ISSN 1061-933X, Colloid Journal, 2018, Vol. 80, No. 3, pp. 339–345. © Pleiades Publishing, Ltd., 2018.
Modeling the Effect of the Relative Humidity on the Manipulation
of Nanoparticles with an Atomic Force Microscope
Li Yang, Kezhao Bai*, and Yunqian Li
College of Physics Science and Technology, Guangxi Normal University, Guilin, 541004 China
Received December 13, 2016
Abstract⎯In the manipulation of nanoparticles, different behaviors are typically observed including sliding,
rolling and rotation. Most of investigations in this field have so far focused on describing the interaction forces
under vacuum (dry air) environmental condition, while the effect of the relative humidity has been poorly
considered. In this work we developed a model for simulating the dynamic nanoparticle motion (rolling and
sliding) in an AFM-based manipulation of nanoparticles in a humid environment. In our method, the inter-
action forces include the adhesion force, mainly consisting of the capillary force and van der Waals force, the
normal force and friction forces. We calculated the adhesion force by considering the contributions from the
wet and dry portions of the particle. Our stimulations show that nanoparticles smaller than the AFM tip tend
to slide before rolling, while in large nanoparticles the rolling occurs first. The particle motion is achieved if
the applied force exceeds a critical value and the direction of the rolling movement depends on the applied
force angle. Furthermore, small nanoparticles are more easily manipulated by the tip in low-humidity con-
ditions while the manipulations with large nanoparticles need high-humidity conditions. Preliminary results
can be used to adjust proper handling force for the accurate and successful assembly of particles.
Micromanipulation can be defined as the manipu-
lation of micro-scale objects using micro-sized end-
effectors. A key component in this manipulation is the
ability to achieve a highly controlled positioning which
enables to assembly new complex micro objects .
The same principle has been applied to nano-scale
objects, in particular for the assembly of structures
based on the arrangement of nanoparticles. In this
context, many different types of the particle move-
ments occur during the assembly, including sliding
, rolling , stick-slip  and spinning (rotation)
. Numerous works have been directed toward the
investigation on physical mechanisms which guide the
manipulation micro and nanoparticles [6–11].
Hashimoto et al.  have manipulated nanoscale latex
particles positioned on Si substrate reaching an accu-
racy of about 30 nm. They analyzed the interaction
forces and dynamics during the pushing operation and
found that it was different from macrorobotics physics.
Rollot et al.  have theoretically and experimentally
studied the adhesion force in picking up micro-parti-
cles from a micro-sphere pile. Saito et al  have ana-
lyzed the interaction forces between microspheres, the
substrate and the manipulation probe. They also eval-
uated the maximum rolling resistance during the pick
and place operation using a needle-shaped tool. They
derived a mode diagram able to indicate the possible
micro-object behavior in specific operation condi-
tions. Tafazzoli and Sitti  have proposed a friction
model to simulate the dynamic behavior of latex
nanoparticles, in particular the rolling, sliding, stick-
ing or rotation in a particle pushing experiment.
Sumer and Sitti  have investigated the slip and roll
of micro and nanoparticles and determined the
boundary conditions for the transition from slipping to
rolling. Korayem  simulated the pushing of the
gold particle and investigated the sensitivity of
nanoparticle parameters in a robust controlled pro-
cess. However, in the previous works, the effects of the
relative humidity and related forces (for example, cap-
illary force and van der Waals force) have been almost
neglected, resulting in a need for more theoretical and
This paper focuses on the dynamic behavior of
nanoparticle motion during atomic force microscopy
(AFM) tip manipulation under ambient conditions.
Adhesion forces, such as van der Waals forces and the
capillary force and the critical force to initiate the par-
ticle motion (by rolling or sliding) have been studied.
The results showed that for the nanoparticles which
are small with respect to the size of the AFM tip the
sliding occurs first and it is preferred over the rolling,
while the rolling occurs first for larger nanoparticles.
The article is published in the original.