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This paper presents three poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) composite-based sensors for detecting volatile organic compunds (VOCs) in the presence of water vapor applicable in breath based sensing. Three sensors with varying sensitivities to acetone, water, ethanol, isoprene, and 2-ethylhexyl acetate (2-EHA), representing VOCs found in breath, have been developed. A sensor fabricated by spray coating PVDF-HFP/C65 composite ( Sensor-1 ) exhibited a 52.6% increase in resistance when exposed to acetone, while the change was less than 0.34% for water. The resistance changes for ethanol, isoprene, and 2-EHA, were 5.6%, 3%, and 0.11%, respectively. The second sensor ( Sensor-2 ), with a two-layer design of PVDF-HFP and PVDF-HFP/C65, was fabricated by a spin coating method, which exhibited improved response times. The response times of Sensor-2 compared to Sensor-1 decreased by 52% for acetone, 92% for water, 30% for ethanol, and 61% for isoprene. In the third sensor ( Sensor-3 ), the addition of carbon nanotube (CNT) in the composite (PVDF-HFP/C65/CNT) caused a decrease in resistance when exposed to water. This is in contrast to Sensors 1 & 2 where resistance increased for all VOCs, and provides a higher selectivity for the system. The results from the three sensors were analyzed using principal component analysis (PCA) and it was demonstrated that the combined responses of these sensors provide a high selectivity. The sensor fabrication, testing methods, and results are presented and discussed.

Utilizing a case study research design, the factors that influence teacher learning and change, as well as the processes by which secondary STEM teachers internalize professional development (PD) content, are explored. The authors argue that conceptualizations of teacher learning often do not adequately account for teacher subjectivity and the role of exogenous variables in teacher development. The outcomes of PD are heavily influenced by teacher subjectivity, which includes perceptions, previous knowledge, and the internalization of the power and influence present in educational policy and socioeconomic realities. This complexity must be accounted for when planning, researching, or evaluating teacher PD.

Presently, nanomanufacturing capabilities limit the commercialization of a broader range of nanoscale structures with higher complexity, greater precision and accuracy, and a substantially improved performance. Atomic force microscopy (AFM)-based nanomachining is a promising technique to address current limitations and is considered a potential manufacturing (MFG) tool for operations such as machining, patterning, and assembling with in situ metrology and visualization. Most existing techniques for fabrication of nanofluidic channels involve the use of electron-beam lithography, which is a very expensive process that requires a lengthy calibration procedure. In this work, atomic force microscopy (AFM) is employed in the fabrication of nanofluidic channels for medical applications. Channels with various depths and widths are fabricated using AFM indentation and scratching. A nanoscale channel is mainly used in the study of the molecular behavior at single molecule level. The resulting device can be used for detecting, analyzing and separating biomolecules, DNA stretching, and separation of elite group of lysosome and other viruses. The nanochannels are integrated between microchannels and act as filters to separate biomolecules. Sharply developed vertical microchannels are produced from deep reaction ion etching. Poly-dimethylsiloxane (PDMS) bonding is performed to close the top surface of the silicon device. An experimental setup is used for testing by flowing fluid through the channels. A cost evaluation shows 47.7% manufacturing-time and 60.6% manufacturing-cost savings, compared to more traditional processes.

Lithium-ion batteries using flexible paper-based current collectors have been developed. These current collectors were fabricated from wood microfibers that were coated with carbon nanotubes (CNT) through an electrostatic layer-by-layer nanoassembly process. The carbon nanotube mass loading of the presented (CNT-microfiber paper) current collectors is 10.1 μg/cm $^{2}$ . The capacities of the batteries made with the current collectors are 150 mAh/g for lithium cobalt oxide (LCO) half-cell, 158 mAh/g for lithium titanium oxide (LTO) half-cell, and 126 mAh/g for LTO/LCO full-cell. The fabrication approach of the CNT-microfiber paper current collectors, the assembly of the batteries, and the experimental results are presented and discussed.

