PMMA/64° YX-LiNbO3 guided SH-SAW based immunosensing system

In this study, a poly methylmethacrylate (PMMA)/64° YX-LiNbO₃ guided shear horizontal mode surface acoustic wave (SH-SAW) sensor was designed and fabricated for the detection of biological antigen-antibody interactions. Various thicknesses of PMMA guiding layer were spin coated on SH-SAW sensor. A test setup utilizing a small-volume flow cell with inlet and outlet ports for the microfluidic cell and employing polydimethylsiloxane (PDMS) based microfluidic channels, was also designed and fabricated using an acrylic material with a reservoir volume of 3 μl. The interactions between protein G and immunoglobulin G (IgG) solutions were measured and analyzed using the PMMA coated SH-SAW devices. The frequency shift of 64° YX-LiNbO₃ device with 0.4 μm PMMA guiding layer was measured from 3 kHz to 68 kHz as the concentration of IgG was increased from 1 μg/ml to 10 μg/ml. The calculated sensitivity of the guided SH-SAW was found to be 7.3 KHz/(μg/ml).