The present work reports on the development of a new generation of Lab-on-a-chip (LOC) to perform in-situ and real-time potentiometric measurements in flowing water. The device consisted of two ...differentiated parts: a poly (dimethylsiloxane) (PDMS) microfluidic structure obtained by soft lithography and a fully integrated chemical sensing platform including four working microelectrodes, two reference microelectrodes and one counter microelectrode for detecting ammonium in a continuous mode. The performance of the device was evaluated following its potentiometric response when analyzing ammonium containing samples. As a key parameter, its time of response was compared to that of a commercially available electrical conductivity sensor used as reference sensor during tests in laboratory using flowing tap water and technical scale using flowing wastewater. As a result, the LOC showed a slope of 55 mV/decade, a limit of detection of 4·10−5 M and a time of full response between 10 and 12 s. It was demonstrated that the device can provide fast and reliable data at real time when immersed in a laminar flow of water. Moreover, the test of robustness showed that it was still functional after immersion in sewage for at least 15 min. Besides, the LOC reported here can be helpful for a wide variety of flowing-water applications such as aqua culture outlets control, in-situ and continuous analysis of rivers effluents and sea waters monitoring among others.
The assembly PDMS-microfluidic structure and silicon transducer lead to the fabrication of a passive-microfluidic Lab-on-a-Chip to perform in-situ and real time electrochemical analysis in aquatic environments. Display omitted
•Lab-on-a-Chips are consolidated as powerful analytical tools•They are especially useful for the real-time and in-situ detection of biomarkers within environmental analysis of waters.•The key feature of this miniaturized Lab-on-a-Chip is its ability to perform electrochemical measurements combined with passive microfluidics.•The passive flow of sample created removes the need of using external pumps and valves what extremely reduces the power consumption.
Abstract
We investigate the benefits of the use of arrays of vertical nanowire (vNW) field-effect transistors (FETs) to implement integrated circuits. By means of technology computer aided design and ...circuit simulations, the optimal dimensions of the vNWFETs are determined. Device and circuit variability levels have been investigated. The benefits of using array configurations are the decrease of the response time and a significant mitigation of the variability level as the number of the elements in the array increases.
Quantum dots (QDs) can be used as conductive islands to build-up single-electron transistors (SETs). The characteristics of the QDs define the functional performance of the SETs. In consequence, ...analyzing the influence of the variations of QD dimensions on the performance of hybrid SET-FET circuits is of high relevance. We employ a self-developed SET compact model which is calibrated to 3-D quantum-mechanics-based simulations in order to obtain realistic model parameters. A method to improve the circuit behavior, i.e., to increase the output current, is proposed. It is concluded that the variation of the QD size presents the largest influence on the overall circuit behavior.
Stacking devices in a 3D configuration by using a vertical topology is considered as the next step to improve electronic devices and circuits performance. For instance, a CMOS inverted can be built ...by continuously depositing both inter-metal and metal layers. This new IC manufacturing proposal has been simulated by using Sentaurus 3D TCAD software. We have analyzed the influence of different device design parameters to optimize its performance. Finally, we have also explored the feasibility to implement a 5-stage ring oscillator circuit by using the proposed stack.
Abstract
This study analyzes feasibility of complementary metal–oxide–semiconductor (CMOS)-compatible manufacturing of a hybrid single electron transistor–field effect transistor (SET-FET) circuit. ...The fundamental element towards an operating SET at room temperature is a vertical nanopillar (NP) with embedded Si nanodot generated by ion-beam irradiation. The integration process from NPs to contacted SETs is validated by structural characterization. Then, the monolithic fabrication of planar FETs integrated with vertical SETs is presented, and its compatibility with standard CMOS technology is demonstrated. The work includes process optimization, pillar integrity validation, electrical characterization and simulations taking into account parasitic effects. The FET fabrication process is adapted to meet the requirements of the pre-fabricated NPs. Overall, this work establishes the groundwork for the realization of a hybrid SET-FET circuit operating at room temperature.
The development of amphetamine-ion-selective microelectrodes using electrochemical polymerization and microfabrication technologies is reported in this study. The microelectrodes include polypyrrole ...films electrochemically polymerized and doped with cosane anion (3,3′-Co(1,2-C
2
B
9
H
11
)
2
−
) as the internal solid contact layer between the polymeric sensitive membrane and platinum working microelectrode. Several poly(vinyl chloride)-type membranes with different compositions of plasticizers/ionophore were drop casted on the conducting polymer layer, polypyrrole3,3′-Co(1,2-C
2
B
9
H
11
)
2
. Potentiometric measurements were performed to calibrate the response of the developed chemical sensors. The sensor was highly sensitive to amphetamine using a membrane composition of 26 wt% poly (vinyl chloride), 63 wt% di-butyl phthalate, 6 wt% sodium tetraphenylborate, and 5 wt% dibenzo-18-crown 6-ether. A high and linear response was demonstrated within the concentration range from 10
−5
to 10
−3
M with a slope of 53 mV/decade and a limit of detection of 4 × 10
−5
M. A Reilley diagram shows that the sensor signal is stable for a working pH between 1.50 and 8.50. The chemical sensor was highly selective to amphetamine when compared to other interfering ions and compounds including K
+
, Na
+
,
, D,L-phenylalanine, caffeine, (±)-epinephrine bitartrate salt, and N-formylamphetamine using the fixed interference method with coefficients of selectivity (Log
) from −1.40 to −1.15.
