Significant Change In Capacitance Research Articles

Pneumatic Bellow Actuator with Embedded Sensor Using Conductive Carbon Grease.

The present work demonstrates the manufacturing process of a pneumatic bellow actuator with an embedded sensor, utilizing a novel manufacturing approach through the complete use of additive manufacturing techniques, such as direct ink writing (DIW) and traditional fused deposition modeling (FDM) methods. This study is innovative in its integration of a dielectric electroactive polymer (DEAP) structure with sensing electrodes made of conductive carbon grease (CCG), showcasing a unique application of a 3D-printed DEAP with CCG electrodes for combined DEAP sensing and pneumatic actuation. Initial experiments, supported by computational simulations, evaluated the distinct functionality of the DEAP sensor by itself under various pressure conditions. The findings revealed a significant change in capacitance with applied pressure, validating the sensor's performance. After sensor validation, an additive manufacturing process for embedding the DEAP structure into a soft pneumatic actuator was created, exhibiting the system's capability for dual sensing and actuation, as the embedded sensor effectively responded to applied actuation pressure. This dual functionality represents an advancement in soft actuators, especially in applications that require integrated and responsive actuation and sensing capabilities. This work also represents a preliminary step in the development of a 3D-printed dual-modality actuator (pneumatic and electrically activated DEAP) with embedded sensing.

Post-service analysis of the degradation and protective mechanisms of chromate-based structural aircraft coatings

The substitution of chromate-containing structural coating systems in aviation with alternatives complying with nowadays strict environmental, health and safety regulations remains a formidable challenge. This complexity is partly due to the absence of a standardized from-test-to-market methodology, including a performance comparison between chromate-containing and alternative coating systems. To address this gap, the present study delves into the identification of crucial degradation factors that merit inclusion in such a methodology. Concurrently, it investigates the protective mechanisms inherent in chromate-containing coating systems and proposes improvements that can be applied to alternative coating systems. This study entails a comprehensive post-service examination of the degradation of paint applied to an aircraft component with over 35 years of service, employing electrochemical, microscopic and spectroscopic techniques. The findings underscore the role of thermo-oxidation as a significant degradation factor in the aging process of such coatings. Furthermore, the investigation elucidates a notable phenomenon in which aluminium ions within the coating pores form an aluminium hydroxide gel onto which chromate adsorbs. This process contributes to an increase in pore resistance upon exposure to electrolyte, leading to a self-healing barrier effect within the coating. Remarkably, this self-healing mechanism continues to offer long-term protection even when the coating matrix is sub-optimally cured due to application errors. Furthermore, this study reveals that the significant changes in capacitance during immersion testing result primarily from inhibitor leaching, emphasizing the effectiveness of combining Electrochemical Impedance Spectroscopy (EIS) with Scanning Electron Microscopy (SEM) analysis for studying coating degradation.

Study of adsorption of household gas molecules on electrophysical properties of porous silicon

Purpose. This research comprehensively investigates the adsorption of household gas molecules on porous silicon surfaces and its impact on the electrophysical properties of the material. The primary aim is to understand how the adsorption process influences the electrical conductivity and capacitance of porous silicon. Methodology. The study employs various electrophysical analysis methods to measure changes in the material's conductivity and capacitance caused by gas adsorption. Furthermore, the research explores optimal conditions for detecting household gas and establishes the correlation between the degree of adsorption and alterations in electrophysical parameters. Originality. The research contributes novelty by not only revealing increased conductivity due to adsorption but also significant changes in capacitance, providing a foundation for developing efficient gas sensors. Additionally, the article discusses the potential applications of porous silicon in developing novel materials for gas sensors to detect various airborne pollutants. Results. In addition to the previously mentioned findings, the article highlights the results of experiments studying the influence of different concentrations of household gas on the electrophysical characteristics of porous silicon. This insight refines optimal parameters for the effective detection of gas pollutants. The research also discusses the applicability of the results in producing environmentally friendly and highly efficient sensor systems. Practical Value. The obtained conclusions deepen our understanding of the interaction between porous silicon and household gas, crucial for advancing gas sensor technologies. The study opens broad possibilities for applying porous silicon in highly sensitive and reliable gas sensors for diverse practical applications, including safety monitoring and air quality control in industrial and domestic settings. The practical implications extend to the development of real-time, eco-friendly sensor systems.

Carbon Nanotube Matrix for Highly Sensitive Biosensors To Detect Pancreatic Cancer Biomarker CA19-9.

