Hyunwoo Bang

Simultaneous counting of two subsets of leukocytes using fluorescent silica nanoparticles in a sheathless microchip flow cytometer

A portable flow cytometer has been recognized as an important tool for many clinical applications such as HIV/AIDS screening in developing countries and regions with limited medical facilities and resources. Conventional flow cytometers typically require multiple detectors for simultaneous identification of multiple subsets of immune cell. To minimize the number of detectors toward portable flow cytometry or to analyze multi-parametric cellular information with minimum number of detectors in conventional flow cytometers, we propose a versatile multiplexed cell-counting method using functional silica nanoparticles (SiNPs). FITC-doped SiNPs, which are 100 times brighter than the FITC molecules itself, were used as new intensity-based fluorescent dye complexes to simultaneously measure two subsets of leukocytes using a single detector. CD45(+)CD4(+) cells tagged with these FITC-doped SiNPs were 50 times brighter than CD45(+)CD4(-) cells tagged only with FITC. To make the overall system compact, a disposable microchip flow cytometer that does not require sheath flow was developed. Combining these dye-doped SiNPs based detection schemes and the sheathless microchip flow cytometer scheme, we successfully identified and counted two subsets of leukocytes simultaneously (R(2) = 0.876). These approaches can be the building blocks for a truly portable and disposable flow cytometer for various clinical cytometry applications.

Serial dilution microchip for cytotoxicity test

Todays pharmaceutical industry is facing challenges resulting from the vast increases in sample numbers produced by high-throughput screening (HTS). In addition, the bottlenecks created by increased demand for cytotoxicity testing (required to assess compound safety) are becoming a serious problem. We have developed a polymer PDMS (polydimethylsiloxane) based microfluidic device that can perform a cytotoxicity test in a rapid and reproducible manner. The concept that the device includes is well adjustable to automated robots in huge HTS systems, so we can think of it as a potential dilution and delivery module. Cytotoxicity testing is all about the dilution and dispensing of a drug sample. Previously, we made a PDMS based microfluidic device which automatically and precisely diluted drugs with a buffer solution with serially increasing concentrations. This time, the serially diluted drug solution was directly delivered to 96 well plates for cytotoxicity testing. Cytotoxic paclitaxel solution with 2% RPMI 1640 has been used while carrying out cancerous cell based cytotoxicity tests. We believe that this rapid and robust use of the PDMS microchip will overcome the growing problem in cytotoxicity testing for HTS.

Functional integration of serial dilution and capillary electrophoresis on a PDMS microchip

For the quantitative analysis of an unknown sample a calibration curve should be obtained, as analytical instruments give relative, rather than absolute measurements. Therefore, researchers should make standard samples with various known concentrations, measure each standard and the unknown sample, and then determine the concentration of the unknown by comparing the measured value to those of the standards. These procedures are tedious and time-consuming. Therefore, we developed a polymer based microfluidic device from polydimethylsiloxane, which integrates serial dilution and capillary electrophoresis functions in a single device. The integrated microchip can provide a one-step analytical tool, and thus replace the complex experimental procedures. Two plastic syringes, one containing a buffer solution and the other a standard solution, were connected to two inlet holes on a microchip, and pushed by a hydrodynamic force. The standard sample is serially diluted to various concentrations through the microfluidic networks. The diluted samples are sequentially introduced through microchannels by electro-osmotic force, and their laser-induced fluorescence signals measured by capillary electrophoresis. We demonstrate the integrated microchip performance by measuring the fluorescence signals of fluorescein at various concentrations. The calibration curve obtained from the electropherograms showed the expected linearity.

