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The desire to directly touch and experience virtual objects led to the development of a tactile feedback device. In this paper, a novel soft pneumatic actuator for providing tactile feedback is proposed and demonstrated. The suggested pneumatic actuator does not use an external air compressor but it is operated by internal air pressure generated by an electrostatic force. By using the actuator, we designed a glove to interact with virtual reality. The finger motions are detected by attached flexible piezoelectric sensors and transmitted to a virtual space through Bluetooth for interconnecting with a virtual hand. When the virtual finger touches the virtual object, the actuators are activated and give the tactile feedback to the real fingertip. The glove is made of silicone rubber material and integrated with the sensors and actuators such that users can wear them conveniently with light weight. This device was tested in a virtual chess board program, wherein the user picked up virtual chess pieces successfully.

Estimating pressure variation is essential in membrane systems because it is the primary factor that affects the energy for system operation. Although numerous researches were conducted studies, most previous studies focused on the hydraulic roles of single membrane. In this study, we examined the pressure variations caused by membranes considering the effects of flow rate, number of membranes, and distance between the membranes. Membranes were integrated into a tygon tube and pressure was measured by using a cell pressure probe with the lapse of time. We evaluated theoretical pressure values by using Poiseuille’s law and compared them with the experimental results. The measured pressure values are well matched with the theoretical results. This indicates that the CPP can be used to reliably measure the pressure of fluid flows in a tube. As a result, when the flow rate increases 200 times, the increasing rate (slope) of pressure increases 25.9 times and the hydraulic resistance increases by 27.5% as the number n increases 1 to 3. In addition, as the distance between two membranes increases more than 6 cm, the flow pressure of the flow passing the two membranes approaches the value for passing a single membrane. This study will be helpful to understand the pressure variations in various porous fluidic systems composed of membranes.

Most Autonomous manipulation studies of robot hands require tactile sensors for accurate detection. Flexible tactile sensor reproduces human skin characteristics and provides important tactile information. This paper presents a flexible and compact touch sensor array that can be applied to robot hands. The sensor is manufactured by laser-cut polyvinylidene fluoride (PVDF). A sensor based on PVDF produces voltage output due to the deformation caused by the applied press. The touching location on the sensor is extracted by data processing of the voltage outputs. By the sensing system, the robot hand including the sensor array can monitor in real-time the contact object. The results show that the robot hand recognizes different contact areas when holding objects of various shapes. In addition, the sensor provides a new and simple strategy for dynamic touch sensing while providing new design ideas for electronic skin.

Robots equipped with an assembly system have significant potential and value because they allow simple modules to be assembled in various forms. A new type of soft assembly robot was recently created by combining a soft robot and an assembly system. In this paper, we introduce an assemblable electromagnetic soft actuator made of silicone. Silicone is very soft and stretchable, and is made to react with electromagnets by mixing with iron oxide. The motion is controlled by the force applied to the electromagnets attached to the floor. A fast and accurate response is displayed according to the input amplitude and frequency. In addition, the range of motion is significant. When the power applied by a single actuator is 9V 1A, the motion is approximately 2.62mm, which is 93.6 % of the entire actuator height, the maximum value that can be moved structurally. Above all, the actuator can be connected to the y- and z-axes without additional line connections to create the desired assembly structure. An additional wire connection is required for the x-axis connection. At the moment a connection is made, the actuators move in accordance with the input signal and all movements are conducted under little voltages.

This study introduces a gait analysis system using a pair of slippers with flexible piezoelectric sensors. We install only one flexible sensor based on polyvinylidene fluoride, which is a flexible piezoelectric material, in each slipper. The flexible sensor is positioned in the slipper sole area under the inner arch of the foot. In this position, the sensor undergoes bending for walking, and generates electrical signals through the piezoelectric characteristic. We focus on the detection of the heel strike and toe-off moments from the sensor output. We then acquire the floor contract information of the slippers from the detection and extract eight gait parameters. We develop a gait analysis system including the sensing slippers, a sensing module for data collection and wireless communication, and an external computer with the data processing program. Moreover, we demonstrate that the proposed total gait analysis system based on the slippers with the flexible piezoelectric sensors works efficiently.

