Search

Multimodal perception can capture more precise and comprehensive information compared with unimodal approaches. However, current sensory systems typically merge multimodal signals at computing terminals following parallel processing and transmission, which results in the potential loss of spatial association information and requires time stamps to maintain temporal coherence for time-series data. Here we demonstrate bioinspired in-sensor multimodal fusion, which effectively enhances comprehensive perception and reduces the level of data transfer between sensory terminal and computation units. By adopting floating gate phototransistors with reconfigurable photoresponse plasticity, we realize the agile spatial and spatiotemporal fusion under nonvolatile and volatile photoresponse modes. To realize an optimal spatial estimation, we integrate spatial information from visual-tactile signals. For dynamic events, we capture and fuse in real time spatiotemporal information from visual-audio signals, realizing a dance-music synchronization recognition task without a time-stamping process. This in-sensor multimodal fusion approach provides the potential to simplify the multimodal integration system, extending the in-sensor computing paradigm.

Flexible static random access memory (SRAM) plays an important role in flexible electronics and systems. However, achieving SRAM with a small footprint, high flexibility, and high thermal stability has always been a big challenge. In this work, an ultraflexible six-transistor SRAM with high integration density is realized based on a monolithic three-dimensional (M3D) design. In this design, vertical stacked n-type indium gallium zinc oxide thin film transistors and p-type carbon nanotube transistors share common gate and drain electrodes, respectively, saving interlayer vias used in traditional M3D designs. This compact architecture reduces the footprint of the SRAM cell from a six-transistor to a four-transistor area, saving 33% of the area, and significantly enables the SRAM to have the highest flexibility among the reported ones, withstanding a harsh deforming process (6000 cycles of bending at a radius of 500 μm) without performance degradation. Moreover, this design facilitates the thermal stability of the SRAM under high temperature (333 K). It also exhibits great static and dynamic performance, with the highest normalized hold noise margin of 73.6%, a maximum gain of 151.2, and a minimum static power consumption of 3.15 μW in hold operation among the reported flexible SRAMs. This demonstration provides possibilities for SRAMs to be used in advanced wearable system applications.

To strengthen the downscaling potential of top-gate amorphous oxide semiconductor (AOS) thin-film transistors (TFTs), the ultra-thin gate insulator (GI) was comparatively implemented using the atomic-layer-deposited (ALD) AlO x and HfO x . Both kinds of high- k GIs exhibit good insulating properties even with the physical thickness thinning to 4 nm. Compared to the amorphous indium-gallium-zinc oxide (a-IGZO) TFTs with 4 nm AlO x GI, the 4 nm HfO x enables a larger GI capacitance, while the HfO x -gated TFT suffers higher gate leakage current and poorer subthreshold slope, respectively originating from the inherently small band offset and the highly defective interface between a-IGZO and HfO x . Such imperfect a-IGZO/HfO x interface further causes noticeable positive bias stress instability. Both ALD AlO x and HfO x were found to react with the underneath a-IGZO channel to generate the interface defects, such as metal interstitials and oxygen vacancies, while the ALD process of HfO x gives rise to a more severe reduction of a-IGZO. Moreover, when such a defective interface is covered by the top gate, it cannot be readily restored using the conventional oxidizing post-treatments and thus desires the reduction-resistant pre-treatments of AOSs., (© 2023 IOP Publishing Ltd.)

Electromagnetic metasurfaces have been intensively used as ultra-compact and easy-to-integrate platforms for versatile wave manipulations from optical to terahertz (THz) and millimeter wave (MMW) ranges. In this paper, the less investigated effects of the interlayer coupling of multiple metasurfaces cascaded in parallel are intensively exploited and leveraged for scalable broadband spectral regulations. The hybridized resonant modes of cascaded metasurfaces with interlayer couplings are well interpreted and simply modeled by the transmission line lumped equivalent circuits, which are used in return to guide the design of the tunable spectral response. In particular, the interlayer gaps and other parameters of double or triple metasurfaces are deliberately leveraged to tune the inter-couplings for as-required spectral properties, i.e., the bandwidth scaling and central frequency shift. As a proof of concept, the scalable broadband transmissive spectra are demonstrated in the millimeter wave (MMW) range by cascading multilayers of metasurfaces sandwiched together in parallel with low-loss dielectrics (Rogers 3003). Finally, both the numerical and experimental results confirm the effectiveness of our cascaded model of multiple metasurfaces for broadband spectral tuning from a narrow band centered at 50 GHz to a broadened range of 40~55 GHz with ideal side steepness, respectively.

