Center for Micro-BioRobotics

The proliferation of soft robotics research worldwide has brought substantial achievements in terms of principles, models, technologies, techniques, and prototypes of soft robots. Such achievements are reviewed here in terms of the abilities that they provide robots that were not possible before. An analysis of the evolution of this field shows how, after a few pioneering works in the years 2009 to 2012, breakthrough results were obtained by taking seminal technological and scientific challenges related to soft robotics from actuation and sensing to modeling and control. Further progress in soft robotics research has produced achievements that are important in terms of robot abilities-that is, from the viewpoint of what robots can do today thanks to the soft robotics approach. Abilities such as squeezing, stretching, climbing, growing, and morphing would not be possible with an approach based only on rigid links. The challenge ahead for soft robotics is to further develop the abilities for robots to grow, evolve, self-heal, develop, and biodegrade, which are the ways that robots can adapt their morphology to the environment.

Cephalopods such as octopuses have a combination of a stretchable skin and color-tuning organs to control both posture and color for visual communication and disguise. We present an electroluminescent material that is capable of large uniaxial stretching and surface area changes while actively emitting light. Layers of transparent hydrogel electrodes sandwich a ZnS phosphor-doped dielectric elastomer layer, creating thin rubber sheets that change illuminance and capacitance under deformation. Arrays of individually controllable pixels in thin rubber sheets were fabricated using replica molding and were subjected to stretching, folding, and rolling to demonstrate their use as stretchable displays. These sheets were then integrated into the skin of a soft robot, providing it with dynamic coloration and sensory feedback from external and internal stimuli.

The octopus is a marine animal whose body has no rigid structures. It has eight arms composed of a peculiar muscular structure, named a muscular hydrostat. The octopus arms provide it with both locomotion and grasping capabilities, thanks to the fact that their stiffness can change over a wide range and can be controlled through combined contractions of the muscles. The muscular hydrostat can better be seen as a modifiable skeleton. Furthermore, the morphology the arms and the mechanical characteristics of their tissues are such that the interaction with the environment (i.e., water) is exploited to simplify control. Thanks to this effective mechanism of embodied intelligence, the octopus can control a very high number of degrees of freedom, with relatively limited computing resources. From these considerations, the octopus emerges as a good model for embodied intelligence and for soft robotics. The prototype of a robot arm has been built based on an artificial muscular hydrostat inspired to the muscular hydrostat of the Octopus vulgaris. The prototype presents the morphology of the biological model and the broad arrangement of longitudinal and transverse muscles. Actuation is obtained with cables (longitudinally) and with shape memory alloy springs (transversally). The robot arm combines contractions and it can show the basic movements of the octopus arm, like elongation, shortening and bending, in water.

In the past few years, soft robotics has rapidly become an emerging research topic, opening new possibilities for addressing real-world tasks. Perception can enable robots to effectively explore the unknown world, and interact safely with humans and the environment. Among all extero- and proprioception modalities, the detection of mechanical cues is vital, as with living beings. A variety of soft sensing technologies are available today, but there is still a gap to effectively utilize them in soft robots for practical applications. Here, the developments in soft robots with mechanical sensing are summarized to provide a comprehensive understanding of the state of the art in this field. Promising sensing technologies for mechanically perceptive soft robots are described, categorized, and their pros and cons are discussed. Strategies for designing soft sensors and criteria to evaluate their performance are outlined from the perspective of soft robotic applications. Challenges and trends in developing multimodal sensors, stretchable conductive materials and electronic interfaces, modeling techniques, and data interpretation for soft robotic sensing are highlighted. The knowledge gap and promising solutions toward perceptive soft robots are discussed and analyzed to provide a perspective in this field.

