The micro-domain provides excellent conditions for performing biological experiments on small populations of cells and has given rise to the proliferation of so-called lab-on-a-chip devices. In order to fully utilize the benefits of cell assays, means of retaining cells at defined locations over time are required. Here, the creation of scale-like cantilevers, inspired by biomimetics, on planar silicon nitride (Si3N4) film using focused ion beam machining is described. Using SEM imaging, regular tilting of the cantilever with almost no warping of the cantilever was uncovered. Finite element analysis showed that the scale-like cantilever was best at limiting stress concentration without difficulty in manufacture and having stresses more evenly distributed along the edge. It also had a major advantage in that the degree of deflection could be simply altered by changing the central angle. From a piling simulation conducted, it was found that a random delivery of simulated particles on to the scale-like obstacle should create a triangular collection. In the experimental trapping of polystyrene beads in suspension, the basic triangular piling structure was observed, but with extended tails and a fanning out around the obstacle. This was attributed to the aggregation tendency of polystyrene beads that acted on top of the piling behavior. In the experiment with bacterial cells, triangular pile up behind the cantilever was absent and the bacteria cells were able to slip inside the cantilever’s opening despite the size of the bacteria being larger than the gap. Overall, the fabricated scale-like cantilever architectures offer a viable way to trap small populations of material in suspension.
Thermal bimorphs are extensively used in engineering applications with its ability to generate large forces and deflections. A new pore-structured thermal microactuator design, which incorporates the thermal bimorph concept, is proposed to trap single biological cells for sensing and imaging. This can act as an alternative to the existing methods as it possesses the potential to trap the cells without any repercussions while being relatively low cost and easy to operate. In this study, the thermal microactuator design is investigated and analysed using finite element analysis (FEA) where the deflection was determined to be dependent on the effective length and the coefficients of thermal expansion (CTE). Upon thermal loading, the internal stresses were found to be tunable by employing several geometric modifications. With determined parameters, prototypes of the design were fabricated on silicon nitride (Si3N4) membrane with Polydimethylsiloxane (PDMS) coating.