Stimuli-sensitive hydrogels have been intensively studied because of their potential applications in drug delivery, cell culture, and actuator design. Although hydrogels with directed unidirectional response, i.e. capable of bending actuated by different chemical components reaction in response to several stimuli including water and electric fields, these hydrogels are capable of being actuated in one direction only by the stimulus. By contrast the challenge of building a device that is capable of responding to the same cue (in this case a temperature gradient) to bend in either direction remains unmet. Here, inspired by the structure of pine cone scales, we design a temperature-sensitive hydrogel with bending directed an imposed fishing line. The layers with same PNIPAAm always shrinks in response to the heat. Even the layers made with different chemical property, bends away from a warm surface, whether the warm surface is applied at its upper or lower boundary. To design the bending hydrogel we exploited the coupled responses of the hydrogel; a fishing line intercalating structure and change its construction. In addition to revealing a new capability of stimulus sensitive hydrogels, our study gives insight into the structural features of pine cone bending.

One of the primary purposes of pine cones is the protection and distant dispersal of pine seeds. Pine cones open and release their embedded seeds on dry and windy days for long-distance dispersal. In this study, how the pine seed attach to/ detach from the pine cone scale for efficient seed dispersal were experimentally investigated by using X-ray micro-imaging technique. The cone and seeds adhere to one another in the presence of water, which could be explained by the surface tension and the contact angle hysteresis. Otherwise, without water, the waterproof seed wing surface permits rapid drying for detach and dispersion. On the other hand, during wildfires, pine cones open their seed racks and detach the pine seeds from pine cones for rapid seed dispersal. Due to these structural advantages, pine seeds are released safely and efficiently on adjust condition. These advantageous structure could be mimicked in practical applications.

In this study, we introduce Fe3O4-silicone flexible composite actuators fabricated by combining silicone and iron oxide particles. The actuators exploit the flexibility of silicone and the electric conductivity of iron oxide particles. These actuators are activated by electrostatic force using the properties of the metal particles. Herein, we investigate the characteristic changes in actuation performance by increasing the concentration of iron oxide from 1% to 20%. The developed flexible actuators exhibit a resonant frequency near 3 Hz and their actuation amplitudes increase with increasing input voltage. We found that the actuator can move well at metal particle concentrations >2.5%. We also studied the changes in actuation behavior, depending on the portion of the Fe3O4-silicone in the length. Overall, we experimentally analyzed the characteristics of the newly proposed metal particle-silicone composite actuators.

Herein, we investigated the feasibility of a flexible ring type energy harvester for a cylindrical shape change similar to that in a bent human finger. We fabricated a ring type energy harvester using a piezoelectric material, polyvinylidene fluoride (PVDF), on a polydimethylsiloxane (PDMS) substrate. We modeled a human finger using a silicone cylinder to mimic the movement of a real human finger and measured the power harvested from its shape change under compression. A series of experiments were conducted under two different conditions, namely the variations in the radius of the cylinder and input frequency. Furthermore, we experimentally and theoretically assessed the output power and analyzed the harvested power as a function of the load resistance. We observed that the maximum harvested power level is of the order of hundreds of nanowatts.

Mimosa pudica has three distinct specialized organs, namely, pulvinus, secondary pulvinus, and pulvinule, which are respectively controlling the movements of petioles, leaflets, and pinna in response to external stimuli. Water flow is a key factor for such movements, but detailed studies on the organization of the vascular system for water transport in these organs have not been published yet. In this study, organizations of the xylem vessels and morphological features of the pulvinus, the secondary pulvinus, and the pulvinule were experimentally investigated by X-ray computed tomography and histological technique. Results showed that the xylem vessels were circularly distributed in the specialized motile organs and reorganized into distinct vascular bundles at the extremities. The number and the total cross-sectional area of the xylem vessels were increased inside the specialized motile organs. Morphological characteristics obtained in this study provided new insight to understand the functions of the vascular networks in the dynamic movements of M. pudica. Microsc. Res. Tech. 76:1204–1212, 2013. © 2013 Wiley Periodicals, Inc.

Stimuli-sensitive hydrogels have been intensively studied because of their potential applications in drug delivery, cell culture, and actuator design. Although hydrogels with directed unidirectional response, i.e. capable of bending actuated by different chemical components reaction in response to several stimuli including water and electric fields, these hydrogels are capable of being actuated in one direction only by the stimulus. By contrast the challenge of building a device that is capable of responding to the same cue (in this case a temperature gradient) to bend in either direction remains unmet. Here, inspired by the structure of pine cone scales, we design a temperature-sensitive hydrogel with bending directed an imposed fishing line. The layers with same PNIPAAm always shrinks in response to the heat. Even the layers made with different chemical property, bends away from a warm surface, whether the warm surface is applied at its upper or lower boundary. To design the bending hydrogel we exploited the coupled responses of the hydrogel; a fishing line intercalating structure and change its construction. In addition to revealing a new capability of stimulus sensitive hydrogels, our study gives insight into the structural features of pine cone bending.

