My recent work on magnetically actuating an array of microridges has been published in Advanced Functional Materials. We have shown that by controlling the angle of the 325 micron long array elements, we can controllably adhere to a range of particle sizes.

Figure_3

Ridge angle can be controlled via an external magnetic field.

Figure_2

Magnetic particles are mixed and cured into the liquid PDMS during casting, and aligned during curing by an external magnetic field.

Here is a link to the article: http://onlinelibrary.wiley.com/doi/10.1002/adfm.201203122/abstract