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Special Issue "On-Chip Sensors"

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Biosensors".

Deadline for manuscript submissions: closed (30 April 2015)

Special Issue Editor

Guest Editor
Prof. Dr. Kwang W. Oh (Website)

Associate Professor, Director of SMALL (Sensors and MicroActuators Learning Lab), Department of Electrical Engineering, State University of New York at Buffalo (SUNY-Buffalo), Buffalo, NY 14260, USA
Interests: BioMEMS; lab-on-a-chip (LOC); microfluidics; droplet-based microfluidics; blood separation; micro PCR; micro SERS; sensors for LOC

Special Issue Information

Dear Colleagues,

The original idea of lab-on-a-chip (LOC) technology involves integrating on-chip sensors with advanced microfluidic technology to build miniaturized devices that can monitor bio/chemical responses in real time (quantitatively), or on/off signals (qualitatively), without a bulky and complex laboratory setup. Such a technique would find broad and numerous applications in genomics, proteomics, point-of-care testing, chemical analysis, drug discovery and environment monitoring.

(1) Ideally, the on-chip sensors are integrated into the LOC devices, which are disposable. For example, CMOS, electrochemical, FET, RF, mechanical and optical sensors have been integrated with the LOC devices for on-chip sensing. The main challenge is not only to enhance the quality of the on-chip sensors but also to fabricate the LOC devices cost-effectively. (2) Alternatively, the sensors can be assembled into the reusable miniaturized hand-held instruments’ side rather than the disposable LOC devices’ side as stand-alone components. For this approach, user-friendly and contamination-free interfacing between the microfluidic devices and the instruments needs to be highlighted, along with compact design of the instruments. Recent examples include a lens-free holographic microscope installed on an existing smart phone camera. (3) Another methodology is to utilize mobile micro/nano particles/cells as a sensing system in microfluidic devices that can be excited and scanned by external optical instruments, such as micro SERS (surface enhanced Raman scattering) and micro SPR (surface plasmon resonance).

In this special issue, we solicit review articles and original research papers addressing technical challenges on developing on-chip sensors for LOC applications. The papers can cover all aspects of on-chip sensors including, but not limited to, recent developments in the following areas: fabrication and application of on-chip sensors; point-of-care sensing; sensor for LOC systems; CMOS sensor; capacitive sensor; electrochemical sensor; FET sensors; RF sensor; on-chip mechanical sensor (e.g., cantilever, QCM, SAW); on-chip optical sensor; lens-free smartphone microscope; micro SERS; micro SPR; cell-based sensors and nanobio sensors. Authors are invited to contact the guest editors prior to submission if they are uncertain whether their work falls within the general scope of this Special Issue.

Dr. Kwang W. Oh
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).


Keywords

  • sensor
  • on-chip sensor
  • biosensor
  • nanobio sensor
  • microfluidics
  • lab-on-a-chip, integrated sensor
  • point-of-care sensing
  • electrochemical sensor
  • CMOS sensor
  • FET (field effect transistor) sensor
  • capacitive sensor
  • on-chip optical sensor
  • on-chip mechanical sensor
  • micro SERS
  • micro SPR

Published Papers (22 papers)

