Centrifugal microfluidics has been widely applied in the sample-in–answer-out systems for the analyses of nucleic acids, proteins, and small molecules. However, the inherent characteristic of unidirectional fluid propulsion limits the flexibility of these fluidic chips. Providing an extra degree of freedom to allow the unconstrained and reversible pumping of liquid is an effective strategy to address this limitation. In this study, a wirelessly charged centrifugal microfluidic platform with two rotation axes has been constructed and the flow control strategy in such platform with two degrees of freedom was comprehensively studied for the first time. Inductively coupled coils are installed on the platform to achieve wireless power transfer to the spinning stage. A micro servo motor is mounted on both sides of the stage to alter the orientation of the device around a secondary rotation axis on demand during stage rotation. The basic liquid operations on this platform, including directional transport of liquid, valving, metering, and mixing, are comprehensively studied and realized. Finally, a chip for the simultaneous determination of hexavalent chromium [Cr(VI)] and methanal in water samples is designed and tested based on the strategy presented in this paper, demonstrating the potential use of this platform for on-site environmental monitoring, food safety testing, and other life science applications.

Microfluidic electric impedance flow cytometry (IFC) chips have strong advantages over the traditional flow cytometry system because they are self-contained, disposable, economic in reagent consumption, and easier to operate. However, the throughput, sensitivity, and simplicity of the microfluidic IFC chips are inversely related to one another, and their reported impedance-based cell differentiation capability is in general limited. In this paper, we designed a sheath-less microfluidic IFC chip with a constriction structure between the detection electrodes to enhance the particle sensing performance, and built the entire sensing system around it, including the sensing circuit and data processing software. The measurement of the volume, limit of detection (∼3 μm), coefficient variation (6.83%) and other characteristics of the device was performed using the standard polymer beads. This sheath-less polydimethylsiloxane microfluidic device had a simple structure, which could maintain a single-cell sequence flow at the detection area, and displayed high signal-to-noise ratio (23.5–32.6 dB) and low coincidence ratio signals for further analysis. The throughput of the chip for single-cell screening can reach up to 172 cells per s, and thus, 10 000 cells could be analyzed in a few minutes for statistical analysis. Moreover, the electrical conductance and susceptance were found to be good at differentiating the bead/cell sizes and membrane/surface characteristics of cells/beads, respectively. These parameters were used to classify the population of a large amount of drug-treated cells (>10 000 cells per sample), displaying good performance in distinguishing apoptotic/necrotic cells from live cells. The ratios of apoptotic, necrotic, and live cells analyzed using our system were consistent with the traditional flow cytometry results (R2 = 0.9796). Along with the miniaturization of the electric sensing circuit, our system can be applicable for novel, compact and easy operative (single) cell analysis systems in the future.

•Conditional siphon priming technique is introduced for liquid manipulations.•It can be triggered by liquid addition or venting at low frequency.•Sequential release of liquids and selective routing are demonstrated.•Ammonium analysis is achieved on centrifugal microfluidic platforms.Centrifugal microfluidics has proven to be successful in biomedical diagnostics, biological analysis and environmental monitoring. However, the automation of multi-step sample processing, reaction and detection remains a great challenge. In this study, a conditional siphon priming technique is introduced for multi-step liquid addition or selective routing. Since the siphon channel is locally modified or venting is blocked by liquid in another chamber, siphon priming can be triggered by liquid addition or venting at low frequency. Using this technique, sequential release of liquids and selective routing in multiple manners were successfully achieved. As a proof of concept, a centrifugal microfluidic platform was designed for on-site ammonium analysis in water samples. The linear range of ammonium concentrations is extended by integration of a dilution process. This novel valving technique provides new solutions for integration of complex liquid handling processes on centrifugal platforms.