An ultrathin atomic-layer-deposited (ALD) AlO x gate insulator (GI) was implemented for self-aligned top-gate (SATG) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). Although the 4.0-nm thick AlO x exhibited ideal insulating properties, the interaction between ALD AlO x and predeposited a-IGZO caused a relatively defective interface, thus giving rise to hysteresis and bias stress instabilities. As analyzed using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and the Hall measurement, the chemical reaction between the ALD precursor and a-IGZO is revealed. This was effectively prevented by preoxidizing a-IGZO with nitrous oxide (N 2 O) plasma. With 4 nm-AlO x GI and low-defect interfaces, high performance and stability were simultaneously achieved on SATG a-IGZO TFTs, including a near-ideal record-low subthreshold swing of 60.8 mV/dec, a low operation voltage below 0.4 V, a moderate mobility of 13.3 cm 2 /V·s, a low off-current below 10 -13 A, a large on/off ratio over 10 9 , and negligible threshold-voltage shifts less than 0.04 V against various bias-temperature stresses. This work clarifies the vital interfacial reaction between top-gate high- k dielectrics and amorphous oxide semiconductors (AOSs) and further provides a feasible way to remove this obstacle to downscaling SATG AOS TFTs.

Ultrathin two-dimensional (2D) semiconductors are regarded as a potential channel material for low-power transistors with small subthreshold swing and low leakage current. However, their dangling bond–free surface makes it extremely difficult to deposit gate dielectrics with high-quality interface in metal-oxide-semiconductor (MOS) field-effect transistors (FETs). Here, we demonstrate a low-temperature process to transfer metal gate to 2D MoS 2 for high-quality interface. By excluding extrinsic doping to MoS 2 and increasing contact distance, the high–barrier height Pt-MoS 2 Schottky junction replaces the commonly used MOS capacitor and eliminates the use of gate dielectrics. The MoS 2 transferred metal gate (TMG) FETs exhibit sub-1 V operation voltage and a subthreshold slope close to thermal limit (60 mV/dec), owing to intrinsically high junction capacitance and the high-quality interface. The TMG and back gate enable logic functions in a single transistor with small footprint.

Vertically aligned carbon nanotube (VACNT) arrays have been explored as an absorber of thermal-type photodetectors. A long and dense VACNT array absorbs a wide spectral range of incident light with high absorption rate, but has a high thermal mass that results in a low response speed. To achieve a small thermal mass, a shorter and less dense VACNT array is needed. In addition, the high temperature needed to grow the VACNTs is detrimental to the functional sensing materials of the photodetector. The height, density, and growth temperature of VACNTs need to be optimized to achieve a working absorber that has high absorption rate and a high response speed. In this work, a low-temperature plasma enhanced chemical vapor deposition process is used to prepare various VACNT arrays with different heights and densities by controlling the CNT growth parameters. The absorption coefficients of the resulting samples are measured with Fourier transform infrared spectroscopy. An effective medium theory (EMT) is adopted to establish a working model of the VACNTs. Using experimentally extracted CNT density and height as fitting parameters, the EMT model is fitted to obtain theoretical absorption coefficients, which are found to be comparable to the experimentally measured absorption coefficients. Our experimental and theoretical investigations pave the way for future studies to integrate CNTs with infrared photodetectors., (© 2021 IOP Publishing Ltd.)

