Biomedical Engineering: Applications, Basis and Communications

The nanorods bundles (urchinlike) ZnO microspheres, consisting of closely packed nanorods with wideness of about 50 nm, have been successfully synthesized by a hydrothermal route at the temperature of 140°C. The individual hierarchical ZnO microsphere ranged from 3.5 to 4.5 μm in diameter. Most importantly, ZnO hierarchical microsphere sensor exhibits excellent selectivity and fast response to acetone. Response and recovery times were 1 s and 3 s when the sensor was exposed to 100 ppm acetone at an operating temperature of 320°C. Thus, hierarchical structures play a significant role in the field of gas sensing.

Uniaxially aligned In₂O₃ nanofibers are prepared by magnetic-field-assisted electrospinning method. The average diameter of the gained nanofibers is about 90 nm. The optimum operating temperature of the sensor based on the uniaxially aligned In₂O₃ nanofibers to ethanol is 120°C, the response and recovery times of the sensor are 0.4 s and 3 s, respectively. Compared with the randomly deposited nanofibers, the uniaxially aligned nanofibers show much rapider response.

The surface modification for immobilization of antibodies on the aluminum oxide surface was developed for biosensing application. The aluminum oxide has been received much attention since it has various advantages including low cost, hardness, resistance to organic solvents, and high capacitance. In addition, the aluminum oxide can prevent the leakage current in the electrical detection. For development of the protein anchorable surface, the aluminum oxide chip was treated with oxygen plasma and directly immersed in ethanol and toluene solution of 3-aminopropyltriethoxysilane (APTES). Next, this amine modified chip was immersed in the glutaraldehyde solution that contained sodium cyanoborohydride. Finally, the fluorescent materials, the Alexa 488, and the FITC conjugated anti-IgG were reacted to the aldehyde-modified surface. To verify the modified surface, the intensity of the fluorescence was measured and compared. The higher intensity of the fluorescence was observed when the APTES was dissolved in toluene rather than in ethanol. From the highest intensity of the fluorescence observed, the FITC conjugated anti-IgG was well immobilized on the modified surface of the aluminum oxide with APTES and glutaraldehyde. Thus, the proposed surface modification method can immobilize the proteins including antibodies, and can be applied for the various biological researches including biosensors and biochips.

We investigated the characteristics of Al₂O₃ gate pH-ISFET which was fabricated by using the standard complementary metal oxide semiconductor (CMOS)-process techniques. The Al₂O₃ film used to sensing membrane was deposited by atomic layer deposition (ALD). Then, thermal temperature annealing process of the Al₂O₃ film was performed in O₂ ambient for 40 min at a temperature of 500°C, 600°C, 800°C and 900°C. We measured the I_D–V_D, I_D–V_G and transconductance of fabricated FET device in order to confirm stability of device before the fabrication of pH-ISFET. Then, the package process was performed. To investigate the pH response characteristics, we measured the I–V curves of the Al₂O₃ gate pH-ISFET sensor using a 4155 probe station. Form the measured results, we confirmed that sensitivity, hysteresis, and long-term stability of the Al₂O₃ pH-ISFET showed the changed characteristics at various annealing temperature. The characteristics of Al₂O₃ gate pH-ISFET annealed at 600°C indicated the best results of the high sensitivity (56 mV/pH), low hysteresis (0.5 ~ 0.7 mV), and low drift (1.35 mV/h) in comparison to Al₂O₃ gate pH-ISFETs annealed other conditions. As measured results, we confirmed that sensitivity, hysteresis, and long-term stability of Al₂O₃ gate pH-ISFET depend on the thermal annealing temperature of Al₂O₃ film and also it is the very important parameter in the pH-ISFET.

