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This paper presents a feasibility study on the design of piezoelectric MEMS lateral bulk acoustic wave resonators with particular reference to the thermal effect on the resonant frequency. This study compares the results obtained from both analytical models as well as finite element simulations with the temperature effects included. This comparative study has been carried out on resonators having a resonant frequency of around 19.5 MHz using two different Thin-Film Piezoelectricon-Substrate (TPoS) MEMS processes: the first process consists of a 1 µm PZT layer over an SOI structure having a thickness of 5.5 µm, while the second process is the PiezoMUMPs MPW process consisting of a 0.5 µm AlN layer over an SOI structure having a thickness of 10 µm. Both the analytical and the finite element models indicate a frequency variation of 300 kHz over a temperature range of 273-573 K. Based on these results, a number of PiezoMUMPs resonator prototypes, including a thermal heating element, have been designed in order to explore the feasibility of fine tuning the resonant frequency using the thermal effect. The possibility of fine tuning can be applied to high precision timing circuits such as frequency counters.

Microgrippers play an important role in the manipulation of biological cells and tissues. This paper presents a horizontal electrothermally actuated microgripper that is designed for the handling and deformability characterisation of human red blood cells (RBCs). Pathological alterations in the mechanical properties of RBCs have been associated with a number of specific diseases. This has accentuated the significance of analysing the deformability characteristics of RBCs within the biomedical field. A polysilicon microgripper structure was designed and fabricated according to the dimensional specifications imposed by the commercial PolyMUMPs TM fabrication process. The microgripper design was developed and numerically modelled using finite element analysis where coupled electrothermomechanical simulations were carried out in CoventorWare. The fabrication method is presented in this paper, together with details of the experimental setup used for the actuation testing. The tip displacement of the microgripper arm when electrothermally actuated is compared with that obtained by means of numerical simulations. Results show that the microgripper arm deflected as designed when electrothermally actuated, with good agreement obtained between simulation and experimental results. This paper also proposes critical design and fabrication considerations that were implied from the experimental campaign performed in this work and that take into account out-of-plane buckling of the hot arm, fracture of the arms in the vicinity of the anchored probe pads, residual stresses, and device stiction. Such considerations are regarded as an important outcome of this work, and they must be thoroughly investigated to mitigate the malfunction or failure of the microgripper.