Spiking neural network, inspired by the human brain, consisting of spiking neurons and plastic synapses, is a promising solution for highly efficient data processing in neuromorphic computing. Recently, memristor-based neurons and synapses are becoming intriguing candidates to build spiking neural networks in hardware, owing to the close resemblance between their device dynamics and the biological counterparts. However, the functionalities of memristor-based neurons are currently very limited, and a hardware demonstration of fully memristor-based spiking neural networks supporting in-situ learning is very challenging. Here, a hybrid spiking neuron combining a memristor with simple digital circuits is designed and implemented in hardware to enhance neuron functions. The hybrid neuron with memristive dynamics not only realizes the basic leaky integrate-and-fire neuron function but also enables the in-situ tuning of the connected synaptic weights. Finally, a fully hardware spiking neural network with the hybrid neurons and memristive synapses is experimentally demonstrated for the first time, and in-situ Hebbian learning is achieved with this network. This work opens up a way towards the implementation of spiking neurons, supporting in-situ learning for future neuromorphic computing systems., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2021 Science China Press. Published by Elsevier B.V. All rights reserved.)

Synthesis of the vertically aligned carbon nanotubes (CNTs) using complementary metal-oxide-semiconductor (CMOS)-compatible methods is essential to integrate the CNT contact and interconnect to nanoscale devices and ultra-dense integrated nanoelectronics. However, the synthesis of high-density CNT array at low-temperature remains a challenging task. The advances in the low-temperature synthesis of high-density vertical CNT structures using CMOS-compatible methods are reviewed. Primarily, recent works on theoretical simulations and experimental characterizations of CNT growth emphasized the critical roles of catalyst design in reducing synthesis temperature and increasing CNT density. In particular, the approach of using multilayer catalyst film to generate the alloyed catalyst nanoparticle was found competent to improve the active catalyst nanoparticle formation and reduce the CNT growth temperature. With the multilayer catalyst, CNT arrays were directly grown on metals, oxides, and 2D materials. Moreover, the relations among the catalyst film thickness, CNT diameter, and wall number were surveyed, which provided potential strategies to control the tube density and the wall density of synthesized CNT array.

A pressure sensor design suitable for a broad sensing range with high sensitivity and good stability is highly desirable for the detection of various pressures and meeting the requirements of different applications. Herein, we report sensing-range-tunable piezoresistive pressure sensors realized by self-patterned-spacer design. In the sensors, the two CNT-array layers embedded in PDMS are separated by the proposed self-patterned spacer. With this structure, the realized sensors with large initial resistance designed show tunable response thresholds from 300 Pa to 6.5 kPa while maintaining high sensitivity, which are realized by controlling the spacer thickness and the CNT length. Besides, the vertical CNT arrays have a large specific surface area, which can dramatically change the resistance of the pressure sensors and lead to high sensitivity with nearly 50 kPa -1 . Benefiting from the designs of the self-patterned spacer and the advantageous combination of CNTs and PDMS, the pressure sensors also exhibit a rapid response/relaxation time of 24/32 ms, and good long-term stability with durability test over 10 000 loading/unloading cycles. On the other hand, the realized pressure sensors with small initial resistance designed show a typical piezoresistive characteristic. For applications, the pressure sensors with large initial resistance designed are suitable for the anti-noise applications with pressure thresholds to filter unnecessary noise and save power consumption, while the pressure sensors with small initial resistance designed show the capability of detecting mechanical forces and monitoring human physiological signals. Moreover, the self-patterned design and fabrication method of the spacers also show potentials to be applied in the existing works to further enhance or adjust the performance of those pressure sensors, showing great flexibility. This design demonstrates great potentials to be applied in future advanced flexible wearable systems such as health monitoring, human-machine interaction and the Internet of Things., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Active spectral tuning of nanophotonic devices offers many fascinating prospects for the realization of novel optical function. Here, switchable spectral response is enabled by the architecture of one-dimensional (1D) photonic crystal (PC) integrated with phase change material of the germanium antimony telluride (GST). Active and precise tuning of the bistable passband and central resonant frequency is demonstrated in the 1D PC composed of alternate SiN and GST nanofilms. An analytical model is derived to specify the tunable spectral features, including the band gap and resonant frequencies. Both the measured and calculated results show distinct red shifts of passband and the resonant minima (or maxima), well confirming theoretical predictions. This work demonstrates a route to construct active photonic devices with the electrically or thermally tunable spectra via 1D PC and potentially extends diverse applications based on the PC platform.

