Setyawan P. Sakti

Development of QCM Biosensor with Specific Cow Milk Protein Antibody for Candidate Milk Adulteration Detection

Adulteration of goat milk is usually done using cow’s milk product. Cow milk is used as it is widely available and its price is cheaper compared to goat milk. This paper shows a development of candidate tools for milk adulteration using cow milk. A quartz crystal microbalance immunosensor was developed using commercial crystal resonator and polyclonal antibody specific to cow milk protein. A specific protein at 208 KDa is found only in cow milk and does not exist in goat milk. The existence of this protein can be used as an indicator of cow milk content in a target solution. To detect the PSS 208 kDa protein, antibody specific to the PSS 208 was developed. The purified antibody was immobilized on top of the sensor surface on a polystyrene layer. The fraction of the immobilized antibody on the sensor was found at 1.5% of the given antibody. Using a static reaction cell, the developed immunosensor could detect the specific cow milk protein in buffer solution. The detection limit is 1 ppm. A linear relationship between frequency change and specific protein of cow milk concentration is found from a concentration of 1 ppm to 120 ppm.

Viscoelastic and Morphological Behavior of Stearic Acid Layer on Top of Polystyrene as Immobilisation Matrix for QCM Sensor

The effect of different solvents on the acoustic property and morphology of polystyrene (PS) and the stearic acid (SA) layer was investigated in this study. The acoustic property was analyzed by using impedance analyzer and morphology of SA layer in a quartz microbalance (QCM) sensor have been studied to quantify their effects on viscoelasticity within the sensor. The polystyrene coating on a QCM sensor was created by spin-coating with various solvents, such as chloroform and toluene, which contains a 3% polystyrene solution by mass. Then, the SA coating was deposited onto the polystyrene layer using a low-vacuum evaporation method. The viscoelasticity was measured by an impedance analyzer coated with the SA layer to determine whether the material used as a coating will effectively immobilize a biomolecule and whether the material produces an acoustic load. The experimental results showed that the impedance value in the series resonant frequency was small (i.e., near 10 Ω), indicating that the deposited SA coating is rigid and that the SA coating does not produce a loading effect on the QCM sensor. Therefore, the coating technique used on the QCM sensor surface to produce the SA coating is likely to be an effective biosensor material for QCM immunosensor. Additionally, the study shows that the frequency change (Δf) of the SA layer deposited onto the polystyrene coating created with chloroform is larger than that of the coating created with toluene. This also shows that the SA layer deposited onto the polystyrene coating created with chloroform is thicker than the coating created with toluene. The Δf correlates with the mass change (Δm), according to the Sauerbrey equation, which requires that the material be rigid. The Δf value also correlates with the deposited SA mass change. From the calculation of Δf, the SA coating created with the chloroform solvent was shown to be thicker than that created with the toluene solvent. In addition, the roughness of the SA surface using a test of non-contact topography measurement system TMS TopMap-1200 showed that the SA surface roughness with the chloroform solution was 763 nm compared to that with the toluene solution, which was 424 nm.

High-resolution multiple channel frequency counter using spartan-3E FPGA

Frequency counter resolution, accuracy and precision are importance parameters of the quartz crystal microbalance signal acquisition. The sensitivity of the quartz crystal microbalance is not only depended on the resonance frequency of the sensor but also the resolution of the counter. Higher counter resolution results in higher sensitivity measurement of the sensor output. In this work, a three-channel reciprocal frequency counter was developed using FPGA and implemented using VHDL code. The precision and resolution of the system depend on the system clock source. In this development, a high-precision TCXO oscillator with a resonance frequency of 100MHz is used as a reference oscillator. From this oscillator, one-second time gate and period measurement is constructed in the FPGA. In each measurement channel, dual digital counters were implemented. One counter counts the incoming signal in between one-second gate, and the other counter is counting the 100MHz signal from the beginning to the end of the counted signal within the one-second gate. The accuracy of the frequency measurement of the counter was calibrated using 10MHz standard rubidium oscillator. The developed system shows a good performance and able to count incoming signal with an accuracy of 0.1 Hz for one second acquisition time.