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Research

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Open AccessArticle Protein Adsorption in Microengraving Immunoassays
Sensors 2015, 15(10), 26236-26250; doi:10.3390/s151026236
Received: 16 June 2015 / Revised: 1 October 2015 / Accepted: 9 October 2015 / Published: 16 October 2015
PDF Full-text (1369 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Microengraving is a novel immunoassay for characterizing multiple protein secretions from single cells. During the immunoassay, characteristic diffusion and kinetic time scales  and  determine the time for molecular diffusion of proteins secreted from the activated single lymphocytes and subsequent binding onto the [...] Read more.
Microengraving is a novel immunoassay for characterizing multiple protein secretions from single cells. During the immunoassay, characteristic diffusion and kinetic time scales  and  determine the time for molecular diffusion of proteins secreted from the activated single lymphocytes and subsequent binding onto the glass slide surface respectively. Our results demonstrate that molecular diffusion plays important roles in the early stage of protein adsorption dynamics which shifts to a kinetic controlled mechanism in the later stage. Similar dynamic pathways are observed for protein adsorption with significantly fast rates and rapid shifts in transport mechanisms when  is increased a hundred times from 0.313 to 31.3. Theoretical adsorption isotherms follow the trend of experimentally obtained data. Adsorption isotherms indicate that amount of proteins secreted from individual cells and subsequently captured on a clean glass slide surface increases monotonically with time. Our study directly validates that protein secretion rates can be quantified by the microengraving immunoassay. This will enable us to apply microengraving immunoassays to quantify secretion rates from 104–105 single cells in parallel, screen antigen-specific cells with the highest secretion rate for clonal expansion and quantitatively reveal cellular heterogeneity within a small cell sample. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessArticle A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection
Sensors 2015, 15(7), 17076-17088; doi:10.3390/s150717076
Received: 21 March 2015 / Revised: 8 June 2015 / Accepted: 6 July 2015 / Published: 14 July 2015
Cited by 1 | PDF Full-text (1323 KB) | HTML Full-text | XML Full-text
Abstract
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass [...] Read more.
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle A Microfluidic Love-Wave Biosensing Device for PSA Detection Based on an Aptamer Beacon Probe
Sensors 2015, 15(6), 13839-13850; doi:10.3390/s150613839
Received: 29 April 2015 / Revised: 29 May 2015 / Accepted: 9 June 2015 / Published: 11 June 2015
Cited by 7 | PDF Full-text (546 KB) | HTML Full-text | XML Full-text
Abstract
A label-free and selective aptamer beacon-based Love-wave biosensing device was developed for prostate specific antigen (PSA) detection. The device consists of the following parts: LiTaO3 substrate with SiO2 film as wave guide layer, two set of inter-digital transducers (IDT), gold [...] Read more.
A label-free and selective aptamer beacon-based Love-wave biosensing device was developed for prostate specific antigen (PSA) detection. The device consists of the following parts: LiTaO3 substrate with SiO2 film as wave guide layer, two set of inter-digital transducers (IDT), gold film for immobilization of the biorecongniton layer and a polydimethylsiloxane (PDMS) microfluidic channels. DNA aptamer, or “artificial antibody”, was used as the specific biorecognition probe for PSA capture. Some nucleotides were added to the 3'-end of the aptamer to form a duplex with the 3'-end, turning the aptamer into an aptamer-beacon. Taking advantage of the selective target-induced assembly changes arising from the “aptamer beacon”, highly selective and specific detection of PSA was achieved. Furthermore, PDMS microfluidic channels were designed and fabricated to realize automated quantitative sample injection. After optimization of the experimental conditions, the established device showed good performance for PSA detection between 10 ng/mL to 1 μg/mL, with a detection limit of 10 ng/mL. The proposed sensor might be a promising alternative for point of care diagnostics. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessArticle Towards a Dynamic Clamp for Neurochemical Modalities
Sensors 2015, 15(5), 10465-10480; doi:10.3390/s150510465
Received: 8 April 2015 / Revised: 27 April 2015 / Accepted: 29 April 2015 / Published: 4 May 2015
Cited by 3 | PDF Full-text (2689 KB) | HTML Full-text | XML Full-text
Abstract
The classic dynamic clamp technique uses a real-time electrical interface between living cells and neural simulations in order to investigate hypotheses about neural function and structure. One of the acknowledged drawbacks of that technique is the limited control of the cells’ chemical [...] Read more.