Recent developments in science and engineering have advanced the atomic manufacturing of nanoscale structures, allowing for improved high-performance technologies. The challenge now is to expand nanomanufacturing capabilities in order to fabricate a broader range of structures with higher complexity, greater precision and accuracy, and with substantially improved performance. Also, reducing the cost by avoiding the use of expensive equipment/processes is highly desirable. While current nanomanufacturing capabilities limit the commercialization of such nanoscale structures, AFM-based nanomachining is a promising tool to address issues and is considered a potential manufacturing tool for operations including machining, patterning, and assembling with in situ metrology and visualization. Most existing techniques used in the fabrication of nanofluidic channels involved the use of electron-beam lithography systems, which are very expensive processes. In addition, one of the issues associated with electron-beam lithography is when the base material is changed; the energy of ejecting electrons needs to be adjusted. This results in time spending on developing the formula for different material. In this work, atomic force microscopy (AFM) is employed in the fabrication of a nanofluidic device for medical applications. Nanofluidic channels with various depths and widths are fabricated using AFM indentation and scratching techniques. Nanoscale channel is mainly used in the study of molecular behavior at single molecule level. The interaction of molecules with the nanochannels at persistence length has led to a new way of detecting, analyzing and separating these biomolecules. The resulting device from the current work can be used for the DNA stretching application and the separation of elite group of lysosome and other viruses. The nanochannels are integrated between the microchannels and act as a filter to separate biomolecules. Sharply developed vertical microchannels are produced from a deep reaction ion etching followed by deposition of different materials such as gold and polymer on the top surface in order to study alternative ways of manufacturing the nanofluidic device. PDMS bonding is performed to close the top surface of the device. An experimental setup is used to test and validate the device by flowing fluid through the channels. A detailed cost evaluation is conducted to assess the economical merits of the proposed process. It is shown that there is 47.7% manufacturing-time savings and 60.6% manufacturing-cost savings, when using the proposed process compared to more traditional processes.

In this work, optical scattering using Raman spectroscopy has been analyzed for various cancer tissues. The Raman shifts obtained at the Indiana University Bloomington (IUB) and Indiana University-Purdue University Indianapolis (IUPUI) laboratories have been processed for diagnosing various types of cancer tissues. The objective of this research is to distinguish between cancerous and non-cancerous tissues. Small size tissue samples have been processed, seeking the minimum size tissue that can be diagnosed via Raman spectroscopy. The tests have been conducted on nearly 20 human tissues. A Matlab program has been written following Parzen-Window classifier to recognize the Raman shift pattern for various types of cancer tissues, including breast cancer, kidney, and Gyn-Uterus. A software visual model has been used for data processing. Unique signals for breast and kidney tumors have been obtained. The approach followed in this paper shows promise for early cancer detection in humans.

A passive capacitor-based ethylene sensor using SnO2nanoparticles is presented for the detection of ethylene gas. The nanoscale particle size (10 nm to 15 nm) and film thickness (1300 nm) of the sensing dielectric layer in the capacitor model aid in sensing ethylene at room temperature and eliminate the need for microhotplates used in existing bulk SnO2-resistive sensors. The SnO2-sensing layer is deposited using room temperature dip coating process on flexible polyimide substrates with copper as the top and bottom plates of the capacitor. The capacitive sensor fabricated with SnO2nanoparticles as the dielectric showed a total decrease in capacitance of 5 pF when ethylene gas concentration was increased from 0 to 100 ppm. A 7 pF decrease in capacitance was achieved by introducing a 10 nm layer of platinum (Pt) and palladium (Pd) alloy deposited on the SnO2layer. This also improved the response time by 40%, recovery time by 28%, and selectivity of the sensor to ethylene mixed in a CO2gas environment by 66%.

In this work, we report the outcomes from the IUPUI STEM outreach program “STEMCorp” that inspires high school students to pursue STEM majors. The STEMCorp program was modeled after the Multidisciplinary Undergraduate Research Initiative (MURI) at IUPUI. MURI research program introduces undergraduate students from at least two different departments with mentors from different disciplines to address research issues that may compose both engineering and sciences. The STEMCorp program brings undergraduate students to work with faculty and high school teachers to create a positive impact in enriching the high school students by introducing them to engineering and science with emphasis on nanotechnology for future careers. The program describes the collaborative activities between faculty, undergraduate students and high school STEM teachers in the creation of project-based, student-centered learning modules in the field of nanotechnology. The paper details the activities of the STEMCorp participants including their experiences in developing working partnerships and creating and implementing learning modules in the designated high school courses. The success of the program is assessed by the measurable outcomes of high school students' research projects. Specifically, two different learning modules are presented, including the processes used in the development of these modules and their outcomes. The collaborative research discussions between the faculty, undergraduate students, and high school teachers are detailed, covering research methodologies, hypothesis, and expected outcomes.

