Jianren Lu

Fabrication of high-Q film bulk acoustic resonator (FBAR) filters with carbon nanotube (CNT) electrodes

FBAR devices with carbon nanotube (CNT) electrodes have been developed with the aim of taking advantage of the low density and high acoustic impedance of the CNTs compared to other known materials. The influence of the CNTs on the frequency response of the FBAR devices was studied by comparing two identical sets of devices, one set comprised FBARs fabricated with chromium/gold bilayer electrodes, and the second set comprised FBARs fabricated with CNT electrodes. It was found that the CNTs had a significant effect on attenuating travelling waves at the surface of the FBARs membranes due to their high elastic stiffness. Finite element analysis of the devices fabricated was carried out using COMSOL Multiphysics, and the numerical results confirmed the experimental results obtained.

Solidly mounted resonators with carbon nanotube electrodes for biosensing applications

The work reported here shows a direct experimental comparison of the sensitivities of AlN solidly mounted resonators (SMR)-based biosensors fabricated with standard metal electrodes and with carbon nanotube electrodes. SMRs resonating at frequencies around 1.75 GHz have been fabricated, some devices using a thin film of multi-wall carbon nanotubes (CNTs) as the top electrode material and some identical devices using a chromium/gold electrode. Protein solutions with different concentrations were loaded on the top of the resonators and their responses to mass-load from physically adsorbed coatings were investigated. Results show that resonators using CNTs as the top electrode material exhibited higher frequency change for a given load due to the higher active surface area of a thin film of interconnecting CNTs compared to that of a metal thin film electrode and hence exhibited greater mass loading sensitivity. It is therefore concluded that the use of CNT electrodes on resonators for their use as gravimetric biosensors is viable and worthwhile.

Isolation of Immunoglobulin from Chicken Egg Yolk using Single-Stage Ultrafiltration with 100-kDa Regenerated Cellulose Membranes

The aim of this work is to develop a membrane-based cost-effective process for the rapid isolation of immunoglobulin from chicken egg yolk. It was found that a single-stage ultrafiltration using a 100 kDa molecular weight cut-off regenerated cellulose membrane could be employed to isolate immunoglobulin from the crude feedstock. The effects of operational parameters (solution pH, ionic strength, stirring speed and permeate flux) on the transmission of immunoglobulin and the presence of impurity protein with molecular weight close to immunoglobulin were quantified using the parameter scanning ultrafiltration technique. Under optimized conditions, the purity of immunoglobulin obtained was about 85 percent after the single-stage ultrafiltration process, and the recovery of immunoglobulin from the feedstock was 91 percent.