Biomedical Engineering: Applications, Basis and Communications

The aim of this study was to investigate the frequency shift of the gold film electrode of a quartz crystal microbalances (QCM) made by steps of applying self-assembling monolayer (SAM), plasma treatment, and UV-induced graft polymerization on the surface. Thiol group containing 11-mercaptoundecanoic acid (MUA) was employed for depositing SAM onto gold surfaces. Oxygen plasma treatment was then applied to the SAM to generate sufficient amounts of peroxides and hydroperoxides, which could further initiate UV-induced graft polymerization. Measurements of contact angle and oscillation frequency on the prepared QCM indicate that the SAM-modified gold film surface provides an effective method of making the surface hydrophilic and altering the frequency of QCM through the plasma treatment and graft copolymerization with an appropriate monomer.

Data fusion is a frequent statistic method that can be applied to sensor development field, such as multisensors and sensors array. In this study, the analytic data fusion methods consist of the arithmetic mean and weighted data fusion used to estimate the measured pH data of flexible pH sensors array. The main part of the flexible 2 × 4 pH sensors array was fabricated by screen printing, and the ruthenium dioxide (RuO₂) thin film on each sensor of the sensor array was deposited by radio frequency (RF)-sputtering method. In accordance with experiment results, the pH values estimated by weighted data fusion method are accurate than by arithmetic mean method. Furthermore, that the flexible sensors array is actually used to detect the pH value of different commercial drinks is also investigated.

In this study, humidity-sensitive polymer layer containing phenol-formaldehyde resin prepared by spinning coating on the comb-shape type electrode followed by UV-graft polymerization of soluble monomer was performed to improve the sensitivity. In this investigation, grafting of P-styrenesulfonic acid sodium salt (NaSS) treated with hexamethyldisilazan (HMDSZ) plasma and acrylic acid (AAc) followed by isopropanol (IPA) plasma were used as monomer for UV surface graft polymerization. Results show the first one adding different ratio of phenol-formaldehyde resin. This type of sensor has linear response with %RH, and high sensitivity (impedance from 10⁶ to 10³). The impedance of second type of sensor was linear response with %RH, impedance varies from 10⁷ to 10⁵.

The sensor is a kind of device about electrochemical science, its applications include clinical and environmental analyses, physiology, and process control; therefore, how to accurately detect the signal of the sensor is one of the most important things for analyzing the characteristics of sensor. For potentiometric device, this study relates to a multielectrode measurement system based on the programable software, LabVIEW, forming a virtual instrument (VI). This system is built as a voltage versus time (V–T) framework and a dynamic detection system. We selected two devices, a digital multimeter (HP 34401A) and a homemade VI, synchronously to measure the sources of a direct current (DC) signal and an electrode cell (EC), respectively. The maximum errors between the two devices are 0.639 mV in DC supply and 0.345 mV in EC supply, which specifies that the efficiency of design measurement system is good for detection.

In this study, the ruthenium dioxide (RuO₂) thin film as sensing film of pH sensor was deposited on polyethylene terephthalate (PET) by radio frequency sputtering. The pH-sensor based on separative extended gate field effect transistor (SEGFET) was fabricated by screen-printed technology through two different fabrication methods. And the calcium ion selective membrane was dropped on sensing window of SEGFET to perform the calcium ion sensor. In addition, the difference between the two fabrication methods was studied, and the hysteresis effect of calcium ion sensor was analyzed in this study. At present, the pH-sensor has been fabricated successfully, its sensitivity and linearity are 60.36 mV/pH and 0.999 from pH1 to pH11 at 30°C, respectively. As well as the sensitivity and linearity of calcium ion sensor are 27.71 mV/pCa and 0.987 in the range of 1 M–10^-4 M CaCl₂ solutions, respectively.

LabVIEW has complete development and compiler environment, so the display, saved and transmission interface, etc. are compiled by LabVIEW software in this study. LabVIEW and microcontroller can be integrated for the platform of ion concentration measurement, as well as the acquisition of sensing signal can be obtained via microcontroller. Moreover, the pCl and pH value can be separated in platform of ion concentration measurement. Besides, the platform of ion concentration measurement is measured in pCl2 standard solution, the results are between pCl1.83 and pCl2.08. Hence, the platform of ion concentration measurement has been successfully realized.

This work describes a portable microsensor for analyzing the silicate concentration in water. Conventionally adopted silicate analysis methods involve bulky instrumentation that are limited in portability and immediateness. The proposed silicate microsensor consists of a microliquid core waveguide, passive spiral micromixer, and bubble traps that possess excellent signal enhancement properties. The microsensor size is 52 × 26 mm, while each measurement requires only 115 μl of a sample and reagents, thereby reducing the sample requirement for a considerable amount of time and work to collect expensive reagents. The spiral micromixer has a mixing capability superior to that of a premix mixture. Bubble traps have been developed to trap air bubbles formed in the microchannel in order to prevent gas bubbles from interfering with the measurements. As a linear function of silicate concentration, the absorbance response ranges from 0 to 250 nM. Additionally, the linearity is excellent with a linear R value of 0.9985 and the experimental detection limit is 8.9 nM. The proposed portable microsensor significantly contributes to aqueous inspection, subsequently creating a highly value-added technology for chemical sensors and microsystems.