In situ thermoelectric cooling of GMR nanowires is a novel method to obtain reliable and more sensitive GMR devices. Bismuth telluride (BixTey) caps were used to provide localized thermoelectric cooling of GMR nanowires. BixTey nanowires were electrodeposited from aqueous acidic solutions containing different Bi3+ and HTeO2+ concentrations. GMR layered structures were electrodeposited from a Co-rich electrolyte using a pulsed potential technique. The highest Seebeck coefficients of -318.7 µV/K and 117 µV/K were measured for n-type and p-type nanowires, respectively. P-type nanowires were obtained for low Te concentrations (

A new method to measure radar cross section (RCS) parameters of antennas is presented in this paper. This method relies on an equation derived for the received signal power which is represented as the superposition of structural-mode scattered, antenna-mode scattered, and leakage signals. The method also measures relative phase and provides the effect of the load connected to the antenna. The received signal power equation is solved using minimum mean square error estimation, and the solution is used to obtain structural-mode RCS, antenna-mode RCS, and relative phase of an antenna by applying short, open, and match load cases. A measurement example of RCS parameters of a microstrip patch antenna using a simple experimental setup is presented. The structural-mode RCS, antenna-mode RCS, and relative phase factor cos(phi0) of the antenna, obtained using minimum mean square error estimation solution, are -18.307 dBsm, -20.386 dBsm, and 0.970, respectively. The present method requires less lengthy experimental measurements, while providing results that are more informative and accurate as obtained from previous methods.

A novel conceptual mechanism for cooling Giant magneto resistance (GMR) nanostructures using bismuth telluride (BixTey) thermoelectric caps is reported for first time. BixTey thin films and nanowires were electrodeposited from an aqueous electrolyte solution using a constant potential method. GMR layered structures were electrodeposited form a Co-rich electrolyte using a pulsed potential technique. Optimal deposition potentials were identified from polarization analysis. Thin film morphology was found to be strongly dependent on deposition potentials. With increased deposition potentials crystalline to polycrystalline transition and decreased Te concentration were observed from XRD and EDS analysis, respectively. A maximum Seebeck coefficient of -200μV/K was obtained at 345K for a thin film sample deposited at -150mV.

A novel microreactor with a network of omega-shaped microchannels has been designed, fabricated, and tested for enhanced chemical species mixing and reaction conversion. Fluidic and mixing properties of the omega channel reactor have been investigated by means of computational fluid dynamic (CFD) simulation. Also, a stochastic model describing particle transport in the axial direction was applied to characterize the residence time distribution or the cumulative probability of a particle exiting the microreactor over time. Both fluidic simulation and stochastic model approaches revealed the advantage of the omega-shaped microchannels as compared to straight or zigzag-shaped microchannels. Fischer-Tropsch reactions were carried out using sol-gel encapsulated iron and cobalt catalysts in the omega-shaped microchannels. The experimental results showed that the conversion rate for the omega-shaped microchannels was considerably higher than that for the conventional straight microchannel or for the zigzag-shape...

Inductively coupled plasma (ICP) system has been widely used for anisotropic silicon etching because it offers high aspect ratio with a vertical side wall. The isotropic etching capability of the ICP system, however, has not gained much attention, even though it possesses advantages in profile control and high etching rate over wet isotropic etching or conventional RIE (reactive ion etching). We report here an isotropic dry etching process to release microcantilever beams. Investigations have covered chamber pressure, plasma source power, substrate power, SF6 (sulfur hexafluoride) flow rate relating to Si etching rate, undercutting rate, and isotropic ratio. The SiO2 (silicon dioxide) cantilevers were successfully released from the Si substrate and the optimized silicon etching rate was 9.1µm per minute. The etching profiles were analyzed by scanning electron micrographs (SEM).