The fabrication of pH-sensitive ISFET devices in an unmodified two-metal commercial CMOS technology (1.0 m from Atmel-ES2) is reported. The ISFET devices have a gate structure compatible with the ...CMOS process, with an electrically floating electrode consisting on polysilicon plus the two metals. The passivation oxynitride layer acts as the pH-sensitive material in contact with the liquid solution. The devices have shown good operating characteristics, with a 47 mV/pH response. The use of a commercial CMOS process allows the straightforward integration of signal-processing circuitry. An ISFET amplifier circuit has been integrated with the ISFET sensors.
► We propose an impedimetric microbial biosensor for trichloroethylene detection. ► A new transducer modified with carbon nanotubes and
Pseudomonas putida is evaluated. ► Functionalization steps are ...controlled by impedance spectroscopy and AFM. ► The biosensor offers good sensitivity, selectivity, linear range and stability. ► The biosensor is successfully applied to spiked natural water samples.
Contamination of soils and groundwaters with persistent organic pollutants is a matter of increasing concern. The most common organic pollutants are chlorinated hydrocarbons such as perchloroethylene and trichloroethylene (TCE). In this study, we developed a bacterial impedimetric biosensor for TCE detection, based on the immobilization of
Pseudomonas putida F1 strain on gold microelectrodes functionalized with single wall carbon nanotubes covalently linked to anti-
Pseudomonas antibodies. The different steps of microelectrodes functionalization were characterized by electrochemical impedance and atomic force spectroscopies, and analytical performances of the developed microbial biosensor were determined. The impedimetric biosensor response was linear with TCE concentration up to 150
μg
L
−1 and a low limit of detection (20
μg
L
−1) was achieved. No significant loss of signal was observed after 4 weeks of storage at 4
°C in phosphate buffer saline pH 7 (three to four measurements a week). After 5 weeks, 90% of the initial value still remained.
cis-1,2-Dichloroethylene and vinylchloride, the main TCE degradation products, did not significantly interfere with TCE. The microbial sensor was finally applied to the determination of TCE in natural water samples spiked at the 30, 50 and 75
μg
L
−1 levels. Recoveries were very good, ranging from 100 to 103%.
Measurement of D-dimer has subsequently become an essential element in the diagnostics of deep vein thrombosis and pulmonary embolism; in this context microelectrodes with an area of 9
×
10
−4
cm
2 ...were used to develop impedimetric immunosensor for detecting deep venous thrombosis biomarker (D-dimer). The biosensor is based on functionalized carbon nanotubes (SWCNT-COOH) where the antibody (anti-D-dimer) was immobilized by covalent binding. The electrical properties and the morphology of the biolayer were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry and atomic force spectroscopy (AFM). Impedimetric microimmunosensor allows to obtain sensitivity of 40.1
kΩ
μM
−1 and detection limit of 0.1
pg/mL (0.53
fM) with linear range from 0.1
pg/mL to 2
μg/mL (0.53
fM to 0.01
μM). We demonstrate that using carbon nanotubes and microelectrodes, high sensitivity and dynamic range were obtained. The biosensor exhibited a short response time of 10
min. Moreover, the studied immunosensor exhibits good reproducibility (R.S.D. 8.2%,
n
=
4).
Validation of a technological process requires an intensive characterization of the performance of the resulting devices, circuits, or systems. The technology for the fabrication of micro and ...nanoelectromechanical systems (MEMS and NEMS) is evolving rapidly, with new kind of device concepts for applications like sensing or harvesting are being proposed and demonstrated. However, the characterization tools and methods for these new devices are still not fully developed. Here, we present an on-wafer, highly precise, and rapid characterization method to measure the mechanical, electrical, and electromechanical properties of piezoresistive cantilevers. The setup is based on a combination of probe-card and atomic force microscopy technology, it allows accessing many devices across a wafer and it can be applied to a broad range of MEMS and NEMS. Using this setup we have characterized the performance of multiple submicron thick piezoresistive cantilever force sensors. For the best design we have obtained a force sensitivity Re(F) = 158μV/nN, a noise of 5.8 μV (1 Hz-1 kHz) and a minimum detectable force of 37 pN with a relative standard deviation of σ(r) ≈ 8%. This small value of σ(r), together with a high fabrication yield >95%, validates our fabrication technology. These devices are intended to be used as bio-molecular detectors for the measurement of intermolecular forces between ligand and receptor molecule pairs.
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