Ultrasound-assited micro-knife for cellular scale surgery

An ultrasound-assisted micro-knife with a 500nm-thick silicon nitride blade is described. The sharp blade can be operated to cut soft cells without lysing. The operation conditions are optimized by finite element analysis and experimental evaluation. For validation of the cutting precision Si_xN_y blades without and with ultrasonic actuation are compared to a commercial scalpel. The commercial scalpel causes lysing of hepatocytes in a mono-layer; the Si_xN_y blade without ultrasonic actuation cut these cells with a ragged cut line; the Si_xN_y blade with 1 V_pp and 70.1kHz ultrasonic actuation cuts these cleanly, as narrow as 2 μm. Due to the controlled ultrasonic mode shape, the high operating frequency, and low applied power (1V_pp), the micro-knife performs highly precise dissection at the cellular scale without the need for high compressive force on the target cell. The Si_xN_y blade with harmonic actuation has potential applications as a tool for minimally invasive surgery.