A soft tactile sensor able to detect both normal and tangential forces is fabricated with a simple method using conductive textile. Owing to the multi-layered architecture, the capacitive-based tactile sensor is highly sensitive (less than 10 mg and 8 μm, for minimal detectable weight and displacement, respectively) within a wide normal force range (potentially up to 27 N (400 kPa)) and natural touch-like tangential force ranges (from about 0.5 N to 1.8 N). Being flexible, soft, and low cost, this sensor represents an original approach in the emulation of natural touch. Furthermore, in addition to being flexible and mechanically robust over a wide pressure range, the sensor is also able to detect in-plane forces. We investigated the performance of the device under tangential stimulation while applying a static normal force Fz of, either, 0.5 N or 1 N; thus mimicking the tactile indentation needed to induce a tangential force through horizontal displacement (Figure 3d). During the experiments, observations of the cross section under an optical microscope suggest that no shear stress is induced in the dielectric fluorosilicone film and that the top electrode is free to slide over the bottom set of electrodes (see video S6, Supporting Information). In particular, the latter aspect is due to the low friction properties of the fluorosilicone. Independently of the static normal applied force, a 0.4 N tangential force is needed before a significant capacitance variation can be observed (see Figure 3d). This minimum force could reflect the shear strain induced in the thick PDMS layer during the transmission of the tangential displacement. Indeed, such shear force could be needed to initiate the sliding of the top electrode over the bottom electrodes. Then, starting from about 0.4 N, a second regime is observed in which varies linearly with the applied tangential force. As a higher static normal force must be applied initially to the device, a higher friction force is needed before sliding occurs, and we can observe that, for the same capacitance variation (same overlapping area of the electrodes), doubling the initial load applied to the sensor contributes to a tangential force divided by a factor two. Minimal detected tangential displacements of 8 μm and 14 μm, under 1 N and 0.5 N initial static normal forces, respectively, were evaluated. It should be noted that this result is about one order of magnitude lower than minimal displacements reported in the literature (i.e., 60 μm).13 Linear behavior is observed within the 0.4–1.2 N and 0.8–1.6 N ranges, for 0.5 N and 1 N static normal forces, respectively. The slope represents the sensitivity of the sensor in the tangential mode. The obtained performances were 0.32 ± 0.02 N−1 and 0.34 ± 0.02 N−1 for the 0.5 N and 1 N initial contact force curves, respectively. Hence, we may conclude that, due to the design of the sensor, in this regime the tangential sensitivities are almost independent of the normal component of the applied force, and they are equal to about 0.3 N−1. Furthermore, when increasing the tangential force, a deviation of the response from the linear behavior is observed, suggesting that the overlapping area of the electrodes is not dictated by a sliding mechanism of the two sets of electrodes, rather it is limited by the deformable properties of the whole device, in particular its stretchability. To conclude, the design and the materials used to develop our sensor generate high performing features for the next generation of three-axis soft tactile sensors. Although our design is simple, we have achieved an improved level of tactile information to mimic natural touch. In parallel, the materials used for the multi-layer structure converge in obtaining a soft, flexible and highly sensitive device that offers a low-cost technological approach. New perspectives are thus open for the design of soft and smart interfaces, and for all kinds of applications where natural-like tactile sensing is desired. Importantly, this sensor could target other specific applications than biomimetic touch, in which very low, for instance, heartbeat monitoring (ca. 100 Pa), to very high, for example, foot pressure-distribution monitoring (300–400 kPa), pressure ranges are required. Finally, we expect that the quest for soft and flexible artificial touch systems will steeply increase as soft technological approaches39 are increasingly being developed in many fields such as exploratory robotics, wearable systems, medicine and rehabilitation, personal robotics, entertainment, and gaming. Preparation of Layers: Polydimethylsiloxane (PDMS) (Dow Corning, Sylgard 184; ratio of base to crosslinker, 10:1 by mass) and fluorosilicone (Dow Corning 730) diluted with acetone were degassed and poured on the surface of a silicon wafer previously covered with adhesive tape. After spin-coating and curing at room temperature for around 24 h, membranes of, respectively, 300 μm and 70 μm thickness were obtained. The PDMS membranes were used as external sealing layers whereas the fluorosilicone film was part of the dielectric layering of the sensor. The dielectric constant of DowCorning730 fluorosilicone is 5.5. Textile-Based Sensor Fabrication: Copper/tin coated woven fabric (Zelt fabric – Mindsets Ltd, UK) with an intrinsic resistance of 50 mΩ ◻−1 was cut by laser (VLS 3.50; Universal Laser Systems, Inc., USA), with a resolution of around 0.5 mm, into four bottom electrodes of 5 mm × 5 mm and one 8 mm × 8 mm top electrode. The textile electrodes were positioned over the PDMS membranes and maintained in position with double-sided adhesive tape. The two layers were then assembled face to face and the fluorosilicone dielectric membrane was placed in between. An air gap of approximately 150 μm thickness was naturally formed because of the low surface free energy of fluorosilicone. The bottom electrodes and top electrodes were manually centered with respect to each other. As the capacitance measurement was differential, the variation in electrode positioning did not affect the sensor behavior. This fabrication aspect emphasizes the simple, fast, and low-cost technological fabrication process of the sensor. Experimental Set Up for Measurements: A schematic of the set up is shown in Figure S2 in the Supporting Information. An 8 × 8 mm2 Delrin ® flat probe was mechanically interfaced to a 6-axis load cell (ATI NANO 17 SI-25-0.25, Apex, NC, USA), which acquired force data during the experiment. The alignment of the load cell to the device was determined with an initial rough manual positioning, by means of three orthogonal manual micrometric translation stages with crossed roller bearings (M-105.10, PI, Karlsruhe, Germany) followed by an accurate controlled positioning, by means of two servo-controlled micrometric translation stages: (M-111.1, PI, Karlsruhe, Germany) for the normal direction (z), and (M-126.1 PI, Karlsruhe, Germany) for the shear direction (x), respectively. Cyclic indentation (static mode) and force incrementing (dynamic mode) experiments were performed at constant speed. For tangential characterizations, the probe was glued to the device and a static normal force of 0.5 N or 1 N was initially applied before translating the stage in the x-direction. In this way, sufficient friction was provided in order to generate a displacement and an overlapping area of top and bottom electrodes, and an experimental protocol that approximates a real tactile event was used. Capacitance measurements were performed by means of custom electronics. Each capacitance output signal was acquired by means of a 24-bit capacitance-to-digital converter (CDC) (AD7747, Analog Devices Inc., Nordwood, MA, USA). The input dynamics of the CDC was 16 pF, which was fully used during sensor characterization. In order to minimize the influence of parasitic capacitances (due to wires, connections, etc), the measuring was done in differential mode, using a dummy reference capacitor for each capacitance channel. In addition, to further reduce parasitic capacitances, the device was connected to the electronic board by means of shielded cables. The capacitance resolution was 1 fF, and, because of the strategies described above, the measured rms noise could be reduced to about 4 fF. Therefore, the minimal detectable signal was about 12 fF (three times larger than the rms noise). Data were acquired by means of a 32-bit PIC micro-controller board (PIC32MX460F512L, Microchip Technology Inc., Chandler, AZ, USA) and sent to a PC via USB. The whole system, comprising the translation stages, the load cell, and the capacitance acquisition board, was connected to a PC. A graphical user interface was implemented to acquire force and capacitance measurements simultaneously, and to control the linear translation stages. In order to determine the initial absolute values needed for normalization, each capacitance was measured in absence of externally applied loads by means of a precision LCR meter (E4980A, Agilent Technologies Inc., Santa Clara, CA, USA). Finally, the sensitivity of the sensor was calculated as the slope of the normalized capacitance variation in function of the force, in different force ranges. For the normal force, the equivalent pressure was considered too and, in the present manuscript, the sensitivity is indicated in kPa−1 in order to better compare the resulting data with state-of-the-art sensors in the literature. This study was partially funded by the PLANTOID project (EU-FP7-FET-Open grant n.: 29343). Note: The licence of this manuscript was changed after initial online publication, as of May 2, 2014. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Soft robotics is a challenging and promising branch of robotics. It can drive significant improvements across various fields of traditional robotics, and contribute solutions to basic problems such as locomotion and manipulation in unstructured environments. A challenging task for soft robotics is to build and control soft robots able to exert effective forces. In recent years, biology has inspired several solutions to such complex problems. This study aims at investigating the smart solution that the Octopus vulgaris adopts to perform a crawling movement, with the same limbs used for grasping and manipulation. An ad hoc robot was designed and built taking as a reference a biological hypothesis on crawling. A silicone arm with cables embedded to replicate the functionality of the arm muscles of the octopus was built. This novel arm is capable of pushing-based locomotion and object grasping, mimicking the movements that octopuses adopt when crawling. The results support the biological observations and clearly show a suitable way to build a more complex soft robot that, with minimum control, can perform diverse tasks.

