Micro-electro-fluidic module to control magnetotactic bacteria for micromanipulation tasks under an optical microscope

This project describes a Multi-Chip Module (MCM) that contains a microelectronic circuit and a microfluidic device that could be combined to implement a “bacterial microfactory”. The microchip contains two decoders connected to arrays of horizontal and vertical wires respectively, forming a matrix used to process commands received from an external computer. The electrical current flowing through the matrix is generated from internal voltage-to-current converters. The electrical current circulating through a metal conductor generates a magnetic field that is used to guide the movement of Magnetotactic Bacteria (MTB) in the microfluidic device. The dedicated microfluidic device is micro-fabricated on a glass wafer. Preliminary results show that a single MC-1 MTB can push a 2 μm microbead at speeds reaching 100μm/s under the control of an external magnetic field of less than 10 Gauss. A Carl Zeiss microscopy software (AxioVision) is used to control and configure the Axio Imager Z1 optical microscope and allows us to develop customized plug-in with Visual Basic for Application (VBA). The control electronic die was hence programmed as a VBA module, simplifying interoperability between the control, data recordings and microscopy observations. The parallel port of an Intel Pentium 4, 3.0 GHz equipped with 2.87 Go of RAM running Windows XP was used to communicate with the circuit. Connected to the parallel port, two demultiplexers interface the chip and the port. Patterns to control the bacteria such as left-right and up-down displacements were implemented and tested. Other more complex patterns to capture, attract and repel the bacteria from the center of the chip were also designed and validated.