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This work presents a unique approach to the design, fabrication, and characterization of paper-based origami robotic systems consisting of stackable pneumatic actuators. These paper-based actuators (PBAs) use materials with high elastic modulus-to-mass ratios, accordion-like structures, and direct coupling with pneumatic pressure for extension and bending. The study contributes to the scientific and engineering understanding of foldable components under applied pneumatic pressure by constructing stretchable and flexible structures with intrinsically nonstretchable materials. Experiments showed that a PBA possesses a power-to-mass ratio greater than 80 W/kg, which is more than four times that of human muscle. This work also illustrates the stackability and functionality of PBAs by two prototypes: a parallel manipulator and a legged locomotor. The manipulator consisting of an array of PBAs can bend in a specific direction with the corresponding actuator inflated. In addition, the stacked actuators in the manipulator can rotate in opposite directions to compensate for relative rotation at the ends of each actuator to work in parallel and manipulate the platform. The locomotor rotates the PBAs to apply and release contact between the feet and the ground. Furthermore, a numerical model developed in this work predicts the mechanical performance of these inflatable actuators as a function of dimensional specifications and folding patterns. Overall, we use stacked origami actuators to implement functionalities of manipulation, gripping, and locomotion as conventional robotic systems. Future origami robots made of paper-like materials may be suitable for single use in contaminated or unstructured environments or low-cost educational materials.

The development of actuators for power sources is essential for the efficient manipulation of fluids in microfluidics systems. In this work, a capacitor-type three-layer paper actuator was fabricated by sandwiching a polyelectrolyte layer between two films of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS). The paper actuator exhibited stable large electromechanical deformations in bilateral symmetry under alternating square-wave electric field. The actuation properties were examined in a function of voltage (±0.5, ±1, ±1.5, ±2, and ±2.5 V) and frequency (1, 0.5, 0.2, and 0.05 Hz). In addition, the PEDOT/PSS electrode films with different thicknesses were prepared, and the effects of actuator thickness on actuation properties were examined. As a result, it was found that the actuator displacement increased considerably with reducing actuator thickness. In addition, the actuator with a thickness of 48 μm demonstrated a maximum displacement of 5.8 mm at a voltage of 1.5 V and a frequency of 0.05 Hz. The proposed actuator can be potentially used in the development of power sources for micropumps and check valves of microfluidic devices.

Control of industrial sheet and film processes involves separate controllers and actuators for minimizing both temporal variations along the machine direction (MD) and spatial variations along the cross direction (CD). Model-based control methods such as model predictive control (MPC) have gained widespread implementation for controlling both the MD and CD processes. One limitation of model-based methods is that changes in the true process pose significant identification challenges for operators which are often resolved with costly open loop identification experiments. The predominant industrial measurement technology acquires a signal of mixed MD and CD variations that requires separation. This work compares various model-free approaches for MD-CD separation as a prerequisite to effective MD control. To address the challenges of model-based control, this paper introduces an adaptive control method for the MD process. Closed loop identification experiments are conducted and compared to benchmarks on an industrial paper machine simulator.

Brain-machine interfaces (BMIs) decode neural activity in real-time, allowing control of sensors and actuators. However, real-time neural decoding requires high computational resources. Recently developed paper-based electronics (e.g., transistors) are likely to reduce the cost of computing devices. In this theoretical study, we propose a roadmap to develop BMIs that take advantage of cellulose based supercomputers. Major milestones will include: 1) an initial prototype with a small number of elements capable of forming a simple brain-controlled On/Off switch, and 2) scaling up the capabilities of the new computing device, such that paper-based electronics lined in the walls of people’s homes will form a supercomputer. The initial prototype will be used to control the lights in a room, but more advanced devices are expected to decode more complex brain commands. As paper-based electronics are very low cost, it is proposed here that paper-based supercomputing capabilities may significantly improve BMIs.

Stimulus-responsive actuators that can respond to the external stimuli and convert external energy into dynamic movement behaviors are highly desired for many applications. Among various driving sc...

A Particle Swarm Optimisation (PSO) based PID controller has been proposed in this paper for a paper machine headbox. The considered headbox model has been perturbed and the proposed controller has been implemented on the perturbed model to assess the robustness of the system. The robustness of the proposed controller has been evaluated on the basis of sensitivity and complementary sensitivity functions. Sensitivity and complementary sensitivity functions provide significant insight into the system's behavior for disturbance, uncertainties, and noise (due to sensors/actuators). Hence, the controller to be designed for a given system should be concerned about these functions. Apart from these functions, worst-case sensitivity analysis has also been carried out for the perturbed headbox. The responses obtained from the proposed controller have been compared with some conventional PID tuning techniques and it is observed that the proposed controller yields better robustness.

