Nanomechanical protein detectors using electrothermal nano-gap actuators

Abstract

This paper presents a new method and an associated device capable of detecting protein presence and concentration based on a protein-induced stiffness change. Compared to the conventional mechanical resonant method based on the protein mass, the present nanomechanical method based on the protein stiffness shows higher precision for protein detection. Compared to conventional electrochemical, optical, and optomechanical methods, the present method also offers simple and inexpensive protein detection by removing the labeling process and optical components. We design and fabricate nanomechanical protein presence and concentration detectors using electrothermal actuators and nano-gaps. The protein presence detector is composed of an electrothermal actuator with a pair of nano-gap electrodes. The protein concentration detector is composed of an electrothermal actuator with two pairs of differential nano-gap electrodes. From the protein presence detector with and without target proteins, we measure the difference of the stiffness changing points. This difference indicates the protein presence and the protein size of 12.4±3.5nm. From the protein concentration detector, we verify the concentration sensing capability as well as the presence sensing capability. We perform the non-specific and reversible binding tests using streptavidin and monoclonal antibiotin, respectively showing selectivity and repeatability of protein presence detection. The protein concentration detector is capable to measure the stiffness changes due to monoclonal antibiotin in the concentration range of 5nM~500nM. The sensitivity and the precision are measured as 2.45N/mㆍnM and 5nM, respectively. Consequently, we have proposed and experimentally demonstrated the nanomechanical protein detectors, applicable to high-precision biomolecule detection.