An N-dodecylated chitosan (CS-12) was synthesized from dodecyl bromide and chitosan and was assembled with DNA to form a polyelectrolyte complex (DNA/ CS-12 PEC). UV was used to examine the thermal stability of DNA embedded in PEC. The results indicate that the incorporation of dodecylated chitosan can enhance the thermal stability of DNA. The analysis of AFM image shows that PEC develops a globule-like structure composed of 40 -115 DNA molecules. Dissociation of PEC was investigated by the addition of low molecular weight electrolytes. The added small molecular salts dissociate the PEC, inducing DNA to release. The ability of Mg 2ϩ to dissociate PEC is greater compared to that of Na ϩ and K ϩ . From AFM images, it can be visualized that DNA remains intact and undamaged due to the protection from DNase offered by alkylated chitosan.

Butyl, octyl and hexadecyl moieties were introduced into chitosan. The adhesion of bovine serum albumin (BSA) onto glucose aldehyde‐crosslinked alkylated chitosan membranes in pH media was investigated by probing the force‐displacement curves with BSA‐coated Atom force microscope (AFM) tips. The results indicated that, at the isoelectric point (IP), the sample membranes exhibited higher adhesion forces; and deviating from IP ie at pH 2, pH 6, the adhesion forces decreased. The adhesion forces at pH 2 are less than those at pH 6 due to the presence of electrostatic repulsive and attractive interactions, respectively. Measurements of the adhesion force confirmed quantitatively that the introduction of hydrophobic side‐chains to chitosan can facilitate protein adsorption; however, longer flexible side‐chains can depress protein adsorption to a certain degree. From an analyses of the adhesion forces, it is proposed that protein adsorption can be tuned by adjusting the lengths of the introduced side‐alkyl moieties.© 2002 Society of Chemical Industry

It is found that the phase position of p-component of reflected light changes with the metal film thickness, while the phase position of s-component almost doesn’t change in the Surface Plasmon Resonance effect. S-polarized light is taken as reference and interferometry is adopted to turn the change of the phase position into the change of interference fringes position in the paper, and the film thickness can be derived from it. The simulation results indicated that, through making use of piecewise quadratic fitting on the phase data, the inaccuracy with the range of film thickness is between 30 and 80 nanometers is not more than 0.33 nm.

SPR phase detection method is adopted in this paper to measure the thickness of nanometer scale metal film. It provided a novel means to calculate the value of thickness through figuring up the relative offset of interference fringes with the TM-polarized and TE-polarized wave reflected from the prism which is covered by a film-substrate step. Simulation results are presented out to illustrate the relations between phase variation and metal film thickness. This method is succeeded in measuring the target metal film with nominal thickness 50 nm and the average measurement value is 50.02 nm. The standard deviation is 0.41 nm and the maximum repeatability error is 0.90 nm.

Long range scanning stages with very small positioning errors are the key elements in the nano-CMM that is used to determine the sizes and coordinates of micromachines and parts in three dimensions to realize MEMS/nano technology. A transmission stage needs six degree-of-freedom precision motion controls. A compact critical angle sensor (CAS) can be mounted on the base or frame to be used to monitor the orientation parameters of the scanning/transmission stage along the 3 axes and feedback the error signal of the sensor output to maintain the stage moving performance. By calibration with an autocollimator, the resolution is better than 0.1 arcsec with a measurement range above 600 arcsec.