The present article shows the development of a gripper for general purposes with grasping and holding capabilities enabled by a simple control scheme. This objective has been reached exploiting the combination of soft materials, underactuated mechanisms, and a bioinspired design. The development of the soft gripper will be explained by reporting the results obtained on three different and sequential versions. The devices are here presented in their main components, underlining the anthropomorphic approach used in the design of the fingers. The used actuation mechanism is based on the control of a single cable tension, which guarantees a grasping adaptable to objects of different shape. Manipulation capability and grasping force have been tested, in order to extract a quantitative comparative analysis between the three proposed devices. The main factor that influences the improvement of the gripper performance results to be represented by the suitable combination of material with the right mechanical properties. Outcomes show how the use of a bioinspired design together with the intrinsic mechanical properties of soft materials can give rise to new soft devices able to show dexterous grasping capabilities with a simple control and actuation system.

Soft robotics is a growing field of research, focusing on constructing motor-less robots from highly compliant materials, some are similar to those found in living organisms. Soft robotics has a high potential for applications in various fields such as soft grippers, actuators, and biomedical devices. 3D printing of soft robotics presents a novel and promising approach to form objects with complex structures, directly from a digital design. Here, recent developments in the field of materials for 3D printing of soft robotics are summarized, including high-performance flexible and stretchable materials, hydrogels, self-healing materials, and shape memory polymers, as well as fabrication of all-printed robots (multi-material printing, embedded electronics, untethered and autonomous robotics). The current challenges in the fabrication of 3D printed soft robotics, including the materials available and printing abilities, are presented and the recent activities addressing these challenges are also surveyed.

Tetragonal barium titanate nanoparticles (BTNPs) have been exploited as nanotransducers owing to their piezoelectric properties, in order to provide indirect electrical stimulation to SH-SY5Y neuron-like cells. Following application of ultrasounds to cells treated with BTNPs, fluorescence imaging of ion dynamics revealed that the synergic stimulation is able to elicit a significant cellular response in terms of calcium and sodium fluxes; moreover, tests with appropriate blockers demonstrated that voltage-gated membrane channels are activated. The hypothesis of piezoelectric stimulation of neuron-like cells was supported by lack of cellular response in the presence of cubic nonpiezoelectric BTNPs, and further corroborated by a simple electroelastic model of a BTNP subjected to ultrasounds, according to which the generated voltage is compatible with the values required for the activation of voltage-sensitive channels.

For better or worse, digital technologies are reshaping everything, from customer behaviors and expectations to organizational and manufacturing systems, business models, markets, and ultimately society. To understand this overarching transformation, this paper extends the previous literature which has focused mostly on the organizational level by developing a multi‐level research agenda for digital transformation (DT). In this regard, we propose an extended definition of DT as “a socioeconomic change across individuals, organizations, ecosystems, and societies that are shaped by the adoption and utilization of digital technologies.” We suggest four lenses to interpret the DT phenomenon: individuals (utilizing and adopting digital technologies), organizations (strategizing and coordinating both internal and external transformation), ecosystems (harnessing digital technologies in governance and co‐producing value propositions), and geopolitical frameworks (regulating the environments in which individuals and organizations are embedded). Based on these lenses, we build a multi‐level research agenda at the intersection between the bright and dark sides of DT and introduce the PIAI framework, which captures a process of perception , interpretation , and action that ultimately leads to possible impact . The PIAI framework identifies a critical research agenda consisting of a non‐exhaustive list of topics that can assist researchers to deepen their understanding of the DT phenomenon and provide guidance to managers and policymakers when making strategic decisions that seek to shape and guide the DT.