Many studies have identified tungsten trioxide (WO₃) as a promising candidate for optical gas sensing applications. WO₃, coated with thin catalytic metals such as Pd, was reported to show a color change from transparent to dark blue upon exposure to oxidizing gas such as hydrogen (H₂). Reliable hydrogen sensor is widely used in medical and energy application area. In this work, WO₃ nanostructured thin films were deposited onto sapphire substrates via pulsed laser deposition (PLD) technique by using ArF Excimer laser operating at very short wavelength of 193 nm, the shortest wavelength used in the fabrication of semiconductor oxide thin films. By ablating the target oxides by high energy photons, we could fabricate good crystalline nanostructure thin films. Electron microscopy studies revealed that the uniform and homogeneous WO₃ nanostructured films consist of nanorods of about 50 nm sizes. XRD and Raman studies verified good crystalline formation. Absorbance response toward H₂ gas was investigated for a WO₃ film coated with 25 Å thick palladium (Pd). The Pd/WO₃ nanostructured thin films exhibited excellent gasochromic response toward H₂ when measured in the visible-NIR range at 100°C. As low as 0.06% H₂ concentration was clearly sensed. The larger dynamic response was measured at NIR wavelength of 900 nm as compared to the response at visible wavelength of 500 nm. The dynamic response of the films observed in the range of 500–800 nm showed more significant response toward H₂ with low concentrations (0.06%–1%) than the one at single wavelength. As a result, H₂ with very low concentration was able to be sensed reliably in real time. The response and recovery times were found to be < 2 min. The results indicated that the Pd/WO₃ nanorod films on sapphire substrates responded to very low H₂ concentration (0.06%) which is well below its lower explosive level threshold (4%).

In this paper, we assess the feasibility of detecting human pancreatic cancer cells using a field effect transistor (FET)-based biosensor with an extended Au gate for medical application. Pancreatic cancer is one of the most fatal cancers, and is very difficult to diagnose in its early stages. Gemcitabine is an anticancer drug, and when used in chemotherapy it induces cell death. During apoptosis, the surface potential of the pancreatic cancer cells is changed by gemcitabine. In the present study, this change was detected using an FET-based biosensor. This biosensor was fabricated with an extended Au gate, whose surface is a sensing area for cancer cells. A null-balancing circuit was used in the measurement system, and the LabVIEW software platform allowed the immune-reaction at the Au gate to be detected as an output voltage. The cancer cells were incubated for one day; during this time, the cancer cells adhered to the Au extended gate surface. As gemcitabine was introduced to the cancer cells in vitro, changes in the output of the biosensor were monitored. Pancreatic cancer cells with a resistance to gemcitabine were used to verify that the change in the output of the biosensor was due only to the interaction between the cancer cells and the gemcitabine. We also investigated the relationship between the starting time of the reaction and the concentration of the anticancer drug.

Recent advances in wireless sensor network (WSN) envisaging ubiquitous healthcare system that simplifies the monitoring and treatment of patients. WSN also pose several challenges to ubiquitous healthcare applications. As healthcare application commonly handle two different types of data such as wave-like data of ECG and linear waveform-independent data of body temperature, blood pressure and oxygen content. As wave-like data requires a higher sampling rate than waveform-independent data, the transmission of wave-like data in WSN causes traffic congestion and, consequently, loss of vital signal in transmission. With the increasing number of sensor nodes involved in the WSN field, network congestion issue is rapidly coming known as a tangible issue in healthcare system that must be addressed in order to maintain data reliability. Sensor nodes have very limited computational resources due to its energy consumption. To reduce traffics in WSN communication, the biomedical data are sent when they had very serious problems. The collaboration among sensors through task mapping based in-network processing is adapted to achieve higher processing power and reduce traffics in WSN. System analysis shows that the data packet loss in the ubiquitous healthcare system is dramatically reduced after the implementation of this process. By adapting fall detection, not only the numbers of packets received by the base station are greatly reduced but also the traffic overload problems in WSN are also resolved.

