Initially this Workpackage will involve the development of a detector for detecting movement of magnetic particles of various types (produced in Workpackage 5). This will involve use of equipment such as MFM and r.f. STM combined with movement of the beads by means of external forces or external magnetic fields.  Other methods that will be investigated include micron-sized Hall effect sensors, flux gates or resonant force detection of the magnetisation.  Micro-scale, non-invasive, SQUID is also a possible as a technology for the most sensitive measurements.

Outcomes:

NPL have provided the Consortium with a report on potential detectors for this Deliverable (this report is available on the Mol Switch Website).  The obvious candidate is, as originally proposed, a Hall Effect Sensor, but a good (but extremely bulky yet freely available) alternative, is a Magnetic Force Microscope (MFM).  MFM will be used to characterise the magnetic properties of commercial beads, currently in use in the Magnetic Tweezer Set-ups, and determine how best to handle single beads in microchannels.  In addition, NPL will develop a simple Hall Effect Sensor that could be used with the current Magnetic Tweezer Setups.

In addition, NPL have shown that detection of individual paramagnetic beads (with the size down to 1 μm) was successfully demonstrated at room temperature using a scanning Hall microscope (fabricated from an InSb/GaAs single quantum well heterostructure, an active area size is about 3x3 μm2). Additionally a prototype of the sensor containing an array of 1 μm size Hall probes on a transparent sapphire substrate, i.e. compatible with the magnetic tweezers set-up, was fabricated.