A moisture microsensor based on poly(3,4-ethylenedioxythiophene–poly(styrene-sulfonate) (PEDOT–PSS) conductive polymer is developed and presented in this paper. The change in electrical characteristics of the PEDOT–PSS polymer film is used to determine its sensitivity and working mechanism when exposed to different levels of moisture content. The output characteristics, the change in electrical sheet resistance of the PEDOT–PSS film versus the percentage change in relative humidity (%RH), show that the conductivity of the film decreases when it is exposed to increasing levels of moisture content. The moisture sensors thus fabricated based on the PEDOT–PSS thin film were used to detect the gravimetric water content present in highly plastic (CH) soil samples (Buckshot Clay) for geological and geotechnical engineering applications. The Fourier transform infrared spectroscopy (FT-IR) study of the PEDOT–PSS film on a glass substrate showed the incorporation of OH molecules in the film when it was exposed to moisture environment. This incorporation of OH molecules caused the change in resistance of the PEDOT–PSS film when exposed to moisture content. The change in the output resistance of the sensor device was observed to be from 2.5 to 4.0 M ohm when exposed to soil samples with 15–35% change in gravimetric water content.

Ultra-sensitive and selective moisture sensors are needed in various industries for processing control or environmental monitoring. As an outstanding sensor platform, surface-stress sensing microcantilevers have potential application in moisture detection. To enlarge the deflection of the microcantilever under surface stress induced by specific reactions, a new SiO2 microcantilever is developed which features a much lower Young’s modulus than conventional Si or SiNx microcantilevers. For comparing SiO2 cantilever with Si cantilevers, a model of the cantilever sensor is given by using both analysis and simulation, resulting in good agreement with the experimental data. The results demonstrate the SiO2 cantilever can achieve a much higher sensitivity than the Si cantilever. In order to fabricate this device, a new fabrication process using isotropic combined with anisotropic dry etching to release the SiO2 microcantilever beam by ICP (Inductively Coupled Plasma) was developed and investigated. This new process not only obtains a high etch rate at 9.1 μm/min, but also provides good profile controllability, and a flexibility of device design. Attributed to the high sensitivity, a significant deflection amplitude of the surface modified SiO2 microcantilever was observed upon exposure to 1% relative humidity. The SiO2 cantilevers are promising for inexpensive and highly sensitive moisture detection.

This paper presents the design, simulation, fabrication, and characterization of a transmission delay line-based RFID tag. The ID generating circuit is designed based on the transmission delay line concept. A compact, inset-fed triangular patch antenna resonant at 915 MHz frequency is developed for integration with the tag application. The layout of the tag has been realized using conventional photolithography. Tags with a 5- and 10-ns delay ID generation circuits have been tested using input signals of 10-ns width. An OOK (On-Off Keying) modulation technique is employed for characterization of the tag. The received output consists of delayed signal from the tag added to the direct signal from the transmitter. Transmission delay line-based RFID technology can be exploited for low-end commercial applications that has a large market. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1900–1904, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22599

In this paper, a three-dimensional computational model for Atomic Force Microscopy (AFM) based nanoindentation processes is being developed. Molecular Dynamics (MD) and Finite Element (FE) techniques are used to model and simulate mechanical indentation at the nanoscale. The correlation between the indentation conditions, including applied force and tip radius, and defect mechanism in substrate is investigated. The tip geometries used in the model are the same as those used in the experiments. The MD simulations of nanoindentation process are performed on different crystal orientations of single-crystal gold substrate, Au(100), Au(110), and Au(111). In MD simulation, the material deformation is extracted from the final locations of atoms, which are displaced by the rigid indenter. The simulation also allows for the prediction of forces at the interface between the indenter and substrate. In addition to the modeling, an AFM is used to conduct actual indentation at the nanoscale, and provide measurements to which the simulation predictions are compared.Copyright © 2015 by ASME

