The design and characterization of a soft gripper with an active palm to control grasp postures is presented herein. The gripper structure is a hybrid of soft and stiff components to facilitate ...integration with traditional arm manipulators. Three fingers and a palm constitute the gripper, all of which are vacuum actuated. Internal wedges are used to tailor the deformation of a soft outer reinforced skin as vacuum collapses the composite structure. A computational finite-element model is proposed to predict finger kinematics. Thanks to its active palm, the gripper is capable of grasping a wide range of part geometries and compliances while achieving a maximum payload of 30 N. The gripper natural softness enables robust open-loop grasping even when components are not properly aligned. Furthermore, the grasp pose of objects with various aspect ratios and compliances can be robustly maintained during manipulation at linear accelerations of up to 15 m/s2 and angular accelerations of up to 5.23 rad/s2.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
A new generation of soft functional materials and actuator designs has ushered the development of highly advanced soft grippers as adaptive alternatives to traditional rigid end-effectors for ...grasping and manipulation applications. While being advantageous over their rigid counterparts, soft gripper capabilities such as contact effort are mostly a consequence of the gripper workspace, which in turn is largely constrained by the gripper design. Moreover, soft grippers designed for highly specific grasping tasks such as scooping grains or wide payloads are usually limited in grasping other payload types or in their manipulation versatility. This article describes a reconfigurable workspace soft (RWS) gripper that exploits compliant structures and pneumatic actuators to reconfigure its workspace to suit a wide range of grasping tasks. To achieve desired kinematics, finite element analysis (FEA) studies are conducted to dictate actuator design and materials used. Various grasping modes and their reconfiguration of the gripper workspace are presented and characterized, including the gripper's capability to reliably scoop granular items with radii as small as 1.5 mm, precisely pick items as thin as 300 μm from flat surfaces, as well as grasp large convex, nonconvex, and deformable items as heavy as 1.4 kg. The RWS gripper can modify and increase its grasping workspace volume by 397%, enabling the widest range of grasping capabilities to date achieved by a single soft gripper.
A microlens array has become an important micro-optics device in various applications. Compared with traditional manufacturing approaches, digital light processing (DLP)-based printing enables ...fabrication of complex three-dimensional (3D) geometries and is a possible manufacturing approach for microlens arrays. However, the nature of 3D printing objects by stacking successive 2D patterns formed by discrete pixels leads to coarse surface roughness and makes DLP-based printing unsuccessful in fabricating optical components. Here, we report an oscillation-assisted DLP-based printing approach for fabrication of microlens arrays. An optically smooth surface (about 1 nm surface roughness) is achieved by mechanical oscillation that eliminates the jagged surface formed by discrete pixels, and a 1–3 s single grayscale ultraviolet (UV) exposure that removes the staircase effect. Moreover, computationally designed grayscale UV patterns allow us to fabricate microlenses with various profiles. The proposed approach paves a way to 3D print optical components with high quality, fast speed, and vast flexibility.
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IJS, KILJ, NUK, PNG, UL, UM
Owing to the favorable energy efficiency and environmental compatibility, capacitive deionization (CDI) has been greatly developed as a potential technology to overcome the ever-growing global water ...shortage. Herein, an effective and simple strategy is reported to boost the desalination performance by 30 percent through an expansion of interlayer spacing. The final redox active hybrid CDI material consists of WS
2
nanoflowers embedded in a highly conductive free-standing rGO-CNT (WS
2
/rGO-CNT) aerogel as an anode and rGO-CNT aerogel as a cathode. WS
2
is applied as a redox-active material for sodium ion intercalation, and three-dimensional (3D) rGO-CNT facilitates the diffusion of the ions to boost the reaction kinetics. Upon charging/discharging, sodium ions intercalate/deintercalate into/from the WS
2
lattice structure which is confirmed
via in situ
XRD measurements, and chloride ions are physically adsorbed/desorbed by the rGO-CNT aerogel. Benefiting from the synergistic effect between the highly conductive and porous rGO-CNT framework and WS
2
nanoflowers with a tuned structure, the as-assembled HCDI device enables stable desalination performance with a superior removal capacity of 80 mg g
−1
, and an excellent removal rate of 3.9 mg g
−1
min
−1
.
