Non-contact Mode Research Articles

Triboelectric Touch‐Free Screen Sensor for Noncontact Gesture Recognizing

AbstractAn intelligent human–machine interface (HMI) is a crucial medium for exchanging information between people and electronics. As one of the most important HMI devices, touch screen sensors are widely applied in personal electronics in daily life. However, as the most commonly used touch screen sensor, capacitive sensors can only detect limited kinds of gestures such as touching and sliding. Here, a triboelectric touch‐free screen sensor (TSS) is reported for recognizing diverse gestures in a noncontact operating mode by utilizing the charges naturally carried on the human body. Compared with conventional capacitive sensors, the TSS is capable of detecting various gestures such as the drop and lift of finger with different speeds, making a fist, opening palm, and flipping palm with different directions. Based on the TSS, an intelligent noncontact screen control system is further developed, which is used to unlock the smartphone interface by the noncontact operating mode. This research for the first time proposes the concept that taking the human body itself to participate in triboelectric self‐powered noncontact sensing and provides a touch‐free design concept to develop the next generation of screen sensors. It can alter the usual way that people operating their personal electronics.

Non-Destructive Characterization of Railway Materials and Components with Infrared Thermography Technique.

Infrared (IR) thermography technology is one of the leading non-destructive evaluation (NDE) techniques based on infrared detection. Infrared thermography, in particular, has the advantage of not only being used in non-contact mode but also provides full images, real-time inspection, and relatively fast results. These advantages make it possible to perform thermal imaging analysis of railway materials and/or components, such as brake disc simulation, monitoring of abnormal heat generation, and monitoring of temperature changes, during mechanical tests. This study introduces the current state of research on railway materials and/or components using IR thermography technology. An attempt was made to characterize the deterioration of electrical equipment of diesel electric locomotives using infrared thermal imaging techniques. In addition, surface temperature monitoring was performed during tensile testing of railway steels using a high-speed infrared camera. Damage evolution due to the hot spot generation of railway brake discs was successfully monitored using high-speed IR cameras. In this paper, IR thermal imaging technology, used as a non-destructive evaluation analysis in the railway field, was introduced, and the results of recent research are presented.

Programmable Ultralight Magnets via Orientational Arrangement of Ferromagnetic Nanoparticles within Aerogel Hosts

The actuation and levitation of air-suspended objects by a magnetic field, due to its noncontact and holonomic manipulation modes, are important technological capabilities for device applications. However, owing to a higher density of conventional ferromagnets or nanoparticle-containing polymers and strong magnetic fields required for actuation, fabricating lightweight materials with a sensitive magnetic response for weight critical applications is challenging. Here, we report ultralight aerogel-based magnets (aero-magnets) comprising assembled ferromagnetic nanomaterials with highly magnetic anisotropy where the magnetic domains can be programmed by external predesigned fields. To demonstrate the breadth of manufacturing methods for this breed of aero-magnet composites, both silica/nanocellulose aerogel hosts and ferromagnetic nanorod/nanoplatelet guests have been explored. Single and double domains with out-of-plane magnetization are programmed into the aero-magnets and characterized by magnetic force microscopy. The levitation and actuation of the aero-magnets are realized while exposed to a small external magnetic field of 11 mT and introduced to a switching circuit. Furthermore, the elastic moduli of the aero-magnets are estimated by dynamic magnetic responses of the ferromagnetic nanoparticles tightly tethered in the aerogel hosts under rapid cyclic fields. These programmable aero-magnets could serve as monolithic magnetic actuator units in the fields of tiny robots and aerospace components.

Piezoelectric displacement mapping of compliant surfaces by constant-excitation frequency-modulation piezoresponse force microscopy

A simple experimental method for piezoresponse force microscopy (PFM) measurements for reliable evaluation of piezoelectric surface displacements even on compliant surfaces is proposed based on atomic force microscopy (AFM) operated in frequency-modulation (FM) dynamic mode with constant excitation (CE), by using non-contact mode cantilevers. Surface displacement by piezoelectric effect after application of an electric potential to the conductive AFM probe translates into a likewise variation of the probe oscillation amplitude, while the related electrostatic forces mainly affect the oscillator resonant frequency, and cantilever bending is limited due to their high stiffness. Our non-contact CE-FM-PFM method is shown to reduce electrostatic force contributions as compared to contact-PFM modes. Converse piezoelectric effect mapping is demonstrated on poly(vinylidenefluoride) nanofibers obtained by electrospinning.

