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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 02 | Feb 2023 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 129
Electrorheological Fluids: Properties, Technology and Modern
Applications
Hanmant Salunkhe1, Ajit Kolekar2, Surendra Thikane3
1Assistant Professor, Department of Technology, Shivaji University, Kolhapur, Maharashtra, India
2Professor, Department of Technology, Shivaji University, Kolhapur, Maharashtra, India
3 Retired Professor, Shivaji University, Kolhapur, Maharashtra, India
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Abstract - Since last three decades, ER fluid has major
importance in science, medical and engineering problems,
which include vibration reduction and suspension.
Electrorheological fluids are smart materials whose
rheological properties are controllable through the
applications of an external electric field. These rheological
properties of ER fluid can be exploited in ERF devices for
advanced technological applications. The optimal design of
ERF devices requires proper mathematical modeling and
basic governing equations. This paper presents the working
principles, governing equations and mathematical
framework for ER fluids. Also in this paper recent progress
of ER devices and their applications have been discussed.
Key Words: Electrorheological Fluid, Controlling
Devices, Electrorheological Damper, Mechanical Polishing,
Smart Materials.
1. INTRODUCTION
Electrorheological (ER) fluids are special viscous fluids,
consisting of solid particles dispersed in an insulating
carrier fluid, and that are undergo significant changes in
their mechanical and rheological properties when an
electric field is applied. Such kind of response takes place
in millisecond scale. This property of the ER fluid can be
exploited in different kinds of technological applications.
They have broad applications potential in dampers,
actuators, clutches, valves, etc [1].
The rheological changes occur in ER fluids when an
external electric force is applied making the uniform
dispersed solid particles to become polarized. After
polarization, they start to interact with one another, and
form chain like structure, parallel to direction of electric
field lines and connecting the two particles. After
strengthening of the electrical force, chains begin to make
thicker column. The electrorheological effect of ER fluid is
known as the Winslow-effect, it was named after scientist
Willis Winslow who discovered it [2,3].
A change in the rheological properties of
electrorheological fluid is related with change in its nature
and structure. The columnar particles chain like structure
provides the fluid a more yields stress. After expelling the
electrical field, the particles of electrorheological fluid lose
their polarization and return to their openly meandering
state. The period of time over, that events happens, is on
the order of milliseconds. An electrorheological material is
a suspension of fine dielectric particles in an insulating
medium showing controllable rheological behaviour by
the application of external electrical force.
The fundamental properties of ER fluids based on particle
size, density, base fluid properties, temperature and
additives. A higher concentration of volume ratio of the
dispersed particulates phase can offer the fluid a
considerably higher electro rheological effect [4].
The rheological behaviour of electrorheological fluid can
be classified under three modes of flow as
i) Flow Mode: - In this type of mode, two electrodes of
the system are fixed and vibrational control is acquired
by adjusting the flow motion between two fixed
electrodes.
ii) Shear Mode: - In this type of mode, one electrode is
free to relative to another fixed
electrode so vibration control acquired by adjusting
shear stress.
iii) Squeeze Mode: - In this type of mode, the electrode
gap is changing and electrorheological fluid squeezed
by normal force.
Among the other factors, the rheological properties of
electrorheological fluid flow depends on particle density,
particle size, particle shape, particle distribution, nature
and properties of the base fluid, types of additives, electric
force and range of temperature. Generally, in absence of
electric field the nature of electrorheological fluids based
on characteristics of base fluid, types of additives, particle
volume ratio, etc., whereas in presence of electric field
nature of electrorheological fluid based on the liquid-solid
phase properties and the volume ratio of the liquid-solid
phase.
2. PROPERTIES OF ER FLUID
ER fluids are generally consists of dispersion of polarized
or electrically active particles in an insulating base fluid
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 02 | Feb 2023 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 130
such as silicon oil or composed of liquid crystal polymers
[5]. Electrorheological fluids are also referred as smart
materials and by the application of external electric force
on these fluids show extreme changes in their rheological
behaviour. In this manner, typical electrorheological fluids
can go from the consistency of a fluid to that of a semisolid
fluid, and back, with reaction time about milliseconds.
Such type of effect is also called the Winslow effect.
Electrorheological fluids contain suspension of micron-
sized particles randomly suspended in a base fluid
(usually oils, silicones, water). In absence of an external
electric force, electrorheological fluids flow freely and
randomly. If we apply a particular electric force then the
micro sized particles polarize and align themselves with
the applied electric force. This type of polarization and
particle alignment enables electrorheological fluid to
quickly increase its own viscosity and transform from fluid
like state to a semi-solid like state. Because of its
adjustable viscosity and quick response time,
electrorheological fluids have attracted much interest in
various areas of science and technology [6].
Fig –1: Alignment of particles
The properties of electrorheological fluids are not only
related to the characteristics of the base fluid and
particles, but also to their volume or mass ratio in relation
to the base fluid. Presently, research concerning the
properties and experimental methods used to produce ER
fluids are kept secret. The fundamental and rheological
properties of electrorheological fluids can be altered by
changing the density of the electric particles and base
fluid. In general, increasing the concentration of electric
particles in the base fluid or increasing the strength of the
electric force will increase the magnitude of the
electrorheological fluid effect on the system. Also, the
behaviour and properties of electrorheological fluids
depends upon particle size, particle density, properties of
base fluid, temperature and additives.
