Synthesis of Stimuli-Sensitive Hydrogels in the μm and sub-μm Range by Radiation Techniques and their Application

Abstract

Abstract. The macroscopic material properties (elasticity, volume in swollen state) of smart stimuli-sensitive hydrogels show a strong dependence on the properties of an aqueous environment (swelling agent). This behavior can be used for sensors or force-generating elements (actuators). Radiochemistry offers the possibility to synthesize smart gels in a wide range of dimensions. As an example of temperature-sensitive polymers we demonstrate the advantages of a radiochemical-based approach for hydrogel synthesis. Structures in the urn and sub-urn range on a support were synthesized using different techniques. The applications of particles and patterned layers in the urn range were demonstrated using the example of devices for handling liquids 1 Stimuli-sensitive hydrogels Polymeric gels are most generally understood to be polymeric networks which absorb enough solvent to cause macroscopic changes in the sample dimension. Hydrogels are crosslinked hydrophilic polymers swollen in water. Most of their properties are directly influenced by the degree of swelling. The volume phase transition of certain hydrogels is one of the most fascinating and important phenomena in the physical chemistry of polymeric networks. Stimuli-sensitive hydrogels (they are also termed smart gels and responsive gels) are materials whose properties change in response to specific environmental stimuli (see Table 1). They change their volume (equilibrium degree of swelling), mechanical properties (elasticity, stiffness) and molecular transport properties, in response to a small change in the properties of the swelling agent, like temperature, solvent composition, pH value, mechanical strain, ion concentration, etc. The change in the degree of swelling may occur discontinuously at a specific value of stimulus or gradually over a (mostly small) range of stimulus values.Polymer gels have found wide application in various fields: medicine, agriculture, biotechnology, nutritive industry, petrochemical industry, etc. For these applications only the ability of a gel to absorb solvent and to swell is important, not the relationship between changes in the environment and swelling.The ability to directly convert chemical energy into mechanical work makes smart gels candidates for actuator and sensor systems, which can operate without additional Barbucci R. (Ed): Hydrogels. Biological Properties and Applications.

Lab-in-a-tube: ultracompact components for on-chip capture and detection of individual micro-/nanoorganisms

“…138 This effect can be used to realize valve-like devices for microfluidics. 139 An important step towards realization of this concept, by fabrication of compact rolled-up heater devices, for fluidic applications using rolled-up nanotech, was recently reported. 54 The heating elements on the surface of these devices should provide a temperature above the LCST value.…”