Peter Rothacher

The Way to High Volume Fabrication of Lab-on-a-Chip Devices—A Technological Approach for Polymer Based Microfluidic Systems with Integrated Active Valves and Pumps

We present a technology platform suitable for the mass production of laboratory-on-a-chip devices made of polymers with integrated active and passive components. The presented microfluidic platform with integrated valves and pumps for active flow management is realized with three layers consisting of two polymer parts separated by a thin elastic TPE (thermoplastic elastomer) membrane welded together in one step. The elastic TPE membrane acts as an integrated deflectable membrane layer between the two outer polymer layers, each made of a weldable thermoplastic polymer (polycarbonate). Valving is realized by applying pressure in a displacement chamber above a hydraulic channel causing the membrane to deform and to seal the channel. A pump is fabricated using a displacement chamber with a valve on the inlet and outlet. The presented components, namely valve and pump, show excellent behavior regarding response time, sealing quality, and pump rate needing only a low actuation pressure. The three-layer-stack is...

Sample Preparation on-chip: Accumulation, Lysis of and DNA Extraction from Bacteria

We present a microfluidic chip that collects and accumulates bacteria from a sample by positive dielectrophoresis and subsequently lyses cells to retrieve DNA / RNA. Biological samples containing Escherichia coli are transferred to a suitable medium (low conductivity) by on-chip dialysis. This sample is pumped through a microchannel comprising an array of interdigitated electrodes at the bottom. An AC-voltage is applied to the electrodes resulting in an inhomogeneous electric field that extends into the channel and induces dielectrophoretic forces acting on the bacteria. Herringbone- mixer structures between the electrodes induce vortices in the flow and thus rotate the fluid volume from top to bottom. This assures that all bacteria are brought under the influence of the electric field and thus may be trapped. In addition, the herringbone structures induce further inhomogeneities in the electric field. Due to this combined effect, the system allows for the trapping of bacteria even at high flow rates which results in high throughput. Bacteria from several mL of sample are concentrated into 20 μL inside the chamber. This is monitored on-line by measuring the impedance between the electrodes.