Urine examination is a basic program in routine check-ups that can reveal multiple parameters about our health and thus has significant meaning. However, instruments for urine analysis in hospitals are usually bulky and expensive. In this study, we have constructed a pocket-sized and CMOS imaging-based analytical device for urine diagnosis at home or on the spot. The shape of traditional dipsticks was transformed into matrix arrays and pasted on a reaction unit for colorimetric arrays. Chromaticity values were used to establish the functional relationship between the red-green-blue intensities of images and the concentrations of different indices. The size of the entire system was reduced to 30 × 30 × 45 mm, and once charged this device can continuously work for >4 h accommodating more than 1000 tests. To validate the performance of our device, more than 200 real human urine samples were tested and the results generated by our portable device and a commercial instrument show a great consistency (the consistency for most results is >90%) between the two systems.

Urine examination is a basic program in routine check-ups that can reveal multiple parameters about our health and thus has significant meaning. However, instruments for urine analysis in hospitals are usually bulky and expensive. In this study, we have constructed a pocket-sized and CMOS imaging-based analytical device for urine diagnosis at home or on the spot. The shape of traditional dipsticks was transformed into matrix arrays and pasted on a reaction unit for colorimetric arrays. Chromaticity values were used to establish the functional relationship between the red-green-blue intensities of images and the concentrations of different indices. The size of the entire system was reduced to 30 × 30 × 45 mm, and once charged this device can continuously work for >4 h accommodating more than 1000 tests. To validate the performance of our device, more than 200 real human urine samples were tested and the results generated by our portable device and a commercial instrument show a great consistency (the consistency for most results is >90%) between the two systems.

•Three typical impedance sensing techniques: ECIS, IFC and EIS, are reviewed.•The theory, electrode fabrication, and applications are introduced.•Applications of impedance sensing have been expanded to all aspects of cell biology.•The development of point-of-need diagnosis devices is predicted to be future trend.Impedance measurement of live biological cells is widely accepted as a label free, non-invasive and quantitative analytical method to assess cell status. This method is easy-to-use and flexible for device design and fabrication. In this review, three typical techniques for impedance measurement, i.e., electric cell-substrate impedance sensing, Impedance flow cytometry and electric impedance spectroscopy, are reviewed from the aspects of theory, to electrode design and fabrication, and applications. Benefiting from the integration of microelectronic and microfluidic techniques, impedance sensing methods have expanded their applications to nearly all aspects of biology, including living cell counting and analysis, cell biology research, cancer research, drug screening, and food and environmental safety monitoring. The integration with other techniques, the fabrication of devices for certain biological assays, and the development of point-of-need diagnosis devices is predicted to be future trend for impedance sensing techniques.

Traditional Chinese medicine (TCM) is one of the unique cultural treasures of Chinese; it represents a significant feature and prominent advantage of the healthcare cause in China. Data in this paper were fromWorld Health Organization, Chinese Bureau of Statistics, China National Knowledge Infrastructure, and PubMed. In recent years, TCM has established a solid foundation in Europe, which made great strides in legislation, education, research, and international exchange, and has enjoyed a vast development space in the continent. Now, TCM is embracing unprecedented development opportunities in Europe. At the same time, the stiff international competition poses a grave threat to China’s TCM industry. With multiple cultural, legal, and institutional challenges, as well as talent shortages in the way, TCM is now facing many difficulties in Europe. To fully prepare and enact active and vigorous steps to seize opportunities, we should have a clear picture about the serious challenges hampering TCM development in Europe. The TCM development at overseas markets has shifted from a spontaneous trade activity into a national strategy spearheaded by the government and participated in by multiple stakeholders. We should make a systematic, comprehensive, and sustainable push in fields such as TCM therapy, healthcare, education, research, culture, and industry development. The ultimate goal is to bring TCMs to the global market and allow them to play a role in safeguarding public health along with modern medicines.

