Direct Measurement of Adhesion Force of Individual Aerosol Particles by Atomic Force Microscopy

Abstract

A new method, namely, force–distance curve mapping, was developed to directly measure the adhesion force of individual aerosol particles by atomic force microscopy. The proposed method collects adhesion force from multiple points on a single particle. It also takes into account the spatial distribution of the adhesion force affected by topography (e.g., the variation in the tip angle relative to the surface, as well as the force imposed upon contact), thereby enabling the direct and quantitative measurement of the adhesion force representing each particle. The topographic effect was first evaluated by measuring Polystyrene latex (PSL) standard particles, and the optimized method was then applied on atmospherically relevant model dust particles (quartz, ATD, and CJ-1) and inorganic particles (ammonium sulfate and artificial sea salt) to inter-compare the adhesion forces among different aerosol types. The method was further applied on the actual ambient aerosol particles collected on the western coast of Japan, when the region was under the influence of Asian dust plume. The ambient particles were classified into sea salt (SS), silicate dust, and Ca-rich dust particles based on individual particle analysis (micro-Raman or Scanning Electron Microscope/Energy Dispersive X-ray Spectroscopy (SEM-EDX)). Comparable adhesion forces were obtained from the model and ambient particles for both SS and silicate dust. Although dust particles tended to show smaller adhesion forces, the adhesion force of Ca-rich dust particles was larger than the majority of silicate dust particles and was comparable with the inorganic salt particles. These results highlight that the original chemical composition, as well as the aging process in the atmosphere, can create significant variation in the adhesion force among individual particles. This study demonstrates that force–distance curve mapping can be used as a new tool to quantitatively characterize the physical properties of aerosol particles on an individual basis.

A review of atmospheric individual particle analyses: Methodologies and applications in environmental research

“…After dry sedimentation or wet sedimentation, atmospheric particles will participate in biogeochemical cycle (Mahowald et al, 2018;Luo et al, 2019). It is known that large amounts of mineral particles are carried into the atmosphere by strong ground winds and transported over long distances (Adachi et al, 2020;Ono et al, 2020). Long-distance transport of mineral particles can alter biogeochemical processes on land and in the ocean.…”

Theoretical and Experimental Analysis of Surface Roughness and Adhesion Forces of MEMS Surfaces Using a Novel Method for Making a Compound Sputtering Target

“…It was found that composite films have greater adhesion than pure aluminum films. An atomic force microscope (AFM) is commonly used for determining the adhesion force [21][22][23]. In this regard, Johnson-Kendall-Roberts (JKR), Derjaguin-Muller-Toporov (DMT) and Hertzian theory (HERTZ), which are theoretical models, are regularly used [24][25][26].…”

Sulfate Doping Promotes Agglomeration of Calcium Fluoride Crystals

“…To further verify this conclusion, the force between the calcium fluoride particles in the presence and absence of sulfate was measured using probes with modified calcium fluoride particles (see details in Text S6). − Compared with the control group, the adhesion between the calcium fluoride particles increased in the presence of sulfate (Figure d). From the typical force curve, the presence of sulfate increased the adhesion force between calcium fluoride particles from 1.62 to 2.46 nN, a 50% increase (Figure e,f).…”