Biosensors fabricated with nanomaterials promise faster, cheaper, and more efficient alternatives to traditional, often bulky devices for early cancer diagnosis. In this study, we fabricated a thin film sensing unit on interdigitated gold electrodes combining polyethyleneimine and carbon nanotubes in a layer by layer fashion, onto which antibodies anti-CA19-9 were adsorbed with a supporting layer of N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide solution. By use of impedance spectroscopy, the pancreatic cancer biomarker CA19-9 was detected in a buffer with limit of detection of 0.35 U/mL. This high sensitivity allowed for distinction between samples of blood serum from patients with distinct probabilities to develop pancreatic cancer. The selectivity of the biosensor was confirmed in subsidiary experiments with HT-29 and SW-620 cell lines and possible interferents, e.g., p53 protein, ascorbic acid, and glucose, where significant changes in capacitance could only be measured with HT-29 that contained the CA19-9 biomarker. Chemisorption of CA19-9 molecules onto the layer of anti-CA19-9 antibodies was the mechanism responsible for sensing while electrostatic interactions drove the adsorption of carbon nanotubes, according to polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). The adsorption behavior was successfully described by the Langmuir-Freundlich isotherm.

Integration of Fractal Biosensor in a Digital Microfluidic Platform

The digital microfluidic (DMF) platform introduces many applications in biomedical assays. If it is to be commercially available to the public, it needs to have the essential features of smart sensing and a compact size. In this paper, we report on a fractal electrode biosensor that is used for both droplet actuation and sensing C-reactive protein (CRP) concentration levels to assess cardiac disease risk. Our proposed electrode is the first two-terminal electrode design to be integrated into DMF platforms. A simulation of the electrical field distribution shows reduced peak intensities and uniform distribution of the field. When compared with a V-notch square electrode, the fractal electrode shows a superior performance in both aspects, i.e., field uniformity and intensity. These improvements are translated into a successful and responsive actuation of a water droplet with 100 V. Likewise, the effective dielectric strength is improved by a 33% increase in the fractal electrode breakdown voltage. In addition, the capability of the fractal electrode to work as a capacitive biosensor is evaluated with CRP quantification test. Selected fractal electrodes undergo a surface treatment to immobilize anti-CRP antibodies on their surface. The measurement shows a response to the added CRP in capacitance within 3 min. When the untreated electrodes were used for quantification, there was no significant change in capacitance, and this suggested that immobilization was necessary. The electrodes configuration in the fabricated DMF platform allows the fractal electrodes to be selectively used as biosensors, which means that the device could be integrated into point-of-care applications.

Environmentally friendly power generator based on moving liquid dielectric and double layer effect.

An electrostatic power generator converts mechanical energy to electrical energy by utilising the principle of variable capacitance. This change in capacitance is usually achieved by varying the gap or overlap between two parallel metallic plates. This paper proposes a novel electrostatic micro power generator where the change in capacitance is achieved by the movement of an aqueous solution of NaCl. A significant change in capacitance is achieved due to the higher than air dielectric constant of water and the Helmholtz double layer capacitor formed by ion separation at the electrode interfaces. The proposed device has significant advantages over traditional electrostatic devices which include low bias voltage and low mechanical frequency of operation. This is critical if the proposed device is to have utility in harvesting power from the environment. A figure of merit exceeding 10000(108μW)/(mm2HzV2) which is two orders of magnitude greater than previous devices, is demonstrated for a prototype operating at a bias voltage of 1.2 V and a droplet frequency of 6 Hz. Concepts are presented for large scale power harvesting.

Characterization of atomic layer deposition HfO2, Al2O3, and plasma-enhanced chemical vapor deposition Si3N4 as metal–insulator–metal capacitor dielectric for GaAs HBT technology