In this study, a new platform based on electric cell-substrate impedance sensing (ECIS) was constructed for the dynamic monitoring of changes in cells during and after hyperthermia treatments. ECIS profiling was compared with traditional methods for monitoring the status of A549 cells under three typical treatment conditions, i.e., 30 min of hyperthermia at 41, 43, and 45 °C. The impedance value rapidly changed, and severe morphological changes were observed during and after the hyperthermia. The impedance curves revealed that different hyperthermia conditions differentially affected the cells: the 41 °C treatment caused a minor decrease in impedance that almost completely recovered in 1–2 h; the 43 °C treatment led to a greater decrease in impedance, which also recovered over several hours before slowly decreasing again, possibly indicating apoptosis; the 45 °C treatment resulted in the greatest decrease in impedance, which never recovered, possibly indicating rapid necrosis. Further, these three hyperthermia treatment regimens were applied to four additional cell lines. By comparing the impedance curves of different cell lines, we found that cancer cells (HepG2) may be more sensitive to hyperthermia than normal cells (LO2). Moreover, different cancer cell lines (HeLa, MCF-7, A549, and HepG2) exhibited different thermal sensitivities. These results fit previous theories on hyperthermia, demonstrating that the platform established in this study is a useful analytical tool for the in vitro research of thermal therapy, and the dynamic data generated will enable us to examine phenomena and theories.

Nephrotoxicity is one of the major concerns for anticancer drug safety because most drugs are metabolized and excreted by the kidneys. Convenient tools able to perform rapid in vitro cytotoxicity analysis and identify drug side effects in kidney cells during early phases of drug discovery could be beneficial to drug development programs. Here we developed an electrical cell-substrate impedance sensing system (ECIS) capable of continuously measuring the dosage and time response of human proximal tubular epithelial (HK2) cells exposed to four drugs throughout the experimental period. These drugs induced HK2 cell apoptosis/death in a dose-dependent manner, although with very different dose-response effects. DDP (50 μM) was the most cytotoxic and induced obvious HK2 cell apoptosis rapidly after exposure. The other three drugs had much lower cytotoxicity, even at concentrations approaching 1 mM. The results obtained from our ECIS system correlated well with conventional in vitro assays such as flow cytometry and cell viability assays. Notably, the continuous and automatic measurements provided by ECIS system allow for better resolution for drugs with different temporal toxicity profiles. Furthermore, we investigated the effect of DDP's antidotes, glutathione and sodium subsulfite, on DDP-induced cytotoxicity, both of which decreased nephrotoxicity of DDP in a dose-dependent manner. Overall this study illustrates the convenience of ECIS for direct, continuous assessment of the cytotoxicity of anticancer drugsin vitro. ECIS has the potential to become a useful, non-invasive analytical method for early evaluation of drugs and antidotes of toxins.

In this paper, we describe a comprehensive general system adapted for quantitative fluorescence resonance energy transfer (FRET) measurement using signals from three channels of a fluorescence instrument. The general FRET measurement system involves two established methods, as well as two novel approaches. Unlike the previous measurements, which can be taken correctly only when the quantity of the acceptor is greater than or equal to that of the donor, one of our novel methods can overcome this obstacle and take quantitative FRET measurements when the donor is in excess of the acceptor. Hence the general FRET measurement system allowed one to determine the exact distance when the donor and acceptor were present in different quantities, and integrated the methods for quantitative FRET measurements. The uniformity of measured values and utility of each method were validated using molecular standards based on DNA oligonucleotide rulers. We also discussed and validated the use of a novel method for estimating the relative quantities of the donor and acceptor fluorophores when they were not known before an appropriate method of this system can be selected.

The monitoring and evaluation of cell behaviors under various concentrations of diffusible molecules or drugs are important in drug screening and in many other types of biological studies. In the current study, a novel polydimethylsiloxane (PDMS)-based microfluidic device was established for the real-time monitoring of drug-induced cytotoxicity using electric cell-substrate impedance sensing (ECIS). This device consists of the following three components: a drug gradient generator, planar air-bubble valves, and parallel cell culture cavities that are combined with impedance-sensing electrodes. The gradient generator allows for the simultaneous administration of multiple drug doses to test the functional cytotoxicity, and the incorporated impedance sensing enables the dynamic, automatic and quantitative measurement of in vitro dose-dependent drug responses. The air-bubble valve presented here allows the automatic closure of the valve without the need for any external valve-control instrument. As a proof-of-concept demonstration, this device was applied to dynamically monitor the effects of the anticancer drug cisplatin on apoptosis in four cancer cell lines, which may be useful for drug discovery and other biological studies that require automated analysis combined with concentration gradients.Highlights► We construct a novel device which can generate static concentration gradients. ► This device is combined with impedance-sensing electrodes and air-bubble valves. ► The air-bubble valve works without any external control system. ► Cisplatin induced apoptosis in four cancer cell lines was monitored with this device.

