Twist and Coiled soft Actuator (TCA) is simply fabricated by twisting a polymer fiber. In the previous researches, TCA was mainly fabricated with Nylon 6,6 fiber, and Nylon-TCA (NTCA) showed strong force outputs. However, the strain from NTCA was not much enough for practical application. This paper introduces SPX-TCA (STCA) which is fabricated with Spandex fibers. NTCA and STCA were fabricated, and their performances were compared by using the performance evaluation device. STCA showed larger strain, and it was actuated lower temperature than NTCA.
Polymer film-type slip sensor is presented by using novel working principle rather than measuring micro-vibration. The sensor is comprised of bilayer with Ecoflex and NBR(acrylonitrile butadiene rubber) films divided by di-electric. When slip occur on surface, bilayer have relative displacement from each other because friction-induced vibration make a clearance between two layers. This displacement can be obtained by capacitance difference. CNT(carbon nanotube) was employed for electrode because of flexible and stretchable characteristics. Also normal and shear force can be decoupled by the working principle. To verify developed sensor, slip test apparatus was designed and experiments were conducted.
Human uses various sensational information for identifying an object. When contacting an unidentified object with no vision, tactile sensation provides a variety of information to perceive. Tactile sensation plays an important role to recognize a shape of surfaces from touching. In robotic fields, tactile sensation is especially meaningful. Robots can perform more accurate job using comprehensive tactile information. And in case of using sensors made by soft material like silicone, sensors can be used in various situations. So we are developing a tactile sensor with soft materials. As the conventional robot operates in a controlled environment, it is a good model to make robots more available at any circumstance that sensory systems of living things. For example, there are lots of mechanoreceptors that each of them has different roles detecting simulation in side of human skin tissue. By mimicking the mechanoreceptor, a sensory system can be realized more closely to human being. It is known that human obtains roughness information through scanning the surface with fingertips. During that times, subcutaneous mechanoreceptors detect vibration. In the same way, while a robot is scanning a surface of object, a roughness sensor developed detects vibrations generated between contacting two surfaces. In this research, a roughness sensor made by an elastomer was developed and experiment for perception of objects was conducted. We describe means to compare the roughness of objects with a newly developed sensor.
Previous studies reported that a twisted and coiled polymer actuator (TCA) generates strong force and large stroke by heating. Nylon 6,6 is known to be the most suitable polymer material for TCA because it has high thermal expansion ratio, high softening point and high toughness which is able to sustain gigantic twisting. In order to find the optimal structure of TCA fabricated with silver-coated nylon sewing threads, an equipment for twist-insertion (structuralization), composed of single DC motor, a slider fabricated by 3D printer and a body frame, is developed. It can measure the behaviors of TCAs as well as fabricate TCAs with desired characteristics by structuralizing fibers with controlled rotation per minutes (RPM) and turns. Comparing performances of diverse structures of TCAs, the optimal structure for TCA is found. For the verification of the availability of the optimal TCA, a TCA-driven biomimetic finger is developed. Finally, we successfully demonstrate the flexion/extension of the finger by using the actuation of TCAs.
This paper presents a stretchable proximity-tactile sensor (PTS) using Carbon Micro Coils (CMC). The PTS consists of pairs of multiple active electrodes and a common ground electrode on the same plane. Thus, the sensor is tolerable to the repetitive contacts from external forces. The top layer consists of dielectric elastomer substrate mixed with 5% of CMC, so that it can respond to the proximity and tactile stimuli. Electrodes are located under the top layer and optimally organized to reduce the number of wirings. The sensor is fabricated by molding and casting methods. As the result, a 4 × 4 sensor prototype is made and its performance are experimentally evaluated.
In this paper, we developed a resistance tactile sensor that can detect a slip on the surface of sensor structure. The presented sensor device has fingerprint-like structures that are similar with the role of the humans finger print. The resistance slip sensor that the novel developed uses acrylo-nitrile butadiene rubber (NBR) as a dielectric substrate and graphene as an electrode material. We can measure the slip as the structure of sensor makes a deformation and it changes the resistance through forming a new conductive route. To manufacture our sensor, we developed a new imprint process. By using this process, we can produce sensor with micro unit structure. To verify effectiveness of the proposed slip detection, experiment using prototype of resistance slip sensor is conducted with an algorithm to detect slip and slip is successfully detected. We will discuss the slip detection properties.