Tip-based electron beam induced deposition using active cantilevers

Tip-based electron beam induced deposition is performed using field emission of low-energy electrons from the tip of an active (i.e., self-sensing and self-actuating) atomic force microscope cantilever inside a scanning electron microscope. By using the active cantilever for feature placement and metrology combined with fast switching between field-emission and noncontact imaging mode, high placement accuracy and time-efficient, precise 3D measurement of the deposits are enabled. First results on the effect of electron energy and exposure dose on the growth rates and dimensions of the deposits are presented, and the potential to increase spatial resolution due to the enhanced localization of the dissociation reactions induced by the low-energy electrons is discussed.

Investigation of the axial load effect on the vibration and topography of the AFM oblique four-layered piezoelectric micro-cantilever

In this paper, the vibration behavior of atomic force microscopy (AFM) micro-cantilever (MC) with a piezoelectric layer in the non-contact mode considering the axial load in the air medium was studied. In the dynamic modes of AFM nano-robot, parameters such as amplitude, frequency and motion phase are used as feedback factors in the control system in order to extract sample surface information and the nanoparticle voltage. Consequently, to extract these parameters, the vibration analysis of the MCs of this nano-robot is essential. Additionally, because of the wide-spread applications of oblique MCs, applying the axial and transverse forces into the model is absolutely necessary. In order to simulate the AFM four-layered piezoelectric MC with the axial displacement, Timoshenko beam theory as well as modified couple stress theory has been used. Considering the axial displacement in the modeling not only leads to more degrees of freedom, but also has increased the amount of calculations. To extract the equations of the system, energy method has been used, and then, the FEM was applied to discrete the equations. To verify the accuracy of the results, the frequency and time responses of FEM have been compared with the results of the 3D mode simulation obtained by COMSOL software and experimental results. The comparison of results indicates that modifying the modeling by considering the axial displacement has increased the accuracy of the frequency and time responses. The error percentage of the first frequency response is 0.42% and the error percentage of the time response is 0.0053%. Furthermore, to examine the effect of MC geometry on its vibrational behavior, frequency and time responses of three common geometries of AFM MCs have been extracted. The results illustrate the improvement of modeling in all three geometries. Then, the sample surface topography of MCs at the first and second excitation frequencies in contact with rectangular roughnesses demonstrated the decline of time delay at the second excitation frequency. The results of the topography simulation in the air environment show that the roughness’s trend is better at the second mode than at the first mode. Finally, the effect of MC angle on the topography of the rectangular MC surfaces in contact with the rectangular roughness in 2D and 3D modes was examined in the presence and the absence of axial load. The results show that in the presence of the axial displacement in modeling, by increasing of MC angle, the topography quality increases drastically.

Caries removal with Er:YAG laser followed by dentin biomodification with carbodiimide and chitosan: Wettability and surface morphology analysis.

This study aimed to investigate dentin wettability and surface morphology after selective removal of carious lesion by erbium-doped yttrium aluminum garnet (Er:YAG) laser, followed by dentin biomodification with carbodiimide (EDC) and chitosan (CHI). Seventy-eight bovine dentin specimens were submitted to caries induction. Specimens were distributed according to methods of carious removal (n = 39): bur at low-speed (40,000 rpm) or Er:YAG laser (noncontact mode, 250 mJ/pulse and 4Hz). All specimens were etched with 35% phosphoric acid, and subdivided according to dentin biomodification (n = 13): Control (no biomodification), EDC or CHI. The contact angle (n = 10) between adhesive system (3M ESPE) and dentin surface was measured by a goniometer. Eighteen specimens (n = 3) were analyzed by scanning electron microscopy. Data were analyzed by two-way ANOVA and Tukey's test (α = .05). The method used to remove carious lesion did not influence the wettability of dentinal surface (p = .748). The angles produced on the remaining dentin after biomodification were influenced (p = .007). CHI promoted higher contact angles (p = .007) and EDC did not differ from the control group (p = .586). In the bur-treated group, most tubules were open, regardless of which biomodifier was used. Laser modified the organic matrix layer. CHI promoted partially closed tubules in some areas while EDC exposed dentinal tubules. Regardless of which method was used for selective removal of carious lesion, biomodification with EDC did not affect the dentin wettability, whereas CHI changed the wettability of remaining dentin. Both biomodifiers promoted a slight change on dentin morphology.