Multi-responsive actuators driven by different stimuli (e.g. light, humidity, electricity) have attracted intense attention recently for the advantages of being used in various environments and show enormous actuation. In this work, we propose humidity- and light-driven actuators based on carbon nanotube (CNT)-coated paper and a biaxially oriented polypropylene (BOPP) composite. The CNT-paper/BOPP actuator shows large bending actuation when driven by humidity change (curvature of 1.2 cm-1) and near infrared (NIR) light irradiation (curvature up to 1.6 cm-1). The great actuation performances outperform most other paper-based actuators. Finally, a smart gripper, of which the initial opening width can be enlarged, is fabricated on the basis of the CNT-paper/BOPP actuators. By utilizing the bidirectional bending motion of the actuator, the opening width of the gripper can increase to a width that is 4 times larger than its initial width, so as to grasp a large object. The gripper is also able to raise and move an object that is 20 times heavier than one actuator of the gripper. We assume that this new type of actuator has great potential in artificial muscle, soft robotics and biomimetic applications.

Paper-based advanced functional materials have become the focus of intense research in recent years. Particularly, magnetic papers show strong potential for applications in a wide range of 4.0 technologies including communication, magnetic sensing, electromagnetic filtering, magnetic-based health care tools, point-of-care microfluidic devices, and security. In situ and lumen-loading, the main methods to prepare magnetoactive papers, have problems such as the rigorous reaction conditions, hard control of deposition location, decreased tensile strength, poor retention of magnetic nanoparticles, or the obligation to perform the magnetic impregnation during the papermaking process, that hinder their applicability. Those issues are addressed in the present work, in which approximate to 20 nm Fe3O4 nanoparticles are hydrothermally synthesized and later incorporated in a wax-based home-made cartridge and nanoimpregnated into paper by a thermal process leading to a magnetic paper with improved stress and strain at rupture and Young's modulus, 30 MPa, 4.5%, and 2 GPa, respectively, when compared to neat paper, 15 MPa, 3.5%, and approximate to 1 GPa, respectively. Additionally, the reported magnetic impregnation method provides the paper with a 0.2 emu g(-1) magnetic saturation, allowing it to work as a bending actuator with a bending of 12 mm at an applied magnetic field of 105 mT., The authors thank the FCT- FundacAo para a Ciencia e Tecnologia- for financial support in the framework of the Strategic Funding UID/FIS/04650/2020 and under projects PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. R. B-P. acknowledges also support from FCT (SFRH/BD/140698/2018). P.M. thanks FCT- FundacAo para a Ciencia e Tecnologia for the contract under the Stimulus of Scientific Employment, Individual Support - 2017 Call (CEECIND/03975/2017). The authors thank funding by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033 and from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively. Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, EGEF and ESF) is gratefully acknowledged.

Reduced graphene oxide (rGO) papers prepared by simple self-assembly process were used as electrode material for the fabrication of bimorphic electrical actuators. Initially, the structural studies of the rGO paper confirmed the formation of graphitic structure. The ionic gel electrolyte was prepared separately and used to couple the two rGO paper electrodes. This forms the tri-layered structure as an actuator, the displacement was measured by varying the applied potential with respect to time. The actuation properties were extended for both photon as well as electronic conducting gel electrolyte. The experimental results suggest that the flexible rGO paper can be used for electronic actuators.

The hierarchical structure of multiwalled carbon nanotubes (CNTs), cellulose paper, and the polydimethylsiloxane (PDMS) polymer is realized for a low-power-driven actuator capable of operating unde...

Untethered small-scale soft robots have been widely researched because they can be employed to perform wireless procedures via natural orifices in the human body, or other minimally invasive operations. Nevertheless, achieving untethered robotic motion remains challenging owing to the lack of an effective wireless actuation mechanism. To overcome this limitation, we propose a magnetically actuated walking soft robot based on paper and a chained magnetic-microparticle-embedded polymer actuator. The magnetic polymer actuator was prepared by combining Fe3O4 magnetic particles (MPs, diameter of ~50 nm) and silicon that are affected by a magnetic field, thereafter, the magnetic properties were quantified to achieve proper force and optimized according to the mass ratio, viscosity, and rotational speed of a spin coater. The fabricated polymer was utilized as a soft robot actuator that can be controlled using an external magnetic field, and paper was employed to construct the robot body with legs to achieve walking motion. To confirm the feasibility of the designed robot, the operating capability of the robot was analyzed through finite element simulation, and a walking experiment was conducted using electromagnetic actuation. The soft robot could be moved by varying the magnetic flux density and on&ndash, off state, and it demonstrated a maximum moving speed of 0.77 mm/s. Further studies on the proposed soft walking robot may advance the development of small-scale robots with diagnostic and therapeutic functionalities for application in biomedical fields.

