Song-Bin Huang

Pneumatic micropumps with serially connected actuation chambers

This study presents a new pneumatic micropump featuring three membrane-enclosed air chambers with different volumes, such that serially connected actuation of these membranes can generate fluid movement. When compressed air fills the chambers, the membranes are pushed downward sequentially, resulting in the liquid in the underlying fluid channels being pumped forward peristaltically. Since the chambers are filled up sequentially with compressed air, from the smallest to largest chamber, this time delay generates a peristaltic motion in the membranes and forces the liquids to flow only along one direction. The pneumatic micropump is made of polydimethylsiloxane (PDMS) using soft lithography techniques. When compared with other pneumatic micropumps that usually require at least three electromagnetic valves (EMV), this new micropump can be operated by using a single EMV. Experimental results show that the micropump provides good performance even at low flow rates. The back pressure of the pneumatic micropump is measured at a fixed peak frequency to demonstrate the functionality of the micropump. The optimum operating conditions and geometric parameters of the micropump are systematically explored. A maximum flow of 108 µl min−1 is obtained at a driving frequency of 10 Hz and an air pressure of 25 psi (172.4 kPa) when a membrane with a thickness of 80 µm and a microchannel with a width of 500 µm are tested. The development of these micropumps could be crucial for automatic miniature biomedical and chemical analysis systems.

A membrane-based serpentine-shape pneumatic micropump with pumping performance modulated by fluidic resistance

This paper reports a new membrane-based pneumatic micropump with new serpentine-shape (S-shape) pneumatic channels intended for achieving high-throughput pumping in a microfluidic system at a relatively low pumping rate and a board flow rate range. The key feature of this design is the ability to modulate the pumping rates by fine-tuning the fluidic resistance of injected compressed air in the designed pneumatic microchannels and the chambers of the micropump. In the study, several S-shape pneumatic micropumps with various layouts were designed and fabricated based on thick-film photoresist lithography and polydimethylsiloxane (PDMS) replication processes. To investigate designs with a suitable pumping performance, S-shape pneumatic micropumps with varied lengths (1000, 5000 and 10 000 µm), varied widths (20, 40 and 200 µm) of the pneumatic microchannel bridging two rectangular pneumatic chambers, and different numbers of pneumatic channel bends (two and four U-shape bends) were designed and evaluated experimentally by using high-speed CCD-coupled microscopic observation of the movement of PDMS membrane pulsation and pumping rate measurements. The results revealed that under the experimental conditions studied, the layout of the S-shape pneumatic micropump with three rectangular pneumatic chambers, 5000 µm long and 40 µm wide pneumatic microchannel and four U-shape bends in the pneumatic microchannel was found to be capable of providing a broader pumping rate range from 0 to 539 µl h−1 compared to the other designs. As a whole, the experimental results demonstrate the use of fluidic resistance of injected air in a pneumatic micropump with S-shape layout to control its pumping performance, which largely expands the flexibility of its pumping application in a microfluidic system.

A microfluidic system enabling continuous characterization of specific membrane capacitance and cytoplasm conductivity of single cells in suspension

This paper presents a microfluidic system enabling continuous characterization of specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm) of single cells in suspension. In this study, cells were aspirated continuously through a constriction channel while cell elongations and impedance profiles at two frequencies (1kHz and 100kHz) were measured simultaneously using microscopy imaging and a lock-in amplifier. 1kHz impedance data were used to evaluate cellular sealing properties with constriction channel walls and 100kHz impedance data were translated to quantify equivalent membrane capacitance and cytoplasm resistance of single cells, which were further translated to Cspecific membrane and σcytoplasm. Two model cell lines (kidney tumor cell line of 786-O (n=302) and vascular smooth muscle cell line of T2 (n=216)) were used to evaluate this technique, producing Cspecific membrane of 3.67±1.00 and 4.53±1.51μF/cm(2) and σcytoplasm of 0.47±0.09 and 0.55±0.14S/m, respectively. Compared to previously reported techniques which can only collect Cspecific membrane and σcytoplasm from tens of cells, this new technique has a higher throughput, capable of collecting Cspecific membrane and σcytoplasm from hundreds of cells in 30min immediately after cell passage.

