A High-Q AFM Sensor Using a Balanced Trolling Quartz Tuning Fork in the Liquid

Abstract

A quartz tuning fork (QTF) has been widely used as a force sensor of the frequency modulation atomic force microscope due to its ultrahigh stiffness, high quality factor and self-sensing nature. However, due to the bulky structure and exposed surface electrode arrangement, its application is limited, especially in liquid imaging of in situ biological samples, ionic liquids, electrochemical reaction, etc. Although the complication can be resolved by coating insulating materials on the QTF surface and then immersing the whole QTF into the liquid, it would result in a sharp drop of the quality factor, which will reduce the sensitivity of the QTF. To solve the problem, a novel method, called the balanced trolling quartz tuning fork (BT-QTF), is introduced here. In this method, two same probes are glued on both prongs of the QTF separately while only one probe immersed in the liquid. With the method, the hydrodynamic interaction can be reduced, thus the BT-QTF can retain a high quality factor and constant resonance frequency. The stable small vibration of the BT-QTF can be achieved in the liquid. Initially, a theoretical model is presented to analyze the sensing performance of the BT-QTF in the liquid. Then, the sensing performance analysis experiments of the BT-QTF have been performed. At last, the proposed method is applied to atomic force microscope imaging different samples in the liquid, which proves its feasibility.

Capillary bridges between unsaturated nano-mineral particles: a molecular dynamics study

“…10 In the present work, a two-dimensional cylindrical model was adopted to allow clearer interpretation and visualisation of results. As quartz is one of the most common geological minerals 20 and is also the material for AFM probes used in nanotechnology, 21 in our study α-quartz was used as the atomic structure of solid bodies to construct nano-asperities with typical surface curvatures. Various scenarios were prepared to cover different conditions, including surface curvature, nanometre distances and humidity, that may occur in nature during the formation of capillary bridges.…”

Measurement and Control System for Atomic Force Microscope Based on Quartz Tuning Fork Self-Induction Probe

“…When fabricating AFM probes with a QTF, tips made of materials such as silicon or tungsten are usually bonded or glued to the tuning fork arm, because of which the symmetry of the two fork arms is destroyed, and the Q value decreases. To maintain a high Q value of the tuning fork, we improved the balanced tuning fork probe structure proposed by Zhang et al [ 27 ], which preserves the symmetry of the two arms of the tuning fork by employing a particular technique to bond the tip in an atmospheric environment. We control the balance of the QTF by bonding tungsten tips of the same length to the two arms of the QTF and maintaining the adhesive mass of the two arms.…”

Resonance and sensing characteristics of quartz tuning fork for force sensor

“…The temperature sensor made of QTF has been used in the field of man-made spaceflight [2] . QTF sensors can also be utilised to make highprecision and rapid humidity detection in the industry [3] , to measure fluid density and viscosity [4] , to make a photoacoustic gas sensor [5] or to use as a force sensor [6,7] .…”

“…QTF has been widely used as a force sensor in atomic force microscopy (AFM) [7][8][9][10][11][12][13][14][15][16][17] . AFM usually utilises a micro-cantilever probe for laser detecting in its measurement and scanning imaging.…”