In vitro fertilization (IVF) technology has been broadly applied to solve human infertility in recent years. However, the physical tools for IVF remain unchanged over several decades before microfluidic technology was introduced in this field. Here, we report a novel microdevice that integrates each step of IVF, including oocyte positioning, sperm screening, fertilization, medium replacement, and embryo culture. Oocytes can be singly positioned in a 4 × 4 array of octacolumn units. The four symmetrical straight channels, crossing at the oocyte positioning region, allowed efficient motile sperm selection and facilitated rapid medium replacement. The fertilization process and early embryonic development of the individual zygote was traced with microscopic recording and analyzed by in situ fluorescent staining. The murine sperm motility was increased from 60.8 ± 3.4% to 96.1 ± 1.9% through the screening channels. The embryo growth rate and blastocyst formation were similar between the routine Petri dish group and the microdevice group. The healthy blastocysts developed in the microdevice could be conveniently retrieved through a routine pipetting operation and used for further embryo transfer.

In basic cell biology research and drug discovery, it is important to rapidly introduce genes, proteins or drug compounds into cells without permanent damage. Here, we report a three dimensional SU-8 micro-well structure sandwiched with an indium tin oxide (ITO) electrode-covered slide from the top and an individually addressable array of microelectrodes on the bottom to allow parallel delivery of exogenous molecules into various cells in a spatially specific manner. A positive dielectrophoretic force was selectively applied by energizing appropriate electrodes to capture the dispersed cells at the bottom electrode, while the micro-wells were designed to confine cellsin situ when the positive dielectrophoretic force is removed. The combination of spatial positive dielectrophoresis (pDEP) and micro-wells made it possible to construct cell microarrays with specific patterns. Once the cells become attached to the electrodes, different plasmids can be introduced sequentially for selective electroporation. The present cell arraying-assisted electroporation chip integrates a pDEP-assisted cell positioning function with selective electroporation to provide a simple and efficient method for gene transfer. This platform is ideal for high throughput screening of compounds in parallel and thus holds promise for applications in cellular and molecular research.

We have established a mobile phone-assisted microarray decoding platform for signal-enhanced mutation detection. A large amount of single-stranded DNA (ssDNA) was obtained by combining symmetric PCR and magnetic isolation, and ssDNA prepared with magnetic bead as label was further allowed to hybridize against the tag-array for decoding purpose. High sensitivity and specificity was achieved with the detection of genomic DNA. When simultaneously genotyping nine common mutations associated with hereditary hearing loss, the detection limit of 1 ng genomic DNA was achieved. Significantly, a mobile phone was also used to record and decode the genotyping results through a custom-designed imaging adaptor and a dedicated mobile phone software. A total of 51 buccal swabs from patients probably with deafness-related mutations were collected and analyzed. The genotyping results were all confirmed by fluorescence-based laser confocal scanning and direct DNA sequencing. This mobile phone-assisted decoding platform provides an effective but economic mutation detection alternative for the future quicker and sensitive detection of virtually any mutation-related diseases in developing and underdeveloped countries.

Two-color DNA microarray platforms are widely used for determining differential amounts of target sequences in parallel between sample pairs. However, the fluorescence (or Förster) resonance energy transfer (FRET) between two fluorophores can potentially result in the distortions of the measured fluorescence signals. Here we assessed the influence of FRET on the two-color DNA microarray platform and developed a reliable and convenient method for the correction of FRET distortion. Compared to current methods of normalization based on the statistical analysis and the hypothesis that only a small part of target sequences are differentially presented between sample pairs, our FRET correction method can recover the undistorted signals by the compensation of fluorescence emission, without considering the number of target sequences differentially presented. The correction method was validated with samples at different target ratios and with microarrays spotted in different probe concentrations. We also applied the FRET correction method to gene expression profiling arrays, and the results show that FRET was present when the content of target sequence was beyond a threshold amount and that the process incorporating our FRET correction method can improve the reliability of the gene expression profiling microarray platform in comparison with the current process without FRET correction.