Investigation of a He micro plasma-jet utilized for treatment of prostate cancer cells

Present study investigated the applicability of the macro-kinetic description for RONS production by an atmospheric pressure micro-plasma jet operated in He gas flow. The concentrations of H2O2, NO2− and NO3− in the deionized water were measured using UV absorption spectroscopy. The contact and non-contact modes were identified and the concentrations of H2O2, NO2− and NO3− were higher in the contact mode. In the contact mode the concentrations of H2O2 and NO3− increased with the applied voltage and treatment duration while He flow rate also influenced the concentrations. The production rates of H2O2 and NO3− correlated with the amount of transferred charge of ionization waves during positive half period. The dependence of the production rates of RONS on the He flow rate suggests that the gas flow influences the gas composition in active discharge zone and limits the applicability of macro-kinetic model with the used plasma jet setup. As a potential application the plasma treated water was applied to prostate cancer cells. The viability of prostate cancer cell decreased linearly with the increase of H2O2 and NO3− concentrations while the NO2− concentration had no clear correlation with cell viability. The H2O2 was found to be the main agent responsible for the decreased cell viability. The amount of dissolved NO3− on the other hand determined the pH of the plasma treated water.

Evaluation of the Effects of Er:YAG Laser for the De-Epithelialization of the Palatal Graft in the Treatment of Multiple Gingival Recessions: A Randomized Clinical Trial.

Objective: The purposes of this split-mouth pilot study were to investigate the efficacy of the Er:YAG laser use for the de-epithelialization of the palatal graft in the treatment of the multiple gingival recessions using the bilaminar procedure and also to evaluate the patient-reported esthetic outcomes after 6 months. Materials and methods: Five systemically healthy participants with total 28 bilateral-multiple adjacent maxillary Miller I recessions were included. The treatment was performed with the bilaminar technique [coronally advanced flap (CAF)+de-epithelialized free gingival graft]. De-epithelialization procedure was done with scalpel (control site) or Er:YAG laser (Versawave, Hoya ConBio, San Francisco, CA; 40 hz, 50 mJ/pulse), under water irrigation, noncontact mode (∼1 mm away from the target tissue) in sweeping motion with chisel-type laser (test site). Root coverage and patient-reported outcomes were evaluated at 6 months after the operations. Results: Clinical outcomes of the both treatment sites did not show any statistically significant differences except for the gingival thickness parameter. However, patient-reported outcomes regarding the esthetic appearance of the gingiva was detected in favor of the Er:YAG laser applied sites. Conclusions: Within the limits of the study, it can be concluded that both de-epithelialization techniques were highly effective at 6 months. However, Er:YAG laser-applied grafted sites revealed more uniform and esthetic gingival appearance compared with scalpel-used grafted sites.

Height determination of single-layer graphene on mica at controlled humidity using atomic force microscopy

Identifying the thickness of the first graphene layer on a substrate is important in graphene-based nanoelectromechanical systems because of the dependence of graphene layers on physical and chemical properties. Identifying the thickness of the first layer is important for determining the number of graphene layers. Herein, we report that the height of single-layer graphene on mica is influenced by the relative humidity in the observation environment and by the scanning modes of in situ atomic force microscopy (AFM). We found that the graphene height is quite dependent on the scan direction of the AFM probe when in the contact mode, while this hysteresis is absent in tapping and noncontact modes. In addition, at low humidity (<10%), the height of the graphene on mica corresponds to the van der Waals distance (∼0.34 nm) of graphite layers, while an increased height (0.67 nm) is observed at higher humidity (≥20%). We associate the variation of the graphene height in the contact mode with different levels of tilting of the cantilever that are clearly dependent on the scanning direction. These results suggest a standard for determining graphene thickness in humid air that is a critical factor for graphene-based electronic devices.

