Dipping speed

Figure 2 Frequency changes of the QCM substrate in air during 4 cycles of vertical dipping processes of cadmium octadecanoate LB films (surface pressure 20 mN m->, 20 °C, dipping speed 100 mm min- )-...

Figure 5 Effect of surface pressures on the amount of incorporated water (W2) and the evaporation speed (v ) in the transfer of cadmium octadecanoate LB films (dipping speed 100 mm min-i, 20 °C, at the 5th transfer cycle).

W 2 and v values at the 5th transfer cycle of cadmium octadecanoate at 20 mN m-i as a function of dipping speed of the QCM substrate are summarized in Table 1. The transfer ratio of LB films (W,) was 0.95 0.05 at the dipping speeds of 40 - 100 mm min. When the dipping speed was decreased, the evaporation speed (v) was decreased the well-oriented LB films could be obtained at the low dipping speed. This is consistent with the report by Pitt, et. al. that the lower transfer speed was favorable to obtain the higher quality LB films in the first 10 layers [31]. 

Effect of dipping speeds on the transfer of cadmium octadecanoate LB films ... 

The incorporated amount of water (W2) seems to increase with decreasing the dipping speed. Since the W2 value may include both the really incorporated water and the swelling with water when the substrate exists in the water subphase, the effect of dipping speed on W2 values should be divided in two factors. We have already reported... 

LB films of various lipids were transferred on a QCM as a substrate under various conditions. The mass of the transferred film (W, the transfer ratio), the amount of incorporated water (W 2), and the evaporation speed (v) were evaluated from the frequency changes of the QCM during transfer processes in situ. We could estimate the deposition state and structures of LB films from these values. When the LB films deposited at the lower surface pressure and at the higher dipping speed on the more hydrophilic surface, the smaller transfer ratio and the larger amount of incorporated water, and the larger evaporation speed of the water were observed, which indicates the deposition of the disordered LB films. On the contrary, when the well-packed LB films are obtained, the good transfer ratio (W ), the small W2... 

The effect of the time at the interface and the time in water on the detached amount was examined separately to clarify whether LB films peeled off mainly at the air-water interface or in the water phase, and the results are summarized in Table 5. Runs 1-8 show the flaking amount of cadmium octadecanoate LB films with the constant dipping speed the constant time at the interface) and the different time in water. The results indicate the detached amount was independent of the time in water. On the contrary, when the time at the interface was increased and the time in water was kept constant, the detached amount of the LB films increased about two times larger (Runs 9 - 15). From these findings, It can be concluded that the LB films peeled off at the air-water interface but not in the water phase when the substrate is lowered slowly with the long contact time at the interface. 

Figure 18 Effect of water temperature on the detached amount of LB films at the first dipping cycle (10 layers of cadmium octadecanoate on each side of the QCM dipping speed, 100 mm min- )-... 

Figure 20 Effect of number of layers of cadmium octadecanoate LB films on the QCM on the detached amount, (at 20 °C dipping speed, 100 mm min-i)-...

A suitable z piezo voltage is applied to dip the tip into the substrate by 3.5 nm while the tip is over an atomically flat surface area. The dipping will coat the tip with Ag atoms. Dipping speeds between 0.2 and 2.5 nm/s and tunneling biases... 

Figure 8. Effect of dipping speed/production speed of weight and thickness of condom.

FIGURE 2 Scanning electron micrograph of a polyaniline film deposited by the L-B technique from a CHCl solution. Aqueous subphase. A dipping speed of 3 mm/min and a pressure of 25 mN/m were employed. (Data reproduced with kind permission from Dr. B. D. Malhotra.)... 

A nanoparticulate Ti02-stearate (Ti02-St) monolayer was obtained directly using Ti02 hydrosol as the subphase. The surface pressure versus surface area isotherm showed that the monolayer could be compressed to a mean molecular area of 0.25 nm The monolayer was transferred onto hydrophobic and hydrophilic /i-type, p-type Si substrates at a dipping speed of 18 cm/min under a surface pressure of 25 mN/m. The transfer ratio was 1.0 0.1. The transmission electron microscopic (TEM) images of TiOi-stearate monolayers showed relatively densely... 

A 0.5 mg ml solution of C[4]RA in chloroform was spread on the surface of 18 MQcm" resistivity Millipore water in order to form a monolayer. The layers were then compressed to a surface pressure of 25 mN m, and this pressure was held constant during the deposition. The dipping speed for the up- and down- stroke of the slide was set to 5 mm min. The transfer ratios were close to unity. The substrates for the LB deposition were prepared by coating standard microscopic glass slides with a 3 nm seed layer of chromium and a 150 nm thick layer of gold using thermal evaporation in vacuum. The slides were left in saturated vapours of dimethyldisilazane for 24 hours in order to improve their hydrophobicity. A sensing membrane typically consisted of 12 monolayers of C[4]RA molecules. 

The two approaches are in fact quite similar. The difference is that in the repelling method, water is added to the monomer solution for the dewetting process, and in the dipping method, the sample with applied undiluted monomer is dipped into a water reservoir accurate control of the dipping speed is achieved through a motorized stage. If the monomer film dewets in air, the monomer remains on the hydrophilic domains of the substrate. This is the case with the withdrawal method [15,16] in which the patterned substrate is completely immersed in the monomer and pulled out at a fixed angle and a controlled speed into ambient air. 

The closely packed monolayer is transferred onto the surface of the magnetic layer at 25 mNm-i with a dipping speed of 5 mmmin-i upon withdrawal from the water. The deposition trace suggested that there is an even deposition and the transfer ratio is about 0.75. Therefore, in the LB film monolayer, the area occupied by one salt molecule is calculated to be about 0.8 nm. The difference in occupied area per molecule indicates that the chain leans slightly to the surface normal. The tilt of the chains in the LB monolayer is induced by the deposition process. 

---