The cell cycle plays a crucial role in many cellular physiological processes and has drawn an increasing interest in past decades. In the current study, we have developed a bioelectronic chip-based system capable of performing real-time dynamic analysis of the cell cycle in live cells via non-invasive cellular impedance sensing. The cells were cultured on the cellular impedance sensing chip comprising microfabricated interdigitated electrode structures. HeLa cells were synchronized with double thymidine block and the cellular impedances were monitored in a time resolution of minutes during the whole 5 days’ experiment. Our results show that real-time impedance sensing can clearly mirror the progression of the cell cycle—in G1 phase and S phase, the cellular impedance increased with time, while in G2 phase and M phase, the cellular impedance decreased. Correspondingly, the time-course impedance curves for the synchronized cells have marked “M-valleys” corresponding to the periods of mitosis of the cells. The cell cycle information revealed by the cellular impedance data was confirmed using flow cytometry and microscopy. This paper presents the first step towards in situ and label-free monitoring of the cell cycle of mammalian cells on chip in a real-time, non-invasive manner.

Fluorescence detection using two spectrally distinct fluorophores has long been used for the determination of the relative abundance of biomolecules, but overlap between the fluorescence spectra of each fluorophore can result in nonradiative Förster resonance energy transfer (FRET) and distorting the signals detected by fluorescence channels. Thus conventional methods for quantifying the relative abundance of fluorophores by fluorescence emission will not be accurate if FRET can occur. In this paper we report the development of a quantitative fluorescence correction method incorporating FRET to measure the relative abundance of fluorophores in dual-labeling experiments. The quantitative fluorescence correction method incorporating FRET is accurate, comprehensive, and convenient for the measurement of the relative abundance of fluorophores in dual-labeling experiments and can also correct the FRET distortion and provide accurate, quantitative, and convenient measurement of the hybridization efficiencies on microarrays.

Bufalin is a natural toxin with anti-leukemic properties. It induces cell differentiation and apoptosis, as well as increasing the sensitivity of leukemia cells to other chemotherapeutic agents. We investigated the biological effects and molecular mechanisms of bufalin triggered apoptosis in HL-60 cells by gene expression profiling. The broad transcriptional response to bufalin was consistent with bufalin’s action of regulating HL-60 cell proliferation and apoptosis, as well as its synergistic effect with other drugs. Further transcription factor ELISA experiments suggested that the transcription factors NFκB and AP-1 were activated to promote bufalin-induced HL-60 cell apoptosis. Our study provides new insights into the molecular mechanisms of bufalin, might prove to be beneficial in leukemia therapy.

The propagation of neuronal activities is a key feature to understanding information processing in networks. The analysis based on first-spikes of bursts in turn plays an important role in the research of neuronal activity propagation. Our focus here is to investigate how spatiotemporal patterns of neuronal first-spikes are affected by disinhibition. Multi-electrode arrays were used to record stimulation-evoked bursts of multiple neurons in randomly cultured neuronal networks. Both the precise timing of and the rank relationships between first-spikes were analyzed. Compared with evoked bursts in the network’s native state, the precise first-spike latencies in its disinhibited state are more consistent and the propagation of its bursting activities is much faster. Additional points of interest are that disinhibited neuronal networks can be evoked to generate stable and distinguishable neuronal first recruitment spatiotemporal patterns specific to the stimulation site, and that the disinhibition may cause the original spatiotemporal patterns to change in a heterogeneous manner with regards to different propagation pathways.

