Nanomechanical protein concentration detector using a nanogap squeezing actuator with compensated displacement monitoring electrodes

Abstract

We present a new class of the protein concentration detector based on the mechanical stiffness measurement of protein-receptor layers in a squeezed nanogap. Compared to the previous protein size detector, the present device reduces the distortion and uncertainty in the displacement measurement by adding an actuated nanogap and reference electrodes. Compared to the conventional protein detectors based on electrochemical, optical, optomechanical, and mechanical principles, the present device also offers simple, inexpensive, and high-precision protein detection. We design and fabricate the protein concentration detector using an electrothermal actuator and two nanogaps with reference electrodes. In an experimental study, we verify that the present protein detector measures the size of the proteins streptavidin and m-antibiotin as 12.1 +/- 2.3 and 13.2 +/- 3.3 nm at the measurement uncertainty of +/- 1.9 nm, respectively, while showing the concentration detection sensitivity of 2.88 N/m/nM in the m-antibiotin concentration range of 5-10 nM.