Q-Switch Nd:YAG Laser-Assisted Decontamination of Implant Surface.

Peri-implantitis (PI) is an inflammatory disease of peri-implant tissues, it represents the most frequent complication of dental implants. Evidence revealed that microorganisms play the chief role in causing PI. The purpose of our study is to evaluate the cleaning of contaminated dental implant surfaces by means of the Q-switch Nd:YAG (Neodymium-doped Yttrium Aluminum Garnet) laser and an increase in temperature at lased implant surfaces during the cleaning process. Seventy-eight implants (titanium grade 4) were used (Euroteknika, Sallanches, France). Thirty-six sterile implants and forty-two contaminated implants were collected from failed clinical implants for different reasons, independent from the study. Thirty-six contaminated implants were partially irradiated by Q-switch Nd:YAG laser (1064 nm). Six other contaminated implants were used for temperature rise evaluation. All laser irradiations were calibrated by means of a powermetter in order to evaluate the effective delivered energy. The irradiation conditions delivered per pulse on the target were effectively: energy density per pulse of 0.597 J/cm2, pick powers density of 56 mW/cm2, 270 mW per pulse with a spot diameter of 2.4 mm, and with repetition rate of 10 Hz for pulse duration of 6 ns. Irradiation was performed during a total time of 2 s in a non-contact mode at a distance of 0.5 mm from implant surfaces. The parameters were chosen according to the results of a theoretical modeling calculation of the Nd:YAG laser fluency on implant surface. Evaluation of contaminants removal showed that the cleaning of the irradiated implant surfaces was statistically similar to those of sterile implants (p-value ≤ 0.05). SEM analysis confirmed that our parameters did not alter the lased surfaces. The increase in temperature generated at lased implant surfaces during cleaning was below 1 °C. According to our findings, Q-switch Nd:YAG laser with short pulse duration in nanoseconds is able to significantly clean contaminated implant surfaces. Irradiation parameters used in our study can be considered safe for periodontal tissue.

Virtual non-contact atomic force microscope

In this paper, the virtual atomic force microscope (AFM) is constructed on the basis of the component models to simulate the conventional and high-speed AFMs. A room temperature conventional AFM with its standard control system is used as a reference. The virtual machine operates in non-contact mode (NC-AFM). The cantilever is oscillated at or near its natural frequency with the amplitude of l nm to 100 nm above the sample. The tip-sample interaction changes the amplitude, frequency, and phase of oscillation. In amplitude modulated-AFM (AM-AFM), by measuring the tip vibration and extracting its amplitude, the control system actuates the piezo-scanner to achieve the amplitude setpoint. By defining a proper cost function, here settling time, optimum gain parameters for the control system are obtained by the particle swarm optimization algorithm, PSO. Simulations are performed in two steps: when only the Z-directional movement of the XYZ stage is considered and when raster motion is considered. The performance of the new AFM is compared with a conventional AFM via simulations.

Calculating electrostatic interactions in atomic force microscopy with semiconductor samples

Electrostatic interactions are important in non-contact atomic force microscopy (AFM) measurement. Previous reports had focused on the calculation of electrostatic interactions in AFM with metal and dielectric samples, and the present work extended the discussion to semiconductor samples based on Green’s function theory and Debye-Hückel theory, considering sample dielectric polarization and free carriers at the same time. In order to enhance the calculation efficiency, an equivalent charge method was implemented and developed with a linear algebra-based algorithm. The calculation results of two limiting cases, metal and dielectric limit with infinite and zero carrier concentrations respectively, were in good agreement with the boundary element method. For a finite carrier concentration, it is found that the electrostatic force on the tip cone is quickly saturated whereas that on the tip apex slowly increases as the carrier concentration increases. On the other hand, the interaction radius on the sample surface is found independent of the sample free carriers, but it linearly increases as the tip-sample distance. Our work can be useful for the carrier concentration detection of semiconductor samples using non-contact electrical AFM modes such as Kelvin probe force microscopy and electrostatic force microscopy.

