on-chip Red Blood Cell (RBC) deformability checker with vision analyzer. The system is composed of a PDMS chip including three microfluidic channels, a microscope for appropriately enlarging RBC, and a high-speed vision for observing both the cell size and behaviors in the channel, respectively. We particularly focus on how to analyze the deformability of single cells by the...
This paper proposes a hybrid actuation for long-term cell manipulation in a microfluidic channel. While a conventional actuation can manipulate a cell, it usually cannot last for a very long time (i.e. less than 10 minutes) due to unavoidable pressure leak or drifts. The hybrid actuation is composed of two actuations where one is a gravity-based pressure system for macro-scale pressure balancing and...
An interesting phenomenon of microfluidic vortices rotating and transmitting like a set of gears has been experimentally observed and is named "Virtual Vortex Gear". We found that the vortices could be serially induced by increasing the driving pressure. Every two closed by vortices were having opposite directions of the swirling. The relation between the vortices and driving pressure has...
We report a simple and effective method for adjusting the gain of cell manipulation in a microfluidic channel. The gain of the manipulation is defined as the ratio of the displacements between the actuator and a target cell. The gain is found adjustable by controlling the offset pressure in the channel. According to the experimental results, the gain is about proportional to the offset pressure within...
A novel microfluidic system for applying cyclic pressure to cells during incubation is developed and tested in this work. The cyclic pressure generates stress stimulus to the cells, and is named “Cell Exercise” in this work. The goal of this paper is to design an “On-Chip Cell Gym” where we can observe what happens during the cell exercise in real-time. We design the cell gym on a PDMS chip composed...
This paper focuses on the comparison of red blood cell (RBC) deformability under continuous and repetitive loadings. We utilized a feedback position-control system and a narrow microfluidic channel for applying different deformation patterns on RBCs. According to the analyses of shape recoveries with different patterns, we found, for the first time, that the mechanical responses of RBCs upon continuous...
“Cell Pinball” is a phenomenon whereby rotating red blood cells (RBCs) move like pinballs inside a microfluidic channel where the cell inertia is negligible. The goal of this paper is to discuss the location of the actual rotational axis through the careful comparison between the contour and contact shapes of a moving RBC. By switching the reflection interference contrast (RIC) and the phase contrast...
Different cell buckling between positive and negative driving pressure in a microfluidic channel is investigated. Red blood cells under three different osmotic conditions have significant differences between positive and negative driving pressures. Cell insertion length is employed as an index for cell buckling. Greater variations of the insertion length are found with negative driving pressure. This...
A surprising phenomenon is observed in a microfluidic channel where suspending microbeads are spontaneously aligned into lines. Microbeads are randomly distributed in the channel at a relatively high velocity (3.27 µm/ms), but start to align into lines at a relatively low velocity (0.05 µm/ms). The alignment has been repeated with and without obstacles in the channel. The phenomenon is interpreted...
A high-resolution cell manipulation system is presented for investigating red blood cell deformation under long-standing load in this paper. Because the low Reynolds number in microfluidic system, cell position can be manipulated by controlling the flow in a microchannel. A high-speed vision system is embedded in the system for providing cell present position as the feedback signal for the controller...
An automatic system for evaluating single cell viscoelasticity is proposed and tested in this paper. The system includes three main operations, and they are the operations of catch, load and launch. In the catch operation, the system is capable of capturing a target cell by high-speed vision and high-frequency flow control. The captured cell is pushed into a narrow constriction for the load operation...
The frequency responses of a previously proposed on-chip pressure sensor is investigated with two different sizes of deformation chamber. Pressure inputs with the same span of frequencies, from 1 Hz to 64 Hz, are applied to the fabricated pressure sensors, and the pressure sensed by the on-chip sensor is represented by the movement of microbeads inside the sensing area. We found that the sensor with...
A novel pressure transmitter for assisting local pressure sensing in a microfluidic device is proposed aiming to improve on-chip single cell evaluation. By integrating the pressure transmitter into an existing pressure sensing technique, the local pressure in a microchannel can be directly determined. The pressure transmitter transmits the pressure from one microfluidic circuit to another without...
A novel method for sensing local pressure inside a microfluidic device is proposed and developed. The main advantage of the method is that the pressure can be visually seen without attaching any electrical wire or instrument. The method can also be easily integrated into applications, such as micro-robots, because of its single-layer design. The working principle is based on the deformation of Polydimethylsiloxane,...
A novel microfluidic design is proposed for extracting cell deformability under a stable local pressure. In conventional approaches, cell deformability is evaluated based on cell's velocity through a constriction channel where the cell is deformed due to geometrical constraints. A stiff cell would move slower due to a greater resistance generated from the deformation. The pressure driving the flow...
A microfluidic, vision-based pressure sensor is tested with three different concentrations of coloured solution, which serves as sensing fluid for the sensor. The sensor is based on the deformation of the a polymeric chamber, which causes the sensing fluid to flow in or out of the sensing area, resulting in a change of colour intensity. That change is recorded by a digital camera and the average darkness...
A novel pressure sensing technique based on visualizing Polydimethylsiloxane (PDMS) deformation using microbeads is proposed here for measuring local pressure inside a microfluidic device. By the proposed method, the pressure can be directly “seen” without attaching any wire foils, such as a strain gauge, nor complex fabrication process, such as multilayer design or surface grating. Experimental results...
A method for evaluating red blood cell (RBC) deformability by different channel width in a microfluidic device is proposed. While conventional methods usually have only one test channel to deform RBCs for the evaluation, a design including three test channels with different width is utilized in this work. The proposed design have the advantage of generating a wider range of deformation to each RBC,...
This paper proposes a new index for evaluating the stiffness-based deformability of a cell using a microchannel. In conventional approaches, the transit time of a cell through a microchannel is often utilized for the evaluation of cell deformability. However, such time includes both the information of cell stiffness and viscosity. In this paper, we eliminate the effect from cell viscosity, and focus...
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