Fluidic elastomer actuators (FEAs) are popular actuation ways in soft robotics due to their low cost and simple fabrication process. To realize intelligent soft robotic systems, real‐time monitoring of their deformation and interactions with surrounding objects including shape and proximity is important. Thus, integration of sensors into FEAs while considering cost reduction and mass production is required. Because paper features low cost and recyclability, herein, two paper‐based sensors, resistive strain sensors (RSSs) and capacitive proximity sensors (CPSs), are incorporated into FEAs as the strain‐limiting layers. The RSS exhibits the ability to detect the actuated bending angle with hysteresis ≈0.01% and high repeatability for 30 cycles. The RSS is also able to detect different object sizes being grasped by the FEA. In contrast, the CPS starts detecting object proximity 8 mm away from the sensor surface and functions well at various approaching speeds. The CPS is also capable of distinguishing objects of different materials by their permittivity. Finally, an intelligent soft gripper which carries these two sensors is demonstrated, where bending curvature, object proximity, contact, and release are monitored in real time. The results provide a pathway for the development of low‐cost sensorized soft robotic systems with advanced sensing functionalities.

In this work, the fabrication of Rochelle salt based piezoelectric structures is illustrated. Structures composed of paper and Rochelle salt are easily manufactured using simple processes. Both manufacturing and the material itself are environmental friendly. Additionally Rochelle salt is biocompatible. In the paradigm of a cleaner piezoelectric technology, the fabrication of active sensing or actuating devices is developed. Thus processing method, material and piezoelectric properties have been studied: (1) pure crystals are used as acoustic actuator, (2) properties of paper impregnated with Rochelle salt are detailed, (3) charge generation is demonstrated on the impregnated material. Actuating and sensing devices are reported in order to highlight the potential of this green piezoelectric material. © 2015 The Authors. Published by Elsevier Ltd.

Failure to utilize valving and automation techniques has restricted the complexity of fluidic operations that can be performed in paper microfluidic devices. We developed a toolkit of paper microfluidic valves and methods for automatic valve actuation using movable paper strips and fluid-triggered expanding elements. To the best of our knowledge, this is the first functional demonstration of this valving strategy in paper microfluidics. After introduction of fluids on devices, valves can actuate automatically a) after a certain period of time, or b) after the passage of a certain volume of fluid. Timing of valve actuation can be tuned with greater than 8.5% accuracy by changing lengths of timing wicks, and we present timed on-valves, off-valves, and diversion (channel-switching) valves. The actuators require ~30 μl fluid to actuate and the time required to switch from one state to another ranges from ~5 s for short to ~50s for longer wicks. For volume-metered actuation, the size of a metering pad can be adjusted to tune actuation volume, and we present two methods – both methods can achieve greater than 9% accuracy. Finally, we demonstrate the use of these valves in a device that conducts a multi-step assay for the detection of the malaria protein PfHRP2. Although slightly more complex than devices that do not have moving parts, this valving and automation toolkit considerably expands the capabilities of paper microfluidic devices. Components of this toolkit can be used to conduct arbitrarily complex, multi-step fluidic operations on paper-based devices, as demonstrated in the malaria assay device.

The superior mechanical flexibility, mechanical strength, electrical conductivity, high specific surface area, and a special two-dimensional crystalline structure make graphene a very promising building block material for flexible electromechanical actuators. However, graphene papers have exhibited limited electromechanical actuation strain in aqueous electrolyte solution. In this paper, we show an easy approach to significantly improve the electromechanical actuation of reduced graphene oxide (rGO) papers via fine tuning the oxygen functional groups in rGO sheets, which was achieved by careful control of quantity of the reduction agent used in the chemical reduction process of graphene oxide. The actuation strains are enhanced up to 0.2% at an applied voltage of −1 V, which is more than a 2 fold increase compared to the regular pristine rGO paper. Further theoretical and experimental analyses reveal that the change of the capacitance and the stiffness of the rGO papers are two key factors responsible for the observed improvement.

Actuators, detectors and controllers associated with most current microfluidic chips continue to be bulky and costly. The ability of paper (and other porous materials) to wick fluids circumvents the need for a pump, making such devices portable, low-cost, and ideal for use in low-resource settings. Such devices are known as “paper microfluidic devices” and when combined with smartphones as recording devices, represent an ultimate achievement in green analytical chemistry. The carbon footprint of such an approach to chemical analysis is almost negligible. In this paper, recent developments in the field of paper microfluidic devices are described with an emphasis on the simplest variant of paper microfluidics: microzones on paper. The role of smartphones as an inexpensive and green counterpart to paper microzones with a similarly low environmental impact level and simplicity of operation is also described.

The cross-directional model predictive control (CD-MPC) tuning problem is investigated for multiple-array paper-making process with parametric uncertainty. A systematic spatial tuning method is proposed to tune the penalty matrices such that the harmful high frequency elements in each actuator profile can be eliminated. A multivariable temporal filter is employed to adjust the output references, and a temporal tuning algorithm is developed for the filter parameters to achieve the pre-specified 2 σ performance indices. The computational time of the proposed methods is reduced via event-based sampling strategy. The effectiveness of the techniques is shown via a CD system from paper-making industry.

