Nina Korlina Madzhi

Design and Fabrication of Polysilicon‐based Piezoresistive Microcantilever For Biological Sensing

This paper describes the fabrication process of a piezoresistive microcantilever sensor that is used as a platform for biological sensing such as salivary amylase‐activity. The 0.5 μm‐thick piezoresistive sensors are made on polysilicon‐based cantilever beam. This surface micromachined microcantilever is based on silicon wafers and fabricated using 0.5 μm CMOS process technology . The range of microcantilevers is 40–140 μm long, 0.5–1 μm thick, and 40 μm wide. The force sensitivity of implemented sensors ranges from 2–10 Pa is corresponding to salivary amylase‐activity adsorbed on the piezoresistive microcantilever.

Smart helmet with sensors for accident prevention

The impact when a motorcyclist involves in a high speed accident without wearing a helmet is very dangerous and can cause fatality. Wearing a helmet can reduce shock from the impact and may save a life. There are many countries enforcing a regulation that requires the motorcycles rider to wear a helmet when riding on their motorcycle, Malaysia is an example. With this reason, this project is specially developed as to improve the safety of the motorcycles rider. Motorcyclist will be alarmed when the speed limit is exceeded. A Force Sensing Resistor (FSR) and BLDC Fan are used for detection of the riders head and detection of motorcycles speed respectively. A 315 MHz Radio Frequency Module as wireless link which able to communicate between transmitter circuit and receiver circuit. PIC16F84a is a microcontroller to control the entire component in the system. Only when the rider buckled the helmet then only the motorcycles engine will start. A LED will flash if the motor speed exceeds 100 km/hour.

Development of a low cost self-sensing Piezoresistive Microcantilever biosensor and read-out circuitry for measuring salivary-amylase activity

This paper deals with the development of a low cost self-sensing Piezeoresistive Microcantilever Biosensor to detect human stress using salivary alpha amylase activity. The salivary alpha amylase enzyme will immobilize on to the Piezeoresistive Microcantilever biosensor to detect activity during the enzyme responses. When the Microcantilever beam deflects it caused the stress change within the microcantilever beam and applied strain to the piezoresistor material thereby causing the resistance change and the Piezoresistive Microcantilever biosensor integrated with transducer components coverts the biochemical signal into measurable signal. The enzyme concentration signal is converted to a voltage by the transducer. A novel Piezeoresistive Microcantilever biosensing method and its application is described. The device was designed specifically that it enables the small resistivity change due to the enzymatic reaction to be measured.

A study into salivary-based measurement of human stress subjected to ellestad stress test protocol

Previous works on the effects of salivary alpha amylase in respond to various stressors report encouraging findings on it being a good indicator of stress. Ellestad protocol is a clinical procedure to screen for coronary artery disease by introducing exercise induced physical stress. If a salivary based biomarker profile in accordance to a stress test protocol could be established, the critical stress state which disables rational decision making could be ascertained in a standardized procedure. This technique would serve to aid human resource management in times of critical events such as rescue, firefighting or even military, that would potentially prevent unnecessary sacrifice of human lives. In this pilot study with five healthy volunteers performing the Ellestad protocol treadmill, a measurement profile with physiologic and salivary based biomarker is obtained. It is found that the alpha amylase levels or the changes in it as workload changes from resting-walking-running at ease-exhaustive running, is relatively more significant in reflecting the stress state than heart rate and blood pressure. Moreover, it is strongly associated with mood state with correlation coefficient of 0.8 and significance of 0.01.

Development of a transduction circuit for piezoresistive MEMS sensor for biosensing

This paper concerns the development of a potentiometric transduction circuit for a piezoresistive MEMS sensor to detect human stress. The biosensor is comprised of a bioreceptor and a transducer. The sensing principle is based on immobilization of the bioreceptor to produce a biochemical reaction. The novel piezoresistive microcantilever sensor integrated with a transduction circuit converts this biochemical event into a measurable electrical signal. From previous work, it has been found that the level of alpha amylase activity corresponds to human stress. The piezoresistive MEMS sensing and transduction method are described, with enzyme concentration as the input and voltage as the output. The transduction circuit designed enables the small change in resistivity due to the enzymatic reaction to be detected. The circuit has been designed and tested through theoretical, simulation and experimental studies. It has been found that for a sensor input range of 1.2 to 1.3 kilo ohms, an output range of −100 to +100 millivolts is obtained. A discrepancy within 3.69% is found between simulation and experimental results, on the average. The null bridge condition is designed at 1.2 kilo ohms while the offset rate is found to be 10 millivolts per ohm.

