Journal of Mechanical Science and Technology 30 (1) (2016) 429~436
www.springerlink.com/content/1738-494x(Print)/1976-3824(Online)
DOI 10.1007/s12206-015-1247-y
Estimation and validation of maxwell stress of planar dielectric
elastomer actuators†
Raj Kumar Sahu1, Abhishek Saini2, Dilshad Ahmad2, Karali Patra2,*and Jerzy Szpunar3
1
Department of Mechanical Engineering, National Institute of Technology Raipur, Raipur-492010, India
2
Department of Mechanical Engineering, Indian Institute of Technology Patna, Patna-800013, India
3
Department of Mechanical Engineering, University of Saskatchewan, Saskatoon SK S7N 5A9, Canada
(Manuscript Received October 9, 2014; Revised July 11, 2015; Accepted September 16, 2015)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Abstract
In this paper, Maxwell stress of circular planar actuator at different applied voltages was estimated and then validated with the uniaxial
compression test of three different dielectric elastomers (VHB, silicone and natural rubber). Pelrine’s equation was revisited to estimate
Maxwell stress which causes the actuation in the planar direction. More precise and accurate estimation of Maxwell stress could be made
in this work by considering variation of dielectric constant with respect to frequency and pre-strain. Estimated Maxwell stress was validated through (i) out-of-plane strain or thickness strain obtained from measured area strain considering constant volume deformation, and
(ii) out-of-plane mechanical compressive test results. The estimated Maxwell stress agrees well with the corresponding experimental
compressive stress values for different pre-straining cases considered in this work.
Keywords: Uniaxial compression test; Dielectric elastomers; Maxwell stress; Pre-strain; Planar actuator
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1. Introduction
Dielectric elastomer (DE) is a smart material which produces large strain with the application of voltage. Due to its
tunable mechanical properties, robust and reliable performance, high net energy efficiency and high power density, it can
be used to design lightweight and compact actuators [1]. DE
actuator can be appealing alternative to conventional actuators
for numerous applications, including robotics, adaptive optics,
Braille displays, micro-fluidics, prosthetics, biomedical, etc [2,
3, 27].
Description of mechanical forces generated by the electric
field, i.e., electromechanical coupling is considered as one of
the key steps for the design and optimization of the DE actuators [4]. Electromechanical coupling is commonly described
by the Maxwell stress proposed by Pelrine et al. [5]. Maxwell
stress which is shown in the Eq. (1) has been derived for free
boundary conditions and is generally accepted as a representation of electromechanical coupling in any DE actuator system
[5, 6].
æV ö
p = e re 0 E 2 = e re 0 ç ÷
èt ø
*
2
Corresponding author. Tel.: +91 612 2552012, Fax.: +91 612 2277384
E-mail address: kpatra@iitp.ac.in
†
Recommended by Associate Editor Gang-Won Jang
© KSME & Springer 2016
(1)
Fig. 1. Sketch of the considered electromechanical system showing DE
film thickness and active actuation area.
where, p is the Maxwell stress, E is the electric field, e r is the
relative permittivity, e 0 is the permittivity of free space
(8.85x10-12 F/m), V is the applied voltage, and t is the polymer
thickness.
Due to the Maxwell stress, the elastomer film contracts in
the thickness direction and expands in the film’s planar directions. The direction of Maxwell stress which acts in perpendicular to the DE film and the mechanical stress in radial direction (σr) during planar actuation are shown in Fig. 1.
Ideally, the coated electrodes are to be compliant in order to
minimize the resistance to the deformation, and the dielectric
elastomers are pre-stretched in their in-plane directions, in
order to improve their performance [6]. Maxwell stress (Eq.
(1)) has been coupled with mechanical stresses acting on the
elastomeric film to predict the actuation strain in different
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R. K. Sahu et al. / Journal of Mechanical Science and Technology 30 (1) (2016) 429~436
actuators so far [6-13].
With reference to the circular planar actuator as shown in
Fig. 1, the electromechanical coupling stress-stretch relation
described earlier [12] can be modified as
s r + e 0e r E 2 = lr
¶Ws (lr , lt )
¶lr
(2)
(a)
where, Ws (lr , lt ) is the Helmholtz free energy associated with
stretching the elastomer [12]. lr , lt are the stretch ratio in
radial and thickness direction, respectively.