A humanoid robot hand has received significant attention in various fields of study. In terms of dexterous robot hand,
slip detecting tactile sensor is essential to grasping objects safely. Moreover, slip sensor is useful in robotics and
prosthetics to improve precise control during manipulation tasks. In this paper, sensor based-human biomimetic structure
is fabricated. We reported a resistance tactile sensor that enables to detect a slip on the surface of sensor structure. The
resistance slip sensor that the novel developed uses acrylonitrile-butadiene rubber (NBR) as a dielectric substrate and
carbon particle as an electrode material. The presented sensor device in this paper has fingerprint-like structures that are
similar with the role of the human’s finger print. It is possible to measure the slip as the structure of sensor makes a
deformation and it changes the resistance through forming a new conductive route. To verify effectiveness of the
proposed slip detection, experiment using prototype of resistance slip sensor is conducted with an algorithm to detect slip
and slip was successfully detected. In this paper, we will discuss the slip detection properties so four sensor and detection
In this paper, we propose the resistive type tactile sensor with a liquid pocket. The tactile sensor with polymer substrate has two components which are the sensing element and the structural part. The sensing part is surrounded by PDMS (Sylgard 184) which is relatively solid. To make the sensor more sensitive, we design the upper part of the sensing element in a shape of half-sphere filled with a liquid (silicone oil). When the force is applied to the sensor, the liquid pressure increases and evenly presses down the sensing element to deform. The size of sensor is 7 x 3 x 1 mm including the wiring part. The good sensitivity (0.012 S/kPa-1) of the fabricated sensor is experimentally verified.
This work presents a dual purpose sensor for collecting proximity and tactile information by using a composite with dielectric elastomer (DE) and Carbon Micro Coils (CMC). CMC is a coil-like carbon microstructure with the size of several hundred micrometers, and its electrical characteristics change with the distance between the object or via physical contact. Especially, the impedance change of the composite depending on the distance can be used as the principle for proximity sensing. We present a method to process the materials by using dielectric materials and additives. A prototype of the sensor is fabricated and its feasibility is experimentally validated.
In previous work, a dual-axis hybrid-type tactile sensor using PDMS (Polydimethylsiloxane) with a pair of metal electrodes, (which were deposited directly on the PDMS surface), was proposed. The hybrid sensor can measure the normal force and the shear force from the measurement of the change of capacitance and resistance values from the one pair of electrodes. However, the metal is hard to be deposited on the surface of the PDMS because the PDMS is hydrophobic. The hydrophobic surface can be changed to hydrophilic using O2 Plasma treatment or UV treatment. When O2 plasma treatment or UV treatment is used, there is the problem that the processing of the metal deposition and the wiring completed in a very short period of limited time. Also, the deposited metal on the surface of the PDMS is easy to break because the deposited metal is exposed in the air. In this paper, we propose a dual-axis hybrid-type tactile sensor where the PET (polyethylene terephthalate) film is inserted between the PDMS films. The deposited metal is not removed easily from the PET film because the adhesion is strong. Also, the PDMS surrounding the PET film plays the roles of dielectric elastomer and shielding the deposited metal from the external environment at same time. Experimental results verify the effectiveness of the fabricated dual-axis hybrid-type force sensor.
The six axis F/T sensor is a primary component for the robotic technologies, but its high unit cost hampers the popularization to the robotic applications. In this paper, we present a six-axis force-torque capacitive sensor based on dielectric elastomer. Dielectric elastomer is compressed and deformed with external forces acting on it. Its deformation results in the variation of capacitance, which can be used as a kind of capacitive sensing scheme. The proposed sensor consists of plastic structure and dielectric elastomer capacitors. Since it takes a simple structure, it is possible to fabricate by using a plastic molding process, which results in extremely lower cost than existing off-the-shelf products. We present the basic structure and design of the sensor with the explanation of its working principle. A fabrication method dedicated to the sensor is developed and finally, a prototype will be demonstrated with calibration procedures.
Robotic grasping requires not only force and touch sensors but also flexibility of such sensors because most of the
sensors are attached to the finger tip. Many studies are underway in such sensors using polymer because polymer is
flexible and affordable. Polydimethylsiloxane (PDMS) is one of widely used substances because it is very stable
physically and chemically.
