Modification of Chitosan Membranes via Methane Ion Beam.

Chitosan has been used for biomedical applications in recent years, primarily because of its biocompatibility. A chitosan membrane with a 30 µm thickness was prepared and investigated for its surface modification using methane ions. Methane ions were implanted into the chitosan membrane using a Kaufman ion source; bombardment was accomplished using three accelerating voltages of ion beams-30, 55, and 80 keV. The influence of the ion bombardment on morphology, crystallinity, and hydrophilicity was investigated. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy analysis showed that a triplet bond appeared after the implantation of methane ions (acceleration voltage: 80 keV), culminating in the creation of a more amorphous membrane structure. The analyses of atomic force microscopy (AFM) images showed that, with the increase in bombardment energy, the roughness of the surface changed. These results revealed that ion bombardment improved the hydrophilicity of the membranes and the water fluxes of chitosan membranes altered after methane ion bombardment.

Dielectrophoretic spectra of translational velocity and critical frequency for a spheroid in traveling electric field.

An analysis has been made of the dielectrophoretic (DEP) forces acting on a spheroidal particle in a traveling alternating electric field. The traveling field can be generated by application of alternating current signals to an octapair electrode array arranged in phase quadrature sequence. The frequency dependent force can be resolved into two orthogonal forces that are determined by the real and the imaginary parts of the Clausius-Mossotti factor. The former is determined by the gradient in the electric field and directs the particle either toward or away from the tip of the electrodes in the electrode array. The force determined by the imaginary component is in a direction along the track of the octapair interdigitated electrode array. The DEP forces are related to the dielectric properties of the particle. Experiments were conducted to determine the DEP forces in such an electrode arrangement using yeast cells (Saccharomyces cervisiate TISTR 5088) with media of various conductivities. Experimental data are presented for both viable and nonviable cells. The dielectric properties so obtained were similar to those previously reported in literature using other DEP techniques.