This work mainly studies the effect of calcium chloride crosslinking on the bending force properties of sodium alginate-based polymer gel paper actuators (PGPAs), where the driving layer is fabricated by the method of freeze-drying. The results indicate that the concentration of the crosslinking solution strongly affects the performance of the PGPAs and inappropriate concentration of crosslinking solution will even lead to a lower bending force of the PGPA compared with the uncrosslinked one. In particular, the bending force of excessively crosslinked PGPAs is lower than that of uncrosslinked actuators. The bending force of the PGPA achieves the highest value of 3.14 mN (1.94 times than when uncrosslinked) when the concentration of the crosslinking solution is 2 wt%. The driving layer of the PGPA shows optimal performance when the concentration of crosslinking solution is 2 wt%, and the elastic modulus of the driving layer was the smallest under this condition. Compared to the uncrosslinked actuators, the PGPAs consume less force to resist the bending strain produced. The pore structure of the driving layer is more uniform, and the connectivity between the pores is better, which is favorable for the bending force output of the PGPA. Moreover, compared with other concentrations of the crosslinking solution, the 2 wt% crosslinking solution leads to a desirable specific capacitance of the driving layer, which is beneficial for the movement of internal ions. Therefore, the bending force of the PGPA is improved.

The trend to a world with ubiquitous electronics has the need for novel concepts for sensors and actuators that are lightweight, flexible, low-cost, and also sustainable. Piezoelectric transducers on the basis of functional polymers can meet these expectations. In this work, a novel concept for paper-embedded large-area piezoelectric devices realized solely by means of roll-to-roll (R2R) mass printing and post printing technologies including inline poling are introduced. The device set-up, as well as the process technology, offers the great opportunity for a cost-efficient and environmentally friendly mass production of thin and flexible organic large-area piezoelectric devices. As the functional layers are embedded into paper by the hot lamination of two poly(vinylidene fluoride-co-trifluoroethylene) P(VDF-TrFE) layers, the printed electronics is protected and invisible. The paper gives insights to the R2R printing of a 500 m long web including R2R post printing processes and electrical and acoustic inline characterization. Fully R2R processed devices show a high remnant polarization of up to 78 mC m-2 and can be realized with high yield of >90%. Finally, a 360° surround-sound installation realized with a 387 cm long paper web consisting of 56 piezoelectric speakers including wiring is presented.

Significance Much progress has been made in developing bioinspired sensors and actuators based on engineered synthetic materials, although there remains a critical need to incorporate cost-effective and eco-friendly materials. Here naturally abundant pollen grains are used as a material template to produce paper that sensitively and reversibly responds as an actuator to variations in environmental humidity. The actuating properties of the all-natural paper are readily tuned by material characteristics, such as sheet thickness and surface roughness. We demonstrate self-actuation of the pollen-based paper by mimicking flower blooming. The results presented here point to pathways for the creation of self-propelled robots, flexible electronics, and multifunctional devices. They also offer the potential for digital printing and fabrication of complex and programmable natural actuators., Here we describe the development of a humidity-responsive sheet of paper that is derived solely from natural pollen. Adaptive soft material components of the paper exhibit diverse and well-integrated responses to humidity that promote shape reconfiguration, actuation, and locomotion. This mechanically versatile and nonallergenic paper can generate a cyclically high contractile stress upon water absorption and desorption, and the rapid exchange of water drives locomotion due to hydrodynamic effects. Such dynamic behavior can be finely tuned by adjusting the structure and properties of the paper, including thickness, surface roughness, and processing conditions, analogous to those of classical soapmaking. We demonstrate that humidity-responsive paper-like actuators can mimic the blooming of the Michelia flower and perform self-propelled motion. Harnessing the material properties of bioinspired systems such as pollen paper opens the door to a wide range of sustainable, eco-friendly, and biocompatible material innovation platforms for applications in sensing, actuation, and locomotion.

We present Self-powered Paper INterfaces (SPIN) combining folding paper creases with triboelectric nanogenerator (TENG). Embedding TENG into paper creases, we developed a design editor and set of fabrication techniques to create paper-based interfaces that power sensors and actuators. Our SPIN design editor enables users to design their own crease pattern by changing parameters, embed power generating modules into the design, estimate total power generation, and export the files. Then following the fabrication instructions, users can cut and crease materials, and assemble them to build their own interfaces. We employ repetitive push-and-pull based embodied interactions with the mechanism of paper creases and demonstrate four application examples that show new expressive possibilities applying different scales of embodied interactions.