The principle of the capacitive force sensor using polymer is as follows; capacitance values will be changed by
changes in the thickness of the dielectric elastomer under normal force or changes in the overlapping area of electrodes
under shear force. The force and moment are measured by such changes. Conventional one-axis capacitive type force
sensors measure normal or tangential force from one pair of electrodes. The increased number of electrodes can be used
for multi-axis force sensors at the cost of the size of the sensor and resolution of the sensor. In this paper, we propose a
dual-axis capacitive and resistive hybrid-type force sensor using dielectric elastomer with only one pair of electrodes.
The electrodes are made with thermal evaporator. With only one pair of electrodes, the normal force is measured from
the change of capacitance and resistance values and the shear force is measured from the change of only capacitance
values. Experimental results verify the effectiveness of the proposed dual-axis hybrid type force sensor.
In this paper, we propose a tactile display with a rigid coupling based on Dielectric Elastomer Actuator. The proposed
design of the tactile display is explained and its basic operational principles are discussed. It consists of three parts, that
is, actuator layer, coupling and upper layer. The rigid coupling is sandwiched between them. Because of the simplicity of
the design, the fabrication is extremely easy, that is just to bond the upper layer to the actuator layer after making EAP
actuator sheet and upper layer. The device is fabricated with multiply stacked actuators and its effectiveness is validated
Having a combination of a gel-like soft lens, ligaments, and the Ciliary muscles, the human eyes are effectively
working for various focal lengths without a complicated group of lens. The simple and compact but effective
optical system should deserve numerous attentions from various technical field especially portable information
technology device industry. Noting the limited physical space of those deivces, demanding shock durability, and
massive volume productivity, the present paper proposes a biomimetic optical lens unit that is organized with a
circular silicone lens and an annular dielectric polymer actuator. Unlike the traditional optical lens mechanism
that normally acquires a focus by changing its focal distance with moving lens or focal plane. the proposed
optical system changes its lens thickness using a annulary connected polymer actuator in order to get image
focuses. The proposed biomimetic lens system ensures high shock durability, compact physical dimensions, fast
actuations, simple manufacturing process, and low production cost.
In this paper we present a transparent and stretchable dielectric elastomer actuator(DEA). The device, called
"active skin" is under development as a new means of human interfaces. The active skin consists of elastomeric
films sandwiched between compliant patterned electrodes. Thus, depending on the properties of the elastomer
or electrodes, it is possible to realize a wide variety of implementations as transducers. As a critical issue of
the transparent active skin, transparency in the electrode including that of the substrate is challenging, which
has not been solved yet. In this paper, a compliant, transparent and highly conductive electrode layer on the
elastomeric film by using graphene is presented. The fabrication method of graphene electrodes dedicated to the
elastomeric materials is addressed and its compatibility to the existing materials is discussed. Also, preliminary
implementations on the embossed actuator are given to validate the proposed idea.
Sensing and delivering tactile information is of interest not only in robotic researches but in most of broad sensor
technology areas since along with olfactory it is one of the most difficult sensory information to detect and
transfer. Most of the tactile sensors developed are using either brittle ceramic base material or bulky electromagnetic
material. Although those tactile sensors provides some advantages like a certain level of accuracy in
terms of the applied force measurement and reliable fabrication methods such as MEMS, there is still a significant
drawback due to its brittle material characteristics. Especially for biomimetic applications the material flexibility
might be the major concern in order to achieve the application objectives. In the present work, a multi-axis force
sensor using polymeric material are developed. The sensor has ability to differentiate applied force directions
such as normal and tangential and it to be deployed as an massive array so that a set of tactile sensors can
be easily organized. Having the material flexibility, the present work successfully demonstrates a tactile sensor
array affixed on a human-hand-like robot finger tip.
In this paper, we present a new haptic interface, called "active skin", which is configured with a tactile sensor
and a tactile stimulator in single haptic cell, and multiple haptic cells are embedded in a dielectric elastomer.
The active skin generates a wide variety of haptic feel in response to the touch by synchronizing the sensor and
the stimulator. In this paper, the design of the haptic cell is derived via iterative analysis and design procedures.
A fabrication method dedicated to the proposed device is investigated and a controller to drive multiple haptic
cells is developed. In addition, several experiments are performed to evaluate the performance of the active skin.