Blank roasting and bioleaching of stone coal for vanadium recycling

Abstract The recovery and utilization of vanadium from stone coal is of great significance because it is an important metal. In the present study, a cleaner metal extraction method to recover vanadium from low-grade stone coal using a novel strain of Bacillus mucilaginosus (BM) and an enhanced bioleaching procedure was explored. The efficient leaching bacteria of BM-5070 were obtained by the atmospheric and room temperature plasma (ARTP)-hydroxylamine hydrochloride compound mutagenesis technique. The results show that BM-5070 had the highest V leaching rate. After a 20-day bioleaching period, the V leaching rate of BM-5070 was 5.5 percentage points higher than that of the original bacteria. Moreover, the pretreatment of stone coal by blank roasting without any additives can further promote the vanadium dissolution, and the V leaching rate reached 85% after bioleaching for 20 days, which was 57 percentage points higher than that of without roasting. This is due to the decrease in the content of V (III) and the increase in the V (V) and V (IV) content after blank roasting, which is beneficial to the leaching of vanadium. The bioleaching behavior was elucidated through the bacteria-mineral contact leaching and non-contact leaching test. The results show that the V leaching rate (81.0%) in the contact mode was much higher than that in the non-contact leaching mode (64.4%), indicating that the bioleaching of vanadium occurs with direct action and indirect action. The results of our study could significantly contribute to a green method for recovering vanadium from stone coal.

Exploiting the aiming beam to increase the safety of laser lithotripsy: Experimental evaluation of light reflection and fluorescence.

In Holmium laser lithotripsy, usually, the surgeon is guided by a visible beam superimposing the infrared (IR) treatment radiation. It has been shown that a green aiming beam excites stone autofluorescence. This fluorescence signal can be used for calculi detection to check the correct fiber position before triggering the IR laser, thus preventing damage to soft tissue and application devices. However, also the directly reflected green light from the fiber tip gives valuable information on fiber position and its surface condition. An external fiber-fiber-coupling-box (fiber core diameter 365 µm) for pulsed holmium laser radiation (2.1 µm) was set up containing a green diode laser module (520 nm, average power on the sample <0.5 mW) and optics and detectors for measuring the reflected light of this aiming beam as well as the fluorescence excited with it. Measurements were done via a lock-in technique with more than 20 human calculi samples and porcine calix in vitro. After the implementation of automatic data storage signals during ongoing in vitro lithotripsy procedures were recorded with the fiber positioned on tissue, stone, or in/on medical equipment (working channel of an endoscope, stone retrieval basket). Stone fluorescence signals measured were a factor of 7 to >100 higher than those of tissue. Stone fluorescence was detectable in "non-contact mode" with a linear signal decrease over a distance up to ~1 mm in front of the fiber tip (core diameter 365 µm) and with severely damaged fibers (max. decrease: 75% with pinched off fiber). Reflection signals of the fiber tip surface in air and water surrounding decreased significantly when the fiber was damaged; measured ratios of intact to damaged fiber found in the air were (5-17):1 and in water (1.6-3.7):1. Surfaces in front of the fiber aggravated the evaluation of fiber condition due to reflections but enabled to detect, for example, the working channel of a flexible endoscope in combination with the (missing) fluorescence signal. Autofluorescence induced by a green aiming beam can be exploited for stone detection in laser lithotripsy. A reflection measurement can give further information on fiber condition and position. Implementing this kind of safety features for an automatic block of IR laser emission in case of weak or missing fluorescence and un-normal reflections can assist the surgeon by avoiding tissue perforation, and damage to medical devices such as endoscopes. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Fabrication of flexible organic electronic microcircuit pattern using near-field electrohydrodynamic direct-writing method