This paper studies automated tuning of cross-directional model predictive control for industrial paper-making processes under user-specified model parameter uncertainties. Automated parameter tuning algorithms are developed to reduce the variability of the actuator and measurement profiles in the spatial domain and to achieve satisfactory performance in terms of worst case settling times and worst case control signal overshoots in the temporal domain for given parametric uncertainties. Due to decoupling properties of the spatial and temporal frequency components, the controller design and parameter tuning can be realized separately. For the spatial design and parameter tuning in the presence of parametric uncertainties, the undesirable high-frequency components in the actuator profile are suppressed via an appropriate design of the weighting matrix $S_{b}$ using the real-valued Fourier matrix approach. For the temporal design, a temporal filter is adopted to smooth the reference trajectory, where the parameter in the temporal filter is carefully tuned to achieve a tradeoff between the worst case settling time and the worst case control signal overshoot. Finally, the effectiveness of the proposed tuning algorithms is verified using a system model extracted from the pulp and paper industry.

This paper describes the dynamic modelling of a vertical take-off and landing (VTOL) aircraft and shows the flatness of the proposed model. Flat systems have the property that the inputs and the states can be written as functions of a set of the system outputs (called flat outputs) and the derivatives of these flat outputs. The flatness property allows to compute an inverse dynamic model of the given system. This can be used in path planning, nonlinear control and fault detection and isolation. The convertible aircraft presented in this paper uses redundant actuators. The advantage of this design is twofold. Firstly, it is possible to configure actuators to optimize both stationary and fast horizontal flight. Secondly, in case of one actuator failure, it provides sufficient flexibility to reconfigure the actuators in order to land safely. An important contribution of this paper is the demonstration of the flatness property for the proposed dynamical model of the convertible aircraft.

In paper microfluidics, the development of smart and versatile switches is critical for the regulation of fluid flow across multiple channels. Past approaches in creating switches are limited by long response times, large actuation fluid volumes, and use of external control circuitry. We seek to mitigate these difficulties through the development of a unique actuator device made entirely out of chromatography paper and incorporated with folds. Selective wetting of the fold with an actuation fluid, either at the crest or trough, serves to raise or lower the actuator's tip and thus engage or break the fluidic contact between channels. Here the actuator's response time is dramatically reduced (within two seconds from wetting) and a very small volume of actuation fluid is consumed (four microliters). Using this actuation principle, we implement six switch configurations which can be grouped as single-pole single-throw (normally OFF and normally ON) and single-pole double-throw (with single and double break). By employing six actuators in parallel, an autonomous colorimetric assay is built to detect the presence of three analytes - glucose, protein, and nitrite - in artificial saliva. Finally, this work brings the concept of origami to paper microfluidics where multiple-fold geometries can be exploited for programmable switching of fluidic connections.

In the growing pandemic, family healthcare is widely concerned with the increase of medical self-diagnosis away from the hospital. A cobalt metal-organic framework modified carbon cloth/paper (Co-MOF/CC/Paper) hybrid button-sensor was developed as a portable, robust, and user-friendly electrochemical analytical chip for nonenzymatic quantitative detection of glucose. Highly integrated electrochemical analytical chip was successfully fabricated with a flexible Co-MOF/CC sensing interface, effectively increasing the specific area and catalytic sites than the traditional plane electrode. Based on the button-sensor, rapid quantitative detection of glucose was achieved in multiple complex bio-matrixes, such as serum, urine, and saliva, with desired selectivity, stability, and durability. With the advantages of low cost, high environment tolerance, ease of production, our nanozyme-based electrochemical analytical chip achieved reliable nonenzymatic electrocatalysis, has great potential for the application of rapid on-site analysis in personalized diagnostic and disease prevention.

A commercially available membrane filter paper composed of mixed cellulose esters bearing typically an interconnected pore structure was transformed into a stimuli-responsive bilayer actuator by depositing a thin film of poly(ionic liquid)-modified graphene oxide sheets (GO-PIL) onto the filter paper. In acetone vapor, the as-synthesized bilayer actuator bent readily into multiple loops at a fast speed with the GO-PIL top film inwards. Upon pulling back into air the actuator recovered their original shape. The asymmetric swelling of the top GO-PIL film and the bottom porous filter paper towards organic vapor offers a favorably synergetic function to drive the actuation. The PIL polymer chains in the hybrid film were proven crucial to enhance the adhesion strength between the GO sheets and the adjacent filter paper to avoid interfacial delamination and thus improve force transfer. The overall construction allows a prolonged lifetime of the bilayer actuator under constant operation, especially when compared to that of the GO/filter paper bilayer actuator without PIL., 23 pages, 7 figures

Fe3O4 nanoparticle-infiltrated chromatography paper is prepared using a low-cost blending method. Upon characterizing the basic material properties of the Fe3O4/paper nanocomposite, beam-, accordion- and star-shaped actuators are constructed using the nanocomposite and the corresponding actuation performance is investigated experimentally. The beam-shaped actuator exhibits a reversible flexural deformation due to low magnetic hysteresis loop of the Fe3O4/paper nanocomposite, maintaining a stable response after 100 cycles. The accordion-shaped actuator can reach a maximum strain of 100% while the star-shaped actuator can capture a spitball twice heavier than itself.