For the past decade, it is well defined in the literature that fatigue is one of the most prospective factor in affecting the driver behavior. This paper presents a novel evaluation of driver fatigue condition based on multi-classifier technique and fusion of attributes approach. The process involved fusion of attributes including image of eye movement and photoplethysmography (PPG) signals that are given as inputs to multi-classifier. In order to develop the best inference classifiers, artificial neural network (ANN), dynamic bayesian network (DBN), support vector machine (SVM), independent component analysis (ICA) and genetic algorithm (GA) were tested in our study. The output from each inference classifier are scaled and product in an intervention module to indicate driver aptitude in real-time. Implementation of monitoring system is practically designed in Android-based smartphone device where it can received all the sensory information from the dedicated sensors installed at the steering wheel via a small scale wireless sensor network. Device built-in front camera was utilized to capture driver facial image. No supplementary monitor is required to be installed in the vehicle as the all the information is to be displayed on the smartphone device itself. Warning system is triggered to warn driver once fatigue is suspected. System testing statistical results revealed that the manifold used of the proposed system demonstrates the advantages of performing information fusion, particularly with discrete methods, and the multi-classifier enabled a more authentic and ample driver fatigue evaluation.

Nowadays, wireless communication technologies are employed in medical body area networks to enhance flexibility and convenience for caregivers and patients. However, there is always the risk of disturbance from electromagnetic waves toward precision medical equipment. This study demonstrates a novel design and implementation of a medical healthcare information system using the emerging wireless visible light communication (VLC) technology. VLC technology can be implemented using visible light emitting diodes (LED), which is expected to be the main lighting source in the near future due to its energy efficient characteristic compared to conventional incandescent and fluorescent lighting. By manipulating the fast switching characteristic of LEDs, these lighting devices can be used simultaneously for illumination and wireless data communication. The prototype design of the VLC-based medical healthcare system can be used to provide data service and monitoring in radio frequency restricted hospital areas. High brightness LED (HB-LED) is used in the transmitter module to transmit medical and healthcare information using optical modulation method. High speed photodetector is used to detect the optical signal, then the signal is demodulated and conditioned at the receiver module. Medical caregivers or patients can download the biomedical data and healthcare information using a portable device with attached optical sensor.

In this study, organic silicon thin film was deposited on a comb type electrode substrate surface using hexamethyldisilazane (HMDSZ) plasma deposition technique to enhance voltage withstanding capability. The wettability, morphology and capability to withstand voltage were investigated by water contact angle (WCA) measurement, SEM observations, AFM and ampere meter analysis, respectively. The WCA of the substrate is 92.3° after the plasma deposition. As voltage is applied to the electrode, the WCA lowers to 76.4° and the resulting current flow is 0.078 mA. If the voltage is continually applied to the device, the organic silicon film on the substrate starts to peel off, accompanied with a sharp increase in current, which is an irreversible phenomenon. From the SEM and AFM analysis, the voltage withstanding capability of the device can be enhanced by prolonging the plasma processing time in order to obtain thicker thin film.

This study aimed at fabricating a new type temperature sensor device by taking advantages of electrical conductivity of bamboo charcoal powder and temperature sensibility of NIPAAm hydrogel. The resistance of such a composite device will be affected by temperature. Bamboo charcoal powders were first subjected to oxygen plasma treatment. The treated bamboo charcoal powders were then UV graft polymerization with N-isopropylacrylamide (NIPAAm) monomer solution to be immobilized on the electrode which had previously been modified with plasma of tetramethyltin (TMT) and O₂ gas mixture. Using simple environment test to measure resistance, the LCST of bamboo charcoal powders mixed with NIPAAm hydrogel was found to be 31°C. At ambient temperatures higher than LCST, the electrode resistance decreases. The surface morphology of composite hydrogel was observed by SEM.

Quartz crystal microbalances (QCM) are transducers for chemical and biochemical sensing. The oscillation frequency of QCM is affected by the adsorbed mass on the surface. In this work, a new room temperature type gas sensor device fabricated by organically hybridized plasma deposition of tetramethyltin (TMT) and oxygen. Post treatment with poly ethylene glycol (PEG) was developed to detect the ambient environmental smother, and the responses of the fabricated sensor to smother detection were investigated. SnO_xC_y thin films on the sensor electrodes were obtained by plasma deposition from TMT and O₂ gas mixtures at room temperature. A spin coating post treatment on the SnO_xC_y thin films turns into hydrophilic property. The response of the QCM sensor to the smother detection shows a frequency drop during the burning of candle and has good detection sensitivity with Δf equal to 2400 Hz. Repeated smother testing with the QCM type smother detection sensor also indicates the stability of the fabricated sensor.