The classic dynamic clamp technique uses a real-time electrical interface between living cells and neural simulations in order to investigate hypotheses about neural function and structure. One of the acknowledged drawbacks of that technique is the limited control of the cells’ chemical microenvironment. In this manuscript, we use a novel combination of nanosensor and microfluidic technology and microfluidic and neural simulations to add sensing and control of chemical concentrations to the dynamic clamp technique. Specifically, we use a microfluidic lab-on-a-chip to generate distinct chemical concentration gradients (ions or neuromodulators), to register the concentrations with embedded nanosensors and use the processed signals as an input to simulations of a neural cell. The ultimate goal of this project is to close the loop and provide sensor signals to the microfluidic lab-on-a-chip to mimic the interaction of the simulated cell with other cells in its chemical environment. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle Ultra-High Sensitivity Zinc Oxide Nanocombs for On-Chip Room Temperature Carbon Monoxide Sensing
Sensors 2015, 15(4), 8919-8930; doi:10.3390/s150408919
Received: 30 December 2014 / Revised: 9 April 2015 / Accepted: 14 April 2015 / Published: 16 April 2015
Cited by 3 | PDF Full-text (2917 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report an on-chip gas sensor based on novel zinc oxide (ZnO) nanocombs for carbon monoxide (CO) sensing. With ZnO gas sensing nanocombs fully integrated on a single silicon chip, the concept of low cost complementary-metal-oxide-semiconductor (CMOS) microsensor capable [...] Read more.
In this paper, we report an on-chip gas sensor based on novel zinc oxide (ZnO) nanocombs for carbon monoxide (CO) sensing. With ZnO gas sensing nanocombs fully integrated on a single silicon chip, the concept of low cost complementary-metal-oxide-semiconductor (CMOS) microsensor capable of on-chip gas sensing and processing is enabled. Compared with all previous implementations, the proposed ZnO nanocombs feature much larger effective sensing area and exhibit ultra-high sensitivity even at the room temperature. Specifically, at room temperature, we demonstrate peak sensitivities as high as 7.22 and 8.93 for CO concentrations of 250 ppm and 500 ppm, respectively. As a result, by operating the proposed ZnO-nanocomb-based gas sensor at the room temperature, the widely adopted power consuming heating components are completely removed. This leads to not only great power saving, but also full compatibility between the gas sensor and the on-chip circuitry in term of acceptable operating temperature. In addition, the reported fast response/recovery time of ~200 s/~50 s (250 ppm CO) makes it well suited to real-life applications. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle A Reliable and Simple Method for Fabricating a Poly(Dimethylsiloxane) Electrospray Ionization Chip with a Corner-Integrated Emitter
Sensors 2015, 15(4), 8931-8944; doi:10.3390/s150408931
Received: 6 March 2015 / Revised: 9 April 2015 / Accepted: 10 April 2015 / Published: 16 April 2015
Cited by 3 | PDF Full-text (1207 KB) | HTML Full-text | XML Full-text
Abstract
Monolithically integrated emitters have been increasingly applied to microfluidic devices that are coupled to mass spectrometers (MS) as electrospray ionization sources (ESI). A new method was developed to fabricate a duplicable structure which integrated the emitter into a poly(dimethylsiloxane) chip corner. Two [...] Read more.
Monolithically integrated emitters have been increasingly applied to microfluidic devices that are coupled to mass spectrometers (MS) as electrospray ionization sources (ESI). A new method was developed to fabricate a duplicable structure which integrated the emitter into a poly(dimethylsiloxane) chip corner. Two photoresist layers containing a raised base which guaranteed the precise integration of the electrospray tip emitter and ensured that the cutting out of the tip exerted no influence even during repeated prototyping were used to ease the operation of the process. Highly stable ESI-MS performance was obtained and the results were compared with those of a commercial fused-silica capillary source. Furthermore, chip-to-chip and run-to-run results indicated both reliability and reproducibility during repeated fabrication. These results reveal that the proposed chip can provide an ideal ion source for MS across many applications, especially with the perspective to be widely used in portable MS during on-site analysis. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle Development of a Microfluidic-Based Optical Sensing Device for Label-Free Detection of Circulating Tumor Cells (CTCs) Through Their Lactic Acid Metabolism
Sensors 2015, 15(3), 6789-6806; doi:10.3390/s150306789
Received: 30 January 2015 / Revised: 2 March 2015 / Accepted: 17 March 2015 / Published: 19 March 2015