All these works on electromechanical coupling have considered a constant value of relative permittivity even though
these actuators are tested in different operating conditions.
However, recent investigations on the dielectric constant/relative permittivity show that its value varies with prestraining, temperature, frequency and applied complied electrodes [14-16]. Hence, it is important to consider the variation
of relative permittivity/dielectric constant with operating conditions for more accurate estimation of the Maxwell stress.
Earlier, some attempts were made to validate the Pelrine
equation (Eq. (1)) for Maxwell stress by indirect measurement
[17] and numerical simulation technique [18]. Kofod et al.
[17] developed a constant strain experimental setup to measure the blocking force which was related to Maxwell stress by
finite elasticity theory. Wissler and Mazza [18] validated the
same equation through Comsol multiphysics simulation of
circular actuator with energy balance consideration. In these
electromechanical coupling works, Maxwell stress is considered as compression stress acting perpendicular to the insulating elastomer film. So it is imperative to understand the constitutive behaviour of elastomers under the influence of compressive loading for prediction of actuation strain of dielectric
elastomer actuators. Tagarielli et al. [19] determined both
axial strain (Thickness direction strain) and transverse strain
of a dielectric elastomer under uniaxial compression load.
Material response was modelled by a neo-Hookean constitutive model. However, several difficulties such as premature
specimen failure by buckling, specimen barreling due to multiaxial stress state because of friction at the interface between
specimen surface and compression plate are involved in the
uniaxial compression test [20, 21]. To avoid buckling of the
sample, generally short specimen (length to diameter ratio is
less than 1.5) were applied. However, barreling effect could be
observed in such cases [21]. Attempts were also made to reduce barreling effect by applying compliant tape and using
cone compression set-up [20].
In this work, an actuation test setup was developed and actuation area strains of planar dielectric elastomer circular actuators were measured at different pre-straining values and
applied voltage conditions. Dielectric constant values of the
elastomer were estimated from measurements of capacitance
values of the pre-strained samples coated with the same compliant electrode (here it is carbon grease) applied in the actuators. Maxwell stress and thickness strains were next estimated
(b)
Fig. 2. Biaxial pre-straining of VHB 4910 with (a) marked circular
area (radius of 10 mm) before straining; (b) deformed marked area
after straining.
from dielectric constant and area strain values, respectively,
for different applied voltages on pre-strained actuators. Finally,
a new approach to validate Maxwell stress was attempted
using uniaxial mechanical compression test under free boundary condition. The main advantage of this direct method to
relate compression stress of a mechanical test with Maxwell
stress of an actuator is that actuation strain can be directly
predicted from applied voltage or vice versa from the stressstrain values of the mechanical test.
2. Experimental protocol
2.1 Materials
The primary actuator material used in this work for investigating Maxwell stress phenomenon and its analogy with mechanical compressive stress is VHB 4910 (3M, USA). This
material is characterized by low mass density of 960 kg/m3
and operating temperature range -10oC to 90oC [3]. To prove
the effectiveness of this present investigation, experiments are
also performed on other two commercially available dielectric
elastomers i.e., silicone and natural rubber.
2.2 Pre-straining of dielectric elastomer
Pre-straining of dielectric elastomer samples may be done
in one direction or in both directions. In this work, bidirectional straining method is used for pre-straining. Dielectric elastomer films can be pre-strained onto an adjustable
frame to provide equal amount of pre-strain in both directions.
Figs. 2(a) and (b) show biaxial pre-straining of a VHB tape. A
circle of specified radius is marked that increases with the
increase of the distance between four moving arms. The
marked deformed area in Fig. 2(b) can be approximated as
axially symmetric. The samples for actuation tests are prepared from this marked region for having homogeneous
thickness value. The accuracy of the equi-biaxial straining of
the fixture is verified from the measured strain in X and Y
direction as shown in Fig. 3. Measured strain values in Y direction agree well with the same in X direction.
The maximum deviation of strain measurement was found
to be within 5%. Hence, equi-biaxial straining of the sample is
assumed here to estimate the pre-strained film thickness. Final
thicknesses at different biaxial pre-strain values were esti-
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(a)
(b)
Fig. 3. Variation of strain in X and Y directions.
(c)
(d)
Fig. 5. Actuation tests of circular planar VHB 4910 DE actuator: (a)
before actuation; (b) after actuation; (c) close-up view of un-actuated
active area; (d) close-up view of actuated active area sample at 8.4 kV.
