Elastic Magnetic Membrane for Improved Mixing in Microwells

We demonstrate a simple method to fabricate elastic magnetic membrane which could be used to enhance mixing in microwells of a microtitre plate. The magnetic membrane was fabricated using an off-the-shelf flexible magnetic sheet and the elastomer polydimethylsiloxane (PDMS). In order to demonstrate the concept, the membrane was integrated in a single microwell to act as an actuator for improved mixing. A customized electromagnet was used to allow contactless and robust actuation. The membrane can achieve a unidirectional deflection of about 120 µm when a 3 A direct current (DC) is applied. Periodic deflection is achieved by applying a square wave alternating current (AC) of 100 Hz and ±3 A. In the dynamic case, the membrane follows the square wave with the same frequency and provides a peak-to-peak deflection of about 115 µm. The observed oscillation was able to mix the fluorescent dye and an aqueous solution within 18 seconds. The proposed method has the potential to be implemented in microtiter plate arrays to improve mixing.