An innovative processing strategy for fabricating soft structures that possess electric- and humidity-driven active/passive actuation capabilities along with touch- and humidity-sensing properties is reported. The intrinsically multifunctional material comprises an active thin layer of poly(3,4-ethylenedioxythiophene):poly­(styrene sulfonate) in a double-layered structure with a silicone elastomer and provides an opportunity toward developing a new class of smart structures for soft robotics. The emergence of responsive polymers is of fundamental interest, and their ability to reversibly reply to a given stimulus, such as heat, electric voltage, or light, has practical applications in several fields, including soft robotics, active sensing, and actuation.1 Notably, conjugated polymers (CP), such as polypyrrole (PPy), polyaniline, and poly(3,4-ethylenedioxythiophene) (PEDOT), have shown great potential with respect to actuation and significant efforts have been focused in particular on the realization of “dry” CP actuators that can function in air.[2] Recently, Okuzaki et al.3 proposed a new class of CP actuators that function in ambient air based on the cooperation between the electrical conductivity and hygroscopic nature of conductive polymers. These authors discovered that electrochemically synthesized PPy films exhibit a significant reversible volume expansion in air resulting from the absorption and desorption of water vapor present in ambient air.4 Furthermore, a volume contraction was observed under the application of an electric current, which was attributed to the desorption of water vapor as a result of Joule heating.5 A similar electrically induced isotropic dimensional change was subsequently observed in ≈20 μm thick poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films prepared using the solution-casting method.6 The ubiquitous presence of humidity in ambient air and its variation makes the development of humidity-responsive actuators both appealing and of importance. By chance, the capability to convert simple environmental stimuli, such as humidity, into mechanical reversible motion is regularly observed in living systems, particularly plants.7 These systems are capable of converting the sorption and desorption of water into driving forces for movement. A well-known example is the release of ripe seeds from pine cones, which open due to a bending movement of their scales during drying in ambient air and close in wet conditions.8 Similarly, seeds from wild wheat are propelled into soil after being released, which is solely due to the daily change in humidity that induces a curvature of the awns depending on the moisture level.9 Interestingly, many actuation systems in plants have a common structural feature: the humidity-responsive actuation results from the coupling of two differently structured tissue layers with different elongations along a specific direction. These layers are interfacially bound to each other to form a laminated, double-layered composite structure.10 Although the aforementioned actuators developed by Okuzaki's group undergo isotropic dimensional changes, anisotropic motions have not been thoroughly explored. Inspired by the differential swelling or shrinking of natural double-layered structures, one approach for achieving anisotropic motion in artificial actuators is to use a bilayer system in which the active layer is composed of a humidity-responsive material and the other layer is a passive material that is inert to humidity, that provides mechanical strength and that converts the isotropic volume change into a bending motion. In this work, we present a double-layered, anisotropic humidity-driven actuator based on an ultrathin active layer of PEDOT:PSS and a passive layer composed of poly(dimethylsiloxane) (PDMS), with intrinsic sensing capability, and able to be controlled both by joule effect or directly by environmental humidity variations. PDMS elastomer was selected as the passive substrate because of its elasticity, good flexibility, chemical and humidity inertness, remarkable durability against repeated deformation, and resistance to high temperature. Because of these properties, in our system, PDMS should easily deform as a result of the contraction/expansion of the active layer and should withstand repeated and reversible deformation. PEDOT:PSS was selected as the active material due to the good combination of several features that influence actuator performance, such as its suitable electrical conductivity, humidity responsiveness, mechanical properties, and chemical and thermal stability.11 Moreover, PEDOT:PSS is commercially available in the form of a ready-to-use waterborne dispersion; therefore, the active conducting polymer layer can be deposited by spin-coating, which results in a well-controlled homogeneous and reproducible thickness in a range between a few tens to several hundreds of nanometers, as we reported in some recent works.12 The proposed actuator has the potential to simultaneously combine active/passive actuation and sensing within a single-composite material. Movement can be controlled through the application of an electric current or by changes in environmental humidity (Figure 1a and Video S1, Supporting Information). In addition to actuation, the hygroscopic properties of the PEDOT:PSS layer impart sensing capabilities because a variation in the environmental humidity induces a reversible, reproducible variation in its electrical resistance, typically on the order of 1.25%/10% relative humidity (RH).[12] Furthermore, because of the piezoresistive behavior of PEDOT:PSS, where its gauge factor has been reported to be between 5.2 and 17.8, this material has been proposed for use as a sensitive layer in strain and touch sensors.13 All of the aforementioned unique features along with the tailorability of the fabrication process provide possibilities for a series of interesting applications for these structures as active bioinspired elements with intrinsic sensing and actuation capabilities. A schematic representation of the developed fabrication procedure (see also Experimental Section), is shown in Figure 1b. We followed a mask-free, time- and material-saving approach based on direct machining of the PEDOT:PSS/PDMS structures using a commercial CO2 laser cutting system, which allowed actuators to be fabricated with different shapes and circuit patterns (see Video S2, Supporting Information). By varying the laser cutting parameters, we were able to simultaneously cut and pattern the surface of the actuators, thereby avoiding misalignment problems and reducing the processing time and manipulation. The patterning of the active surface in the form of electric circuits was performed by engraving only a thin PEDOT:PSS layer. This allowed the current flow between the electrodes to be driven along specific paths, thereby inducing local bending of selected portions of the structure (Figure 1c–d). Due to the silanization of the silicon wafers, the PEDOT:PSS/PDMS structures could easily be peeled off from the substrate after laser machining and used as free-standing actuators. The electrical connection was easily established using small flat alligator clips. Notably, the ratio of the active-to-passive layer thickness is extremely small, as clearly evidenced in the scanning electron microscopy (SEM) images of an actuator cross section (Figure 1e), in which the thicknesses of the PEDOT:PSS and PDMS layers were 600 ± 29 nm and 120 ± 10 μm, respectively. The maximum moisture desorption-related contraction in PEDOT:PSS was estimated to be on the order of 2%.6 Despite the thinness of the active layer, the properties of the selected materials and the actuator design are such that this small contraction is capable of causing a large bending displacement of the relatively thick bilayer. However, the use of a thin active layer allows for a rapid sorption/desorption of water, which results in a rapid actuation time. Moreover, the PEDOT:PSS film is characterized by a multilayered structure due to the multiple spin-coating deposition steps (magnified part of Figure 1e). We believe that this stacked layer microstructure has a beneficial role in relaxing the stress induced by bending and in reducing the effect of crack propagation within the active layer. For characterization, the electro-thermo-mechanical responses of our actuators were tested on beam-shaped structures. To evaluate how the surface patterns affect actuator performance, three beam structures were fabricated (namely s1, s2, s3) that had the same dimensions (3 mm wide, 10 mm long) but different pattern lengths (h = 2, 5, and 8 mm, respectively) above the base of the beam (Figure 2a). The resistances of the resulting conductive paths were 1.13 ± 0.03, 1.63 ± 0.03, and 2.50 ± 0.18 kΩ for samples s1, s2, and s3, respectively. The electro-thermomechanical characterization was performed on cantilever beams in which one end was fixed and the other end was free to move. A rectangular area was provided at one end of the beam for clamping and for the electrical connection. Step input voltages of 5, 10, 15, 20, 25, and 30 V were applied to the samples, and the resulting bending displacements were recorded using a digital camera. Depending on the pattern length, different portions of the beam were heated by the current, which induced different bending behaviors (Figure 2a). Indeed, s3 was bent along almost its entire length, i.e., almost to the tip, whereas s1 and s2 exhibited shorter bending regions, which corresponded to the heated portion, with the rest of beam remaining essentially straight. For each input voltage, the surface temperature, curvature, and blocking force were determined, and the measurement results are summarized in Figure 2b–d. Regarding the surface temperature, the actuators were tested up to a maximum temperature of ≈200 °C, which was considered to be the safe limit for reliable performance of the materials. The three samples exhibited a linear temperature increase as the power increased and an increased curve slope as the pattern length decreased (Figure 2b). This trend was expected because a longer line pattern (s3) resulted in heating throughout a wider portion of the actuator compared with that of a smaller portion (s1, s2); hence, a lower temperature was reached under the same applied power. The curvatures of samples s1–3 were estimated by image processing, as described in the Experimental Section, by considering the heated beam portions. Examples of the