A method to synthesize high-density, vertically-aligned, multi-wall carbon nanotubes (MWCNTs) on an insulating substrate at low temperature using a complementary metal⁻oxide⁻semiconductor (CMOS) compatible process is presented. Two factors are identified to be important in the carbon nanotube (CNT) growth, which are the catalyst design and the substrate material. By using a Ni⁻Al⁻Ni multilayer catalyst film and a ZrO₂ substrate, vertically-aligned CNTs can be synthesized at 340 °C using plasma-enhanced chemical vapor deposition (PECVD). Both the quality and density of the CNTs can be enhanced by increasing the synthesis temperature. The function of the aluminum interlayer in reducing the activation energy of the CNT formation is studied. The nanoparticle sintering and quick accumulation of amorphous carbon covering the catalyst can prematurely stop CNT synthesis. Both effects can be suppressed by using a substrate with a high surface energy such as ZrO₂.

Carbon nanotubes (CNTs) and graphene are potential candidates for future interconnect materials. CNTs are promising on-chip via interconnect materials due to their readily formed vertical structures, their current-carrying capacity, which is much larger than existing on-chip interconnect materials such as copper and tungsten, and their demonstrated ability to grow in patterned vias with sub-50 nm widths; meanwhile, graphene is suitable for horizontal interconnects. However, they both present the challenge of having high-resistance contacts with other conductors. An all-carbon structure is proposed in this paper, which can be formed using the same chemical vapor deposition method for both CNTs and graphene. Vertically aligned CNTs are grown directly on graphene with an Fe or Ni catalyst. The structural characteristics of the graphene and the grown CNTs are analyzed using Raman spectroscopy and electron microscopy techniques. The CNT-graphene interface is studied in detail using transmission electron microscopic analysis of the CNT-graphene heterostructure, which suggests C-C bonding between the two materials. Electrical measurement results confirm the existence of both a lateral conduction path within graphene and a vertical conduction path in the CNT-graphene heterostructure, giving further support to the C-C bonding at the CNT-graphene interface and resulting in potential applications for all-carbon interconnects.

Microelectrode array (MEA) can be used in the study of neurodegenerative diseases by monitoring the chemical neurotransmitter release and the electrical potential simultaneously at the cellular level. Currently, the MEA technology is migrating to more electrodes and higher electrode density, which raises power and area constraints on the design of acquisition IC. In this paper, we report the design of a 200-channel dual-mode acquisition IC with highly efficient usage of power and area. Under the constraints of target noise and fast settling, the current channel design saves power by including a novel current buffer biased in discrete time (DT) before the TIA (transimpedance amplifier). The 200 channels are sampled at 20 kS/s and quantized by column-wise SAR ADCs. The prototype IC was fabricated in a 0.18 μm CMOS process. Silicon measurements show the current channel has 21.6 pArms noise with cyclic voltammetry (CV) and 0.48 pArms noise with constant amperometry (CA) while consuming 12.1 μW . The voltage channel has 4.07 μVrms noise in the bandwidth of 100 kHz and 0.2% nonlinearity while consuming 9.1 μW. Each channel occupies 0.03 mm(2) area, which is among the smallest.