Characterization was performed on the application of atomic layer deposition (ALD) of hafnium dioxide (HfO2) and aluminum oxide (Al2O3), and plasma-enhanced chemical vapor deposition (PECVD) of silicon nitride (Si3N4) as metal–insulator–metal (MIM) capacitor dielectric for GaAs heterojunction bipolar transistor (HBT) technology. The results show that the MIM capacitor with 62 nm of ALD HfO2 resulted in the highest capacitance density (2.67 fF/μm2), followed by capacitor with 59 nm of ALD Al2O3 (1.55 fF/μm2) and 63 nm of PECVD Si3N4 (0.92 fF/μm2). The breakdown voltage of the PECVD Si3N4 was measured to be 73 V, as compared to 34 V for ALD HfO2 and 41 V for Al2O3. The capacitor with Si3N4 dielectric was observed to have lower leakage current than both with Al2O3 and HfO2. As the temperature was increased from 25 to 150 °C, the breakdown voltage decreased and the leakage current increased for all three films, while the capacitance increased for the Al2O3 and HfO2. Additionally, the capacitance of the ALD Al2O3 and HfO2 films was observed to change, when the applied voltage was varied from −5 to +5 V, while no significant change was observed on the capacitance of the PECVD Si3N4. Furhermore, no significant change in capacitance was seen for these silicon nitride, aluminum oxide, and hafnium dioxide films, as the frequency was increased from 1 kHz to 1 MHz. These results show that the ALD films of Al2O3 and HfO2 have good electrical characteristics and can be used to fabricate high density capacitor. As a result, these ALD Al2O3 and HfO2 films, in addition to PECVD Si3N4, are suitable as MIM capacitor dielectric for GaAs HBT technology, depending on the specific electrical characteristics requirements and application of the GaAs devices.

Anodized aluminum oxide-based capacitance sensors for the direct detection of DNA hybridization

We fabricated a capacitance sensor based on an anodized aluminum oxide (AAO) nanoporous structure to detect DNA hybridization. We utilized Au film deposited on the surface of the AAO membrane and Au nanowires infiltrating the nanopores as the top and bottom electrodes, respectively. When completely complementary target DNA molecules were added to the sensor-immobilized DNA molecule probes, the capacitance was reduced; with a concentration of 1pM, the capacitance decreased by approximately 10%. We measured the capacitance change for different concentrations of the target DNA solution. A linear relationship was found between the capacitance change and DNA concentration on a semi-logarithmic scale. We also investigated the possibility of detecting DNA molecules with a single-base mismatch to the probe DNA molecule. In contrast to complementary target DNA molecules, the addition of one-base mismatch DNA molecules caused no significant change in capacitance, demonstrating that DNA hybridization was detected with single nucleotide polymorphism sensitivity.

Changes of three physiological parameters after subclinical skin irritation.

Objective To evaluate the diagnostic significance oftransepidermal water loss (TEWL), skin capacitance (CAP) and skin surface pH in subclinical irritant dermatitis. Methods Thirty healthy females took part in the 8-day study. Four areas were delineated on the flexor side of both forearms of each subject: one area received no irritation and served as the control, one was challenged by 1% sodium lauryl sulphate (SLS), one by repeated tape stripping, and one by irradiation with 0.75 MED UVB. Irritations were continuously given for 5 days. Clinical evaluation was performed everyday before irritation. TEWL, CAP and skin surface pH were measured at baseline, on day 6, 7 and 8 after the first irritation. Results Clinical score maintained at 0 for all subjects through the 8-day study. After SLS irritation, TEWL was 3.17 ± 3.07 g/m2h on day 6, 3.32 ± 2.84 g/m2h on day 7 and 3.22 ± 2.36 g/m,Zh on day 8, and all were significantly higher than that on day 0 (0.40 ± 1.35 g/m2h, P < 0.01). Similarly, increased skin surface pH was observed on day 6, 7 and 8 after SLS irritation compared with that at baseline (all P < 0.05). On the contrast, CAP decreased on day 6, 7 and 8 after SLS irritation (all P < 0.05). After tape-stripping, a significant increase was observed in TEWL on day 6, 7 and 8 compared with that at baseline (2.54 ± 1.85 g/m2h, 2.40 ± 2.16 g/m2h and 2.17 ± 1.99 g/m2h vs 0.11 ± 1.10 g/m2h, all P < 0.01); significant increase of pH was noted only on day 8; meanwhile, there was no any significant change in CAP. UVB irradiation induced no obvious changes in any of these physiological parameters. Conclusions These three physiological parameters can be applied m the diagnosis of subclinical irritant contact dermatitis, and their diagnostic value varies with the pattern of irritation. Key words: Dermatitis, allergic contact; Skin irritancy tests; Transepidermal water loss; Skincapacitance; Skin surface pH

Coupled nonlinear effects of surface roughness and rarefaction on squeeze film damping in MEMS structures

Many MEMS devices employ parallel plates for capacitive sensing and actuation. The desire to get a significant change in capacitance has been pushing the need to reduce the gap between the moving plate and the fixed plate. With fabrication processes making rapid strides, it is now possible to push the gap to be so small that it becomes comparable to the mean free path of gas or air molecules present in the gap. In all MEMS devices, where the essential function of the device depends on the dynamics of the mechanical components, the presence of air or a gas in such narrow gaps leads to energy dissipation if the gas is squeezed between the two plates due to transverse motion of the movable plate. This energy dissipation, known as squeeze film damping, plays a critical role in determining the quality factor of such devices. For many devices, simple approximation of squeeze film damping based on the linearized Reynolds equation is sufficient. However, under moderate vacuum and very narrow gaps, the linearized Reynolds equation does not give satisfactory results, especially if large amplitude motions of the movable plate are desired. In this paper, we carry out an analysis of the fluid flow in the narrow gap taking rarefaction and surface roughness into account and show that both these factors have a significant effect on the squeeze film damping of the devices.