processed images are presented in Figure S1 (Supporting Information), in which a straight portion closer to the tip is clearly visible, particularly for higher curvatures. As expected, at the same temperature, the curvature of the bending segment was found to be independent of the pattern length, which is highlighted by the similar trends of curvature versus temperature shown in Figure 2c, where the maximum curvature was ≈0.4 mm−1. The blocking force was measured on sample s3 by contacting the tip of the sample with the force sensor. The maximum force detected here (0.32 mN, 32 mg) was already 12 times of the actuator weight (2.7 mg) (Figure 2d). The actuation dynamics was investigated by evaluating the time profiles of the surface temperature and corresponding curvature of sample s3 in response to a step input voltage of 20 V (Figure 2f). Such a voltage caused a temperature increase of ΔT = 80 °C, and a stable maximum temperature of 112 °C was reached in ≈10 s. The corresponding curvature profile was characterized by three different trends: rise (0–10 s, red), bent state (10–60 s, green), and recovery (60–85 s, blue). The rise time was relatively short, with the curvature rapidly increasing from the initial (off) state, which exhibited a negative curvature, as the input voltage was applied. Once the bent state (on) was reached, with a maximum curvature of nearly 0.3 mm−1, it remained approximately stable as long as current was supplied. When the voltage was switched off, the actuator recovered its initial curvature within 25 s, which was the time required to reset at room temperature (see also Video S4, Supporting Information). The forward and backward curvature paths exhibited a remarkable overlap with no evidence of hysteresis (Figure 2g). To determine the operating frequency range of the actuators, we applied square wave input voltages with different frequencies to the samples. As the actuation frequency increased, we observed a reduced curvature change between the on and off states because the step voltage duration was insufficient for both the bent and relaxed states to reach stability (Figure 2e). Nevertheless, the actuator bending movement was appreciable up to 5 Hz. The long-term reliability of the actuator performance was evaluated by repetitive cycling of the actuator, up to 1000 cycles, and negligible changes in the curvature were observed (Figure 2h). As previously mentioned, in addition to electrical actuation, the bilayer is able to macroscopically react to variations in environmental humidity through passive movements without requiring any electrical or thermal stimulus. The humidity-responsive passive actuation behavior of the PEDOT:PSS/PDMS films was demonstrated by placing the beam-shaped samples inside a humidity chamber and exposing them to variations in RH at a constant temperature (30 °C). The bilayer responded to the variations in humidity with a bending movement in a fully reversible manner and in the opposite direction with respect to that for electrical stimulus (Figure 3a). Because the humidity chamber is slow to reach a preset humidity level, it is not possible to appreciate the speed of the response from these results. The speed of the response is better evidenced, although only qualitatively, in the second part of Video S3 (Supporting Information), which shows a leaf-shaped actuator bending when a finger comes in close proximity to the PEDOT:PSS surface. A rapid response to the moisture evaporating from the skin is clear, where the leaves move away and then quickly reset back to the resting position when the finger is removed. The features of this passive behavior make this material interesting for the development of hygromorphic actuators. Because humidity is ubiquitous in real-world applications, it is important to assess how variations in RH levels influence electrically induced actuation. Indeed, different equilibrium states are established between the water content of the PEDOT:PSS film and the surrounding environmental humidity, which affects the bending radii of electrically activated actuators, with each input voltage changing with the RH level (Figure S2, Supporting Information). The proposed bilayer actuators have applications as soft grippers, manipulators, or as active elements in millimeter-scale walking robots. Due to the mask-free and rapid fabrication process, it is easy to change the design of the actuators to meet the requirements of the target application in terms of geometry, bending behavior, and force. Site-specific electrical actuation was demonstrated with a patterned bilayer film cut in the shape of a small hand with individually addressable fingers. Five insulated and independent circuits were used to control the bending of each finger, as shown in Figure 3b (see also Video S5, Supporting Information). As a first proof-of-concept manipulator, we created a 2 cm long, 6-finger gripper that was able to grasp and lift lightweight objects with a weight comparable with its own (Figure 3c). Moreover, a similarly shaped actuator, lying flat on a plane, was able to stand up on its legs and lift an object with a weight three times that of its own (Figure 3d). In this case, the electrical connection was established by attaching two thin copper wires to the gold electrode with silver paint. One of the most interesting features of the proposed bilayered composites is the possibility of functioning simultaneously as a structural and functional (actuation, sensing) material. This capability indeed has long been pursued by engineers and robot designers in the search for multifunctional materials and structures for the construction of smarter and simpler tools and robots.15 Recently, significant advances have been reported in the development of artificial muscles with tactile sensitivity (sensing muscles) which can sense by themselves while working any mechanical perturbation, not requiring additional sensors.16 Considering this feature, this multifunctional material can be useful for mimicking the behaviors of materials often encountered in nature. Indeed, several species of plants are capable of sensing and responding to mechanical stimuli, e.g., closing their leaves for protection (Mimosa pudica) or even to catch prey (Dionaea muscipula).17 As an example of the potential of our approach, we attempted to imitate the behavior of M. pudica by exploiting the variation in electrical resistance induced in PEDOT:PSS layer structures when the bilayer is mechanically deformed. For this purpose, a simple prototype was with a leaf-shaped this M. pudica was able to close its leaves when (see Figure and Video S5, Supporting Information). The sensing of touch is performed by that the resistance of the PEDOT:PSS layer with a small current through a suitable The system the Joule heating when a rapid resistance variation is variations in resistance were observed even for small resulting from a touch on the are reported in Figure Supporting Information). In this provided a and for fabricating bioinspired soft actuators and provided into how the of humidity sorption/desorption and Joule heating affect the actuation properties of the proposed bilayer The role of on the performance of the beam-shaped actuators was also from and The processing which of a few steps of direct laser and is particularly appealing because it rapid and simple fabrication to soft actuators with The proposed smart material structure intrinsic such as structural properties, sensing, and actuation capabilities that exhibit with in plants and that the of multiple in bioinspired soft of PEDOT:PSS/PDMS μm were by placing them in a for 30 along with a that a few of A film of PDMS ratio of base elastomer to silicone elastomer base and was then the for at a speed of and then at = °C for in an A air was applied with a power of = 5 for s. A commercially available PEDOT:PSS PEDOT:PSS content was of μm, and with of the 12 layers of PEDOT:PSS were deposited by at a of = for the PDMS each deposition the samples were on a in ambient air for 5 at °C and air at 5 for 10 s. the samples were to a thermal = °C). A CO2 laser with laser and was then used to cut and pattern the samples, it to a range of soft actuator and To provide the electrical input voltage to the gold electrodes were to the of the actuators. A gold layer nm was deposited on the PEDOT:PSS surface by through The actuators were then peeled off from the of the were performed using a For the PDMS layer, were performed on PDMS that had been peeled off from the substrate to the deposition of For the PEDOT:PSS layer, the PEDOT:PSS was from the PDMS substrate with and the of the profile was measured the images were with a were of the cross section of the bilayer cut using a The electro-thermo-mechanical response of the actuators was investigated by the responses of the actuators to different step voltages with a digital and images of the samples during the were recorded with a with a The temperature at the film surface was by thermal using an thermal The were performed in ambient air 25 °C, have been performed processing images of the activated samples using procedure in (see Supporting for The measurement of the blocking force of the actuators was performed using The tip of the force was in with sample s3 8 mm from the actuator base the beam Once current was the bending induced in the actuator was by the tip which was then by the sensor. s1 and s2 were not considered because the relatively long beam section not to resulted in the measurement being on the specific of the sensor. In other the to the blocking and the blocking were only for sample PDMS Because the for the bending actuator is extremely sensitive to of the substrate and because the of PDMS is on the process, we measured the of our PDMS samples using from the were performed with up to a applied strain on samples with dimensions of 10 mm mm mm using a described To the humidity-responsive of the bilayer PEDOT:PSS/PDMS actuators in a homogeneous air the samples were inside a chamber with controlled humidity and this chamber was with a to of the samples. The samples were to humidity at a controlled temperature (30 from RH up to RH while simultaneously the bending of the samples. The RH inside the chamber was using a humidity The authors to the of the for This was in part by within the for of the As a to our authors and this provides by the Such materials are and be for but are not or from should be to the The is not for the content or of any by the should be to the corresponding for the

