Characterization and separation of Cryptosporidium and Giardia cells using on-chip dielectrophoresis.

Dielectrophoresis (DEP) has been shown to have significant potential for the characterization of cells and could become an efficient tool for rapid identification and assessment of microorganisms. The present work is focused on the trapping, characterization, and separation of two species of Cryptosporidium (C. parvum and C. muris) and Giardia lambia (G. lambia) using a microfluidic experimental setup. Cryptosporidium oocysts, which are 2-4 µm in size and nearly spherical in shape, are used for the preliminary stage of prototype development and testing. G. lambia cysts are 8-12 µm in size. In order to facilitate effective trapping, simulations were performed to study the effects of buffer conductivity and applied voltage on the flow and cell transport inside the DEP chip. Microscopic experiments were performed using the fabricated device and the real part of Clausius-Mossotti factor of the cells was estimated from critical voltages for particle trapping at the electrodes under steady fluid flow. The dielectric properties of the cell compartments (cytoplasm and membrane) were calculated based on a single shell model of the cells. The separation of C. muris and G. lambia is achieved successfully at a frequency of 10 MHz and a voltage of 3 Vpp (peak to peak voltage).

Automatic hole repairing for cranioplasty using Bézier surface approximation.

Cranioplasty is the procedure that repairs holes or defects in the skull with cranial implants. When the bone from the hole is missing, damaged, or infected, the defect needs to be covered with an artificial plate to protect the brain. In this study, a hole-repairing algorithm is developed to aid shaping artificial plates for cranioplasty by describing a method for filling holes in defective biomodels with unstructured triangular surface meshes or in stereolithography format. The resulting patching meshes interpolate the shape and density of the surrounding mesh. The steps in repairing a hole include hole identification, hole triangulations using genetic algorithm (GA) optimization, and a customized advancing-front meshing technique using surface approximations based on a Quartic Bézier Gregory patch.