Field-effect pH Control in Nanochannels

We demonstrate a novel capacitive method to change the pH in nanochannels. The device employs metal electrodes outside an insulating channel wall to change the electrical double layer potential by the field effect (‘voltage gating’). We demonstrate that this potential change is accompanied by a release or uptake of protons from surface groups, resulting in a pH shift in the nanochannel, and a titration of solution compounds present. This pH actuation method avoids redox reactions and can be very useful as a “soft��? way to change the pH in small volumes e.g. in bioassays or cell-based research, but also for detection in separation methods. We demonstrate the detection of 100 attomol of TRIS in the detection volume by titration. Importantly, the proton release mechanism does not rely on double layer overlap.