Advances in nanomedicine, coupled with novel methods of creating advanced materials at the nanoscale, have opened new perspectives for the development of healthcare and medical products. Special attention must be paid toward safe design approaches for nanomaterial-based products. Recently, artificial intelligence (AI) and machine learning (ML) gifted the computational tool for enhancing and improving the simulation and modeling process for nanotoxicology and nanotherapeutics. In particular, the correlation of in vitro generated pharmacokinetics and pharmacodynamics to in vivo application scenarios is an important step toward the development of safe nanomedicinal products. This review portrays how in vitro and in vivo datasets are used in in silico models to unlock and empower nanomedicine. Physiologically based pharmacokinetic (PBPK) modeling and absorption, distribution, metabolism, and excretion (ADME)-based in silico methods along with dosimetry models as a focus area for nanomedicine are mainly described. The computational OMICS, colloidal particle determination, and algorithms to establish dosimetry for inhalation toxicology, and quantitative structure-activity relationships at nanoscale (nano-QSAR) are revisited. The challenges and opportunities facing the blind spots in nanotoxicology in this computationally dominated era are highlighted as the future to accelerate nanomedicine clinical translation.

Soft robotics is a current focus in robotics research because of the expected capability of soft robots to better interact with real-world environments. As a point of inspiration in the development of innovative technologies in soft robotics, octopuses are particularly interesting 'animal models'. Octopus arms have unique biomechanical capabilities that combine significant pliability with the ability to exert a great deal of force, because they lack rigid structures but can change and control their degree of stiffness. The octopus arm motor capability is a result of the peculiar arrangement of its muscles and the properties of its tissues. These special abilities have been investigated by the authors in a specific study dedicated to identifying the key principles underlying these biological functions and deriving engineering requirements for robotics solutions. This paper, which is the second in a two-part series, presents how the identified requirements can be used to create innovative technological solutions, such as soft materials, mechanisms and actuators. Experiments indicate the ability of these proposed solutions to ensure the same performance as in the biological model in terms of compliance, elongation and force. These results represent useful and relevant components of innovative soft-robotic systems and suggest their potential use to create a new generation of highly dexterous, soft-bodied robots.

