MEMS Biosensor Characterisation
Description: The University of Newcastle used a Zygo NewView Scanning White Light Interferometer to characterise their MEMSens biosensor
Recommended Product: Zygo NewView 7000
MEMSens is a biosensor being developed at the University of Newcastle by the Biomedicine Group . It is targeted at ultra low concentration analyte detection, for example thyroglobulin mRNA for the detection of thyroid cancer. Once the device is manufactured, it undergoes a series of tests. A Zygo surface profilometer is extensively used in this process.
Firstly, a surface profile gives a quick indication of the quality of the device.
Although the device is modelled as planar, the underlying electrodes leave their impression on the membrane. The curvature in the membrane indicates stresses are present in the layer. A voltage (in this case 200V) is applied between the electrodes and the membrane and a second profile is taken. The first profile is subtracted from this second measurement and the deflection of the membrane under this applied voltage is clearly visible.
This methodology gives a rapid check to see if the device is free to vibrate as expected. After further dynamic testing, the device must be functionalised. PDMS printing has been investigated as a technique to immobilize the required antibodies onto the sensor surface. The surface profiler is used to check the quality of the stamp and printed image. A 7um deep silicon template was created from which the PDMS stamp was produced.
The printed antibodies demonstrated the high resolution which can be obtained from this technique. Note that the antibodies are transparent and therefore appear as a recess in the surface profile.
Drying marks left over after use can be seen on the base of the stamp