A microfluidic system for cell type classification based on cellular size-independent electrical properties

This paper presents a microfluidic system enabling cell type classification based on continuous characterization of size-independent electrical properties (e.g., specific membrane capacitance (C(specific membrane)) and cytoplasm conductivity (σ(cytoplasm)). In this study, cells were aspirated continuously through a constriction channel, while cell elongation and impedance profiles at two frequencies (1 kHz and 100 kHz) were measured simultaneously. Based on a proposed distributed equivalent circuit model, 1 kHz impedance data were used to evaluate cellular sealing properties with constriction channel walls and 100 kHz impedance data were translated to C(specific membrane) and σ(cytoplasm). Two lung cancer cell lines of CRL-5803 cells (n(cell) = 489) and CCL-185 cells (n(cell) = 487) were used to evaluate this technique, producing a C(specific membrane) of 1.63 ± 0.52 μF cm(-2) vs. 2.00 ± 0.60 μF cm(-2), and σ(cytoplasm) of 0.90 ± 0.19 S m(-1)vs. 0.73 ± 0.17 S m(-1). Neural network-based pattern recognition was used to classify CRL-5803 and CCL-185 cells, producing success rates of 65.4% (C(specific membrane)), 71.4% (σ(cytoplasm)), and 74.4% (C(specific membrane) and σ(cytoplasm)), suggesting that these two tumor cell lines can be classified based on their electrical properties.

Application of optically-induced-dielectrophoresis in microfluidic system for purification of circulating tumour cells for gene expression analysis- Cancer cell line model.

Circulating tumour cells (CTCs) in a blood circulation system are associated with cancer metastasis. The analysis of the drug-resistance gene expression of cancer patients’ CTCs holds promise for selecting a more effective therapeutic regimen for an individual patient. However, the current CTC isolation schemes might not be able to harvest CTCs with sufficiently high purity for such applications. To address this issue, this study proposed to integrate the techniques of optically induced dielectrophoretic (ODEP) force-based cell manipulation and fluorescent microscopic imaging in a microfluidic system to further purify CTCs after the conventional CTC isolation methods. In this study, the microfluidic system was developed, and its optimal operating conditions and performance for CTC isolation were evaluated. The results revealed that the presented system was able to isolate CTCs with cell purity as high as 100%, beyond what is possible using the previously existing techniques. In the analysis of CTC gene expression, therefore, this method could exclude the interference of leukocytes in a cell sample and accordingly contribute to higher analytical sensitivity, as demonstrated in this study. Overall, this study has presented an ODEP-based microfluidic system capable of simply and effectively isolating a specific cell species from a cell mixture.

Pneumatically driven micro-dispenser for sub-micro-liter pipetting

In this study, we report a pneumatically driven micro-dispenser for precise pipetting of sub-micro-liter samples. The key feature of this micro-dispenser is the use of a suction membrane to provide a driving force for precise and quick aqueous liquid sampling and pipetting. The control of the release time of the suction membrane can generate precise pipetting of liquid volumes ranging from 0.05 µl to 0.45 µl (with 2.9% variation). Experimental results reveal that the micro-dispenser is able to perform liquid dispensing in a high reproducible manner and with a superior performance compared to commercial pipettors. This micro-dispenser is fabricated using standard soft lithography of PDMS (polydimethylsiloxane). Hence it can be easily integrated with other microfluidic devices for subsequent microfluidic applications. The developed pneumatically driven micro-dispenser is promising for further integration into micro-total-analysis systems in the field of drug dosing or for other biomedical analysis applications.

