Controlled liquid flow in a microfluidic network with pressure sensitive valves based on polydimethylsiloxane (PDMS) /neodymium (NdFeB) composites

We present the application of a composite material, consisting of a ferromagnetic neodymium powder and a silicone elastomer, alone to realize a microfluidic network with pressure sensitive passive valves. The mixing ratio of the composite and the degree of magnetization can be utilized to adjust the switching point of each single valve. By combining differently adjusted valves within a microfluidic network it is possible to realize a sort of liquid logic and to control the flow in the network just by changing the inward flow respectively pressure. This concept holds the advantage that it is purely passive, the switching points can be adjusted over a wide pressure range and the valves are not sensitive to contamination and/or chemical degradation. In our contribution we report on details of the fabrication technology and on the performance of the valves in a test device.