IONIC SELF-ASSEMBLY AND HUMIDITY SENSITIVITY OF POLYELECTROLYTE MULTILAYERS

Multilayer thin films of alternately adsorbed layers of polyelectrolytes PDDA and PS-119 were formed on bothplanar silica substrates and optical fibers through the ionic self-assembly technique. Intrinsic Fabry-Perot cavities werefabricated by stepwise assembling the polyelectrolytes onto the ends of optical fibers for the purposes of fiber optical deviceand sensor development. Ionically assembled polyelectrolyte multilayer thin films, in which there are hydrophilic side groupswith strong affinity towards water molecules, are a category of humidity-sensitive functional materials. The polyelectrolytemultilayer thin film Fabry-Perot cavity-type fiber optical humidity sensor can work over a wide range from about 0% RH toabout 100% RH with a response time less than 1s.