Fig. 4. Layout diagram of experimental setup for actuation experiment.
mated from initial thickness, initial area and deformed final
area assuming incompressible deformation of the material, i.e.,
constant volume deformation.
The estimated thickness values used for estimating Maxwell
stress of planar actuator are described later.
2.3 Planar Actuator test setup
Fig. 4 shows the test setup for planar circular actuators. In
this setup, high voltage was applied on pre-strained dielectric
elastomeric sample coated with carbon grease electrode. The
high voltage was generated by a DC to high voltage DC convertor (Model no. Q101-5, made by Emco, Austria) which
was used to scale the input voltage of 0-5 V to output voltage
of 0-10 kV. The positive output side of the DC converter was
connected with one end of the pre-strained dielectric elastomeric sample through wire and copper tape. The other end
of the sample on opposite surface was fixed with negative
output side. The output voltage was measured in digital multimeter through high voltage testing probe (Model No. HV40T, made by APLAB Ltd, India). A camera fixed to a tripod
was used for capturing the images of the planar actuator under
actuation. The digital camera (Sony DSC-W620 made by
Sony Corporation, Japan) used for the experiment was having
resolution of 4320 X 3240 and color representation of sRGB.
The images were captured for different applied voltages and
for different pre-strain values of the DE film. Increase of actu-
ated area of the active region (coated area) can be observed at
high applied voltage as shown in Figs. 5(a) and (b). Close up
views of the active area are shown in Figs. 5(c) and (d) for unactuated and actuated state, respectively.
Image processing technique in MATLAB tool box has been
used to process the actuation images of different samples. The
basic idea in calculating the strain is to find the area of the DE
film in terms of number of pixels and then to multiply it with
area of a pixel. For calculating the actuated area from the image processing tool box in MATLAB, first we have set the
camera at a definite position and the pixel size is calibrated
with known active area. Next, the images of different prestrained samples with different input voltages are captured.
RGB image was converted to gray-scale image. Now grayscale image was further converted to binary image by setting
the threshold value in order to find a region of interest i.e., a
portion of the image that was of interest for further processing.
Area of the ‘region of interest’ or ‘active region’ was calculated from number of pixels in it. Finally area strain (εA) due to
actuation was calculated from the following equation [22].
eA =
A - A0
.
A0
(3)
Where, A = actuated active area and A0 = un-actuated active
area.
Considering DE as incompressible material it can be assumed that the volume remains constant in the actuation process. The procedure for determining thickness strain from area
strain of a planar actuator has been described in Sec. 3.2.
Similar planar actuation test setups for natural rubber and
silicone elastomer were also developed in this work and
shown in Figs. 6 and 7, respectively. For natural rubber, the
increase of actuated area (coated area) can be observed at high
applied voltage as shown in Figs. 6(a) and (b). Close up views
of the active area are shown in Figs. 6(c) and (d) for unactuated and actuated state, respectively.
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R. K. Sahu et al. / Journal of Mechanical Science and Technology 30 (1) (2016) 429~436
(a)
(b)
Fig. 8. LCR meter with sample.
termined from capacitance measurement using the following
Eq. (4).
(c)
(d)
Fig. 6. Actuation tests of circular planar natural rubber DE actuator: (a)
before actuation; (b) after actuation; (c) close-up view of un-actuated
active area; (d) close-up view of actuated active area sample at 8.4 kV.
(a)
(c)
(b)
(d)
Fig. 7. Actuation tests of circular planar silicone DE actuator: (a) before actuation; (b) after actuation; (c) close-up view of un-actuated
active area; (d) close-up view of actuated active area sample at 6.4 kV.
Similarly, for silicone based rubber, the increase of actuated
area (coated area) can also be observed at high applied voltage
as shown in Figs. 7(a) and (b). Close up views of the active
area of this planar actuator are shown in Figs. 7(c) and (d) for
un-actuated and actuated state, respectively.
2.4 Experimental procedure for relative permittivity measurement
Estimation of permittivity under different operating conditions is important to calculate Maxwell stress for actuator [5]
or sensor applications [23]. Relative permittivity can be de-
er =
Ct
Ae 0
(4)
where, e r is the relative permittivity of the material, e 0 is the
dielectric permittivity of free space (8.854 x 10-12 F/m), C is
the capacitance of the material, A is the electrode area and t is
the film thickness.
