Abstract
Sensitivity and speed of detection are contradicting demands that profoundly impact the electrical sensing of molecular biomarkers. Although single-molecule sensitivity can now be achieved with single-nanotube field-effect transistors, these tiny sensors, with a diameter less than 1 nm, may take hours to days to capture the molecular target at trace concentrations. Here, we show that this sensitivity-speed challenge can be addressed using covalently functionalized double-wall CNTs that form many individualized, parallel pathways between two electrodes. Each carrier that travels across the electrodes is forced to take one of these pathways that are fully gated chemically by the target-probe binding events. This sensor design allows us to electrically detect Lyme disease oligonucleotide biomarkers directly at the physiological high-salt concentrations, simultaneously achieving both ultrahigh sensitivity (as low as 1 fM) and detection speed (<15 s). This unexpectedly simple strategy may open opportunities for sensor designs to broadly achieve instant detection of trace biomarkers and real-time probing of biomolecular functions directly at their physiological states.