@Article{icces.2023.09169,
AUTHOR = {Fujian Zhang, Xiang Gao, Zhongqiang Zhang},
TITLE = {Self-Driving	Behavior	and	Pinning	Effect	of	Droplets	on	GrapheneCovered	Functional Textured	Surfaces},
JOURNAL = {The International Conference on Computational \& Experimental Engineering and Sciences},
VOLUME = {26},
YEAR = {2023},
NUMBER = {4},
PAGES = {1--1},
URL = {http://www.techscience.com/icces/v26n4/54074},
ISSN = {1933-2815},
ABSTRACT = {Biological	 features	 such	 as	 the	 bumps	 on	 the	 back	 of	 desert	 beetles	 and	 the	 spikes	 of	 cacti	 enable the	
directional	 transport	 of	 water	 droplets,	 creating	 conditions	 for	 their	 survival	in	 nature. Inspired	 by	the
interesting	natural	phenomenon, a	novel	design of	nanopillared surface	with	a	gradient	density	of	structural	
pillar	matrix	covered	by	a	monolayer	graphene	is	proposed to	realize	ultrafast	self-driving	of	water	droplets.
The	droplet	can	move	spontaneously	at ultrahigh	speed	of	75.7	m/s	(272.52 km/h)	from	sparsest	to	densest	
regions	of	pillars	while	a	wettability	gradient	is	created	by	the	gradient	distribution density	of	pillar	matrix	
relying	on	the	wetting	transparency	of	monolayer	graphene. In	particular,	the gradient	short	pillared	texture	
triggers	 an	 opposite	 self-driving	 regularity	 in	 which	 the	 water	 droplet	 moves	 from densest	 to	 sparsest	
regions	of	pillars,	intrinsically	because	the	gradient	short-pillared	surface	leads	to	a	wetting transition	from	
hydrophobic	to	hydrophilic	since	the	monolayer	graphene	can	be	adsorbed	into	the	sparsest short-pillared	
texture. Furthermore,	a monolayer	graphene-covered	nanocone	(GNC)	is	proposed	to	realize	ultrafast	water	
droplet transport	 from	 the	 tip	 to	 the	end	of	 the	GNC. The	 rule of	energy	change	during	 the	droplet	selfdriving	process	indicates	that	the	potential	energy	of the	droplet	and	the	interaction	energy	between	the	
droplet	 and	 the	 GNC	 undergo	 cooperation and	 competition	 successively,	 resulting	 in	 the	 droplet	 first	
speeding	up	and	 then	 slowing	down	 to a	 steady	moving	 state. Continuum	 theory	in	 the self-driving	 of	a	
droplet	at	a	microscale	is	used	to	describe	the	steady	moving	process,	in	order to	further	understand	the	
rule	in	GNC-based	water	transport. However,	the	pinning	effect	induced	by	surface	defects	usually	restrain
the	self-driving	of	droplets	on	functionalized	surfaces. Thus,	the	mechanism	of	pinning	effect	in	droplet selfdriving	is	further	revealed	based	on	the	molecular	dynamic	simulations	for	motion	behaviors	of droplet	on	
copper	substrate with	different	shaped	defects. The	results	show	that	the	monolayer	graphene	covered	on	
the defected	solid	surface	can	remarkably	reduce	the	pinning	effect	in	droplet	self-driving	processes. A large	
damping	force	will	appear	when	the	droplet	initially	approaches	and	finally	moves	away	from the	defects	
on	pure	copper	substrate,	whereas	a	tiny	damping	force	can	be	observed	for	the	droplet	moving across	the	
defects	covered	by	a	monolayer	graphene. Particularly,	a	consequent	extra-damping	force	appears because	
the	nano-configuration	of	the droplet	is	changed	after	passing	the	defects	on	pure	copper substrate induced	
by	 the	 large	 deformation	 in	 pinning	 process. These	 findings	 explore	 the role	 of	 graphene	 in	 reducing	
resistance	and	pinning	in	droplet	self-driving,	and	have	theoretical	significance	for the	design	of	graphenecovered	functional	surfaces	in	droplet	transport.},
DOI = {10.32604/icces.2023.09169}
}