MoS2 and other atomic-level thick layered materials have been shown to have a high potential for outperforming Si transistors at the scaling limit. In this work, we demonstrate a MoS2 transistor with a low voltage and high ON/OFF ratio. A record small equivalent oxide thickness of ∼1.1 nm has been obtained by using ultra high-k gate dielectric Pb(Zr0.52Ti0.48)O3. The low threshold voltage (<0.5 V) is comparable to that of the liquid/gel gated MoS2 transistor. The small sub-threshold swing of 85.9 mV dec(-1), the high ON/OFF ratio of ∼10(8) and the negligible hysteresis ensure a high performance of the MoS2 transistor operating at 1 V. The extracted field-effect mobility of 1-10 cm(2) V(-1) s(-1) suggests a high crystalline quality of the CVD-grown MoS2 flakes. The combination of the two-dimensional layered semiconductor and the ultra high-k dielectric may enable the development of low-power electronic applications.

Nanocomposites that contain reinforcements with preferred orientation have attracted significant attention because of their promising applications in a wide range of multifunctional fields. Many efforts have recently been focused on developing facile methods for preparing aligned graphene sheets in solvents and polymers because of their fascinating properties including liquid crystallinity and highly anisotropic characteristics. Self-aligned in situ reduced graphene oxide (rGO)/polymer nanocomposites are prepared using an all aqueous casting method. A remarkably low percolation threshold of 0.12 vol% is achieved in the rGO/epoxy system owing to the uniformly dispersed, monolayer graphene sheets with extremely high aspect ratios (>30000). The self-alignment into a layered structure at above a critical filler content induces a unique anisotropy in electrical and mechanical properties due to the preferential formation of conductive and reinforcing networks along the alignment direction. Accompanied by the anisotropic electrical conductivities are exceptionally high dielectric constants of over 14000 with 3 wt% of rGO at 1 kHz due to the charge accumulation at the highly-aligned conductive filler/insulating polymer interface according to the Maxwell-Wagner-Sillars polarization principle. The highly dielectric rGO/epoxy nanocomposites with the engineered structure and properties present high performance electromagnetic interference shielding with a remarkable shilding efficiency of 38 dB., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Microelectrodes are widely used in the physiological recording of cell field potentials. As microelectrode signals are generally in the μV range, characteristics of the cell-electrode interface are important to the recording accuracy. Although the impedance of the microelectrode-solution interface has been well studied and modeled in the past, no effective model has been experimentally verified to estimate the noise of the cell-electrode interface. Also in existing interface models, spectral information is largely disregarded. In this work, we developed a model for estimating the noise of the cell-electrode interface from interface impedances. This model improves over existing noise models by including the cell membrane capacitor and frequency dependent impedances. With low-noise experiment setups, this model is verified by microelectrode array (MEA) experiments with mouse muscle myoblast cells. Experiments show that the noise estimated from this model has <;10% error, which is much less than estimations from existing models. With this model, noise of the cell-electrode interface can be estimated by simply measuring interface impedances. This model also provides insights for micro- electrode design to achieve good recording signal-to-noise ratio.

The microelectrode array (MEA) can be used to study extracellular field potentials (exFPs) of electrogenic cells. Microcontact printing, which must be repeated after each experiment, is often used to promote accurate positioning of cells onto electrodes. The present study used MEAs with evenly spaced detection electrodes aligning along permanent SU-8 topographical guidance channels to measure propagation direction and speed. Chronotropic agents, isoproterenol (ISO, 1 nM-1 mM), and verapamil (VP, 1 nM-10 μM); and potassium channel openers (KCOs), pinacidil (PIN), and SDZ PCO400 (SDZ), were used to characterize these MEA chips. ISO (1 mM) enhanced the propagation speed from 247.25 ± 50.58 μm/ms 381.29 ± 92.01 μm/ms (n = 9, p < 0.05), whereas VP (10 μM) reduced the propagation speed completely (n = 12, p < 0.001). PIN (1 mM) significantly reduced the propagation speed from 278.6 ± 43.7 μm/ms to 49.7 ± 27.7 μm/ms (n = 10, p < 0.001), whereas SDZ (1 mM) completely stopped the propagation (n = 9, p < 0.001). Both KCOs induced conduction pattern changes similar to those observed in cardiac arrhythmia. The MEA chips with SU-8 guidance channels may be used to study cardiovascular diseases that are related to conduction disruption.