This paper presents the design and experimental testing of the robotic elbow exoskeleton NEUROBOTICS Elbow Exoskeleton (NEUROExos). The design of NEUROExos focused on three solutions that enable its use for poststroke physical rehabilitation. First, double-shelled links allow an ergonomic physical human-robot interface and, consequently, a comfortable interaction. Second, a four-degree-of-freedom passive mechanism, embedded in the link, allows the user's elbow and robot axes to be constantly aligned during movement. The robot axis can passively rotate on the frontal and horizontal planes 30° and 40°, respectively, and translate on the horizontal plane 30 mm. Finally, a variable impedance antagonistic actuation system allows NEUROExos to be controlled with two alternative strategies: independent control of the joint position and stiffness, for robot-in-charge rehabilitation mode, and near-zero impedance torque control, for patient-in-charge rehabilitation mode. In robot-in-charge mode, the passive joint stiffness can be changed in the range of 24-56 N·m/rad. In patient-in-charge mode, NEUROExos output impedance ranges from 1 N·m/rad, for 0.3 Hz motion, to 10 N·m/rad, for 3.2 Hz motion.

Abstract Bacterial wound infection is one of the most common nosocomial infections. The unnecessary employment of antibiotics led to raising the growth of antibiotic‐resistant bacteria. Accordingly, alternative armaments capable of accelerating wound healing along with bactericidal effects are urgently needed. Considering this, we fabricated chitosan (CS)/polyethylene oxide (PEO) nanofibers armed with antibacterial silver and zinc oxide nanoparticles. The nanocomposites exhibited a high antioxidant effect and antibacterial activity against Staphylococcus aureus , Escherichia coli , and Pseudomonas aeruginosa . Besides, based on the results of the cell viability assays, the optimum concentration of ZnONPs and AgNPs in the nanofibrous mats is 0.2% w/v and 0.08% w/v respectively and had no cytotoxicity on fibroblast cells. The scaffold also showed good blood compatibility according to the effects of coagulation time. As well as significant fibroblast migration and proliferation on the wound margin, according to wound‐healing assay. All in all, the developed biocompatible, antioxidant, and antibacterial Ag‐ZnO NPs incorporated CS/PEO nanofibrous mats showed their potential as an effective wound dressing.