For VHB 4910, capacitance measurements were carried out
in the frequency range of 25 Hz to 1 MHz by using a properly
calibrated LCR Meter (GWINSTEK LCR-8101G, made by
Good will Instrument Co. Ltd., Taiwan) at room temperature
(27 OC). The two ends of conductive electrode were connected
with the LCR meter through crocodile probes as shown in Fig.
8. The VHB 4910 has the ability to change in thickness with
the application of very high voltage. To avoid the change in
thickness during experiment, small voltage alternating signal
(sinusoidal signal of 2 V) has been applied on the sample.
Average value of the three readings was taken under the same
conditions to minimize inaccuracies (random error) in the
measurement.
Similarly, capacitance measurements for natural rubber and
silicon were carried out in the frequency range of 1Hz to 1
MHz by using LCR meter (PSM1735, made by Newtons4th
Ltd) at room temperature of (27oC). Procedure of calculation
of dielectric constant of these materials was same as that of
VHB 4910.
2.5 Sample preparation and uniaxial compression test set-up
In order to prepare specimens for the uniaxial compression
test, two monolithic plates of thickness 3 mm each were produced first by stacking three layers of VHB 4910 film of 1
mm thickness. Due to good self adhesive nature of the film it
is impossible to separate the layers and the original interfaces
between the layers are not visible. Then circular cylindrical
specimens of diameter d of 6.5 mm were cut from these
monolithic plates with sharp circular punches, lubricated with
vaseline, which were pressed with low speed to avoid the
straining of the material during the punching process. The
punched samples were again stacked to get the desired length l
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R. K. Sahu et al. / Journal of Mechanical Science and Technology 30 (1) (2016) 429~436
Table 1. Estimated Maxwell stress, thickness strain and corresponding
compression test results of VHB 4910 (for 150% x 150% pre-strained
planar actuator).
Input
voltage
(kV)
Area
strain
(%)
Thickness
strain
Relative
permittivity
at 25Hz
(for
carbon
grease)
Film
thickness
(mm)
Fig. 9. Uniaxial compression testing.
of 6 mm. The aspect ratio l/d considered in this study is less
than 1 for avoiding buckling and shear failure during uniaxial
compression test [20].
Specimens were placed between two flat steel platens and
were compressed in transverse direction using universal testing machine (Instron model no. 3366) as shown in Fig. 9.
Compressive force applied on the specimen was measured by
a 500 N load cell and specimen deformation was determined
by a strain sensor attached with the cross-head. Cross-head
movement of the machine was fixed at very slow compressive
rate of 2 mm/min. During compression test barreling effect
was avoided by coating compression plates with silicone
based lubricant in order to limit friction between them and the
samples.
The Maxwell stress values of different pre-strained planar
actuators at different applied voltages are estimated with the
following assumptions: (i) electrostrictive effects are negligible for VHB 4910 elastomer, (ii) carbon grease electrode is
ideally compliant (it does not constraint the elastomer mechanically) and (iii) the elastomer is incompressible.
In the estimation of Maxwell stress using Pelrine equation,
the relative permittivity e r is considered as a variable which
varies with the applied frequency, pre-straining of the DE film
and type of compliant electrode. Experimentally obtained
dielectric constant values of VHB 4910 at different biaxial
pre-straining using carbon grease electrode are shown in Fig.
10. These dielectric constant values and DE film thicknesses
corresponding to the different pre-strained planar actuators
were used to calculate the Maxwell stress for different applied
voltages. Estimated Maxwell stress against different applied
voltages for three different pre-strained planar actuators are
shown in Tables 1-3. Maximum applied voltage in a prestrained planar actuator depends on the dielectric breakdown
strength and thickness of the elastomer film [24, 25]. Even
though dielectric strength increases with the increase in prestrain value, reduction of film thickness with pre-straining
may affect the maximum applied voltage values. In this actuation test, breakdown voltage was 8.4, 6.4 and 6.4 kV for 150%
x 150%, 200% x 200%, and 250% x 250% planar circular
actuator, respectively.