A Microfluidic System for Automatic Cell Culture

This study presents a new chip capable of automating the cell culture process by using microfluidic technology. This microfluidic cell culture system comprising of microheaters, a micro temperature sensor, micropumps, microvalves, microchannels, a cell culture area and several reservoirs was fabricated by using micro-electro-mechanical-systems (MEMS) fabrication processes. Manual cell culture processes can be performed on this chip without using incubators. A typical cell culturing process for human lung cancer cells (A549) was successfully performed to demonstrate the capability of the developed microfluidic system. This automatic cell culturing system can be eventually integrated with subsequent microfluidic modules for cell purification, collection, counting and lysis to form a cell-based micro-total-analysis-system.

The Study of the Frequency Effect of Dynamic Compressive Loading on Primary Articular Chondrocyte Functions Using a Microcell Culture System

Compressive stimulation can modulate articular chondrocyte functions. Nevertheless, the relevant studies are not comprehensive. This is primarily due to the lack of cell culture apparatuses capable of conducting the experiments in a high throughput, precise, and cost-effective manner. To address the issue, we demonstrated the use of a perfusion microcell culture system to investigate the stimulating frequency (0.5, 1.0, and 2.0 Hz) effect of compressive loading (20% and 40% strain) on the functions of articular chondrocytes. The system mainly integrates the functions of continuous culture medium perfusion and the generation of pneumatically-driven compressive stimulation in a high-throughput micro cell culture system. Results showed that the compressive stimulations explored did not have a significant impact on chondrocyte viability and proliferation. However, the metabolic activity of chondrocytes was significantly affected by the stimulating frequency at the higher compressive strain of 40% (2 Hz, 40% strain). Under the two compressive strains studied, the glycosaminoglycans (GAGs) synthesis was upregulated when the stimulating frequency was set at 1 Hz and 2 Hz. However, the stimulating frequencies explored had no influence on the collagen production. The results of this study provide useful fundamental insights that will be helpful for cartilage tissue engineering and cartilage rehabilitation.

Circulating epithelial cell enumeration facilitates the identification and follow-up of a patient with early stage papillary thyroid microcarcinoma: A case report.

BACKGROUND This study examines whether the measurement of circulating epithelial cells (CECs) facilitates the identification and follow-up of a patient with thyroid cancer. METHODS A 29-y-old woman with no cancer history was enrolled as a healthy control in a CEC study. CECs were enriched from the peripheral blood by the negative selection system PowerMag. Various medical examinations were performed on the patient to establish the diagnosis and to follow-up her disease status during treatment. RESULTS This patient had unexpectedly high CEC counts that were sustained for more than two weeks. Thyroid gland ultra-sonography revealed lesions in the left lobe that could not be confirmed as cancer by magnetic resonance imaging, (18)F-fludeoxyglucose-positron emission tomography-computed tomography or cytopathological analysis, but were histologically confirmed after thyroidectomy as papillary thyroid microcarcinoma. Both the CEC count and serum thyroglobulin (Tg) concentration were significantly decreased after thyroidectomy, and they and the patients disease status were correlated during remnant ablation therapy. The CEC count returned to normal when the patient was disease-free 10 months after thyroidectomy. CONCLUSIONS CEC testing facilitates the identification of individuals at risk for cancer. Longitudinal follow-up of the CEC count may complement serum Tg testing for monitoring the status of patients with thyroid cancer.

Classification of Cells with Membrane Staining and/or Fixation Based on Cellular Specific Membrane Capacitance and Cytoplasm Conductivity

Single-cell electrical properties (e.g., specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm)) have been regarded as potential label-free biophysical markers for the evaluation of cellular status. However, whether there exist correlations between these biophysical markers and cellular status (e.g., membrane-associate protein expression) is still unknown. To further validate the utility of single-cell electrical properties in cell type classification, Cspecific membrane and σcytoplasm of single PC-3 cells with membrane staining and/or fixation were analyzed and compared in this study. Four subtypes of PC-3 cells were prepared: untreated PC-3 cells, PC-3 cells with anti-EpCAM staining, PC-3 cells with fixation, and fixed PC-3 cells with anti-EpCAM staining. In experiments, suspended single cells were aspirated through microfluidic constriction channels with raw impedance data quantified and translated to Cspecific membrane and σcytoplasm. As to experimental results,