Detection of resonant frequency of QCM by using Chirp Z-Transform

One of the main working principles of the Quartz Crystal Microbalance (QCM) is the relationship between the series of resonance frequency and mass change. Commonly, the sensor works as an oscillator system, where the resonant frequency is measured using a frequency counter. For a heavy damped condition, the oscillator stops to operate. This paper deals with the use of the spectral analysis approach to detect the QCM resonant frequency. The scenario is that the QCM sensor is subject to an input signal consisting of multi-frequency components; its frequency and magnitude of the output signal are then analyzed. The resonant frequency must be within the signal frequency input range and have the largest magnitude in the output of signal spectrum. Using FFT, there would be a heavy burden of computation in finding the resonant frequency since the high sampling frequency is larger than at least twice of the required resonant frequency of QCM; while the required bin size of the output signal spectrum is expected as small as possible. Thus, a large portion of unwanted frequencies is computed in FFT yet then ignored. This paper elaborates the use of the Chirp Z-Transform (CZT) to overcome this problem since its computation is less costly and can focus on a limited desired range of the frequency spectrum with smaller bin size. For a case study, A BVD model of QCM of the AT-cut quartz crystal type in HC49/U standard package was numerically simulated and tuned at 10 MHz series resonant frequency. Using the CZT method, a fair estimation of the QCMs resonant frequency was obtained from the spectral analysis of the output signal of QCM, which was subject to the narrow range of the multi frequency input signal adjusted at 40 MHz frequency as a sample.

Low-cost wireless sensor network for small area in a building

Multisensor system can be found in many areas. In a modern laboratory, houses or other buildings, multiple sensors are used to monitor different quantities. Data from each sensor are sent to the data server for further processing. Data communication between the sensor and the server using cabling system are disorganized and inconvenient. The solution for that problem is by using wireless communication. For such approach, the energy consumption and radiation power of the system are important factors. This paper presents a model of wireless sensor network for multipoint measurement in a building. A multipoint monitoring system for temperature and humidity was implemented using distributed sensor system connected with IEEE 802.15.4 wireless communication. The system was implemented using Microchip MiWi wireless transceiver module, low power microcontroller, and sensors. At the server side, a network controller was built using a microcontroller and MiWi transceiver. The microcontroller and data server were connected using HID protocol. The HID protocol was chosen because the data rate from the sensor node to the server is low. The network configuration was a star configuration with a direct link between the sensor node and network controller. Packet length, the maximum distance between transceiver and power consumption, was measured. The result shows that at the power of −30dBm, the communication can be established well within 15 meters. At the minimum power, the sensor node can operate up to 5 days using the 3.3V, 2500mAh lithium battery.

Solvent effect on polystyrene surface roughness on top of QCM sensor

Quartz Crystal Microbalance (QCM) has been used as a basis for many chemical sensors and biosensor. Its sensitivity to mass change which can detect a mass change on its surface down to sub ng/cm2 is one of its interesting aspects. Another interesting feature is its ability to work in liquid environment. However, there are many aspects which influence QCM sensor properties in contact with liquid. One of the aspects is surface roughness of the matrix layer where on top of it a biological sensitive layer will be immobilized. One of matrix layers in the immobilizing biological sensitive layer was polystyrene. Polystyrene was coated on the QCM sensor by using the spin coating method. During the coating process, polystyrene was solved using non-polar solvent. It is known that the physical and chemical properties of the solvent affect a transition process from soluble polymer becoming rigid polymer layer. In this work, we show that polystyrene solved in chloroform has a higher surface roughness compare to one so...