Cited by 7 | PDF Full-text (4143 KB) | HTML Full-text | XML Full-text
Abstract
This study reports a microfluidic-based optical sensing device for label-free detection of circulating tumor cells (CTCs), a rare cell species in blood circulation. Based on the metabolic features of cancer cells, live CTCs can be quantified indirectly through their lactic acid production. [...] Read more.
This study reports a microfluidic-based optical sensing device for label-free detection of circulating tumor cells (CTCs), a rare cell species in blood circulation. Based on the metabolic features of cancer cells, live CTCs can be quantified indirectly through their lactic acid production. Compared with the conventional schemes for CTC detection, this label-free approach could prevent the biological bias due to the heterogeneity of the surface antigens on cancer cells. In this study, a microfluidic device was proposed to generate uniform water-in-oil cell-encapsulating micro-droplets, followed by the fluorescence-based optical detection of lactic acid produced within the micro-droplets. To test its feasibility to quantify cancer cells, experiments were carried out. Results showed that the detection signals were proportional to the number of cancer cells within the micro-droplets, whereas such signals were insensitive to the existence and number of leukocytes within. To further demonstrate its feasibility for cancer cell detection, the cancer cells with known cell number in a cell suspension was detected based on the method. Results revealed that there was no significant difference between the detected number and the real number of cancer cells. As a whole, the proposed method opens up a new route to detect live CTCs in a label-free manner. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle An Ultra-Low Power CMOS Image Sensor with On-Chip Energy Harvesting and Power Management Capability
Sensors 2015, 15(3), 5531-5554; doi:10.3390/s150305531
Received: 7 January 2015 / Revised: 28 January 2015 / Accepted: 4 March 2015 / Published: 6 March 2015
Cited by 4 | PDF Full-text (1526 KB) | HTML Full-text | XML Full-text
Abstract
An ultra-low power CMOS image sensor with on-chip energy harvesting and power management capability is introduced in this paper. The photodiode pixel array can not only capture images but also harvest solar energy. As such, the CMOS image sensor chip is able [...] Read more.
An ultra-low power CMOS image sensor with on-chip energy harvesting and power management capability is introduced in this paper. The photodiode pixel array can not only capture images but also harvest solar energy. As such, the CMOS image sensor chip is able to switch between imaging and harvesting modes towards self-power operation. Moreover, an on-chip maximum power point tracking (MPPT)-based power management system (PMS) is designed for the dual-mode image sensor to further improve the energy efficiency. A new isolated P-well energy harvesting and imaging (EHI) pixel with very high fill factor is introduced. Several ultra-low power design techniques such as reset and select boosting techniques have been utilized to maintain a wide pixel dynamic range. The chip was designed and fabricated in a 1.8 V, 1P6M 0.18 µm CMOS process. Total power consumption of the imager is 6.53 µW for a 96 × 96 pixel array with 1 V supply and 5 fps frame rate. Up to 30 μW of power could be generated by the new EHI pixels. The PMS is capable of providing 3× the power required during imaging mode with 50% efficiency allowing energy autonomous operation with a 72.5% duty cycle. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessCommunication Ultra-Sensitive Nanofiber Fluorescence Detection in a Microfluidic Chip
Sensors 2015, 15(3), 4890-4898; doi:10.3390/s150304890
Received: 30 December 2014 / Revised: 11 February 2015 / Accepted: 13 February 2015 / Published: 26 February 2015
Cited by 3 | PDF Full-text (1738 KB) | HTML Full-text | XML Full-text
Abstract
We report an ultra-sensitive and robust fluorescence sensor made by using a biconical taper with a waist diameter of 720 nm for both excitation and fluorescence collection. To enhance the stability of the fluorescence sensor, the biconical taper has been embedded in [...] Read more.
We report an ultra-sensitive and robust fluorescence sensor made by using a biconical taper with a waist diameter of 720 nm for both excitation and fluorescence collection. To enhance the stability of the fluorescence sensor, the biconical taper has been embedded in a 125 µm wide microchannel with a detection length of 2.5 cm. Investigated by measuring the fluorescence intensity of rhodamine 6G (R6G), the sensor shows a detection limit down to 100 pM, with excellent reversibility in a concentration range of 0–10 nM. The sensor has also been applied to quantum dot (QD)-labeled streptavidin measurements, yielding a detection sensitivity down to 10 pM for QDs. In addition, the small sample volume (ca. 500 nL), high sampling throughput, and seamless connection between the biconical taper and standard optical fibers offer a number of attractive advantages for chemical and biosensing applications. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessArticle Development of a Passive Liquid Valve (PLV) Utilizing a Pressure Equilibrium Phenomenon on the Centrifugal Microfluidic Platform