Human muscles can sense external stimuli and generate forces as well. To emulate these capabilities, we design a paper-based transducer capable of both sensing and actuation. Utilizing the origami technique, we develop a soft transducer with attributes of simple structure, easy fabrication and low cost. The origami transducer can function as a deformable capacitive sensor to measure contract forces/pressures. It can achieve a sensitivity up to 0.051 kPa −1, comparable to soft capacitive sensors in the literature. During cyclic tests up to 1000 cycles, this soft sensor exhibits excellent repeatability and negligible hysteresis, thus enabling a high accuracy. On the other hand, this origami transducer can act as a soft actuator to generate haptic feedback. The voltage-induced output force can be 0.4 N, comparable to haptic devices based on soft actuators in the literature. This origami transducer is finally demonstrated for application to breath monitoring of a subject, functioning as both a wearable sensor and actuator. It is believed that paper-based origami transducers can offer a unique option to soft robots and wearable devices, due to their simple design, low cost, and capability for simultaneous sensing and actuation.

Over the past few years, researchers have focused on stimulus-responsive soft materials and their applications in the design of soft actuators. The key factor of the soft actuators to achieve various applications is the programmable and controllable shape deformations. Here, a versatile and simple surface patterning method consisted of pencil drawing and pasting polymer films is proposed to design the soft actuators with programmable deformations. Due to the thermal expansion effect and the hygroexpansion effect, the graphite paper/polymer actuator performs a bending motion with a curvature of 1.4 cm−1 under light irradiation and 1.2 cm−1 under high humidity. Owing to the convenience of the patterning method, different patterns on both two surfaces of the paper substrate are designed without effort. Thus, through tuning the grayscale of the graphite on one surface of the paper, three types of T-shaped actuators can be obtained with different deformations under light irradiation. In addition, by pencil drawing or hydrophobically modifying specific patterns on the two surfaces of the paper, three types of strip-shaped actuators are also proposed to demonstrate that different 3D shape deformations can be obtained under different stimuli. Finally, a helix-shaped actuator inspired by the natural plant tendrils is fabricated by the thermal-induced shaping method. The helix-shaped actuator performs twisting/untwisting motion under different stimuli and can be used as a grasping robot. These results demonstrate the diversified programmability of the graphite paper/polymer actuator. Hence, the simple and versatile programming methods of soft actuators have great potential to be used in the field of biomimetic applications, intelligent robotics, and lab-on-paper devices.

This paper addresses the problem of reliable control of a vehicle active suspension system under actuator faults.The methodology based on event-triggering scheme is employed to design the controller and the proposed results are expressed in the form of linear matrix inequalities (LMIs). The motivation for introducing event-triggering control is to reduce the amount of data transmission in the system. The problem is contrived as a co-design problem to find both controller gain and event-triggering parameters. Finally, the efficacy of the proposed results is demonstrated for the system under fault through a simulation example. Also, a comparison is drawn between the sampled-data control and the proposed event-triggered control strategy.

Exceptionally high specific surface area, mechanical strength, electrical conductivity, and a special two-dimensional structure make graphene a highly promising material for electromechanical actuators. Electromechanical actuators are fabricated using flexible graphene-based paper prepared via a filtration process, and the stroke of these graphene-based actuators is directly measured during electrochemical double-layer charge injection. Actuation strain up to 0.064% was obtained for pristine graphene paper in response to an applied potential of –1 V in 1 M NaCl solution. Double-layer charge injection in graphene sheets is believed to induce actuation strain through a combination of coulombic and quantum-chemical-based expansion. To increase electrochemical-double-layer capacitance and actuator performance, Fe3O4 nanoparticles were used to partially prevent graphene sheets from restacking and allow the electrolyte ions to infiltrate the resulting magnetic graphene paper more easily. The magnetic graphene paper exhibits actuation strain as large as 0.1% at –1 V applied potential, which is about 56% higher than that of the pristine graphene paper.

During paper manufacture, system actuators need to control the properties of the entire sheet based on a restricted set of data measured by a scanning sensor that traverses the moving sheet. Cross direction variations (CD) are those along an axis perpendicular to the motion of the sheet, while machine direction (MD) variations are those along the axis of motion, and are assumed uniform in CD. Current industrial practice is to separate the relatively slow variations of the CD profile from the higher bandwidth MD variations using low pass filtering, although the spacing and timing of the scanned data measurements makes it inevitable that some process variations will be distorted or lost to aliasing in the filtered data. In this paper, a novel approach to estimation of MD and CD variations is proposed – compressive sensing. In this approach, knowledge of the process is used to help characterize the expected process variations, allowing accurate reconstruction of the true process variations from far fewer measurements than would be indicated by simple bandwidth-based uniform sampling theory. Instead, a random sampling protocol is used to accurately reconstruct the sheet properties. The approach is found to be effective, using simulated and actual industrial process data.