A layer-by-layer (LbL) self-assembly of poly(3,4-ethylenedioxythiophene)?poly(styrenesulfonate) (PEDOT?PSS) on lignocellulose wood microfibres was used to make conductive fibres and paper. Polycations such as poly(allylamine hydrochloride) (PAH), and poly(ethyleneimine) (PEI) were used in alternate deposition with anionic conductive polythiophene (PEDOT?PSS) to construct the multilayer nanofilms on wood microfibres. Current?voltage characterization was measured on single fibres using a Keithley probe measurement system after deposition of every PEDOT?PSS monolayer to study the electrical properties of the coating. The conductivity of the microfibres increased linearly with increasing number of bilayers of PEDOT?PSS/polycation. The measured conductivities of the coated microfibres ranged from 1 to 10?S?cm?1. It was also observed that the conductivity of the fibres (i.e., coating of PEDOT?PSS) depends upon the type of polycations used to alternate with the polythiophene. In this work we have demonstrated successful scale integration from nano to micro and macroscale (nanocoating?microfibres?macropaper) in developing new paper material. The conductive paper that has been produced (and its fabrication method) can be used for the development of smart paper technology on monitoring of electrical, and optical/electrical signals.

Photodetectors operating in the visible spectrum have been realized using composites of the semiconducting polymer poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and the organic material ethyl viologen dibromide (EVD). Active polymer-organic thin film thicknesses were ∼ 70 nm. The external quantum efficiency of the MEH-PPV/EVD blend photodiodes was found to be twice that of pure MEH-PPV devices. The increase in photoconductivity of blended MEH-PPV/EVD photodiodes may be due to ultra fast charge transfer by EVD dication. The breakdown voltage was dependent on the EVD concentration and ranged between − 12 and − 20 V. Hysteresis behavior was observed in studied devices and could be due to a charge trapping.

In this paper, we use layer-by-layer (LbL) nano-assembly for deposition of ultrathin poly(anilinesulfonic acid) (SPANI) films for fabrication of highly sensitive and rapid response humidity sensors. Spin coating was also used for fabrication of SPANI based humidity sensors for comparison. The change in electrical sheet resistance of the sensing film was monitored as the device was exposed to humidity. For 5% change in relative humidity, the sensitivity was measured to be 11 and 6% from layer-by-layer based and the spin coated humidity sensors, respectively. An intended application for these layer-by-layer assembled devices is in disposable handheld instruments to monitor the presence of humidity in humidity sensitive environments.

Pentacene-based organic thin film transistors have been fabricated with and without the presence of a modifying monolayer at the interface between the silicon dioxide insulator and the organic semiconductor. The monolayer consists of poly(dimethyldiallylammonium chloride) (PDDA), and is deposited by electrostatic self-assembly. The interface modification by the PDDA monolayer has resulted in improved device performance, including 33% higher effective hole mobility, 42% lower threshold voltage, about 50% lower subthreshold slope, and 100% higher on/off ratio. Scanning electron microscopy (SEM) profiles reveal the morphology of pentacene is affected by the insertion of the PDDA monolayer. The presence of this monolayer appears to improve the interface characteristics of the deposited pentacene layer, resulting in better thin film transistors.

Silver tracks for source/drain (S/D) electrodes in low-cost polymer thin film transistors (TFTs) have been realized through inkjet printing technique, using heavily n-doped silicon wafer with thermally grown silicon dioxide as the substrate and poly(3-hexylthiophene) (P3HT) as the channel material. Spin coating a layer of poly-4-vinylphenol (PVPh) onto the substrate was found to enhance the silver track uniformity and lower the cure temperature (from 300 to 210^oC). The surface roughness of the PVPh film was optimized to improve the device performance. The fabricated P3HT TFT with a channel length of [email protected] exhibited a saturation mobility of 3.5x10^-2cm^2/V/s which was three times higher than that obtained in P3HT TFTs with gold S/D electrodes.

This article uses finite element design for optimization of piezoresistive Si covered SiO 2 microcantilevers. The maximum resistance changes were systematically investigated by varying piezoresistor geometries and doping concentration. Our simulation results show that both cantilever deflection displacement andR/R change decrease when the thickness of piezoresistors increases; the highest sensitivity can be obtained when the piezoresistor length is approximately 2/5 of the SiO 2 cantilever length; increase of both Si width and leg width result in decrease in cantilever deflection and sensitivity; the sensitivity of cantilevers with lower doping concentrations is more significant than those with higher doping concentrations. Temperature control is critical for thin piezoresistor in lowering the S/N ratio and increasing the sensitivity. © 2005 Elsevier B.V. All rights reserved.

