Quartz Crystal Microbalance (QCM) is a high sensitivity piezoelectric sensor that enables it to detect loads in the nanogram order. QCM usually consists of a thin quartz plate with an AT-cut orientation. The sensor resonance frequency and its stability are affected by the sensor parameter and its placement in the reaction cell. Previous studies have shown that the physical parameters and geometric shapes of the QCM sensor greatly affected the sensitivity and stability of the sensor. As the sensor is thin, only in the order of hundredths micrometer, pressure, or force on top of the sensor surface also affects the sensor resonance frequency. In this study, we conducted a deformation analysis due to the placement of QCM on the Printed Circuit Board (PCB). The simulation is done by Finite Element Method using ANSYS 19.2. Variations in the shape of the electrodes on the PCB and O-ring elastic modulus that used in the QCM system has been investigated O-rings that have a smaller elastic modulus that will cause greater deformation. From the two types of PCB electrodes, electrodes in the form of ¾ circular arcs give smaller deformations than electrodes in the form of ½ circular arcs. The deformation occurs in the order of 10−6 m.

Piezoelectric material produces electric fields due to a change of material dimension as an impact of external force/stress applied. One of the piezoelectric materials that widely used for a sensor is quartz crystals. Cutting crystal at its AT-Cut angle causes this material to have piezoelectric properties. Phenomena that occur on quartz surfaces can be observed and expressed as changes in the resonance frequency of sensors. In this experiment, a continuous uniaxial force from 0 N to 10 N was applied to the surface of the quartz crystal microbalance (QCM). The result shows that the resonance frequency of the QCM depends on the applied force. The resonance frequency increases as the applied force is increased. When the applied force is gradually decreased, the resonance frequency is also decreased and back to its original resonance frequency when there is no applied force. The frequency change of the sensor was linearly depend on the applied uniaxial force to the sensor.

The thermoelectric device has advantages for heating and cooling element. The thermoelectric can be used easily as a heater. In applications for small volumes, the temperature distribution of the heating element is necessary to ensure that different samples at different locations receive the same heat treatment. This experiment shows an aluminum fin’s temperature distribution heated using different heat amount. TEC-12706 was used to heat an aluminum fin with a dimension of 40×40×20 mm. The aluminum was placed in an chamber made using a 3D printer with a material of ABS. The surface temperature distribution of the aluminum fin was measured using a thermal camera Fluke-Ti20S. The measurement data showed that the fin’s surface temperature is not the same at all points at the surface, especially the center and the edge. During the heating process, the temperature at the aluminum fin’s center has a higher temperature than the fin’s edge. The lower the duty cycle used, the better the temperature distribution on the heatsink. For 50% duty cycle or more, the temperature variation in the middle with a square dimension of 20×20 mm has a temperature variation of less than 1°C. Therefore, if the temperature distribution between points is important, it is recommended to use an aluminum fin around the center.

Thermal Cycler is the main part of the Polymerase Chain Reaction (PCR), which becoming a gold standard for Covid-19 diagnosis. The virus multiplication in an order to a detectable concentration is done by placing the virus solution at a deterministic temperature cycle. The solution is placed in a small tube inserted in a temperature block. Temperature distribution of the thermal block is important to make all the tube with sample treated at the same at desired target temperature. Study on the thermal block made of aluminium 7075 was simulated using fluid dynamic finite element method. Heating and colling to the target temperature was done by providing heat source and heat absorber. The temperature distribution on the surface was mapped. The temperature gradient perpendicular to the heat source was calculated. Assuming the environment of the thermal block was still air, the heating and cooling speed at given heat source and heat removal were calculated using the model. The temperature gradient from the top surface to the bottom surface is less than 2.5°C. The temperature difference among point at the surface is less than 0.1°C.

No abstract