Cell migration is crucial in many physiological and pathological processes including embryonic development, immune response and cancer metastasis. Traditional methods for cell migration detection such as wound healing assay usually involve physical scraping of a cell monolayer followed by an optical observation of cell movement. However, these methods require hand-operation with low repeatability. Moreover, it's a qualitative observation not a quantitative measurement, which is hard to scale up to a high-throughput manner. In this article, a novel and reliable on-chip cell migration detection method integrating surface chemical modification of gold electrodes using self-assembled monolayers (SAMs) and real-time cellular impedance sensing is presented. The SAMs are used to inhibit cell adherence forming an area devoid of cells, which could effectively mimic wounds in a cell monolayer. After a DC electrical signal was applied, the SAMs were desorbed from the electrodes and cells started to migrate. The process of cell migration was monitored by real-time impedance sensing. This demonstrates the first occurrence of integrating cellular impedance sensing and wound-forming with SAMs, which makes cell migration assay being real-time, quantitative and fully automatic. We believe this method could be used for high-throughput anti-migratory drug screening and drug discovery.

Molecular systematics involves the description of the regulatory networks formed by the interconnections between active transcription factors and their target expressed genes. Here, we have determined the activities of 200 different transcription factors in six mouse tissues using an advanced mouse oligonucleotide array-based transcription factor assay (MOUSE OATFA). The transcription factor signatures from MOUSE OATFA were combined with public mRNA expression profiles to construct experimental transcriptional regulatory networks in each tissue. SRF-centered regulatory networks constructed for lung and skeletal muscle with OATFA data were confirmed by ChIP assays, and revealed examples of novel networks of expressed genes coregulated by sets of transcription factors. The combination of MOUSE OATFA with bioinformatics analysis of expressed genes provides a new paradigm for the comprehensive prediction of the transcriptional systems and their regulatory pathways in mouse.

Transcription factors (TFs) are crucial components of regulatory networks that control gene transcription. Current TF assays are limited to the analysis of a single TF or require TF-specific antibodies. Here we report the Single Primer Amplification assisted Oligonucleotide Array-based Transcription Factor Assay (SPA-OATFA) which can directly analyze the binding activities of 240 human TFs simultaneously. Examining early events during serum-stimulation of HeLa cells as a model, we demonstrated the utility of SPA-OATFA combined with whole genome gene expression to systematically map the temporal activation of signaling pathways. Both TFs known to function in this stimulation response such as EGR1 and AP1 and new TFs such as HSF1 were identified. This information, combined with mRNA profiling, provided novel insights into the activities of regulatory pathways, and illustrates the potential of SPA-OATFA in detailed systems biology analysis of cell responses.

A PDMS-glass based micro-device was designed and fabricated with 12 coplanar impedance sensors integrated for electrical cell–substrate impedance sensing (ECIS). The sensitivity and frequency characteristics of the sensors were investigated both theoretically (equivalent circuit model) and experimentally for the commonly used micro-electrode dimension scale (20–80 μm). The experimental results matched well with the theoretical model analysis and revealed that, within this micro-electrode dimension scale, as the electrode width decreased or as the total electrode length decreased the sensitivity of sensor increased over the whole sensing frequency range, whilst electrode to electrode distance had no influence on sensitivity. Through our frequency characteristics analysis, the whole frequency range could be divided into four parts. New functions describing the dominant components in each frequency range were defined and validated experimentally, and could be used to explain the phenomenon of an ECIS sensing frequency window. The contribution to the impedance measurement of cells growing on the edges of the electrodes was determined for the first time. Finally, novel proposals for ECIS sensor design and ECIS measurements were presented.

MicroRNAs (miRNAs) and mRNAs constitute an important part of gene regulatory networks, influencing diverse biological phenomena. To discover novel regulatory pathways during myeloid differentiation, we performed miRNA as well as mRNA expression profiling of in vitro-differentiating HL-60 cells treated with 12-O-tetradecanoylphorbol-13-acetate (TPA). The main findings were up-regulation of miR-146a/b, miR-21, miR-221, miR-222, miR-155, miR-26a and down-regulation of miR-199a*, miR-181c, miR-142-3p, miR-92. After integrating the miRNA and mRNA expression data into a Transcriptome Interaction Database by Molecule Annotation System (MAS) software, a number of differently expressed mRNAs were revealed as potential targets of these miRNAs.

