Hydrogel tip attached quartz tuning fork for shear force microscopy

Abstract

Abstract This paper reports the first demonstration of hydrogel conical tip attachment onto quartz tuning fork (QTF) by using an elastomeric tip mold that is soft-lithographically replicated from an electrochemically etched tungsten wire. The tungsten tip of 10–100 nm radius obtained by time-controlled electrochemical etching is replicated with h-polydimethylsiloxane (h-PDMS) to make negative conical tip molds large enough to be used for QTFs. By approaching a QTF to the negative h-PDMS tip mold filled with polyethylene glycol-diacrylate (PEGDA), a PEGDA tip is attached to the QTF without using an adhesive. Then, the PEGDA tip attached QTF is employed for shear force microscopy for calibration grating and atomic layers of hexagonal silicon carbide and also compared with a silicon tip attached QTF. Exclusively for the PEGDA tip attached QTF, we demonstrate that the imaging tip could be regenerated multiple times to address issues associated with tip wear. In a stark contrast with conventional QTF probes in attachment of electrochemically etched metallic wires or microfabricated AFM cantilevers, photocuring of liquid phase prepolymer within a tip mold demonstrated herein allows adhesive-free and exclusive attachment of the imaging tip onto a QTF. The relatively large PEGDA tip enables facile operation during approach and engagement. Moreover, the organic and inorganic combination of imaging tip and resonating body offers regeneration of the imaging tip upon its degradation.

Keywords

• Atomic force microscopy (AFM)
• Hydrogel tip
• Shear force
• Tip attachment
• Quartz tuning fork (QTF)