Initial quantitative comparison of 940nm and 950nm infrared sensor performance for measuring glucose non-invasively

This project uses a non-invasive method for measuring the blood glucose concentration levels. By implementing two infrared light with different wavelength; 940nm and 950nm based on the use of light emitting diodes and measure transmittance through solution of distilled water and d-glucose of concentration from 0mg/dL to 200mg/dL by using a 1000nm photodiode. It is observed that the output voltage from the photodiode increased proportionally to the increased of concentration levels. The relation observed was linear. Nine subjects with the same age but different body weight have been used to observe the glucose level during fasting and non-fasting. During fasting the voltage is about 0.13096V to 0.236V and during non-fasting the voltage range is about 0.12V to 0.256V. This method of measuring blood glucose level may become a preferably choice for diabetics because of the non-invasive and may extend to the general public. For having a large majority people able to monitor their blood glucose levels, it may prevent hypoglycemia, hyperglycemia and perhaps the onset of diabetes.

A Rudimentary Optical System in Detecting Ripeness of Red Watermelon

The purpose of this project is to detect the ripeness and quality of the watermelon particularly for red watermelon. The ripeness of the watermelon will be evaluated by using near-infrared spectroscopy sensor (NRIS). The color wavelength will classify the ripeness of the watermelon. An infrared light will be used to get the appropriate wavelength from the watermelon either from the rind or inner of it and the signal received will be analyzed. An appropriate algorithm is used to extract the information of the inner of the watermelon. A microcontroller namely Programmable Interface Controller (PIC) will be used to execute the algorithm and the result will be displayed on Liquid Crystal Display (LCD). Based on the result obtain from the device, the data is computed by using Statistical Package for the Social Sciences (SPSS). This approach is vital to verify the relationship between unripe and ripeness of red watermelon. The objective of this project is to produce an efficient system to detect the ripeness of the watermelon.

Statistical Discrimination of Latex between Healthy and White Root Infected Rubber Tree based on Dry Rubber Content

Dry rubber content (DRC) is one of main material existing inside latex. It is usually in ranged of 25% - 45% of rubber latex. Statistical analysis are done to determine the discrimination of dry rubber content of latex between healthy and white root infected rubber tree. Based on 150 rubber trees and 10 clones tested, parametric test which include normality test, error-bar plot, and paired samples test are done. The result outcomes have shown that both data of dry rubber content of latex for healthy and white root infected rubber tree are normally distributed. Error-bar plot test is clearly indicated that there is visible discrimination between both cases. Paired samples test are done to reinforce this findings in terms of numerical p- value which is found to be less than 0.05. Thus, this indicate overwhelming evidence that healthy group can be discriminated from white root. Conclusively, changes in DRC content in latex can be correlated with white root disease infections of rubber tree.

Development of low pass filtering and linearization for piezoresistive microcantilever biosensing

This paper concerns the development and design of filtering and linearization stage of potentiometric transducer to measure human stress level based on salivary amylase activity. The design of this new way approached is implemented using Cadence OrCAD Capture CIS 15.7 software and hardware construction and troubleshooting. From the previous research, it has been found that for a sensor input range of 1.1 to 1.3 kilo ohms, an output range of −100 to +100 millivolts is obtained. The design for filtering stage used the first order passive low pass filter to accommodate the stress signal frequency for 0.4Hz. Besides the design also focus to boost up the low voltage input of 108.6mV–(−100mV) to 0V–5V output voltage. Its involved low pass filter, voltage follower and linearization stages. The result indicates discrepancy within 4.5% and 3.7% were found between the simulation and experimental results for voltage follower after filtering and linearization circuit respectively, on the average. This development allowed stress measurement with relatively high precision and accuracy.

A study on electrode for amperometric measurement of human stress with flow injection analysis biosensing system

This paper presents a study on electrode for the amperometric detection of human stress based on salivary alpha amylase, emulated with different concentration of glucose, with the flow injection analysis biosensing system. Amperometric detection is an electrochemical voltammetric measurement approach, where the current intensity in a detection cell is regarded as a function of the concentration of the analyte. Flow injection analysis is a chemical analysis method that injects a test sample into a flowing carrier stream. The screen printed electrode is used to detect the amount of glucose concentration, which is proportional to the amount of output current. The objective of the study is to conduct a comparative study between the gold and carbon electrode, as a choice for amperometric detection of human stress with flow injection analysis biosensing system. It has been found that, the [initial, steady state current output at first injection of glucose, current output at second injection of glucose] for carbon and gold printed electrode are [0–80, 0–20, 0–20] μA and [0–35, 0–10, 0–5] μA respectively. This shows measurement resolution of the carbon screen printed electrode is better, which results in higher measurement sensitivity. However, it is found that the gold printed electrode exhibits higher rate of reaction with the steeper gradients and the current reaches its steady state values faster. Yet, in view of the cost, the gold printed electrode is about three times more than the carbon printed electrode and also the ease in handling the zero baseline, the latter is thus made as the choice electrode.