There had been little progress in development of the theoretical basis of rectangular chromatography columns until Spangler made great progress by using a more exact model than Golay's. Unfortunately, there was a deficiency in his calculations, which led to a conclusion inconsistent with the previous theories. In this paper, a simpler formula with defined variables was first established to calculate the mean permeability coefficient for a rectangular GC column. A formula was also established to calculate the height equivalent to a theoretical plate (HETP) for a rectangular column based on this work and the correction of Spangler's theory. By comparing both our predictions and Spangler's predictions with Golay's, respectively, we could demonstrate that our theory is more exact. Further, one parameter (A) was found to be not monotonous. This finding leads to the conclusion that the square column has the highest performance among all the rectangular-shaped columns used for chromatography, and that a width/depth ratio of around three is desirable if the column is used for mixing reactants in lab-on-a-chip systems, instead of for chromatography. The conclusions are applicable not only for gas but also for liquid chromatography columns.

A sample preparation method for gas chromatography using a two-phase, laminar flow extraction PDMS/glass chip has been developed. A stable two-phase laminar interface was obtained by surface modification, and the organic extraction phase and the aqueous sample phase were separated effectively when the two-phase laminar flows exit the chip. Experiments were conducted on the chip to extract ephedrine from aqueous solution. Good reproducibility was obtained over the entire range of ephedrine concentration using the extraction chips (CV range 2.7%–4.5%). Effects of salt and solvent on extraction efficiency were studied.

Electrorotation and traveling-wave dielectrophoresis are non-invasive methods and can be used to determine the dielectric properties of particles. In the present study, we have developed an electrokinetic system using microfabricated electrorotation and traveling-wave dielectrophoresis electrodes to determine the dielectric differences of algal cells. Chlorella protothecoides is a microalgae that can be photoautotrophically or heterotrophically grown under different culture conditions. Different culture conditions resulted in biochemical differences between autotrophic and heterotrophic cells of C. protothecoides, and therefore, distinctions of dielectric properties. We presented differences in their electrorotational responses, which were also confirmed by traveling-wave dielectrophoresis. Based on these electrical and biochemical effects. It was suggested that electrorotation and traveling-wave dielectrophoresis responses could be used to reflect the biochemical differences of biological particles including algal cells.

Rapid heat transfer is crucial for an efficient polymerase chain reaction (PCR), and this makes temperature control one of the most essential features in a micro-PCR system, which always includes a heater and a sensor composing a closed-loop. Yet, the fabrication of the heater and the sensor often prevented micro-PCR systems from achieving both cost-effectiveness and fabrication-easiness. For most of the early researches micromachining techniques were used to allow sensors and heaters be integrated on a silicon or glass chip. However, the cost prevented them from wide applications. The work described in this paper is part of our effort to solve the cost/fabrication dilemma. An innovative digital temperature control system was developed by introducing a heater/sensor switching procedure. Only one temperature controlling element fabricated by flexible printed circuit technology was utilized in the constructed PCR device with minimum fabrication steps. The glass chip-based device was made from low cost materials and assembled with adhesive bonding. Through seemingly simple steps, we obtained both disposability and portability at the same time. Temperature stability within ±0.3 °C and a transitional rate of 8 °C/s during heating/cooling was achieved. A 244 bp DNA fragment of hepatitis C virus was successfully amplified in our device by a three-stage thermal cycling process. Further improvement was assisted by finite element analysis, and demonstrated by experiment.

A base stacking hybridization-based microarray method was developed for rapid identification of clinical isolates within 2 h. The oligonucleotide probe sequences for species or genus-level identification were targeted against ribosomal RNA. Isolates were lysed and directly hybridized to the microarray-bound capture probes without conventional DNA or RNA isolation and prior polymerase chain reaction amplification. Five bacterial species encountered frequently in the clinical setting, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae, and one genus Enterococcus, could be discriminated by the microarray-based assay. Identification by this method matched biochemical identification for 150 of 152 clinical strains. This base-stacking hybridization microarray offers a simple, fast (≤2 h), and accurate identification of bacterial cultures and is a potential tool for routine clinical diagnosis.