The present invention relates to a process for sensing biological or chemical changes in molecular structural shape or mass of molecules attached to the surface of a transverse shear piezoelectric oscillating molecular sensing device driven by a network analyzer. The process comprises the steps of i) exciting the sensor device at a series of predetermined frequencies, ii) collecting data to determine values for the predetermined parameters of series resonance frequency shift (fS), motional resistance (RM), motional inductance (LM), motional capacitance (CM), electrostatic capacitance (Co) and boundary layer slip parameter (); and iii) determining relative changes in the measured parameters to detect thereby any changes in molecular structural shape or mass at sensing device surface.