This work focuses on flow control concepts for microfluidics devices based on thermally responsive polymer solutions are presented. In particular, this work uses the thermally triggered reversible phase change of thermally responsive fluid. Selective heating of small regions of microfluidic channels, which leads to localized gel formation in these channels and reversible channel blockage, is used to control a membrane valve that controls flow in a separate channel. This new technology will allow generating inexpensive portable bioanalysis tools where microvalve actuation occurs simply through heaters at a constant pressure source without a need for large external pressure control systems as is currently the case. Furthermore, a concept for controlled cross-channel transport of particles and potentially cells has been developed presented that relies on the continuous regeneration of a gel wall at the diffusive interface of two co-streaming fluids in a microfluidic channel.