Direct laser writing methods based on two-photon polymerization (2PP) are powerful tools for the on-demand printing of precise and complex 3D architectures at the micro and nanometer scale. While much progress was made to increase the resolution and the feature size throughout the years, by carefully designing a material, one can confer specific functional properties to the printed structures thus making them appealing for peculiar and novel applications. This Review summarizes the state-of-the-art of functional resins and photoresists used in 2PP, discussing both the range of material functions available and the methods used to prepare them, highlighting advantages and disadvantages of different classes of materials in achieving certain properties.

Abstract The inert nature of most commercial polymers and nanomaterials results in limitations of applications in various industrial fields. This can be solved by surface modifications to improve physicochemical and biological properties, such as adhesion, printability, wetting and biocompatibility. Polymer functionalization allows to graft specific moieties and conjugate molecules that improve material performances. In the last decades, several approaches have been designed in the industry and academia to graft functional groups on surfaces. Here, we review surface decoration of polymers and nanomaterials, with focus on major industrial applications in the medical field, textile industry, water treatment and food packaging. We discuss the advantages and challenges of polymer functionalization. More knowledge is needed on the biology behind cell–polymer interactions, nanosafety and manufacturing at the industrial scale.

Cancer accounts for millions of deaths every year and, due to the increase and aging of the world population, the number of new diagnosed cases is continuously rising. Although many progresses in early diagnosis and innovative therapeutic protocols have been already set in clinical practice, still a lot of critical aspects need to be addressed in order to efficiently treat cancer and to reduce several drawbacks caused by conventional therapies. Nanomedicine has emerged as a very promising approach to support both early diagnosis and effective therapy of tumors, and a plethora of different inorganic and organic multifunctional nanomaterials have been ad hoc designed to meet the constant demand for new solutions in cancer treatment. Given their unique features and extreme versatility, nanocarriers represent an innovative and easily adaptable tool both for imaging and targeted therapy purposes, in order to improve the specific delivery of drugs administered to cancer patients. The current review reports an in-depth analysis of the most recent research studies aiming at developing both inorganic and organic materials for nanomedical applications in cancer diagnosis and therapy. A detailed overview of different approaches currently undergoing clinical trials or already approved in clinical practice is provided.

Epithelial-mesenchymal transition (EMT) is a complex process with a primordial role in cellular transformation whereby an epithelial cell transforms and acquires a mesenchymal phenotype. This transformation plays a pivotal role in tumor progression and self-renewal, and exacerbates resistance to apoptosis and chemotherapy. EMT can be initiated and promoted by deregulated oncogenic signaling pathways, hypoxia, and cells in the tumor microenvironment, resulting in a loss-of-epithelial cell polarity, cell-cell adhesion, and enhanced invasive/migratory properties. Numerous transcriptional regulators, such as Snail, Slug, Twist, and ZEB1/ZEB2 induce EMT through the downregulation of epithelial markers and gain-of-expression of the mesenchymal markers. Additionally, signaling cascades such as Wnt/β-catenin, Notch, Sonic hedgehog, nuclear factor kappa B, receptor tyrosine kinases, PI3K/AKT/mTOR, Hippo, and transforming growth factor-β pathways regulate EMT whereas they are often deregulated in cancers leading to aberrant EMT. Furthermore, noncoding RNAs, tumor-derived exosomes, and epigenetic alterations are also involved in the modulation of EMT. Therefore, the regulation of EMT is a vital strategy to control the aggressive metastatic characteristics of tumor cells. Despite the vast amount of preclinical data on EMT in cancer progression, there is a lack of clinical translation at the therapeutic level. In this review, we have discussed thoroughly the role of the aforementioned transcription factors, noncoding RNAs (microRNAs, long noncoding RNA, circular RNA), signaling pathways, epigenetic modifications, and tumor-derived exosomes in the regulation of EMT in cancers. We have also emphasized the contribution of EMT to drug resistance and possible therapeutic interventions using plant-derived natural products, their semi-synthetic derivatives, and nano-formulations that are described as promising EMT blockers.

Boron nitride nanotubes (BNNTs) represent an innovative and extremely intriguing class of nanomaterials. Thanks to their special chemical and physical characteristics, they have already found a large number of applications in the field of nanotechnology, and recent studies have shown their possible exploitation in the biomedical domain, both as nanocarriers and, more interestingly, as nanotransducers. In this review, the latest findings on the interactions between BNNTs and living systems are summarized, starting with the major issues of their stabilization in physiological media and their functionalization with bioactive molecules. Thereafter the biocompatibility data which have so far been made available are discussed, and the need for further extensive and standardized tests is highlighted. Finally, the appealing diagnostic and therapeutic opportunities offered by BNNT-based systems are described, envisioning the potential spill-over effects of such 'smart' and 'active' nanoparticles in nanomedicine.