A Capacitance Type Chemical Sensor Based on AlPO4-5 Molecular Sieves

Thin films of AlPO4-5 molecular sieves have been employed as the dielectric phase in a capacitance type chemical sensor. AlPO4-5 was deposited onto titanium nitride (bottom electrode) coated silicon wafers by laser ablation. A subsequent hydrothermal treatment of the ablated AlPO4-5 films was found to enhance the crystallinity. The capacitance sensor configuration was completed by the deposition of Pd/Au pads (upper electrode) through a mask. AlPO4-5 based sensors exhibited significant changes in capacitance upon exposure to small molecules such as CO2, CO, N2, and H2O.

Molecular Sieve Based Chemical Sensors

ABSTRACTBy virtue of their shape selectivity and stability, molecular sieves are ideal components for discriminating chemical sensors. In this paper we report the preparation of capacitance type sensors based on aluminum phosphate molecular sieves. Thin films of the molecular sieves AlPO4-5, A1PO 4-H3 and AlPO4-H1, which cover a range of pore dimensions, were deposited on titanium nitride coated silicon wafers by laser ablation. A subsequent hydrothermal treatment followed by a Pd/Au coating and the application of standard photoresist/masking techniques were used to generate the capacitors. The molecular sieves exhibit significant changes in capacitance upon exposure to target molecules, including CO2, CO, N2, H2O and toluene.

Apical membrane area of rabbit urinary bladder increases by fusion of intracellular vesicles: an electrophysiological study.

Mammalian urinary bladder undergoes, in a 24-hour period, a series of slow fillings and rapid emptying. In part the bladder epithelium accommodates volume increase by stretching the cells so as to eliminate microscopic folds. In this paper we present evidence that once the cells have achieved a smooth apical surface, further cell stretching causes an insertion of cytoplasmic vesicles resulting in an even greater apical surface area per cell and an enhanced storage capacity for the bladder. Vesicle insertion was stimulated by application of a hydrostatic pressure gradient which caused the epithelium to bow into the serosal solution. Using capacitance as a direct and nondestructive measure of area we found that stretching caused a 22% increase in area. Removal of the stretch caused area to return to within 8% of control. An alternate method for vesicle insertion was swelling the cells by reducing mucosal and serosal osmolarity. This perturbation resulted in a 74% increase in area over a 70-min period. Returning to control solutions caused area to decrease as a single exponential with an 11-min time constant. A microtubule blocking agent (colchicine) did not inhibit the capacitance increase induced by hypoosmotic solutions, but did cause an increase in capacitance in the absence of a decreased osmolarity. Microfilament disrupting agent (cytochalasin B, C.B.) inhibited any significant change in capacitance after osmotic challenge. Treatment of bladders during swelling with C.B. and subsequent return to control solutions increased the time constant of the recovery to control values (22 min). The Na+-transporting ability of the vesicles was determined and found to be greater than that of the apical membrane. Aldosterone increased the transport ability of the vesicles. We conclude that some constituent of urine causes a loss of apical membrane permeability. Using electrophysiological methods we estimated that the area of cytoplasmic vesicles is some 3.3 times that of the apical membrane area. We discuss these results in a general model for vesicle translocation in mammalian urinary bladder.

466—Effects of UO 22+ ions on the properties of bilayer lipid membranes

The effect of uranyl ions on the background conductance, capacitance, viscoelastic properties, surface tension and surface potentials of bilayer lipid membranes (BLM) is studied. Considerable increase of BLM, viscosity and surface tension in the presence of UO 2 2+, which is not accompanied by significant changes in capacitance and conductance at low potentials, is observed. It is shown that after establishing the maximum value of the surface potential U s *, corresponding to the given concentration of UO 2 2+ and electrolyte U s decreases in time, the charge of the BLM trans-side remaining unchanged. This effect is explained by formation of the interface layer with a considerable dipole moment at the cis-side.