Periodic convection of superparamagnetic beads within a microfluidic channel by interlocked, electroplated structures activated by a static field

• Implementation of a simple method for bead manipulation in a lab-on-a-chip device
• No complex switching field required, since the magnetic field can be designed
• Up-concentration and labeling of biomarker with superparamagnetic beads
• Combination of magnetic actuation forces and hydrodynamic forces
• Periodic convection of superparamagnetic beads within a static field

To enhance point-of-care analysis by means of lab-on-a-chip devices, functionalized superparamagnetic beads can be used in combination with micro-sensing. Prior to detection of specific low-concentrated biomarkers a pretreatment step is necessary in most cases. Here we present a novel approach for the periodic convection of superparamagnetic beads for intensified up-concentration and biomarker labeling. In contrast to previous approaches, where dynamic switching fields were applied, our system can be activated within a static field, but still allows a controlled movement in two directions. By introducing softmagnetic structures, the magnetic field as well as the field gradient can be periodically modulated along the microfluidic channel. Suitable shapes of pole pieces were analyzed using Finite Element Method simulation before the microsystem was micro-fabricated and tested. Experiments show how the flow rate within the channel and the magnetic field cooperate to establish an operational regime in which periodic convection can be established and controlled.

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