KOH wet etching technique for patterned formation on surface of quartz crystal with AuPd mask

Surface patterning is one of importance aspect in the development of a QCM biosensor. This paper describes a method by which a KOH (Potassium Hydroxide) etchant is utilized for the pattern formation on the surface of the quartz crystal sensor. The etching process is preferable in order to produce a flat surface roughness. The etchant concentration affects etching rate and surface roughness. In this experiment, the effect of etchant concentration on the etching rate and surface roughness was investigated. The etching of the quartz crystal was carried out using KOH concentration of 25 %, 30% and 35 % by weight at a temperature of 80°C for 2 hours. Aurum palladium (AuPd) was used as a mask to protect the rest of the quartz crystal. The AuPd mask was coated on the quartz crystal by a sputter coater in a high vacuum chamber. The etched surfaces were observed using a white light profilometer TMS 1200. The results show that best anisotropic patterns formation were obtained in 30% wt KOH solution. Furthermore, the TMS indicates that the surface roughness of the etched surface tends to increase with the increasing of KOH concentration.

Modification of Polystyrene Morphology and its Influence to the Coated Zinc Phthalocyanine Layer and Frequency Change in QCM Sensor

This study observed the influence of solvents on polystyrene regarding the layered morphologies of zinc phthalocyanine (ZnPc) and its influence on the bovine serum albumin (BSA) immobilization on quartz crystal microbalance (QCM) sensor. The larger surface width introduced by surface roughness of the polystyrene due to chloroform (CHCl3) as the solvents allows more ZnPc to be trapped within the polystyrene. Moreover, the wider surface width also increases the amount of ZnPc to be deposited on top of the polystyrene surface. Therefore, the ZnPc layer deposited onto polystyrene created with CHCl3 solvent is thicker than other solvents, which result in the largest ∆f of the ZnPc layer.

Effect of Xylene and Tetrahydrofuran Solvent Type on Polystyrene Layer Thickness With Spin Coating Method

Surface modification of QCM by applying polystyrene (Ps) as a coating layer has been investigated. The PS layer was coated onto QCM sensor by using spin coating method. Polystyrene was dissolved in two different solvents i.e., xylene and Tetrahydrofuran (THF) with various concentration i,e 1%, 2%, 3%, 4%, 5% and the velocity angular of spin coater were 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, dan 4000 rpm. The results show that different solvent result in the difference of thickness of polystyrene coating layer. By calculation with the Sauerbrey equation, the thickness of Ps layer using xylene solvent show 0.1 µm, 0.28 µm, 0.35 µm, 0.59 µm, and 0.81 µm. While by using THF, the thickness of each Ps layer are 0.15 µm, 0.43 µm, 0.84 µm, 0.97 µm, 1.28 µm. On the other hand, by applying different velocity of spin coater, the thickness of polystyrene with xylene are 0.486 µm, 0.445 µm, 0.432 µm, 0.350 µm, 0.320 µm, 0,290 µm, respectively. Moreover, the thickness of PS layer by using THF show 1.05 µm, 0.93 µm, 0.87 µm, 0.84 µm, 0.67 µm, 0.52 µm. Vapor pressure of each solvent is considered as the main property of solvent which influence the thickness of coating. The vapor pressure of THF (143 mmHg) is higher than the vapor pressure of xylene (72 mmHg), the thickness Ps layer with THF is thicker than that of by xylene solvents.

Solvent Effect on Morphology of Polystyrene Coating and their Role to Improvement for Biomolecule Immobilization in Application of QCM Based Biosensor

This research is focused on the synthesis of a polystiren layer for biosensors based on a Quartz Crystal Microbalance sensor (QCM) to immobilize the biomolecule. The polystyrene thin film was deposited by means of spin coating method with various solvents, such as chloroform, toluene, xylene, and tetrahydrofuran (THF), containing a 3% polystyrene solution by mass. The morphologies of the polystyrene layers were observed via SEM/EDx. The polystyrene surface coated using chloroform as the solvent has a rougher morphology and the largest diameter pores compared with the other solvents. The result show the polystyrene surface coating produced with chloroform caused a higher frequency change, which resulted in the binding of a wider range of biomolecules.