An all-polymer field-effect transistor (FET) fabricated using an inkjet printing technique is presented in this paper. Poly(3,4-ethylenedioxythiophe), works as the conductivity. Polypyrrole acts as the semiconducting layer. the polymers are diluted with dionized water, and can be printed with a piezoelectric inkjet printing system. The device functions at a depletion mode with low operation voltage. It has a field-effect mobility of 0.1 cm 2 . V -1 . s -1 , an on/off ratio of 29 × 10 3 , and a subthreshold slope of 2.81 V.decade -1 .

The degradation of poly[2-methoxy-5-(2-ethylhexoxy)-1,4-phenylene vinylene] (MEH-PPV), affected by the presence of oxygen and moisture traps, is a major concern in the use of this electroluminescent polymer in light emitting diodes. This paper reports on a novel way of studying presence of oxygen in MEH-PPV through the Metal-Insulator-Semiconductor (MIS) Capacitance–Voltage (C–V) analysis, and the Attenuated Total Reflection Infrared (ATR-IR) spectroscopy technique. The presence of oxygen detected by ATR-IR has also been verified by X-ray photoelectron spectroscopy (XPS). In quasi-static C–V measurements of the MIS (Al/MEH-PPV/p-Si) capacitors made, an extension of the weak inversion region was measured before strong inversion. Moreover, the observed extension in the weak inversion region became more pronounced with aging in ambient environmental conditions. This increase in the weak inversion region is attributed to electron trapping by oxygen to form negative ions in the MEH-PPV layer. An increase in the trapped charge density of MEH-PPV from 1.2×10+11 cm−2 to 1.7×10+11 cm−2 has been observed. ATR-IR spectroscopy shows the formation of carbonyl peak at 1651 cm−1 with aging, which is due to the presence of oxygen. Atomic concentration table from XPS analysis shows the increase in the oxygen concentration of the MEH-PPV polymer with aging, further supporting the ATR-IR results. Both the C–V analysis and ATR-IR spectroscopy are powerful tools for investigating the degradation of MEH-PPV polymer.

Pentacene-based thin film transistors (TFTs) have been fabricated and analyzed to investigate the temperature and electric field dependence of hole mobility. At room temperature, the TFT device characteristics have displayed the hole mobility of 0.26 cm 2 /V s, threshold voltage of −3.5 V, subthreshold slope of 2.5 V/decade, and on/off ratio of 10 5 . Over the temperature range of 300–450 K, the hole mobility is found to increase to a peak value, followed by decrease to very low values. Similar behavior has also been observed in TFTs fabricated at a higher pentacene deposition rate. However, in this case over 20 times reduction in the extracted hole mobility values has been observed, due to the less ordered layered structure of the pentacene film present. No annealing effects have also been observed up to a temperature of about 410 K. The field dependence of hole mobility has also been evaluated at room temperature, and observed to noticeably increase with increase in electric field, over the biasing conditions considered.

Ink-jet printed thin films of conductive polymers such as polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrene sulfonate) and polymer dielectric material poly(4-vinylphenol) (PVP) were used to make RC filters. Both high-pass and low-pass filters were tested. The fabrication process and device characteristics of the RC filters have been demonstrated. Degradation of the ink-jet printed RC filters has been investigated, and the results indicate that PEDOT/PSS RC filters are more stable than those made from PANI.

MEH-PPV (poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene]) based Schottky diodes have been fabricated and investigated through the analyses of current density-voltage and capacitance-voltage characteristics. Temperature-dependent hole mobility of MEH-PPV is extracted by the space-charge limited conduction (SCLC) model from 300 to 400 K, and the use of the SCLC model is examined in high electric field. The highest measured hole mobility is 0.013 cm2/Vs at 353 K. The thickness of MEH-PPV in the structures consisting of ITO/MEH-PPV/Al, largely affects the performance of the diodes, and the thinner film displays better device performance. According to capacitance-voltage relations, the effective carrier density and Schottky barrier height of MEH-PPV have been determined to be 2.24×1017 cm-3 and 0.64 eV, respectively.