Sensors 2015, 15(3), 4658-4676; doi:10.3390/s150304658
Received: 17 October 2014 / Revised: 12 December 2014 / Accepted: 17 December 2014 / Published: 25 February 2015
Cited by 4 | PDF Full-text (2729 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this paper, we propose an easy-to-implement passive liquid valve (PLV) for the microfluidic compact-disc (CD). This valve can be implemented by introducing venting chambers to control the air flow of the source and destination chambers. The PLV mechanism is based on [...] Read more.
In this paper, we propose an easy-to-implement passive liquid valve (PLV) for the microfluidic compact-disc (CD). This valve can be implemented by introducing venting chambers to control the air flow of the source and destination chambers. The PLV mechanism is based on equalizing the main forces acting on the microfluidic CD (i.e., the centrifugal and capillary forces) to control the burst frequency of the source chamber liquid. For a better understanding of the physics behind the proposed PLV, an analytical model is described. Moreover, three parameters that control the effectiveness of the proposed valve, i.e., the liquid height, liquid density, and venting chamber position with respect to the CD center, are tested experimentally. To demonstrate the ability of the proposed PLV valve, microfluidic liquid switching and liquid metering are performed. In addition, a Bradford assay is performed to measure the protein concentration and evaluated in comparison to the benchtop procedure. The result shows that the proposed valve can be implemented in any microfluidic process that requires simplicity and accuracy. Moreover, the developed valve increases the flexibility of the centrifugal CD platform for passive control of the liquid flow without the need for an external force or trigger. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessArticle Simultaneous Characterization of Instantaneous Young’s Modulus and Specific Membrane Capacitance of Single Cells Using a Microfluidic System
Sensors 2015, 15(2), 2763-2773; doi:10.3390/s150202763
Received: 6 December 2014 / Revised: 12 January 2015 / Accepted: 19 January 2015 / Published: 27 January 2015
Cited by 2 | PDF Full-text (4110 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a microfluidics-based approach capable of continuously characterizing instantaneous Young’s modulus (Einstantaneous) and specific membrane capacitance (Cspecific membrane) of suspended single cells. In this method, cells were aspirated through a constriction channel while the [...] Read more.
This paper presents a microfluidics-based approach capable of continuously characterizing instantaneous Young’s modulus (Einstantaneous) and specific membrane capacitance (Cspecific membrane) of suspended single cells. In this method, cells were aspirated through a constriction channel while the cellular entry process into the constriction channel was recorded using a high speed camera and the impedance profiles at two frequencies (1 kHz and 100 kHz) were simultaneously measured by a lock-in amplifier. Numerical simulations were conducted to model cellular entry process into the constriction channel, focusing on two key parameters: instantaneous aspiration length (Linstantaneous) and transitional aspiration length (Ltransitional), which was further translated to Einstantaneous. An equivalent distribution circuit model for a cell travelling in the constriction channel was used to determine Cspecific membrane. A non-small-cell lung cancer cell line 95C (n = 354) was used to evaluate this technique, producing Einstantaneous of 2.96 ± 0.40 kPa and Cspecific membrane of 1.59 ± 0.28 μF/cm2. As a platform for continuous and simultaneous characterization of cellular Einstantaneous and Cspecific membrane, this approach can facilitate a more comprehensive understanding of cellular biophysical properties. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle Micro-Fabricated DC Comparison Calorimeter for RF Power Measurement
Sensors 2014, 14(11), 20245-20261; doi:10.3390/s141120245
Received: 15 July 2014 / Revised: 9 October 2014 / Accepted: 9 October 2014 / Published: 27 October 2014
PDF Full-text (1132 KB) | HTML Full-text | XML Full-text
Abstract
Diode detection and bolometric detection have been widely used to measure radio frequency (RF) power. However, flow calorimeters, in particular micro-fabricated flow calorimeters, have been mostly unexplored as power meters. This paper presents the design, micro-fabrication and characterization of a flow calorimeter. [...] Read more.