Stimuli-sensitive hydrogels have received attention because of their potential applications in various fields. Stimuli-directed motion offers many practical applications, such as in drug delivery systems and actuators. Directed motion of asymmetric hydrogels has long been designed; however, few studies have investigated the motion control of symmetric hydrogels. We designed a pine cone scale-inspired movable temperature-sensitive symmetric hydrogel that contains Fe3O4. Alignment of Fe3O4 along the magnetic force is key in motion control in which Fe3O4 acts like fibers in a pine cone scale. Although a homogeneous temperature-sensitive hydrogel cannot respond to a temperature gradient, the Fe3O4-containing hydrogel demonstrates considerable bending motion. Varying degrees and directions of motion are easily facilitated by controlling the amount and alignment angle of the Fe3O4. The shape of the hydrogel layer also influences the morphological structure. This study introduced facile and low-cost methods to control various bending motions. These results can be applied to many fields of engineering, including industrial engineering. Implanting iron oxide powder in a temperature-sensitive hydrogel produced a material that bends and opens similar to a pine cone. Most approaches to fabricating muscle-like hydrogel actuators rely on combining two materials that have different volume expansions. The approach developed by Kahye Song and Sang Joon Lee of Korea's POSTECH now makes it possible to manipulate single-component hydrogels in a low-cost manner. The team poured thin coatings of iron oxide powder over single layers of poly(N-isopropylacrylamide), PNIPAAm, and then hardened the layers together while applying a permanent magnetic field. By fine tuning the field direction, this procedure generated fiber-like structures that introduced origami-like folds into the PNIPAAm gel. Octagonal folding patterns gave concave structures that resembled closed pine cones; a subsequent temperature stimulus provoked the structures to stretch out and open like flower petals. We designed various bending hydrogels with symmetric structure that responds to temperature gradient, with inspiration from pine cone. We verified the motion changes based on the amount of content, alignment angle and shape of the layer. The developed system can be applied to various fields, because the direction and curvature can be controlled easily.

Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system.

Mimosa pudica is a plant that rapidly shrinks its body in response to external stimuli. M. pudica does not perform merely simple movements, but exhibits a variety of movements that quickly change depending on the type of stimuli. Previous studies have investigated the motile mechanism of the plants from a biochemical perspective. However, an interdisciplinary study on the structural characteristics of M. pudica should be accompanied by biophysical research to explain the principles underlying such movements. In this study, the structural characteristics and seismonastic reactions of M. pudica were experimentally investigated using advanced bio-imaging techniques. The results show that the key factors for the flexible movements by the pulvinus are the following: bendable xylem bundle, expandable/shrinkable epidermis, tiny wrinkles for surface modification and a xylem vessel network for efficient water transport. This study provides new insight for better understanding the M. pudica motile mechanism through structural modification.

Mimosa pudica has three distinct specialized organs, namely, pulvinus, secondary pulvinus, and pulvinule, which are respectively controlling the movements of petioles, leaflets, and pinna in response to external stimuli. Water flow is a key factor for such movements, but detailed studies on the organization of the vascular system for water transport in these organs have not been published yet. In this study, organizations of the xylem vessels and morphological features of the pulvinus, the secondary pulvinus, and the pulvinule were experimentally investigated by X-ray computed tomography and histological technique. Results showed that the xylem vessels were circularly distributed in the specialized motile organs and reorganized into distinct vascular bundles at the extremities. The number and the total cross-sectional area of the xylem vessels were increased inside the specialized motile organs. Morphological characteristics obtained in this study provided new insight to understand the functions of the vascular networks in the dynamic movements of M. pudica.

To cope with poor quality in cryo-electron tomography images, electron-dense markers, such as colloidal goldbeads, are often used to assist image registration and analysis algorithms. However, these markers can create artifacts that occlude a specimen due to their high contrast, which can also cause failure of some image processing algorithms. One way of reducing these artifacts is to replace high contrast objects with pixel densities that blend into the surroundings in the projection domain before volume reconstruction. In this paper, we propose digital inpainting via compressed sensing (CS) as a new method to achieve this goal. We show that cryo-ET projections are sparse in the discrete cosine transform (DCT) domain, and, by finding the sparsest DCT domain decompositions given uncorrupted pixels, we can fill in the missing pixel values that are occluded by high contrast objects without discontinuities. Our method reduces visual artifacts both in projections and in tomograms better than conventional algorithms, such as polynomial interpolation and random noise inpainting.