A higher concentration of volume ratio of the dispersed
phase of electrorheological fluid can offer the fluid a much
higher electro rheological effect, but also it can create
problems. Sedimentation of particles is a major factor,
since higher concentration of particles in ER fluid increase
the amount of particle settling. The another major
problem is temperature. When the temperature on
electrorheological fluid increases, the viscosity of fluid
decreases this results in diminishes yield stress.
Rheological properties of electrorheological fluids are
presented in Table 1. [7];
Table -1: Properties of Electrorheological Fluids
Properties
Normal Range
Maximum Yield Stress
Maximum Field
(limited by breakdown)
Viscosity of Fluid
Pa-sec
Operable Temperature
Range
(Ionic, DC)
(Non-ionic, DC)
Stability
Can't endure impurities
Response Time
Density
Maximum
Energy Density
External Power
Supply
(Typical)
(2-50 Watts)
One of the major properties of an electrorheological fluid
is its variable yield stress that is the minimum stress need
to cause the ER fluid to flow under the electric force. Often
higher yield stress is expected and in recent
electrorheological fluids its approximate range from
. However, it is not easy to compare
various electrorheological fluids and its behaviour because
of lacking in standard analysis and different internal forces
as well as the strong dependence of electrorheological
behaviour on particle composition.
The main advantages of electrorheological fluids are:
Electrorheological fluids are controllable and
undergo a reversible change in their properties
when exposed to an electric force.
Electric forces are easy to supply and control.
Electrorheological fluids are reasonable for
analytical modelling and dynamic applications.
The low density of the electric particles also helps
to keep the density of the entire
electrorheological fluid at a moderate level,
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 02 | Feb 2023 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 131
The controllable behaviour of ER fluid is used in many
engineering applications where variable performance is
greatly desired. The rheological response of
electrorheological fluid to an external applied electric field
could be observed in a variety of material rheological
properties.
3. BASIC GOVERNING EQUATIONS
The set of governing equations for ER fluids in presence of
electromagnetic field are given as [8],
Where is given by,
Moreover, the thermodynamic pressure is defined as;
The material and balance equations i.e. equations from (1)
to (5), excluding the terms because of the interactions of
the electromagnetic fields and the material, are remain
invariant under Galilean transformation equations is given
by,
In addition, the set of Maxwell equations from (6) to (10)
are remain invariant under Lorentz transformations is
given by,
Where
is the Lorentz contraction factor and if
and then , then the Lorentz
transformation reduces to Galilean transformation for
small velocities comparable to light.
4. APPLICATIONS
Electrorheological fluids belongs to a class of smart
materials and mostly used as a controllable fluids. The
working behaviour of the ER fluids are utilized into three
distinct modes of operation, as a) shear mode, b) flow
mode and c) squeeze mode [4,9]. Electrorheological fluid
technology has a many applications in the coming
generation. This technology is utilized in the places where
controlled fluid with varying viscosity is requisite. The
important features of this technology are quick response,
intelligent controllability and straightforward interface
between electrical input and mechanical response or
output.
This ERF technology is simple and includes less moving
parts. Consequently, ERF based devices require less
maintenance and have long lasting. Now day’s automobile
industries are utilizing this ERF technology. This type of
technology is also used in medical and aerospace field.
There is an implication for future research in ERF
technology. In coming years, improved ERF technology
will make it smart and advanced technology of future.
The applications of ER fluids can be categorized into four
main areas: controlling devices, sensor devices,
mechanical polishing and in detection of drugs delivery.
The ER dampers, brakes, hydraulic valves, clutches, shock
absorbers, robotic arms, gripping devices, human muscle
stimulator and seismic frame structures are the examples
of controlling devices of ER fluid.
4.1 ER Applications for Controlling Devices
The main characteristics of electrorheological fluid is that
the mechanical properties of ER fluid can be continuously
and reversibly balanced from the fluid state to solid like
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 02 | Feb 2023 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 132
state by changing the effect of electric field on
electrorheological fluid. From automobile industry, there
is high requirement of ER fluid for preparation of
automotive controlling devices like dampers, clutches,
shock absorbers, brakes and hydraulic valves [10-12]. The
ER fluid is smart material that has been designed as a
workable engineering material, non-toxic to human, with
high strength, low power consumption, wide temperature
range, non corrosive to devices and good compatibility
with sealing systems.
The ER damper is most common application of ER
fluid in mechanical system. Actual ER damping devices are
designed for meeting practical needs like suspension of
system, shock absorber, control of system, automotive
engine mount and design/ structure of system. There is lot
of research addressing how ER damper works in semi-
active suspension and its applications in automobile
industry. In ER damper, in presence of applied electric
field, ER fluid forms fibrillated chain like structure and it
increases yield stress.