Diode detection and bolometric detection have been widely used to measure radio frequency (RF) power. However, flow calorimeters, in particular micro-fabricated flow calorimeters, have been mostly unexplored as power meters. This paper presents the design, micro-fabrication and characterization of a flow calorimeter. This novel device is capable of measuring power from 100 \(\mu\)W to 200 mW. It has a 50-Ohm load that is heated by the RF source, and the heat is transferred to fluid in a microchannel. The temperature change in the fluid is measured by a thermistor that is connected in one leg of a Wheatstone bridge. The output voltage change of the bridge corresponds to the RF power applied to the load. The microfabricated device measures 25.4 mm \(\times\) 50.8 mm, excluding the power supplies, microcontroller and fluid pump. Experiments demonstrate that the micro-fabricated sensor has a sensitivity up to 22 \(\times\) \(10^{-3}\) V/W. The typical resolution of this micro-calorimeter is on the order of 50 \(\mu\)W, and the best resolution is around 10 \(\mu\)W. The effective efficiency is 99.9\% from 0–1 GHz and more than 97.5\% at frequencies up to 4 GHz. The measured reflection coefficient of the 50-Ohm load and coplanar wave guide is less than \(-25\) dB from 0–2 GHz and less than \(-16\) dB at 2–4 GHz. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle Temperature and Magnetic Field Driven Modifications in the I-V Features of Gold-DNA-Gold Structure
Sensors 2014, 14(10), 19229-19241; doi:10.3390/s141019229
Received: 13 September 2014 / Revised: 10 October 2014 / Accepted: 11 October 2014 / Published: 15 October 2014
Cited by 6 | PDF Full-text (675 KB) | HTML Full-text | XML Full-text
Abstract
The fabrication of Metal-DNA-Metal (MDM) structure-based high sensitivity sensors from DNA micro-and nanoarray strands is a key issue in their development. The tunable semiconducting response of DNA in the presence of external electromagnetic and thermal fields is a gift for molecular electronics. [...] Read more.
The fabrication of Metal-DNA-Metal (MDM) structure-based high sensitivity sensors from DNA micro-and nanoarray strands is a key issue in their development. The tunable semiconducting response of DNA in the presence of external electromagnetic and thermal fields is a gift for molecular electronics. The impact of temperatures (25–55 °C) and magnetic fields (0–1200 mT) on the current-voltage (I-V) features of Au-DNA-Au (GDG) structures with an optimum gap of 10 μm is reported. The I-V characteristics acquired in the presence and absence of magnetic fields demonstrated the semiconducting diode nature of DNA in GDG structures with high temperature sensitivity. The saturation current in the absence of magnetic field was found to increase sharply with the increase of temperature up to 45 °C and decrease rapidly thereafter. This increase was attributed to the temperature-assisted conversion of double bonds into single bond in DNA structures. Furthermore, the potential barrier height and Richardson constant for all the structures increased steadily with the increase of external magnetic field irrespective of temperature variations. Our observation on magnetic field and temperature sensitivity of I-V response in GDG sandwiches may contribute towards the development of DNA-based magnetic sensors. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle A CMOS Smart Temperature and Humidity Sensor with Combined Readout
Sensors 2014, 14(9), 17192-17211; doi:10.3390/s140917192
Received: 15 July 2014 / Revised: 25 August 2014 / Accepted: 3 September 2014 / Published: 16 September 2014
Cited by 1 | PDF Full-text (3255 KB) | HTML Full-text | XML Full-text
Abstract
A fully-integrated complementary metal-oxide semiconductor (CMOS) sensor for combined temperature and humidity measurements is presented. The main purpose of the device is to monitor the hermeticity of micro-packages for implanted integrated circuits and to ensure their safe operation by monitoring the operating [...] Read more.
A fully-integrated complementary metal-oxide semiconductor (CMOS) sensor for combined temperature and humidity measurements is presented. The main purpose of the device is to monitor the hermeticity of micro-packages for implanted integrated circuits and to ensure their safe operation by monitoring the operating temperature and humidity on-chip. The smart sensor has two modes of operation, in which either the temperature or humidity is converted into a digital code representing a frequency ratio between two oscillators. This ratio is determined by the ratios of the timing capacitances and bias currents in both oscillators. The reference oscillator is biased by a current whose temperature dependency is complementary to the proportional to absolute temperature (PTAT) current. For the temperature measurement, this results in an exceptional normalized sensitivity of about 0.77%/°C at the accepted expense of reduced linearity. The humidity sensor is a capacitor, whose value varies linearly with relative humidity (RH) with a normalized sensitivity of 0.055%/% RH. For comparison, two versions of the humidity sensor with an area of either 0.2 mm2 or 1.2 mm2 were fabricated in a commercial 0.18 μm CMOS process. The on-chip readout electronics operate from a 5 V power supply and consume a current of approximately 85 µA. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle Graphene-Based Nanoresonator with Applications in Optical Transistor and Mass Sensing
