Biomolecule Patterning

The Nanofountain Probe (NFP) is capable of patterning biomolecules (e.g., proteins [1], DNA [2]) in buffer solution with sub-100-nanometer resolution. The figure below shows examples of linear (a) and dot (b) arrays of proteins patterned using the NFP. In the case of line features, deposition rates as high as 80 microns/second were demonstrated, which is two orders of magnitude faster than has been demonstrated using conventional DPN.

In some cases, biomolecule deposition was initially found to be relatively slow and somewhat sporadic during passive deposition. To overcome this, we explored the use of electric fields to assist and control the deposition. A potential was applied between the NFP reservoir and the substrate to assist the transport of charged molecules (e.g. proteins). The field induced transport enabled a rapid deposition of BSA in the form of dots and line features at a speed of 80 microns/second. Reversal of the field resulted in the suppression of transport. Modeling of the deposition process confirmed the importance of the electric field energy to achieve the transport of charged proteins. Overall, the use of electric fields in NFP-based depostion provides an additional degree of control over the patterning process.

(a) Rapid-rate protein line deposition: Size of the patterned dot depends on the dwell time (b) tapping mode afm image of Biotin-BSA lines written at 80 μm/sec using electric field assisted patterning (c) Effect of liquid solution contact angle (left) and tip geometry (right) on meniscus shape and patterning resolution (d) numerical study of the electric field at the probe tip.





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