Technical note: GaFinC: Gaze and Finger Control interface for 3D model manipulation in CAD application

Natural and intuitive interfaces for CAD modeling such as hand gesture controls have received a lot of attention recently. However, in spite of its high intuitiveness and familiarity, their use for actual applications has been found to be less comfortable than a conventional mouse interface because of user physical fatigue over long periods of operation. In this paper, we propose an improved gesture control interface for 3D modeling manipulation tasks that possesses conventional interface level usability with low user fatigue while maintaining a high level of intuitiveness. By analyzing problems associated with previous hand gesture controls in translation, rotation and zooming, we developed a multi-modal control interface GaFinC: Gaze and Finger Control interface. GaFinC can track precise hand positions, recognizes several finger gestures, and utilizes an independent gaze pointing interface for setting the point of interest. To verify the performance of GaFinC, tests of manipulation accuracy and time are conducted and their results are compared with those of a conventional mouse. The comfort and intuitiveness level are also scored by means of user interviews. As a result, although the GaFinC interface posted insufficient performance in accuracy and times compared with a mouse, it shows applicable level performance. Also users found it to be more intuitive than a mouse interface while maintaining a usable level of comfort.

Active sealing for soft polymer microchips: method and practical applications

This paper presents a new sealing method for soft polymer (elastomer) microchips. A robust and reversible sealing method, which allows various materials to be bonded and sealed tightly with each other even in aqueous solutions, is developed. A poly (dimethylsiloxane) microchip system, which can actively generate bonding and sealing forces by itself, is invented. By inducing negative pressure into additional closed areas, an instant sucking disc is made. This disc is used to tighten up the conformal contact of soft polymers. Other functionalities of active sealing such as making reusable microchips, patterning cells and performing cellular assays in a single dish have also been examined and will be discussed hereunder. This technique gives a robust and universal solution for microchip sealing issues by sealing soft polymers with diverse materials under various conditions. Active sealing will simplify numerous assays in lab-on-a-chip industry and will open a new era for cellular microchip assays.

Upper Extremity Functional Evaluation by Fugl-Meyer Assessment Scoring Using Depth-Sensing Camera in Hemiplegic Stroke Patients.

Virtual home-based rehabilitation is an emerging area in stroke rehabilitation. Functional assessment tools are essential to monitor recovery and provide current function-based rehabilitation. We developed the Fugl-Meyer Assessment (FMA) tool using Kinect (Microsoft, USA) and validated it for hemiplegic stroke patients. Forty-one patients with hemiplegic stroke were enrolled. Thirteen of 33 items were selected for upper extremity motor FMA. One occupational therapist assessed the motor FMA while recording upper extremity motion with Kinect. FMA score was calculated using principal component analysis and artificial neural network learning from the saved motion data. The degree of jerky motion was also transformed to jerky scores. Prediction accuracy for each of the 13 items and correlations between real FMA scores and scores using Kinect were analyzed. Prediction accuracies ranged from 65% to 87% in each item and exceeded 70% for 9 items. Correlations were high for the summed score for the 13 items between real FMA scores and scores obtained using Kinect (Pearson’s correlation coefficient = 0.873, P<0.0001) and those between total upper extremity scores (66 in full score) and scores using Kinect (26 in full score) (Pearson’s correlation coefficient = 0.799, P<0.0001). Log transformed jerky scores were significantly higher in the hemiplegic side (1.81 ± 0.76) compared to non-hemiplegic side (1.21 ± 0.43) and showed significant negative correlations with Brunnstrom stage (3 to 6; Spearman correlation coefficient = -0.387, P = 0.046). FMA using Kinect is a valid way to assess upper extremity function and can provide additional results for movement quality in stroke patients. This may be useful in the setting of unsupervised home-based rehabilitation.

A kinematic analysis of directional effects on mouse control.