Tactile information is prerequisite for dexterous manipulation of objects with robots. In this paper a novel tactile sensor using dielectric elastomer is presented. The sensor is a capacitive type and it can be easily covered onto any curved surface due to the intrinsic flexibility of the dielectric elastomer. The practical design and fabrication of a tactile sensor for the robot fingertip are described in details in this paper. Also,a fingertip shaped tactile sensor with twelve tactile cells is developed. The sensor is mounted on a multi-fingered robot hand, called "SKKU Hand III", and its effectiveness is validated with experimental results.
Previously, the dielectric elastomer based on Acrylonitrile Butadiene Rubber (NBR), called synthetic elastomer
has been reported by our group. It has the advantages that its characteristics can be modified according to
the requirements of performances, and thus, it is applicable to a wide variety of applications. In this paper, we
address the effects of additives and vulcanization conditions on the overall performance of synthetic elastomer.
In the present work, factors to have effects on the performances are extracted, e.g additives such as dioctyl
phthalate (DOP), barium titanium dioxide (BaTiO<sub>3</sub>) and vulcanization conditions such as dicumyl peroxide
(DCP), cross-linking times. Also, it is described how the performances can be optimized by using DOE (Design
of Experiments) technique and experimental results are analyzed by ANOVA (Analysis of variance).
As a major human sensory function, the implementation of the tactile sensation for the human-machine interface
has been one of the core research interests for long time. In this research, tactile display devices based on
dielectric elastomer are introduced among the works recently done by ourselves. Using dielectric elastomer for
the construction of the tactile interface, it can provide stimulation on the human skin without any additional
electromechanical transmission. Softness and flexibility of the device structure, ease of fabrication, possibility for
miniaturization, and cost effectiveness are the representative benefits of the presented devices. Especially, the
device application is open to a wide variety of purposes since the flexible structure offers excellent adaptability
to any contour of the human body as well as the other objects. In this paper, the design of the interfaces is
briefly explained and several examples of implementation are introduced.
The objective of the present work is to demonstrate the efficiency and feasibility of NBR (Nitrile Butadiene Rubber)
based conducting polymer actuator that is fabricated into a micro zoon lens driver. Unlike the traditional conducting
polymer that normally operates in a liquid, the proposed actuator successfully provides fairly effective driving
performance for the zoom lens system in a dry environment. And this paper is including the experiment results for an
efficiency improvement. The result suggested by an experiment was efficient in micro optical zoom lens system. In
addition, the developed design method of actuator was given consideration to design the system.
In this paper we present a dielectric elastomer actuator, which has the ability to sense the force acting on it
without any additional sensing device. Basic physical behaviors of the dielectric elastomer are experimentally
investigated and it is noted that the impedance of the dielectric elastomer varies depending on external forces
acting on it. Based on that concept, we propose the principle of a self-sensing actuator according to experimental
result. In addition, a multi-stacked actuator with self-sensing capability is realized to validate its feasibility.
Normally, various micro-scale devices adopt electromechanical actuators for their basic mechanical functions.
Those types of actuators require a complicated power transfer system even for generating a tiny scale motion.
Since the mechanical power transfer system for the micro-scale motion may require many components, the
system design to fit those components into a small space is always challenging. Micro-optical zoom lens systems
are recently popularly used for many portable IT devices such as digital cameras, camcorder, and cell phones,
Noting the advantages of EAP actuators over the conventional electromechanical counterparts in terms of simple
actuator mechanisms, a micro-optic device that is driven with the EAP actuator is introduced in the present
work. EAP material selection, device design and fabrication will be also delineated.