A room-temperature nitric oxide (NO) gas sensor is prepared by using electrochemical synthesis of conducting polymer, poly-(3,4-ethylene dioxythiophene) (PEDOT) and characterized by surface plasmon resonance (SPR) method. Guided by SPR angle simulation, the optimal thickness of deposited PEDOT thin film is 25 nm and the resultant lowest detection limit of NO is 8 ppm. It exhibits 1.3 times higher responses to 25 ppm of NO gas than NO₂.

This article reports a new class of silicon-based microgas sensors utilizing hexagonally-ordered mesoporous carbon powders (MCPs) as the sensitive film. The mesoporous carbon powders featuring high-specific surface area are replicated by the SBA-15 silica template and immobilized between Cr electrodes on a 9 × 9 cm silicon chip by using a.c. dielectrophoresis (DEP) process at room temperature. The silicon sensor platform comprises Cr microheaters embedded in a dielectric thin membrane manufactured by microelectromechanical systems back-etching techniques. It is shown that MCPs can be satisfactorily aligned along electric fields and accumulated to the electrode area. Investigations into CO detection are carried out to verify gas-sensitive characteristics of the MCP nanofilm. Our experimental results disclose the mesoporous carbon powders are successfully chemoresistive to CO, and demonstrate distinct resistance change with respect to ppm-level variation. In addition, response time, recovery time, and reproducible sensing behavior are experimentally obtained.

Quartz crystal microbalance (QCM) has been constructed and used for chemical sensing and biochemical detecting. Frequency shift has a relation with mass changed in the gaseous condition. However, the velocity, density, and viscosity also cause frequency changed in liquid solution. We develop a new method and system to investigate the variable value of amplitude and frequency from the oscillator of quartz. In this system, piezoelectric quartz crystal (10 MHz, AT-cut) with gold electrodes was mounted under liquid solution. Crystal was exposed to the different concentrations of glucose and sodium chloride solution. The results show that the ramp-up speed of amplitude was faster as frequency in the alternative state. We figure out the largest skew through the differential curve of amplitude in different solutions. The dramatic results give a QCM more meanings to be a biochemistry detecting utility.

A potentiometric glucose biosensor based on a SnO₂/ITO/PET substrate is presented in this study. The sensing membrane of SnO₂ is coated on ITO/PET substrate by utilized radio frequency (RF)-sputtering method of semiconductor fabrication. The potentiometric glucose biosensor is established on an FET-type pH sensor. Therein, the glucose oxidase (GOD) and chitosan/multi-wall carbon nano-tubes (chitosan/MWCNTs) are immobilized by 3-glycidoxypropyl trimethoxysilane (3-GPTS). Finally, the drift characteristic and calibration curve of the potentiometric pH sensor and potentiometric glucose biosensor is discussed in the following article. We find the nonideal effect of device reduced significantly, due to the coating of SnO₂ thin film.

Using quartz crystal microbalance (QCM) to design a cell detection platform is an important application of QCM. In the process of system design and application, there still have some points, which are easily overlooked or are not understood by researchers. Most of the problems can be separated into three types. One is the cell culture environment conditions that affect the system signals, another is the system unification or lack of communication over regulations, and the other is the over-analysis of the experimental data.

This research provides a microarray bio-probe device, integrated with Thin-Film-Transistor (TFT) amplifier formed of top-gate MOS (Metal-Oxide Semiconductor) transistors on an active RFID tag, to improve the signal-to-noise (S/N) ratio and impedance matching problems. The bio-probe device can be disposed to conform to the profile of a living body's portion so as to improve the electrical contact property.

In this study, we proposed a portable electronic nose (e-nose) system based on a microcontroller (MSP430-FG439) combined with a tin oxide (SnO₂) gas sensor, which was heated by a cyclic heating method, to recognize the volatile organic compounds (VOCs). We had demonstrated that this e-nose system can classify and quantify VOCs, such as methanol and ethanol. The sensitivity of the e-nose system had good linearity in the concentration range of 10–40 ppm of these two VOCs, respectively. This portable e-nose system was implemented with a microcontroller acted as CPU, an LCD for displaying information of gases in real time, a wireless communication system, ZigBee, and a warning system.

A simple, fast, real-time, and nondestructive analysis of protein expression in biological samples, such as membranes, based on dielectrophoresis is described. On the basis of the distinct differences in the dielectrophoretic properties of individual cell types, the wild-type BabA-positive Helicobacter pylori isolates and its BabA-negative isogenic mutant can be identified and separated. The herein-presented approach of using microelectrodes should be an easy-to-use, cheap, and rapid alternative to separate and distinguish the presence or absence of important outer-membrane proteins.

