In this cumulative thesis, six publications are presented which summarize the researched topics during the PhD studies. The research work revolved around acoustic sensors and transducers for fluid properties sensing and particle manipulation in microfluidic devices. This is reflected in the choice of the presented publications and is the binding factor between them. An introductory chapter briefly discusses the theory behind some of the concepts discussed in the publications, as well as give a view into the state of art for some of the presented technologies. The publications are then introduced in a manner that highlights their dependency and separated into two sections: journal publications and conference papers. The first four publications follow the research work done on electromagnetically actuated suspended plate resonating sensors for viscosity and density measurements. The first publication discusses the optimization of the single plate resonator setup to counteract clamping and magnetic circuit ensued intrinsic damping, and a study of the sensor's sensitivity. The second of the journal publications discusses a symmetric plate suspended resonator, which has a reduced intrinsic damping as a result of the tuning fork based design and counteracted eddy current damping when operated in the tuning fork mode with the discussed magnetic circuit configuration. In the same publication the validity of a generalized model for resonating sensors is studied for the case of the shearing plate resonator and the results presented show that the observed resonance frequency and quality factor shifts are dependent on the square root of the viscosity and mass density product. The symmetric plate resonating sensor also opens the way for multi-modal analysis of fluids with relative ease due to the possibility of actuating two different shear modes with the same measurement setup configuration. The third publication introduces the parallel plate sensor setup for highly viscous and viscoelastic fluid characterization. In it is shown that by using shear wave transmission between fluid-coupled, parallelly set up, resonating plates, viscosities of 17 Pa.s or more can be measured with fluid samples not exceeding 10 micro liters in volume. The sensor is characterized and a lumped element model of it is introduced and validated. In the fourth publication, and the first of the conference proceedings papers, a suspended plate resonator array setup is presented, for multi-modal characterization of the viscoelastic synovial fluid, the joint lubricant in humans and mammals, where the measured sample is immersed in a fluid medium instead of being surrounded with air in order to avoid sample coagulation. The fifth publication introduces a PZT sensor setup for polymer flow characterization in extruder dies, the introduced sensor is designed for operation at polymer melt temperatures and pressures reaching 300 bar. The sixth and last of the papers discusses a developed microfluidic H-filter for particle transfer between different fluidic media, where dielectrophoresis and acoustophoresis are implemented and used in combination as transfer and separation methods. In addition to the introduction and the presented publications, additional information is given after each paper to explain some points mentioned in the publications in more detail and facilitate the replication of devices and results, or just to give some extra details about the work that did not make it to the published versions or that are still in progress.