A new polymer microlens with variable focusing properties is designed and fabricated. The microlens consists of a thin diaphragm with 3D convex lens, chamber and microchannel, which are made of polydimethyl-siloxane (PDMS). A novel fabrication approach has been developed to cast the PDMS microlens film using a PDMS mold. The elastomeric PDMS microlens film acts as a diaphragm. The flexible PDMS microlens and diaphragm are integrated on a microfluidic chip. By varying the pressure in the microfluidic chamber, which produces a shift in the microlens' focal plane, this can change the back focal length of lens. The new fabrication method provides easy fabrication, low-cost production and precise dimension control. Measurement with an atomic force microscope reveals that the surface roughness of the lens is 18.6 nm, and real-time contact-angle measurements show the back focus length tuning range is from 3.8 mm to 10.6 mm. The variable focal length of the microlens is critical to increase the efficiency of the light detection in optical or biophotonic applications. In this paper, the fabrication processing, mechanical and optical property testing, and simulation results are presented in detail.

An n-type organic material, 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA), was successfully deposited and patterned on a SiO2/Si wafer by the ink-jet printing technique. Dimethylformamide (DMF) was selected as the solvent in the processing of the ink-jet solution, NTCDA. After thermal annealing, the NTCDA thin film showed higher conductivity than the NTCDA thin film deposited by vacuum sublimation. Degradation of conductivity with time was found when the thin film was open to an ambient atmosphere.

The depletion-mode n-channel organic field-effect transistors (OFETs) based on naphthalene-tetracarboxylic-dianhydride (NTCDA) were fabricated and characterized. Electrical characteristics of the OFETs were demonstrated and analyzed under the depletion-mode operation. The mobility of NTCDA is about 0.016 cm2 V−1 s−1. The threshold voltage is −32 V, and cut off current is 1.76 nA. The on/off ratio extracted from transfer characteristics at saturation region (Vds=60 V) is 2.25 × 102.

All-polymer capacitors have been fabricated only by the inkjet printing technique. A conductive polymer, poly(3,4-ethylenedioxythiophene), has been employed as the electrode material of the capacitor. A precursor-route polyimide was applied as the insulator of the device. The fabrication process of the inkjet printed all-polymer capacitor has been demonstrated. The electrical characteristics of the polymer capacitor, analogous to that of the common parallel plate capacitor, are discussed in detail. The all-polymer capacitor has been applied to the polymer RC filter circuits. The characteristics of the inkjet printed polymer RC filter are also demonstrated.

Polymer materials are attracting more and more attentions for applications to microelectronic devices due to their flexibility, lightweight, and low cost. In this paper, fabrication and characteristics of an all-polymer capacitor, using polypyrrole and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) as a semiconductor and a gate layer, are reported. Dielectric polymer, polyvinylphenol, was applied as the insulator to the device. The all-polymer capacitor analogous to metal oxide semiconductor (MOS) device was fabricated by the conventional UV lithography techniques. The fabricated device was measured and characterized electrically. The results are compared with the electrical behavior of analogous silicon-based MOS devices. It demonstrates that the device operates in a very similar fashion to its conventional counterparts.

Organic field-effect transistors (OFETs) have been fabricated by the simple and low-cost fabrication processes of spin coating and reactive ion etching (RIE) with poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) as the p-type semiconductor, poly(4-vinylphenol) as the gate dielectric layer, and polypyrrole (PPy) as the electrodes of gate, source, and drain. The dielectric, semiconductor, gate, and source/drain layers are deposited by low-cost spin coating and patterned with the RIE technique using an aluminum thin film as the mask. The electrical characteristics of the device and the influence of PPy on the device performance have been investigated by comparing two types of OFETs with different gates, PPy as one gate and low-resistivity silicon as the other gate in an ambient atmosphere at room temperature. The OFET with PPy as the gate has a field-effect mobility of 0.58 /spl times/ 10/sup -4/ cm/sup 2//V/spl middot/s with threshold voltage of -13.3 V and subthreshold slope of 6.77 V/decade.

All-polymer RC filter circuits by all-inkjet printing technology are fabricated for the first time. Conductive polymers such as polyaniline and poly(3, 4-ethylenedioxythiophene) have been used as the electrode material of the capacitor as well as the resistor material. The fabrication process and the characteristics of the printed capacitor and RC filter have been demonstrated. Simulation of the printed RC circuit has been demonstrated and compared with the experimental measurement results. A detail discussion has been given about the all-polymer capacitor and RC filter.