Papers by Author: Maan M. Alkaisi

Abstract: AC electrokinetics is one of many methods used to move particles in microfluidic channels. This paper presents single cell trapping efficacy using dielectrophoresis (DEP) force of two biochip designs; a planar biochip and the new sandwiched-insulation with back contact (SIBC) biochip. The new biochip, is structured on a glass slide, consists of microelectrode arrays patterned on top of Nickel-Chromium (NiCr) and Gold (Au) layers. Prior to the microelectrode patterning, a back contact layer of NiCr and Au was coated with SU-8 2005. Then, the SU-8 2005 or the insulation layer was patterned with arrays of microcavities. In contrast, the planar biochip consists of 2 layers; an SU-8 2005 insulation layer and NiCr and Au metal layers constructed on a Silicon Nitride (Si₃N₄) substrate. The electric field intensity results simulated using Comsol v3.5a software indicated that DEP force generated from the SIBC biochip are greater than the planar biochip design. Results from experiment with polystyrene microbeads and Ishikawa cancer cells also showed that the SIBC biochip has higher trapping efficiency than the planar biochip. These promising results indicate that the SIBC biochip is capable of trapping single cells and can be used to facilitate studies on intracellular activities using surface the replicating technique known as the Bioimprint technique.

Abstract: With a reduced set of 300 neurons and a fully sequenced genome, the multicellular nematode Caenorhabditis elegans has recently gained increasing interest as a model organism for neurobiological studies. One particular area of interest is related to worm locomotion and the investigation of the correlation between individual genes, neurons, muscle arms and the motion pattern of the nematodes. To characterize motion patterns of moving C. elegans we have previously demonstrated an automated force measurement setup using microfabricated polydimethylsiloxane (PDMS) pillars and image processing. In this paper we introduce an integrated microfluidic device for worm sorting and force measurement. The device allows for high-throughput measurements by combining sorting functions on-chip with the existing force pattern measurement system. A horizontal sorting channel and branching vertical pillar array channels are utilized for worm sorting. Using the former, the nematodes can be flow-directed into arrays of 40 µm and 60 µm diameter pillars based on worm size and type. This improves animal survival and increases the relevance of the force measurement by allowing one to match the amplitude of the worm movement to the pillar spacing. The PDMS based device consists of three layers: a fluidic layer with pillars for force measurement at the bottom, a gas layer on top and a thin PDMS layer sandwiched between them. By applying pressure to the gas layer, the membrane in the middle will be deflected thus restricting the worms’ movement in the fluidic channel.