Ratno Nuryadi

CO Gas-Induced Resonance Frequency Shift of ZnO-Functionalized Microcantilever in Humid Air

Resonance frequency shift of a zinc oxide- (ZnO-) functionalized microcantilever as a response to carbon monoxide (CO) gas has been investigated. Here, ZnO microrods were grown on the microcantilever surface by a hydrothermal method. The measurement of resonance frequency of the microcantilever vibrations due to the gas was carried out in two conditions, that is, gas flow with and without air pumping into an experiment chamber. The results show that the resonance frequency of the ZnO-functionalized microcantilever decreases because of CO in air pumping condition, while it increases when CO is introduced without air pumping. Such change in the resonance frequency is influenced by water vapor condition, and a possible model based on water-CO combination was proposed.

CO gas response of ZnO nanostructures using microcantilever in dynamic mode operation

We present a carbon monoxide (CO) gas response of nanostructured ZnO sensitive layer formed on a microcantilever. The ZnO nanostructures (nanorods) were prepared by a crystal growth method, and coated on microcantilever surface. The response of gas is indicated by increasing resonance frequency of microcantilever vibration in dynamic mode operation, where the gas molecules are detected in picogram level. The experimental result shows the consistent sensing behavior, indicating good sensing performance with good repeatablility and reproducibility.

Gas Sensing Using Static and Dynamic Modes Piezoresistive Microcantilever

A microcantilever has attracted interest in an application of high sensitivity sensor for chemical, physical, or biological objects. In this paper, we investigate a possibility of a piezoresistive microcantilever for gas sensing using a static and a dynamic modes operation. The gas used here is a liquefied petroleum gas (LPG). The measurement was performed by a Wheatstone bridge circuit in order to measure the microcantilever deflection or resonance frequency shift of the microcantilever vibration. The result shows that in the static mode, an output of Wheatstone bridge circuit, which attributes to the microcantilever deflection, changes due to the gas detection. For the dynamic mode, a voltage of peak-to-peak, which represents the microcantilever vibrations, decreases with increasing the gas flow time. This occurs due to the resonance frequency shift caused by the addition of gas molecules on the microcantilever surface. These results indicate that the developed system can be used as the gas sensor.

Sensitive Layer Thickness Dependence on Microcantilever Sensor Sensitivity

A sensitive layer is a main component in detecting an analyte target in a microcantilever-based biosensor. The sensitive layer coated on the microcantilever surface can induce a surface stress change as consequence of adsorbate-surface interaction. Therefore, a presence of stress is necessary to be investigated because it determines a deflection which influences the sensor sensitivity. In this work, we study a dependence of the film stress and microcantilever deflection on the gold or 3-Aminopropyltriethoxysilane (aminosilane) layers thickness in static mode operation. It is found that the optimum thickness of the sensitive layer for both aminosilane and gold can be obtained by analyzing the maximum film stress and the maximum microcantilever deflection. We also investigated the effect of Youngs moduli on the maximum stress and the maximum deflection. It is obtained that the Youngs moduli is a function that determines the peaks on the maximum stress and the maximum deflection. Our results indicate that the material properties and the thickness of sensitive layer should be considered to obtain a high sensitivity of microcantilever biosensor.

A simulation of the applied bias effect of tunnelling probability in quadruple barrier Si/SiO 2 system

Recently, multiple quantum wells structure are often used in the laser and diode applications in order to increase their efficiency. In this structure, electron tunnelling phenomena from a quantum well to another well play a key role in electronic transport itself. Tunnelling is a quantum mechanical phenomenon where an electron is commonly represented by its wavefunction. This paper presents a numerical simulation of electron tunnelling probability on three quantum wells (quadruple barrier) Si/SiO2 system focusing the applied bias effect on the tunnelling probability. The tunneling probability is calculated by solving the Schrodingers equations through potential barrier using transfer matrix method. The simulation results show the mini-band formation due to the appearance of discrete energy group. We also found that the applied bias on this structure causes the changes in tunnelling probability and discrete energy gap. Therefore, the control of voltage bias and device structure is required in order to obtain expected characteristic of multiple quantum well structure.

Simulation of mini-band formation in triple si quantum wells based resonant tunneling diode

In this work, we investigate the formation of mini-band energy in triple Si quantum wells-based resonance tunnelling diode focusing on the effect of applied bias on the band. The formation of mini-bands is obtained from the calculation of electron tunnelling probability through the wells. The calculation is done based on transfer matrix method. The simulation results show the mini-band formation due to the appearance of discrete energy group. The changes of applied bias, quantum well width and barrier thickness causes the change of the mini-band width. These results indicate that the device structure and applied bias condition play a key role on the formation of mini-band energy in the quantum wells.

Preparasi Lapisan Hidroksiapatit pada Substrat Stainless Steel 316 dengan Metode Deposisi Elektroforesis

Hidroksiapatit (HA) sangat berpotensi untuk digunakan dalam implantasi jaringan keras. Makalah ini memaparkan pelapisan HA pada substrat stainless steel 316 untuk meningkatkan sifat mekanis HA dengan menggunakan metode deposisi elektroforesis. Pengaruh tiga parameter yaitu variasi waktu deposisi (15 menit dan 60 menit), kehalusan permukaan (600 grit dan 1200 grit ), dan suhu sintering (800 o C, 900 o C, 1000 o C, dan 1200 o C) terhadap lapisan HA diamati. Hasil penelitian menunjukkan bahwa pelapisan HA pada substrat SS 316 lebih tebal pada waktu deposit 60 menit, dengan hasil padat dan homogen didapatkan pada kondisi permukaan substrat yang telah diamplas dengan kertas silikon karbida 1200 grit dan suhu sintering 900 o C.