| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 100 === With the advance of micro- and nano-fabrication technologies, a micro-cantilever sensor has been used routinely to detect physical as well as biological signals. It can transfer the physical phenomenon such as temperature change and chemical phenomenon such as bonding or adsorption into mechanics form that can be measured.
It is believed that the self-assembled monolayers (SAM) created by alkanethiol molecules are not well-packed at initial stage of adsorption. At first, those molecules are in the lying-down phase and it takes time to transfer to standing-up phase. When those molecules are in the lying-down phase, most of the reaction areas are covered by the alkyl chain. Once they transfer to standing-up phase, those areas will be released. The different reaction areas will cause different adsorbed molecules.
This thesis studies the kinetics-induced surface stress of SAM adsorbed on gold-coated micro-cantilevers. We use an optical method to measure the surface stresses change among different concentrations, different chain lengths, and different time due to the adsorption of alkanethoil. We found two distinct chain-length effects. During 20 to 60 minutes of adsorption, surface stress will decrease when the chain length increase. After 3 to 5 hours, surface stress will increase when the chain length increase. In terms of different concentration effects, higher concentration will in general induce higher surface stress. Nevertheless, the concentration effect vanish when chain length increase.
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