Enhanced desalination kinetics achieved by tuning the interlayer spacing of the redox-active material, and its incorporation into a highly conductive and free-standing three-dimensional structure.
•A dual splitter plate flow control device for a square cylinder is introduced.•Fluctuating drag, lift forces and aerodynamic moments are characterized.•Wake regime as functions of the splitter ...plate(s) length and their gap is reported.•Optimum splitter plate(s) length and their gap for lowest drag is determined.•Benefits of dual splitter plates over long single splitter plate is discussed.
In this paper, a dual splitter plate flow separation control device is introduced for a low Reynolds number flow (Re = 100) around the square cylinder of length L to achieve higher drag reduction and improved wake regime control compared to the conventional single splitter plate control devices. Here, two splitter plates of the same length W (ranging from 0.25 L to 2.50 L) are symmetrically attached on the rear surface along the horizontal centerline of the square cylinder with a spacing H (ranging from 0.0 L to 1.0 L) between them. The numerical study is performed using the in-house developed flexible forcing immersed boundary-lattice Boltzmann solver 1 to investigate the effects of dual splitter plate on the flow regime and flow-induced forces. The shear layer interaction with the splitter plates, as well as the vorticity and pressure distribution in the near wake region, are significantly modified by varying W and H, and four different flow regimes (Type I to Type IV) are identified from the observations. Among these flow types, the Type III flow pattern displays an accelerating flow in the wake region that is found to be most beneficial for higher base pressure recovery and drag reduction. Furthermore, dual splitter plates suppress von-Karman vortex shedding and lift force fluctuation, and produce higher drag reduction (≈ 21%) at less than half of the plate length of a single splitter plate. It is also noticed that a dual splitter plate configuration seems to be an optimum arrangement, since adding more splitter plates (up to 5 numbers were tested) on the rear surface of the square cylinder does not change the wake characteristics nor shows any improvements in the drag reduction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Capacitive deionization (CDI) is considered as a promising approach to sustain fresh water supply with environmental friendliness and convenient electrode regeneration. As a novel CDI system, ...flow-through electrode (FTE) CDI is drawing researchers' attention due to its structural simplicity, highly compact cells, cost effectiveness, and fast salt adsorption kinetics that are applicable for large-scale desalination of saline water. However, the FTE CDI architecture requires electrodes with robust structures and preferable permeability, considering the direct flow through mechanism, which limits their choices of electrode materials. Herein, we propose a facial electrospinning method to fabricate three-dimensional TiO2 encapsulated carbon nanofiber (TiO2@CNF), which possesses good mechanical stability and highly permeable macroporous-mesoporous structure to endure the reasonable feed pressure upon high-speed influent flushing. Moreover, the TiO2@CNF electrode shows evident pseudo-capacitive performance as well as high electrical conductivity. By integrating the features of both the TiO2@CNF and the FTE CDI architecture, the as-fabricated system displays a salt removal capacity of 15.50 mg g−1 and a desalination rate of 1.26 mg g−1 min−1 at 1.4 V. The TiO2@CNF provides a promising alternative for FTE CDI towards the future desalination technologies.
•TiO2@CNF designed with electrical conductivities and high specific surface areas for CDI applications.•3D nanostructured TiO2@CNF integrates the features of both the TiO2@CNF and the FTE CDI architecture.•A high salt removal rate of 1.26 mg g−1 min−1 in the capactive desalination process.•A removal capacity of 14.5 mg g−1 was obtained under external power ~ 1.4 V.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•An up-scalable electrospinning method for electrode fabrication in HCDI system.•The free-standing Co3O4@CNF@CNT cathode shows high SAC of 58.6 mg g−1.•A high SAR of 12.27 mg g−1 ...min−1 are realized at 1.4 V.