The cross-sectional shape of the stacked silicon nanowires (SiNWs) formed by the Bosch process and stress-limited oxidation is studied in this paper. Under the condition of high temperature oxidation, the resulting nanowires highly resemble the initial shapes resulting by the Bosch process. The effects of etching and passivation in the Bosch process are modeled to provide a guideline to control the cross-section of the stacked nanowires.

A unified drain current model for undoped or lightly doped symmetric double-gate and surrounding-gate MOSFETs incorporating velocity saturation effect is proposed in this paper. The unified charge-based core model for undoped or lightly doped double-gate and surrounding-gate MOSFETs is presented first based on the previously published separate models. Caughey-Thomas engineering mobility model with its exponent factor n = 2 is then integrated self-consistently into the unified drain current model development of the two device structures. Extensive two dimensional and three dimensional device simulations are performed to validate the proposed model. Good agreements of the output and transfer characteristics between the unified model and the numerical simulations are obtained for both the double-gate and surrounding-gate MOSFETs. Symmetry property of the proposed unified current model is obtained with the exponent factor n = 2 in Cauhey-Thomas Model.

The microelectrode array was used to study the pharmacologic preconditioning effect of adenosine triphosphate-sensitive channel activation using potassium channel openers (KCOs) on rat cardiomyocytes over 90 minutes of ischemia. Cell viability and electrophysiological changes between KCOs pretreated and untreated cardiomyocytes were compared. Ischemia caused significant increases in beat frequency, extracellular field potential amplitude, and propagation velocity of spontaneously beating untreated cardiomyocytes. However, these electrophysiological parameters reduced as the duration of ischemia increased. The electrophysiological changes on ischemic cardiomyocytes were abolished by pretreating the cells with KCOs. Pinacidil pretreated cardiomyocytes retained a significantly higher viability than the untreated cardiomyocytes after 90 minutes of ischemia. Because Connexin 43 has a direct correlation with the propagation velocity, the Connexin 43 protein expression was also investigated. Connexin 43 expression levels were lower in KCOs pretreated cardiomyocytes than that of the untreated controls, and this correlated with the propagation velocity results obtained from the microelectrode array. The effect of pinacidil (sarcolemmal adenosine triphosphate-sensitive channel opener) was more prominent than that of diazoxide (mitochondrial K adenosine triphosphate-sensitive channel opener) on ischemic cardiomyocytes as indicated in the present acute ischemia study.

To determine whether changes in membrane potential affect the extent of mast cell degranulation, compound 48/80 was added to rat peritoneal mast cell suspensions in the absence or presence of potassium channel openers (KCOs). Changes were compared between the field potential (FP) and the amount of histamine released. The results demonstrated that (i) the onset and duration of FP, which reflects the hyperpolarizing nature of the response, increased as the concentration of compound 48/80 increased; (ii) both FP and the amount of histamine released increased as the concentration of compound 48/80 increased; (iii) although both KCOs (SDZ PCO400, a benzopyran derivative, and P1060, a cyanoguanidine derivative) potentiated compound 48/80-induced increases in FP and histamine release, without compound 48/80, they had no effect on either parameter; (iv) both glibenclamide and charybdotoxin significantly attenuated the compound 48/80-induced increase in FP; and (v) glibenclamide was able to attenuate the KCO-induced potentiation of FP. The results show that drugs presumably causing hyperpolarization can affect histamine release from rat peritoneal mast cells. The effect of KCOs on compound 48/80-induced response appears to be potentiation in nature rather than synergism. It is possible that KCO hyperpolarizes the cell membrane, enhances Ca2+ influx, and thus increases histamine release. As such, selective blockers of K+ channels may be useful for the treatment of immunological disorders.