Sensors 2014, 14(9), 16740-16753; doi:10.3390/s140916740
Received: 1 July 2014 / Revised: 26 August 2014 / Accepted: 4 September 2014 / Published: 9 September 2014
Cited by 1 | PDF Full-text (632 KB) | HTML Full-text | XML Full-text
Abstract
Graphene has received significant attention due to its excellent properties currently. In this work, a nano-optomechanical system based on a doubly-clamped Z-shaped graphene nanoribbon (GNR) with an optical pump-probe scheme is proposed. We theoretically demonstrate the phenomenon of phonon-induced transparency and show [...] Read more.
Graphene has received significant attention due to its excellent properties currently. In this work, a nano-optomechanical system based on a doubly-clamped Z-shaped graphene nanoribbon (GNR) with an optical pump-probe scheme is proposed. We theoretically demonstrate the phenomenon of phonon-induced transparency and show an optical transistor in the system. In addition, the significantly enhanced nonlinear effect of the probe laser is also investigated, and we further put forward a nonlinear optical mass sensing that may be immune to detection noises. Molecules, such as NH3 and NO2, can be identified via using the nonlinear optical spectroscopy, which may be applied to environmental pollutant monitoring and trace chemical detection. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessArticle A Compact Microelectrode Array Chip with Multiple Measuring Sites for Electrochemical Applications
Sensors 2014, 14(6), 9505-9521; doi:10.3390/s140609505
Received: 20 January 2014 / Revised: 15 May 2014 / Accepted: 22 May 2014 / Published: 28 May 2014
Cited by 8 | PDF Full-text (848 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we demonstrate the fabrication and electrochemical characterization of a microchip with 12 identical but individually addressable electrochemical measuring sites, each consisting of a set of interdigitated electrodes acting as a working electrode as well as two circular electrodes functioning [...] Read more.
In this paper we demonstrate the fabrication and electrochemical characterization of a microchip with 12 identical but individually addressable electrochemical measuring sites, each consisting of a set of interdigitated electrodes acting as a working electrode as well as two circular electrodes functioning as a counter and reference electrode in close proximity. The electrodes are made of gold on a silicon oxide substrate and are passivated by a silicon nitride membrane. A method for avoiding the creation of high edges at the electrodes (known as lift-off ears) is presented. The microchip design is highly symmetric to accommodate easy electronic integration and provides space for microfluidic inlets and outlets for integrated custom-made microfluidic systems on top. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessArticle A Method for Measuring the Volume of Transdermally Extracted Interstitial Fluid by a Three-Electrode Skin Resistance Sensor
Sensors 2014, 14(4), 7084-7095; doi:10.3390/s140407084
Received: 14 November 2013 / Revised: 31 March 2014 / Accepted: 9 April 2014 / Published: 22 April 2014
PDF Full-text (570 KB) | HTML Full-text | XML Full-text
Abstract
It is difficult to accurately measure the volume of transdermally extracted interstitial fluid (ISF), which is important for improving blood glucose prediction accuracy. Skin resistance, which is a good indicator of skin permeability, can be used to determine the volume of extracted [...] Read more.
It is difficult to accurately measure the volume of transdermally extracted interstitial fluid (ISF), which is important for improving blood glucose prediction accuracy. Skin resistance, which is a good indicator of skin permeability, can be used to determine the volume of extracted ISF. However, it is a challenge to realize in vivo longitudinal skin resistance measurements of microareas. In this study, a three-electrode sensor was presented for measuring single-point skin resistance in vivo, and a method for determining the volume of transdermally extracted ISF using this sensor was proposed. Skin resistance was measured under static and dynamic conditions. The correlation between the skin resistance and the permeation rate of transdermally extracted ISF was proven. The volume of transdermally extracted ISF was determined using skin resistance. Factors affecting the volume prediction accuracy of transdermally extracted ISF were discussed. This method is expected to improve the accuracy of blood glucose prediction, and is of great significance for the clinical application of minimally invasive blood glucose measurement. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Review

