Case Study: Electromagnetic MEMs Control & Imaging

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Introduction

We worked with the University of Exeter to develop them a bench-top instrument that could manipulate their magneto-elastic MEMs swimming device. The instrument was to produce a programmable electromagnetic field using a single pair of helmholtz coils. An in-built microscope observed the MEM device from beneath and recorded its movement and position in real-time in correspondance to the excitation field. The instrument was to feature a platform for locating a petri dish which contained the fluid and the swimmer. The user was to control and oberve the swimmer from a simple 7" touchscreen on the front of the instrument.

Key Points

  • Bench-top, self contained electromagnetic excitation and observation instrument.

  • Single Helmholtz coil programmable 5-200Hz at 5mT.

  • In-built inverted microscope with epi-illumination and 20x magnification.

  • Stage for loading petri dish containing fluid and swimmer.

  • 7" touchscreen containing simple slide controls of Frequency, Amplitude & Illumination with REC/STOP for recording.

  • Network options included USB port for storing images/movies and Ethernet forfuture network control.

Project Outcome

Technologies

electromagnetics microscopy software electronics

Customer

External Links & Publications

  • EU MagElastic Project

    • Design & 3D CAD

    The instrument was designed in SolidWorks, this allowed all the mechanical, electronic and magnetic components to be designed such that they could be integrated into the system. The housing was laser cut steel, folded, welded and powder coated. The coils were machined and wound in-house. The coils were mounted on a 3D printed turntable so that they could be rotated independantly of the unit. The electronic control board was designed in KiCAD and assembled in-house.

    Electronic Control Board

    At the heart of the instrument is a custom eletronics control board. It features the coil amplifier, which is driven by a waveform generator from Analog Devices. The waveform generator produces a sinusodial waveform whose frequency and amplitude is programmable. The board contains a STM32F4x microntroller from ST running the control firmware and USB communications to the raspberry Pi controller.

    Software & User Interface

    The software was Python based using a UI library called KIVY. The interface had to be simple, clean and optimised for use with gloved hands. It features simple buttons and sliders for controlling parameters. The instrument featured a Raspberry Pi and communicated with the custom electronics and camera module via USB. It was the Raspberry Pi which provided the Ethernet and USB disk drive connectivity.

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