Compression
stress
(MPa)
0
0
0
5
0.2
0
0
1.4
1.57
-0.0155
5
0.2
0.0022
0.0023
2.4
2.24
-0.0219
5
0.2
0.0064
0.0037
3.4
7.27
-0.0678
5
0.2
0.0128
0.0121
4.4
11.13
-0.1002
5
0.2
0.0214
0.0190
5.4
14.84
-0.1292
5
0.2
0.0323
0.0257
6.4
21.7
-0.1783
5
0.2
0.0453
0.0384
7.4
32.91
-0.2476
5
0.2
0.0606
0.0598
8.4
41.41
-0.2928
5
0.2
0.0781
0.0760
Table 2. Estimated Maxwell stress, thickness strain and corresponding
compression test results of VHB 4910 (for 200% x 200% pre-strained
planar actuator).
Thickness
strain
Relative
permittivity
at 25Hz
(for
carbon
grease)
Film
thickness
(mm)
3. Results and discussion
3.1 Estimation of maxwell stress from planar actuator experiments
Maxwell
stress
(MPa)
Input
voltage
(kV)
Area
strain
(%)
Maxwell
stress
(MPa)
Compression
stress
(MPa)
0
0
0
4.66
0.14
0
0
1.4
2.26
-0.0221
4.66
0.14
0.0041
0.0039
2.4
4.77
-0.0455
4.66
0.14
0.0121
0.0078
3.4
13.68
-0.1203
4.66
0.14
0.0243
0.0234
4.4
18.48
-0.1560
4.66
0.14
0.0407
0.0325
5.4
33.64
-0.2517
4.66
0.14
0.0614
0.0607
6.4
66.31
-0.3987
4.66
0.14
0.0862
0.1028
Fig. 10. Relative permittivity v/s frequency at different biaxial prestrain for VHB 4910.
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R. K. Sahu et al. / Journal of Mechanical Science and Technology 30 (1) (2016) 429~436
Table 3. Estimated Maxwell stress, thickness strain and corresponding
compression test results of VHB 4910 (for 250% x 250% pre-strained
planar actuator).
Input
voltage
(kV)
Area
strain
(%)
Thickness
strain
Relative
permittivity
at 25Hz
(for
carbon
grease)
Film
thickness
(mm)
Maxwell
stress
(MPa)
Compression
stress
(MPa)
0
0
0
4.19
0.11
0
0
1.4
4.27
-0.0410
4.19
0.11
0.0060
0.0035
2.4
6.62
-0.0621
4.19
0.11
0.0177
0.0165
3.4
15.18
-0.1318
4.19
0.11
0.0354
0.0378
4.4
29.98
-0.2307
4.19
0.11
0.0593
0.0575
5.4
61.51
-0.3808
4.19
0.11
0.0894
0.0973
6
102.25
-0.5056
4.19
0.11
0.1103
0.1309
6.4
113.85
-0.5324
4.19
0.11
0.1255
0.1483
Fig. 11. Engineering stress v/s strain.
eA =
A - A0 p r 2 - p r02
=
= lr2 - 1 .
A0
p r02
(9)
From Eqs. (8) and (9), e t and e A can be related by Eq. (10)
3.2 Estimation of thickness strain from planar actuator experiments
Assuming constant volume actuation process, thickness
strain values of the actuator were determined from the actuated area strain. Referring to Fig. 1 and constant volume assumption, one can write
(5)
A0t0 = At
et =
1
-1 .
1+ eA
(10)
Area strain values for different pre-strained cases and for
different applied voltages were estimated as shown in previous section. Thickness strain values were calculated from
these area strain values using the Eq. (10). These thickness
strain values for different pre-strained actuators were also
shown in Tables 1-3.
where,
A0 is area of the active region before actuation.
A is area of the active region after actuation.
t0 is initial thickness of DE film.
t is final thickness of the DE film.
For the circular actuator Eq. (5) can be written as
p r02t0 = p r 2t .
3.3 Uniaxial compression tests
(6)
From Eq. (6), one can get
lt =
t p r02
1
=
=
t0 p r 2 lr2
(7)
where,
lt is compression ratio in the thickness direction.
lr is stretch ratio in radial direction.
The above expression can also be expressed in terms of
thickness strain ( e t )
æ 1
et = ç
2
è lr
ö
- 1÷ .
ø
Again, area strain ( e A ) can be written as,
Uniaxial compression tests on VHB 4910 were performed
to determine the required compressive stress corresponding to
the estimated thickness strain values in Sec. 3.2. The specimen
was compressed upto a strain value of 0.6 as the thickness
strain values in all actuation tests are within this range. The
material response to uniaxial compressive stress is shown in
Fig. 11. Compression test results were compared with the
earlier reported results given by Tagarielli et al. [19] and
found to be in good agreement as shown in Fig. 11.