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Open AccessReview Femtosecond Laser Fabrication of Monolithically Integrated Microfluidic Sensors in Glass
Sensors 2014, 14(10), 19402-19440; doi:10.3390/s141019402
Received: 15 August 2014 / Revised: 28 September 2014 / Accepted: 30 September 2014 / Published: 17 October 2014
Cited by 14 | PDF Full-text (15853 KB) | HTML Full-text | XML Full-text
Abstract
Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D) structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical [...] Read more.
Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D) structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical applications. The present paper presents a comprehensive review of recent advancements in femtosecond laser processing of glass for a variety of microfluidic sensor applications. These include 3D integration of micro-/nanofluidic, optofluidic, electrofluidic, surface-enhanced Raman-scattering devices, in addition to fabrication of devices for microfluidic bioassays and lab-on-fiber sensors. This paper describes the unique characteristics of femtosecond laser processing and the basic concepts involved in femtosecond laser direct writing. Advanced spatiotemporal beam shaping methods are also discussed. Typical examples of microfluidic sensors fabricated using femtosecond lasers are then highlighted, and their applications in chemical and biological sensing are described. Finally, a summary of the technology is given and the outlook for further developments in this field is considered. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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Open AccessReview Various On-Chip Sensors with Microfluidics for Biological Applications
Sensors 2014, 14(9), 17008-17036; doi:10.3390/s140917008
Received: 15 July 2014 / Revised: 29 August 2014 / Accepted: 10 September 2014 / Published: 12 September 2014
Cited by 5 | PDF Full-text (3715 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we review recent advances in on-chip sensors integrated with microfluidics for biological applications. Since the 1990s, much research has concentrated on developing a sensing system using optical phenomena such as surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) [...] Read more.
In this paper, we review recent advances in on-chip sensors integrated with microfluidics for biological applications. Since the 1990s, much research has concentrated on developing a sensing system using optical phenomena such as surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) to improve the sensitivity of the device. The sensing performance can be significantly enhanced with the use of microfluidic chips to provide effective liquid manipulation and greater flexibility. We describe an optical image sensor with a simpler platform for better performance over a larger field of view (FOV) and greater depth of field (DOF). As a new trend, we review consumer electronics such as smart phones, tablets, Google glasses, etc. which are being incorporated in point-of-care (POC) testing systems. In addition, we discuss in detail the current optical sensing system integrated with a microfluidic chip. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessReview Cell Patterning for Liver Tissue Engineering via Dielectrophoretic Mechanisms
Sensors 2014, 14(7), 11714-11734; doi:10.3390/s140711714
Received: 16 April 2014 / Revised: 20 June 2014 / Accepted: 25 June 2014 / Published: 2 July 2014
Cited by 4 | PDF Full-text (1818 KB) | HTML Full-text | XML Full-text
Abstract
Liver transplantation is the most common treatment for patients with end-stage liver failure. However, liver transplantation is greatly limited by a shortage of donors. Liver tissue engineering may offer an alternative by providing an implantable engineered liver. Currently, diverse types of engineering [...] Read more.
Liver transplantation is the most common treatment for patients with end-stage liver failure. However, liver transplantation is greatly limited by a shortage of donors. Liver tissue engineering may offer an alternative by providing an implantable engineered liver. Currently, diverse types of engineering approaches for in vitro liver cell culture are available, including scaffold-based methods, microfluidic platforms, and micropatterning techniques. Active cell patterning via dielectrophoretic (DEP) force showed some advantages over other methods, including high speed, ease of handling, high precision and being label-free. This article summarizes liver function and regenerative mechanisms for better understanding in developing engineered liver. We then review recent advances in liver tissue engineering techniques and focus on DEP-based cell patterning, including microelectrode design and patterning configuration. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessReview Bacteria Inside Semiconductors as Potential Sensor Elements: Biochip Progress
Sensors 2014, 14(6), 11225-11244; doi:10.3390/s140611225
Received: 9 April 2014 / Revised: 10 June 2014 / Accepted: 19 June 2014 / Published: 24 June 2014
PDF Full-text (743 KB) | HTML Full-text | XML Full-text
Abstract
It was discovered at the beginning of this Century that living bacteria—and specifically the extremophile Pseudomonas syzgii—could be captured inside growing crystals of pure water-corroding semiconductors—specifically germanium—and thereby initiated pursuit of truly functional “biochip-based” biosensors. This observation was first made at [...] Read more.
It was discovered at the beginning of this Century that living bacteria—and specifically the extremophile Pseudomonas syzgii—could be captured inside growing crystals of pure water-corroding semiconductors—specifically germanium—and thereby initiated pursuit of truly functional “biochip-based” biosensors. This observation was first made at the inside ultraviolet-illuminated walls of ultrapure water-flowing semiconductor fabrication facilities (fabs) and has since been, not as perfectly, replicated in simpler flow cell systems for chip manufacture, described here. Recognizing the potential importance of these adducts as optical switches, for example, or probes of metabolic events, the influences of the fabs and their components on the crystal nucleation and growth phenomena now identified are reviewed and discussed with regard to further research needs. For example, optical beams of current photonic circuits can be more easily modulated by integral embedded cells into electrical signals on semiconductors. Such research responds to a recently published Grand Challenge in ceramic science, designing and synthesizing oxide electronics, surfaces, interfaces and nanoscale structures that can be tuned by biological stimuli, to reveal phenomena not otherwise possible with conventional semiconductor electronics. This short review addresses only the fabrication facilities’ features at the time of first production of these potential biochips. Full article
(This article belongs to the Special Issue On-Chip Sensors)
Open AccessReview Applications of Micro/Nanoparticles in Microfluidic Sensors: A Review
Sensors 2014, 14(4), 6952-6964; doi:10.3390/s140406952
Received: 8 February 2014 / Revised: 4 April 2014 / Accepted: 10 April 2014 / Published: 21 April 2014
Cited by 5 | PDF Full-text (755 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews the applications of micro/nanoparticles in microfluidics device fabrication and analytical processing. In general, researchers have focused on two properties of particles—electric behavior and magnetic behavior. The applications of micro/nanoparticles could be summarized on the chip fabrication level and on [...] Read more.
This paper reviews the applications of micro/nanoparticles in microfluidics device fabrication and analytical processing. In general, researchers have focused on two properties of particles—electric behavior and magnetic behavior. The applications of micro/nanoparticles could be summarized on the chip fabrication level and on the processing level. In the fabrication of microfluidic chips (chip fabrication level), particles are good additives in polydimethylsiloxane (PDMS) to prepare conductive or magnetic composites which have wide applications in sensors, valves and actuators. On the other hand, particles could be manipulated according to their electric and magnetic properties under external electric and magnetic fields when they are travelling in microchannels (processing level). Researchers have made a great progress in preparing modified PDMS and investigating the behaviors of particles in microchannels. This article attempts to present a discussion on the basis of particles applications in microfluidics. Full article
(This article belongs to the Special Issue On-Chip Sensors)
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