Inorganic materials face enormous challenges in designing and processing flexible devices that can be stretchable, crimped and folded. Organic materials have attracted wide attention because of their flexible properties and advantages in manufacturing flexible electronic devices. In this study, the flexible organic microcircuit pattern of poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) material was fabricated by using the near-field electrohydrodynamic direct -writing method, the experimental results show that the bending deformation of the flexible substrate with different curvatures has no effect on the conductivity of the microcircuit pattern deposited on the flexible substrate, which has no effect on the performance of the flexible microcircuit pattern. In order to improve the conductivity of the flexible organic electronic microcircuit, the multi-layer microcircuit pattern was fabricated by using the near-field electrohydrodynamic direct-writing method. With the increase of the number of the direct-writing micro-pattern layer, the conductivity of the microcircuit patterns sintered at 105 °C for 10 min increase from 168.32 to 313.05 S/cm. Atomic force microscope was used to observe the morphology of the direct-writing microcircuit patterns. With the increase of the layer number of the microcircuit pattern, the internal density of the microcircuit pattern increases, and the microcircuit-pattern morphology becomes smoother. The experimental results show that the multi-layer direct- writing method can effectively improve the conductivity of the flexible organic electronic microcircuit pattern. This study provides a new method to fabricate the flexible organic microcircuit pattern with high conductivity by a non-contact and low-cost mode.

The Adhesion and Removal Mechanism of Ceria Particles for STI Post-CMP Cleaning Process

Chemical mechanical planarization (CMP) is an essential step to remove overburden oxide surface and form STI (Shallow Trench Isolation) structures during the semiconductor manufacturing. This is usually carried out with ceria slurry due to high selectivity between oxide and nitride surfaces. However, strong ceria adhesion to oxide surface is a major concern, as it cannot be removed easily during the post-CMP cleaning step. Generally, it is performed by a combination of physical and chemical cleaning. Conventional cleaning solutions such as DHF (Dilute Hydrogen Fluoride), SC1(NH4OH: H2O2: H2O mixture), SPM (H2SO4:H2O2 mixture) solutions are used with optimized concentrations and sequences with the support of physical forces such as PVA brush scrubbing or megasonic. However, the adhesion and removal mechanism of ceria particles from the oxide surface is not clear yet. The ceria particles would attach to the oxide to the surface may be due to electrostatic interaction or valence (Ce3+/Ce4+) effect or chemical bonding linkage of Ce-O-Si. These interactions are strongly affected and changed based on the pH of ceria used for polishing. In this work, it was emphasized to identify the specific individual mechanisms of physical cleaning and chemical cleaning in removing ceria particles from the oxide surface. Two types of physical cleanings, one is the non-contact mode (megasonic) cleaning and another one is contact mode (PVA brush) cleaning, were performed. The effect of different chemicals on removing the ceria particles was also performed. The key mechanism for the ceria particle cleaning was hypothesized. TEOS coupons (4´4 cm) were polished with ceria slurry (100nm) of pH 4 and 8, containing no additives. The optimization of physical cleaning experiments, performed with only DIW, was carried out with a single wafer megasonic cleaning (Akrion, 0.83MHz) and brush cleaning tool (lab designed pin type brush). Chemical cleaning was performed with various chemistries (SC1, DHF, SPM) to compare and understand the ceria removal performance from the oxide surface. The particles before and after cleaning were observed by FESEM and optical microscopy. To understand chemical interactions, the polished samples were analyzed for XPS, ATR FTIR, and Raman analysis before and after cleaning. The type of chemical interactions before cleaning and their modifications with the type of chemistry used were discussed. The comparative study of physical cleaning (megasonic vs. brush) were performed for the removal of ceria particles attached to the surface after polishing with slurries of pH 4 and 8. It was observed that the polished oxide surface was more contaminated with ceria in the pH 8 than in pH 4. Megasonic cleaning was able to remove partially, whereas brush scrubbing removed completely for pH 4 samples. However, the ceria particles from pH 8 samples were strongly attached not removed by megasonic and partially removed by brush cleanings. It could be expected that particles would attach electrostatically at pH 4, whereas chemically through Ce-O-Si bond at pH 8. It may be necessary to use chemical forces to break the chemical bonds between ceria-silica. It was suspected that the change of valence of ceria before and after cleaning with cleaning chemistries also would play a key role. Hence different chemistries were used to check the removability of ceria. The samples before and after cleaning were analyzed with different techniques to understand the chemical forces required to break the ceria-silica bonding. Detailed hypothesis for the ceria removal was explained by their chemical interactions with different chemistries.