The work presented in this paper addresses the issues of fault detection and isolation properties of the partial PCA method and the isolation-enhanced PCA method. In order to increase the sensitivity of the residuals with respect to various faults, the structured residuals generated from both partial PCA and isolation-enhanced PCA are optimized. For the residual evaluation, the bootstrap technique is combined with the CUSUM method to achieve fast and robust detection. Three sensor faults and three actuator faults were studied using simulations employing a rigorous, first principles based, paper machine simulator. All the faults were correctly detected and isolated with both studied methods, and the results are compared with the classical T 2 and SPE contribution plot methods.

Polymers and papers, which exhibit piezoelectricity, find a wide range of applications in the industry. Ever since the discovery of PVDF, piezo polymers and papers have been widely used for sensor and actuator design. The direct piezoelectric effect has been used for sensor design, whereas the inverse piezoelectric effect has been applied for actuator design. Piezo polymers and papers have the advantages of mechanical flexibility, lower fabrication cost and faster processing over commonly used piezoelectric materials, such as PZT, BaTiO3. In addition, many polymer and paper materials are considered biocompatible and can be used in bio applications. In the last 20 years, heterostructural materials, such as polymer composites and hybrid paper, have received a lot of attention since they combine the flexibility of polymer or paper, and excellent pyroelectric and piezoelectric properties of ceramics. This paper gives an overview of piezoelectric polymers and papers based on their operating principle. Main categories of piezoelectric polymers and papers are discussed with a focus on their materials and fabrication techniques. Applications of piezoelectric polymers and papers in different areas are also presented.

Electro-active paper (EAPap) is a cellulose-based smart material that has shown promising results in a variety of smart applications (e.g., vibration sensor, piezo-speaker, bending actuator) with the merits of being flexible, lightweight, fracture tolerant, biodegradable, naturally abundant, cheap, biocompatible, and with the ability to form hybrid nanocomposites. This paper presents a review of the characterization and application of EAPap as a flexible mechanical vibration/strain sensor, bending actuator, and vibration energy harvester. The working mechanism of EAPap is explained along with the various parameters and factors that influence the sensing, actuation, and energy harvesting capabilities of EAPap. Although the piezoelectricity of EAPap is comparable to that of commercially available polyvinylidene fluoride (PVDF), EAPap has the preferable merits in terms of natural abundance and ample capacity of chemical modification. The article would provide guidelines for the characterization and application of EAPap in mechanical sensing, actuation, and vibration energy scavenging, along with the possible limitations and future research prospects.

The abstraction and implementation of plant movement principles into biomimetic compliant systems are of increasing interest for technical applications, e.g., in architecture, medicine, and soft robotics. Within the respective research and development approaches, advanced methods such as 4D printing or 3D-braiding pultrusion are typically used to generate proof-of-concept demonstrators at the laboratory or demonstrator scale. However, such techniques are generally time-consuming, complicated, and cost-intensive, which often impede the rapid realization of a sufficient number of demonstrators for testing or teaching. Therefore, we have produced comparable simple handcrafted compliant systems based on paper, wood, plastic foil, and/or glue as construction materials. A variety of complex plant movement principles have been transferred into these low-cost physical demonstrators, which are self-actuated by shrinking processes induced by the anisotropic hygroscopic properties of wood or paper. The developed systems have a high potential for fast, precise, and low-cost abstraction and transfer processes in biomimetic approaches and for the “hands-on understanding” of plant movements in applied university and school courses.

The introduction of inorganic nanoparticles into carbon nanotube (CNT) papers can provide a versatile route to the fabrication of CNT papers with diverse functionalities, but it may lead to a reduction in their mechanical properties. Here, we describe a simple and effective strategy for the fabrication of mechanically robust magnetic CNT papers for electromagnetic interference (EMI) shielding and magnetomechanical actuation applications. The magnetic CNT papers were produced by vacuum filtration of an aqueous suspension of CNTs, CoFe2O4 nanoparticles, and poly(vinyl alcohol) (PVA). PVA plays a critical role in enhancing the mechanical strength of CNT papers. The magnetic CNT papers containing 73 wt % of CoFe2O4 nanoparticles exhibited high mechanical properties with Young’s modulus of 3.2 GPa and tensile strength of 30.0 MPa. This magnetic CNT paper was successfully demonstrated as EMI shielding paper with shielding effectiveness of ∼30 dB (99.9%) in 0.5–1.0 GHz, and also as a magnetomechanical actuator i...