Hybrid capacitive deionization (HCDI) is emerging as an energy-efficient alternative for brackish water desalination with low expenditure cost and favourable ion removal effectiveness by adopting battery-type electrodes in the traditional capacitive deionization (CDI) system. Herein, an unscalable electrospinning method is introduced to contrive cathode material for HCDI system. Co3O4 and nitrogen-doped carbon nanotube decoration are formed successfully and uniformly distributed with the hollow structure of free-standing carbon nanofibers (Co3O4@CNF@CNT). The conductive “bridges” provided by the CNF matrix significantly shorten the diffusion length of Na+ and promote the electrical conductivity of the Co3O4 nanoparticles. Moreover, benefiting from the incorporation of nitrogen-doped CNTs, the electrical conductivity is further enhanced. The as-prepared Co3O4@CNF@CNT cathode shows excellent pseudocapacitive performance of 395F g−1 at a scan rate of 1 mV s−1 and superior rate performance of 279F g−1 at 100 mV s−1. The HCDI system delivers an outstanding salt adsorption capacity (SAC) of 58.6 mg g−1 and a highest salt adsorption rate (SAR) of 12.27 mg g−1 min−1 with a potential difference of 1.4 V, indicating the great potential of applying Co3O4@CNF@CNT in the practical HCDI system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Freeform liquid three-dimensional printing (FL-3DP) is a promising new additive manufacturing process that uses a yield stress gel as a temporary support, enabling the processing of a broader class ...of inks into complex geometries, including those with low viscosities or long solidification kinetics that were previously not processable. However, the full exploitation of these advantages for the fabrication of complex multilateral structures has been hindered by difficulties in controlling the interfaces between inks and supports. In this work, an in-depth study of the rheological properties and interfacial stabilities between a nanoclay-modified support and silicone-based inks enabled a better understanding of the impact printing parameters have on the extruded filament morphology, and thus on printing resolutions. With these improvements, the fabrication of functional multimaterial pneumatic components applied to soft robotics could be demonstrated, exhibiting superior capabilities compared to casting or traditional extrusion-based additive manufacturing in terms of geometric freedom (overhanging and multimaterial structures), tunability of the component’s functionality, and robustness between different phases. Overall, the full exploitation of FL-3DP advantages enables a broader design space for features and functionalities in soft robotic components that require complex and robust combinations of materials.
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IJS, KILJ, NUK, PNG, UL, UM
Emerging soft machines require high-performance strain sensors to achieve closed-loop feedback control. Machine learning is a versatile tool to uncover complex correlations between fabrication ...recipes and sensor performance at the device level. Here a three-stage machine learning framework was realized for a high-accuracy prediction model capable of automating the design of strain sensors. First, a support-vector machine classifier was trained by using 351 compositions of various nanomaterials. Second, through 12 active learning loops, 125 strain sensors were stagewise fabricated to enrich the multidimensional dataset. Third, to address the challenge of data scarcity, data augmentation was implemented to synthesize >10,000 virtual data points, followed by genetic algorithm-based selection to optimize the model’s prediction accuracy. Several data-driven design rules for piezoresistive nanocomposites were generalized and validated by in situ microscopic studies. As final demonstrations, model-suggested strain sensors can be integrated into/onto various soft machines to endow them with real-time strain-sensing capabilities.Piezoresistors can be used in strain sensors for soft machines, but the traditional design process relies on intuition and human ingenuity alone. Haitao Yang and colleagues present a method built on genetic algorithms and other machine learning methods to design and fabricate strain sensors with improved capabilities.
A major difference between manmade underwater robotic vehicles (URVs) and undersea animals is the dense arrays of sensors on the body of the latter which enable them to execute extreme control of ...their limbs and demonstrate super-maneuverability. There is a high demand for miniaturized, low-powered, lightweight and robust sensors that can perform sensing on URVs to improve their control and maneuverability. In this paper, we present the design, fabrication and experimental testing of two types of microelectromechanical systems (MEMS) sensors that benefit the situational awareness and control of a robotic stingray. The first one is a piezoresistive liquid crystal polymer haircell flow sensor which is employed to determine the velocity of propagation of the stingray. The second one is Pb(Zr0.52Ti0.48)O3 piezoelectric micro-diaphragm pressure sensor which measures various flapping parameters of the stingray's fins that are key parameters to control the robot locomotion. The polymer flow sensors determine that by increasing the flapping frequency of the fins from 0.5 to 3 Hz the average velocity of the stingray increases from 0.05 to 0.4 BL s−1, respectively. The role of these sensors in detecting errors in control and functioning of the actuators in performing tasks like flapping at a desired amplitude and frequency, swimming at a desired velocity and direction are quantified. The proposed sensors are also used to provide inputs for a model predictive control which allows the robot to track a desired trajectory. Although a robotic stingray is used as a platform to emphasize the role of the MEMS sensors, the applications can be extended to most URVs.