Biocompatibility and surface properties of hydrogenated amorphous silicon-germanium thin films prepared by LF-PECVD

We studied the surface morphology and biocompatibility of hydrogenated amorphous silicon-germanium (a-Si1-xGex:H) thin films prepared by Low Frequency Plasma Enhanced Chemical Vapor Deposition (LF-PECVD). These films were deposited on a Corning 2947 glass substrate having a thickness of 3 μm, the electrical performance showed a decreased electrical resistance for low regime voltage. The root mean square (RMS) surface roughness of the films was measured by atomic force microscopy (AFM) in a non-contact mode. A biocompatibility tests was carried out using primary cultures of dorsal root ganglion (DRG) of Wistar rats. The DRG neurons were incubated for 18 hours on a-Si1-xGex:H thin films, and subsequent electrophysiological recording was performed. These neurons displayed typical ionic currents, including a fast-inward current at the beginning of voltage clamp pulse (Na+ current) and ensuing outward currents (K+ current). In current clamp experiments, depolarizing current pulse injection caused typical action potential discharge of the neurons. These results confirmed the feasibility of using a-Si1-xGex:H thin films as a biocompatible material.

Alignment of polymer dispersed nanometric films of ferroelectric liquid crystalline molecules

Composite films of polyvinyl alcohol dispersed in ferroelectric liquid crystal (FLC) matrix are fabricated by using Langmuir–Blodgett technique. Pressure–area isotherms show that the composite system formed well aligned monolayer as compared to undoped FLC. Due to molecular interactions, monolayers and multilayers possess good spreading properties and we are able to transfer them onto solid substrates from air-liquid interface. FTIR spectroscopy was used to examine presence of all transferred functional groups on substrate. X-Ray spectrum indicates that even due to presence of PVA in FLC matrix, smectic layer ordering of FLC molecules remains unaltered. During non-contact mode of atomic force microscopy, dense and well aligned homogenous pattern is observed in scanned images.

Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation.

Controlling the work function of transition metal oxides is of key importance with regard to future energy production and storage. As the majority of applications involve the use of heterostructures, the most suitable characterization technique is Kelvin probe force microscopy (KPFM), which provides excellent energetic and lateral resolution. In this paper, we demonstrate precise characterization of the work function using the example of artificially formed crystalline titanium monoxide (TiO) nanowires on strontium titanate (SrTiO3) surfaces, providing a sharp atomic interface. The measured value of 3.31(21) eV is the first experimental work function evidence for a cubic TiO phase, where significant variations among the different crystallographic facets were also observed. Despite the remarkable height of the TiO nanowires, KPFM was implemented to achieve a high lateral resolution of 15 nm, which is close to the topographical limit. In this study, we also show the unique possibility of obtaining work function and conductivity maps on the same area by combining noncontact and contact modes of atomic force microscopy (AFM). As most of the real applications require ambient operating conditions, we have additionally checked the impact of air venting on the work function of the TiO/SrTiO3(100) heterostructure, proving that surface reoxidation occurs and results in a work function increase of 0.9 eV and 0.6 eV for SrTiO3 and TiO, respectively. Additionally, the influence of adsorbed surface species was estimated to contribute 0.4 eV and 0.2 eV to the work function of both structures. The presented method employing KPFM and local conductivity AFM for the characterization of the work function of transition metal oxides may help in understanding the impact of reduction and oxidation on electronic properties, which is of high importance in the development of effective sensing and catalytic devices.