Introduction: Simultaneous recording of electrical potentials from multiple cells may be useful for physiological and pharmacological research. The present study aimed to establish an in vitro cardiac hypoxia experimental platform on the microelectrode array (MEA)., Methods: Embryonic rat cardiac myocytes were cultured on the MEAs. Following >or=90 min of hypoxia, changes in lactate production (mM), pH, beat frequency (beats per min, bpm), extracellular action potential (exAP) amplitude, and propagation velocity between the normoxic and hypoxic cells were compared., Results: Under hypoxia, the beat frequency of cells increased and peaked at around 42.5 min (08.1+/-3.2 bpm). The exAP amplitude reduced as soon as the cells were exposed to the hypoxic medium, and this reduction increased significantly after approximately 20 min of hypoxia. The propagation velocity of the hypoxic cells was significantly lower than that of the control throughout the entire 90+ min of hypoxia. The rate of depolarisation and Na(+) signal gradually reduced over time, and these changes had a direct effect on the exAP duration., Discussion: The extracellular electrophysiological measurements allow a partial reconstruction of the signal shape and time course of the underlying hypoxia-associated physiological changes. The present study showed that the cardiac myocyte-integrated MEA may be used as an experimental platform for the pharmacological studies of cardiovascular diseases in the future.

We performed this study to demonstrate the applicability of the microelectrode array (MEA) to study electrophysiological changes of rat peritoneal mast cells in the presence of compound 48/80 under normal, Ca(2+)-free, Ca(2+)-free with EDTA, and Cl(-)-free conditions. The use of high extracellular K(+) (KCl, 150 mM), charybdotoxin (ChTX, 100 nM), and Cl(-)-free containing ChTX buffers verified that the hyperpolarizing signal was due to the activation of mainly K(+) and, to a lesser extent, Cl(-) channels. Compound 48/80 concentration-dependently shortened the latent periods (the onset of response) and increased both the spatial (the K(+) and Cl(-) hyperpolarizing field potentials, HFP) and temporal measurements (the duration of response). Ca(2+)-free buffer had no effect on the latent period of compound 48/80 but increased the HFP at high concentrations. The latent period increased while the HFP diminished when cells were equilibrated in Ca(2+)-free buffer containing EDTA. Durations of the HFP were generally longer when cells were in either Ca(2+)-free or Ca(2+)-free containing EDTA buffers than when cells were in normal buffer. The EC(50) values confirmed that effects were only affected in Ca(2+)-free buffer containing EDTA but not in Ca(2+)-free or Cl(-)-free buffers, further reinforcing the hypothesis that the presence of Ca(2+) is not essential to the action of compound 48/80. The present study is the first application of MEA to study rat peritoneal mast cells, and our results indicate that it could be of value in future pharmacological research on other non-excitable cells.

A microconcentration concept is proposed to enhance the sensitivity of deoxyribonucleic acid (DNA) hybridization due to evaporation of the hybridization solution on a patterned hydrophobic fluorocarbon polymer (FCP) surface. The combination of microconcentration and hybridization processes provides a tool to manipulate nanoliter solution. To fabricate a patterned DNA microarray with hydrophobic surrounding surface, a plasma polymerization and lift-off protocol was designed so that the process can be carried out in a standard microelectronic fabrication laboratory with minimal adjustments on the equipment. After microconcentration, a 1 microL hybridization solution can be concentrated to below 10 nL, which improves the hybridization sensitivity by a factor of 100.

This paper describes a versatile method for amplifying the signals of Au-nanoparticle-based DNA hybridization detecting systems. The Au nanoparticles usually serve as labels to enhance DNA hybridization signal. We further assembled several layers of nanoparticles to selectively increase the number of labelled nanoparticles. Through silver enhancement, the multilayer nanoparticles may produce significantly higher amounts of metal silver on the their surfaces than the monolayer nanoparticles did. This finally accounts for the greatly enhanced DNA hybridization signal. Particularly, the amplification of electrical detection system was demonstrated here. Electrical measuring results indicated that the current values were enhanced by approximately 3 orders of magnitude, and the single nucleotide mismatch discrimination ratio was enlarged to approximately 10(9):1.