ER dampers [13] have been vastly used to control
vibrations in the field of automobiles, railwayroad vehicles
and civil structures. This applications are used to achieve a
stability and comfortable journeys in vehicle. Smart
structure applications of ER fluids incorporate aircraft
wings, dash panels, robotic arms and helicopters.
Vehicle brake system, is the another possible
application of ER fluid. A brake is a mechanical design that
inhibits movement by absorbing energy from a
moving system. Brakes are applied to rotating wheels to
stop a vehicle system and it converts kinetic energy into
heat. The friction brake is the most common technique
utilized in brake system. However, in this system there are
certain limitations like periodic replacement, time-delay,
bulky size and so on. Electrorheological fluids are a type of
controllable fluids, and inducing a great attention in these
days. In this fluid shear stress is almost independent of the
shear rate, but vary according to the applied electric field
[14]. Making use of this property of ER fluid, the ER brake
system is developed. MR brakes commonly work in the
shear mode but might also work in the flow mode.
A haptic devices based on an electrorheological
fluid developed for preparation of joystick that adjust the
movement of a cursor on a system screen [15]. This type
of haptic devices can be utilized in various fields like
assisting interface for blind persons working with
computer, computer games, and operation of machines.
4.2 ER Sensors
ER fluid has potential applications in smart and
advanced electronics, with the fluid incorporated in
components such as sensors, rollable screens, and keypads
sticks. The ER fluid sensors are active sensors and used for
self-monitoring and control in building structure design.
This kind of sensor also utilized as a detector of
seismography and to find the working performance of
bridge vibrations [10]. Another study of ER sensor
proposes the response for active vibration for dynamic
system.
4.3 ER Mechanical Polishing
Electrorheological (ER) fluid assisted mechanical
polishing operation is the ultra precision finishing
technology that has been used to polish lenses, dies and
diamonds. The rheological properties of ER fluids are key
to their successful implementation into a precision
finishing and polishing process. This method of polishing
developed to overcome fundamental limitations of
traditional finishing methods [16]. The mechanism of the
ER polishing is shown in Fig. 2.
The technology of ER mechanical polishing of
finishing for optics, lenses, ceramics and semiconductors
is one of the most promising uses of the electrorheological
effect.
Fig –2: ER polishing mechanism
The process of ERF polishing is shown in Fig. 3. A
convex lens is located at some fixed distance from moving
wall. The electromagnet is located below the moving wall
which generates variable magnetic field on the MR fluid.
The essential characteristics required for
electrorheological fluid polishing are as follows [17]:
High concentration of particles
High yield stress
Resistance to corrosion
Sedimentation stability
High polishing efficiency
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 02 | Feb 2023 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 133
Fig –3: ER polishing process
The advantages of ER finishing over traditional
methods are given below [18]:
1. ER finishing is a non-contact process of treatment
that generates no surface and surface damages
during finishing process.
2. Electric field on ER fluid resulting high efficiency
of finishing and polishing. There is no limitation
on the size of the particles.
3. This process is very safe and there are no wearing
parts or system elements to be periodically
restored. Hence, the polishing area provides
stable and reproducible conditions for finishing.
4. The mechanism of the ER finishing provides
predictable quality of finishing and polishing of
desired product.
4.4 ER Applications for Detection of Drug
Delivery
The feature of ER fluid is also used for detection of
drugs delivery process. In this process, the fundamental
simulation shows that partial ordering of the fluid
particles may decrease the diffusion pathlength of the
electrorheological fluid [10]. By using this property of ER
fluid, the drugs molecules may have minimum distance to
travel before being released, effecting in higher stress
rates. The arrangement and ordering degree of freedom of
ER particle can be regulated by applied electric force, and
hence release rate can also be regulated by an external
electric force. Hence this type of equipments used for
detection of drug delivery with ER fluid gives quick and
significant response for prediction of possibility.
5. CONCLUSIONS
The devices based on ER fluids have a very promising
potential future including dampers, polishing devices,
robotic arms, hydraulic valves, clutches, brakes, etc.. Most
of them have been utilized commercially in advanced
engineering applications like polishing machines, cars and
exercise equipment. This paper deeply explains the
common applications of electrorheological fluids in
various areas of science and technology.
ACKNOWLEDGEMENT
This research was supported by the Department of
Technology Shivaji University Kolhapur. The authors are
thankful to Shivaji University Kolhapur for financial
assistance to carry out the research work.
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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 02 | Feb 2023 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 134
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BIOGRAPHIES
Hanmant Salunkhe has received
Ph. D degree in Mathematics from
Shivaji University, Kolhapur. He is
currently working as a Assistant
Professor in Engg. Mathematics at
Department of Technology,
Shivaji University, Kolhapur.
Ajit Kolekar has received Ph. D
degree in Mechanical Engineering
from Shivaji University, Kolhapur.
He is currently working as a
Professor at Department of
Technology, Shivaji University,
Kolhapur
Surendra Thikane has received
Ph. D degree in Mathematics from
Shivaji University, Kolhapur. He is
a retired Professor in
Mathematics. He has published
many research papers in reputed
journals.