(8)
4. Validation of maxwell stress with uniaxial compression test results
4.1 Validation of maxwell stress of VHB 4910 planar actuator
From uniaxial compression test results of VHB 4910, compressive stress values corresponding to the calculated thickness strains were identified and shown in Tables 1-3. Estimated Maxwell stress and corresponding compressive stress
were plotted against applied voltage at different pre-straining
values and shown in Fig. 12. It can be observed that Maxwell
stress increases with the increase in pre-strain value at a particular applied voltage. This may be due to the reduction in
R. K. Sahu et al. / Journal of Mechanical Science and Technology 30 (1) (2016) 429~436
435
Fig. 14. Maxwell stress v/s applied voltage for silicone.
Fig. 12. Maxwell stress v/s applied voltage for VHB.
The estimated Maxwell stress values of natural rubber and
silicone planar actuators also agree well to the corresponding
compressive stress values for different applied voltages and
pre-straining conditions.
5. Conclusions
Fig. 13. Maxwell stress v/s applied voltage for natural rubber.
thickness for pre-straining of DE film. The effect of thickness
reduction on Maxwell stress is more significant than that of
reduction of dielectric constant value for a pre-strained sample.
With the increase of Maxwell stress, thickness strain also increases. It leads to selection of compressive stress to a higher
value for higher pre-strained sample. The estimated Maxwell
stress agrees well with the corresponding experimental compressive stress values for all three different pre-straining cases.
4.2 Validation of maxwell stress of natural rubber and silicone planar actuators
Applying similar procedure, Maxwell stress and thickness
strain for different pre-strained (70% x 70%, 150% x 150%
and 200% x 200%) silicone and natural rubber based planar
actuators were estimated applying similar procedures used for
VHB 4910 planar actuator. However, mechanical compressive
stress data corresponding to different thickness strain values of
natural rubber and silicone elastomers were extracted from
uniaxial compression test results given by Daniela et al. [26]
and Meunier et al. [27], respectively. Estimated Maxwell
stress and corresponding compressive stress for natural rubber
and silicon are plotted against applied voltage at different prestraining values and shown in Figs. 13 and 14, respectively.
The trends of Maxwell stress with respect to applied voltage
and pre-strained values are similar to those of VHB 4910.
This work reported the estimation of Maxwell stress of
three different dielectric elastomers (VHB, silicone and natural rubber) planar circular actuator at different levels of operating voltage and pre-strain values. Pre-straining was shown to
improve the actuation performance because of the significant
reduction of thickness and increase of dielectric strength. Estimation of Maxwell stress could be more precise and accurate
by considering variation of dielectric constant with respect to
applied frequency and pre-straining of elastomer film. This
work proposed a novel method to re-validate the Pelrine’s
equation for Maxwell stress using mechanical compression
test analogy. These results may have important consequences
in designing and fabrication of dielectric elastomer actuator
for real practical applications.
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Raj Kumar Sahu received his B. Tech.
Degree from MIT Purnea in 2008 (Bihar,
India), and his M. Tech. degree from
National Institute of Technology Jamshedpur in 2010 (Jharkhand, India), and
his Ph.D. degree from Indian Institute of
Technology Patna in 2014 (Bihar, India).
All degrees are in mechanical engineering. He is currently an assistant professor at Department of
Mechanical Engineering, National Institute of Technology
Raipur, India (Chhattisgarh, India). His research interests are
focused on smart materials, materials characterization using
modern techniques, material development, etc.
Karali Patra is an Assistant Professor
in the Department of Mechanical Engineering, Indian Institute of Technology
Patna (IIT Patna), Patna, India. He did
his BTech, MTech and Ph.D. from BE
College, Shibpur (IIEST, Shibpur), IIT
Guwahati and IIT Kharagpur in 1997,
2003 and 2008, respectively. He worked
as research associate at Robotics Research Center, Nanyang
Technological University in 2007-2008 and as Reader in Manipal Institute of Technology, Manipal, India before joining
IIT Patna in 2008. His current research interests are actuators
and energy harvesting applications of electroactive polymers,
bio-robotics and micro-manufacturing processes.