Dextran-coating iron oxide (DCIO) nanoparticles were prepared by co-precipitation method and using dextran as the stabilizing agent. A glucose biosensor was successfully constructed firstly by simply drop-coating ferricyanide (Ferri)-DCIO onto screen-printed carbon electrodes (SPCEs), and then by layering-on glucose oxidase. The electrochemical characteristics of the modified SPCEs were analyzed by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The optimal DCIO and enzyme loadings were 16 mg ml^-1 and 0.7 U, respectively, and the sensitivity of the resulting biosensor was 0.4 μA mM^-1 at 0.45 V with a wide linearity up to 44.4 mM glucose and the lower detection limit of about 1.23 mM.

A double potassium and sodium ions sensor based on separated extended gate field effect transistor (SEGFET) and a new entrapment method are proposed in this study. Having high sensitivity, reproducibility, and a simple manufacturing process, the sensors are quickly able to supply information and detect human blood within an abnormal range. The sensing membranes were fabricated using a Poly(vinyl chloride) carboxylated (PVC-COOH) matrix; sodium ionophore (B12C4) or potassium ionophore (valinomycin). The sensitivity of ion-selective biosensors is 42.55 mV/decade for Na⁺ between 1 M and 10^-7 M, 42.75 mV/decade for K⁺ between 1 M and 10^-6 M.

Burn injuries could be local or systemic problems, so multiple disciplines should be considered, including nutrition. Vitamin C is a cofactor of prolyl and lysyl hydroxylation for collagen maturation and ceramide synthesis and an important water-soluble free radical scavenger. Clinically, supplement of vitamin C is part of burn care for improving the healing process and decreasing further damage. With modified interdigitated microelectrode plate (IMP), electrical burn of MDCK cells was produced with constant current for few seconds. Healing process of cells damaged by different duration of direct constant current and damaged cells treated with 100 μM vitamin C were recorded by modified IMP and impedance-sensing system. The rate of change of conductivity is fast in the group of shorter exposure time and vitamin C-treated cells. Compared with the result of MTT test, we concluded that vitamin C decreased the duration of healing through increase cell proliferation.

The aim of this study was to discuss the hysteresis effect of SnO₂ pH sensor based on separative extended gate field effect transistor (SEGFET). Based on the theorem of three time-constants model, hysteresis model is linked with drift effect. Function relationship of pH value and time constant is also derived from the drift effects with difference pH value. Besides, electrochemical impedance spectroscopy (EIS) is utilized to interpret the mechanism of hysteresis effect. Experiments of EIS are carried out in different pH buffer solutions. An equivalent model of sensing membrane is obtained by theorem of EIS. The experimental results indicate that the equivalent circuit elements, such as membrane capacitance and membrane resistance, change with pH. This phenomenon is compared with other literatures and discussed on hysteresis effect.

The soft sensors for monitoring respiratory and heart sound were composed of polyurethane and microphones. In this study, silica was blended with polyurethane to change the hardness of the chambers. The hardness would influence the frequency response of the sensors. The material composed of 60 phr silica was chosen to make the chamber of the sensor. It had higher hardness and resulted in the flatten frequency response across the range of 100–1200 Hz. By the filter band designed for heart sound and respiratory sound signal, the heart sound and respiratory sound can be collected. The measured sound was verified by the physician and showed no distortion.

A simple and sensitive high performance liquid chromatographic method for simultaneous determination of sulfachloropyridazine and sulfapyridine has been developed. This method was developed by using self-prepared molecularly imprinted polymers (MIPs) as the stationary phase. The polymers were prepared by a noncovalent method with sulfachloropyridazine as the template, methacrylic acid as the functional monomer and ethylene glycoldimethacrylate as the cross-linker in the presence of chloroform as the solvent. In order to compare the chromatographic data from the stationary phase, the retention time of sulfachloropyridazine and sulfapyridine was given. The separation factors (α) were 1.79–1.89 that showed that the MIPs were able to recognize sulfachloropyridazine and sulfapyridine.

We propose an improved immunoassay method with EWOD-based microfluidic biochip. Electro-wetting on dielectric (EWOD) is based on contact angle-changed phenomenon of droplet on the channel surface. The reactant-containing droplet can be moved from reservoir to a modified electrode area, which a stir function can be provided by controlling AC electro-osmosis flow (ACEOF). The immunochemistry reaction takes place on our modified area via electro-wetting actuation, and the signal from fluorescent or electrochemical impedance spectroscopy (EIS) was used to confirm the performance of designed element.

The copper phthalocyanine (CuPc) thin film gas sensors detect to organic acids that its detection behaviors will be affected morphology with quartz crystal microbalance (QCM) method. The amorphous structure has looser surface and finer particles; therefore, it has smaller surface area. Although it has more active sites to adsorb acid molecular, it gets smaller value of frequency change (Δf) than α-phase morphology. The β-phase morphology has the largest surface area, so it gets the smallest value of Δf. The response behavior is more rapid than recovery behavior with any morphology CuPc thin film gas sensors. The film surface of amorphous structure has more porous, it has faster response time and recovery time than other structures. The β-phase morphology can get slowest response and recovery time. The results show that the CuPc thin film gas sensors detect to organic acid behavior, for example methyl acid and ethyl acid, etc.; it was affected to its surface morphology change.