In the fields of smart materials there is still a demand for a material featuring high modulus, low density and large strain. Carbon materials catch enormous scientific attention not only since carbon fibers were used for highperformance composite structures. But more and more the scientific attention moves from the macroscale to the nanoscale. This paper focuses with a adaptive point of view on one of the carbon allotropes: carbon nanotubes (CNTs). Beside excellent electromechanical properties another interesting feature was first mentioned 1999 - the active behavior of paper-like mats (bucky-papers) made of CNTs. CNT-papers are electrically activated using a double-layer interaction of ions provided by an electrolyte and the charged, high specific surface area of the paper formed by carbon nanotubes. Until now the detailed mechanism behind the strain/force generation of CNT-based architectures is unknown. A clarification of this principle reveals the potential of carbon tubes to be or not to be a resilient smart material in order to use their strong covalent carbon bonds instead of weak van der Waals force as tube-linking. This paper presents further investigations about the composition of CNT-papers and their performance in contrast to vertical aligned CNT-arrays using an actuated tensile test set-up. For better comparison the experiments of both specimen-types are carried out in dry, wet and wet/charged conditions. Especially in the case of CNT-arrays it is essential to preload the specimens because the curly CNT-structure superimposes the vertical orientation. While the CNT-paper is tested in an aqueous solution of one molar sodium chloride, the hydrophobic character of CNT-arrays requires an ionic liquid (IL) as electrolyte. It is found that the mechanical properties of CNT-papers drop significantly by wetting and can be controlled by charging what indicates an electrostatic dominated effect. In contrast the CNT-arrays show identical results regardless of the test conditions and furthermore an active, reversible behavior of tube elongation by charging. These results indicate strongly a quantum mechanical effect as reason of a CNT-array actuation.

In this paper, we present high-performance and versatile inkjet-printed paper photo-actuators based on two-dimensional (2D) nanomaterials. As a rapid fabrication method, inkjet printing of 2D materials is used to promptly fabricate photo-actuators in a bi-layer paper/polymer structure. Water-based and biocompatible inks based on graphene and molybdenum disulfide are developed based on liquid phase exfoliation and differential centrifugation technique. It is shown that incorporation of 2D materials with inkjet printing techniques and liquid phase exfoliation can lead to rapid fabrication of photo-actuators with huge opto-mechanical energy release and versatility with a broad range of applications due to specific design and methods presented in this paper.

The strong interaction between graphene oxides (GO) and water molecules has trigged enormous research interest in developing GO-based separation films, sensors, and actuators. However, sophisticated control over the ultrafast water transmission among the GO sheets and the consequent deformation of the entire GO film is still challenging. Inspired from the natural "quantum-tunneling-fluidics-effect," here quantum-confined-superfluidics-enabled moisture actuation of GO paper by introducing periodic gratings unilaterally is reported. The folded GO nanosheets that act as quantum-confined-superfluidics channels can significantly promote water adsorption, enabling controllable and sensitive moisture actuation. Water-adsorption-induced expansion along and against the normal direction of a GO paper is investigated both theoretically and experimentally. Featuring state-of-the-art of ultrafast response (1.24 cm-1 s-1 ), large deformation degree, and complex and predictable deformation, the smart GO papers are used for biomimetic mini-robots including a creeping centipede and a smart leaf that can catch a living ladybug. The reported method is simple and universal for 2D materials, revealing great potential for developing graphene-based smart robots.

Basic operation mechanisms of newly proposed reflective display mode using metal coated ball were investigated for novel electronic-paper displays, named as Floating Metal Ball Actuator (FMBA) mode. Most appropriate structures and driving conditions were simulated by Poisson's equation solver, and the optimized cell design and driving voltage can be determined. To confirm the conducting property of floating metal ball (FMB), electrical potential of FMB directly contacted on electrode was measured by non-contact Kelvin probe microscopy and identical with that of the contact electrode. These are useful results to apply the FMBA mode to electrical-paper displays.

In a professional printer, the paper handling system consists of numerous independently driven actuators that manage the placement of the printing media during the entire print job. This research presents a state estimation procedure for closed-loop operation of hybrid stepper motors (HSMs) that are typically used as actuators under a wide range of operational speeds. The presented method facilitates closed-loop control of HSMs without any additional sensor.

Janus-materials were processed though different characteristics integrate to achieve important functions which have aroused great interest among the scientific research and industrial applications. However, the facile fabrication of Janus-materials with the attributes of chemical-free, low-cost, and simple process is still a great challenge. Herein, inspired by the mimosa and lotus leaf, a Janus-paper with superhydrophobicity /superhydrophilicity is successfully fabricated by a conjunction of PDMS and candle soot coating. The water and sliding contact angles of the superhydrophobic surface are 162° and 1°, respectively, and it also shows a good antifouling properties and mechanical durability. Additionally, the cell biocompatibility of superhydrophobic surface is significantly improved, holding the potential as a cell culture carrier. Due to the inhomogeneous swelling inside the internal structure, the Janus-paper exhibits a mimosa-like behavior when immersed in water, endowing the actuation of a boat model on the water surface. