Citation: Yang, H.; Mei, Z.; Li, Z.; Liu,
H.; Deng, H.; Xiao, G.; Li, J.; Luo, Y.;
Yuan, L. Integrated Multifunctional
Graphene Discs 2D Plasmonic
Optical Tweezers for Manipulating
Nanoparticles. Nanomaterials 2022, 12,
1769. https://doi.org/10.3390/
nano12101769
Academic Editors: Ki-Hyun Kim and
Deepak Kukkar
Received: 27 April 2022
Accepted: 16 May 2022
Published: 23 May 2022
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Article
Integrated Multifunctional Graphene Discs 2D Plasmonic
Optical Tweezers for Manipulating Nanoparticles
Hongyan Yang
1,2
, Ziyang Mei
1
, Zhenkai Li
1
, Houquan Liu
1,2
, Hongchang Deng
1,2
, Gongli Xiao
3,
*,
Jianqing Li
4
, Yunhan Luo
5
and Libo Yuan
1
1
College of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China;
hyyang@guet.edu.cn (H.Y.); 19082203004@mails.guet.edu.cn (Z.M.); 19082203009@mails.guet.edu.cn (Z.L.);
liuhouq@guet.edu.cn (H.L.); cdeng@guet.edu.cn (H.D.); lbyuan@guet.edu.cn (L.Y.)
2
Guangxi Key Laboratory of Optoelectronic Information Processing, Guilin University of Electronic
Technology, Guilin 541004, China
3
Guangxi Key Laboratory of Precision Navigation Technology and Application, Guilin University of Electronic
Technology, Guilin 541004, China
4
Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology,
Macau University of Science and Technology, Macau 999078, China; jqli@must.edu.mo
5
College of Science & Engineering, Jinan University, Guangzhou 510632, China; luoyunhan@jnu.edu.cn
* Correspondence: xiaogl.hy@guet.edu.cn
Abstract:
Optical tweezers are key tools to trap and manipulate nanoparticles in a non-invasive
way, and have been widely used in the biological and medical fields. We present an integrated
multifunctional 2D plasmonic optical tweezer consisting of an array of graphene discs and the
substrate circuit. The substrate circuit allows us to apply a bias voltage to configure the Fermi
energy of graphene discs independently. Our work is based on numerical simulation of the finite
element method. Numerical results show that the optical force is generated due to the localized
surface plasmonic resonance (LSPR) mode of the graphene discs with Fermi Energy E
f
= 0.6 eV
under incident intensity I = 1 mW/
µ
m
2
, which has a very low incident intensity compared to other
plasmonic tweezers systems. The optical forces on the nanoparticles can be controlled by modulating
the position of LSPR excitation. Controlling the position of LSPR excitation by bias voltage gates to
configure the Fermi energy of graphene disks, the nanoparticles can be dynamically transported to
arbitrary positions in the 2D plane. Our work is integrated and has multiple functions, which can be
applied to trap, transport, sort, and fuse nanoparticles independently. It has potential applications in
many fields, such as lab-on-a-chip, nano assembly, enhanced Raman sensing, etc.
Keywords: plasmonic optical tweezers; graphene; optical manipulation
1. Introduction
Since Ashkin first introduced the concept of optical tweezers through experiments
and theoretical works in the 1970s [
1
,
2
], this technology has gained widespread application
in the biological and medical fields with its ability to trap and manipulate nanoparticles in
a non-invasion way [
3
–
6
]. Conventional laser optical tweezers based on tightly focused
laser beams are powerful tools for trapping metal nanowires [
7
], dielectric particles [
8
],
proteins [
9
], viruses [
3
], and cells [
10
], and have been widely and intensively studied.
The particle trapping can be achieved by balancing the gradient force and scattering
force on the particles through the strong electric field gradient formed by the focused
lens laser beams [
1
]. However, due to the diffraction limit, the focal size of the focused
beams cannot be smaller than the incident light wavelength, which greatly limits the
application of focused laser beams to trap nanoparticles [2,11]. To obtain greater trapping
stiffness to overcome Brownian motion, conventional focused beam tweezers need to
induce high-power laser light to increase the electric field gradient. However, high-power
Nanomaterials 2022, 12, 1769. https://doi.org/10.3390/nano12101769 https://www.mdpi.com/journal/nanomaterials