In this paper we present a new artificial muscle actuator for rectilinear motion made of synthetic elastomer,
which is mainly focused on the robotic applications. Previously, we have developed a new material for actuating
means, named "synthetic elastomer". Synthetic elastomer allows their material properties such as mechanical as
well as electrical properties to be adjusted according to the requirements. Using the synthetic elastomers made
of the recipe adjusted for the robotic application, a new design of the artificial muscle actuator, called multi
stacked actuator is proposed. The actuator is comprised of multiple stacks of synthetic elastomer coated with
compliant electrodes and connecting disks. This unique design enables its linear actuation with the large strain
of active length as well as large force. Experimental works are conducted and the effectiveness of the actuator is
The conducting polymer actuator was presented. The solid polymer electrolyte based on nitrile rubber (NBR) activated with different ionic liquids was prepared. The three different grades of NBR films were synthesized by emulsion polymerization with different amount of acrylonitrile, 23, 35, and 40 mol. %, respectively. The effect of acrylonitrile content on the ionic conductivity and dielectric constant of solid polymer electrolytes was characterized. A conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was synthesized on the surface of the NBR layer by using a chemical oxidation polymerization technique, and room temperature ionic liquids (RTIL) based on imidazolium salts, e.g. 1-butyl-3-methyl imidazolium X [where X= BF<sub>4</sub><sup>-</sup>, PF<sub>6</sub><sup>-</sup>, (CF<sub>3</sub>SO<sub>2</sub>)<sub>2</sub>N<sup>-</sup>], were absorbed into the composite film. The effects of the anion size of the ionic liquids on the displacement of the actuator were examined. The displacement increased with increasing the anion-size of the ionic liquids.
This paper presents a new artificial muscle actuator produced from
dielectric elastomer, called Tube-Spring Actuator(TSA). The new
actuator construction includes two steps: the first part is a
cylindrical actuator manufactured with dielectric elastomer and
the second is a compressed spring inserted inside the tube. An
inner spring is used to maximize the axial deformation while
constraining the radial one. This unique design enables linear
actuation with the largest strain of active length up to 14%
without any additional means. As a result this actuator was
applied to a robot hand. This study lays the foundation for the
future work on dielectric polymer actuator.
A new material, called synthetic rubber in this paper, is proposed
as a material for artificial muscle actuator based on dielectric
elastomer. The presented material displays enhanced electrical as
well as mechanical characteristics in terms of higher dielectric
constant, elastic strength and lower stress relaxation. Several
experiments are performed to evaluate actuation performance of the
material. Also, its advantages are proved by conducting
comparative studies with the other existing materials.
Among ElectroActive Polymers (EAPs) the dielectric elastomer actuator
is regarded as one of the most practically applicable in the near
future. So far, its effect on the actuation phenomena has not been discussed sufficiently, although its strong dependency on prestrain is a significant drawback as an actuator. Recent observations clarifies that prestrain has the following pros and cons: prestrain plays an important role in generating large strain, whereas it rather contributes to the reduction of the strain. Prestrain provides the advantages of improving the response speed, increase of the breakdown voltage, and removing the boundary constraint caused by the inactive actuation area of the actuator. On the contrary, the elastic forces by prestrain makes the deformation smaller and the induced stress relaxation is severely detrimental as an actuator. Also, the permittivity decreases as prestrain goes up, which adds an adverse effect because the strain is proportional to the permittivity. In the present work, a comprehensive study on the effects of prestrain is performed. The key parameters affecting the overall performances are extracted and it is experimentally validated how they work on the actuation performance.
The solid polymer electrolyte based conducting polymer actuator was presented. In the preparation of acutuator module, an ionic liquid impregnated a synthetic rubber (NBR) and PPy were used as a solid polymer electrolyte and conducting polymer, respectively. An ionic liquid, 1-butyl-3-methylimidazolium bis (trifluoromethyl sulfonyl)imide (BMITFSI) is gradually dispersed into the NBR film and the conducting polymer, PPy was synthesized on the surface of NBR. The ionic conductivity of new type solid polymer electrolyte as a function of the immersion time was investigated. The cyclic voltammetry responsed and the redox switching dynamics of PEDOT in NBR matrix were studied. The displacement of the actuator was measured by laser beam.
Tactile sensation is one of the most important sensory functions along with the auditory sensation for the visually impaired because it replaces the visual sensation of the persons with sight. In this paper, we present a tactile display device as a dynamic
Braille display that is the unique tool for exchanging information
among them. The proposed tactile cell of the Braille display is based on the dielectric elastomer and it has advantageous features over the existing ones with respect to intrinsic softness, ease of fabrication, cost effectiveness and miniaturization. We introduce
a new idea for actuation and describe the actuating mechanism of the Braille pin in details capable of realizing the enhanced spatial density of the tactile cells. Finally, results of psychophysical experiments are given and its effectiveness is confirmed.