The directional effects associated with cursor movement controlled by a computer mouse have long been studied to improve mouse performance during precise tasks. However, those studies have rarely considered the kinematic variables associated with directional effects and have only analysed the projection of trajectories along the main axes of movement, eventually reducing the original dimensions of the data. In addition, as the angle of approach has a limited number of levels, it has been difficult to observe singular behaviour in the horizontal directions. In this study, we investigated the directional effects on kinematic variables when using a mouse to select circular targets. In this experiment, the measured trajectory of 16 different angles of approach was measured after separating the x and y components. The results revealed interesting biomechanical and cognitive features of mouse control and led to the suggestion of two improvements to be made upon the typical mouse design. Practitioner Summary: The angle of approach was varied to determine its effect on the kinematic variables of a cursor trajectory. We analysed both the x and y coordinates separately without reducing the original dimensions of the data. Therefore, we succeeded in identifying previously unknown characteristics of mouse control.

Combined microchannel-type erythrocyte deformability test with optical tweezers

A combined microchannel-type erythrocyte deformability test with optical tweezers has been developed especially for more sensitive detection of cancerous diseases. To demonstrate the performance and sensitivity of the microchannel-type method, we measured the transit velocity of individual erythrocytes passing through a specific confinement region and calculated the modified elongation index defined by the ratio of the width of the microchannel to the elongated length of the squeezed erythrocytes. To know exactly the effect of optical tweezers on erythrocytes, we investigated several morphologies of optically deformed erythrocytes and measured the shape recovery time of erythrocytes in a static aqueous solution under various powers (~ 24 mW) of 1064-nm laser by a dual-trap optical tweezers. Finally we combined these two methods by considering the key parameters of erythrocyte deformability. The results show that the ambiguity of the overlapped experimental data from microchannel-type erythrocyte deformability test was conspicuously reduced, and that the subtle change (≈ 100-200 ms) in shape recovery time which is one of mechanical properties of erythrocyte membrane surface was remarkably amplified to readily discriminate the difference (≈ 2-3 s) between normal and cancerous blood. This suggests the combined method is more sensitive enough to pinpoint the minor quantitative differences between individual erythrocytes, especially in the field of cancer and cardiovascular diseases.

A Mouse With Two Optical Sensors That Eliminates Coordinate Disturbance During Skilled Strokes

The computer mouse is rarely used for drawing due to its body-fixed coordinate system, which creates a stroke that differs from the user’s original hand movement. In this study, we resolve this problem by implementing a new mouse called StereoMouse, which eliminates the rotational disturbance of the coordinate system in real-time. StereoMouse is a special mouse with two optical sensors, and its coordinate orientation at the beginning of a stroke is maintained throughout the movement by measuring and compensating for the angular deviation estimated from those sensors. The drawing performance of StereoMouse was measured by means of having users perform the task of repeatedly drawing a basic shape. The results of this experiment showed that StereoMouse eliminated the horizontal drift typically observed in a stroke drawn by a normal mouse. Consequently, StereoMouse allowed the users to draw shapes at a 10.6% faster mean speed with a 10.4% shorter travel time than a normal mouse would. Furthermore, StereoMouse showed 37.1% lower chance of making incorrect gesture input than the normal mouse.

A glasses-type wearable device for monitoring the patterns of food intake and facial activity

Here we present a new method for automatic and objective monitoring of ingestive behaviors in comparison with other facial activities through load cells embedded in a pair of glasses, named GlasSense. Typically, activated by subtle contraction and relaxation of a temporalis muscle, there is a cyclic movement of the temporomandibular joint during mastication. However, such muscular signals are, in general, too weak to sense without amplification or an electromyographic analysis. To detect these oscillatory facial signals without any use of obtrusive device, we incorporated a load cell into each hinge which was used as a lever mechanism on both sides of the glasses. Thus, the signal measured at the load cells can detect the force amplified mechanically by the hinge. We demonstrated a proof-of-concept validation of the amplification by differentiating the force signals between the hinge and the temple. A pattern recognition was applied to extract statistical features and classify featured behavioral patterns, such as natural head movement, chewing, talking, and wink. The overall results showed that the average F1 score of the classification was about 94.0% and the accuracy above 89%. We believe this approach will be helpful for designing a non-intrusive and un-obtrusive eyewear-based ingestive behavior monitoring system.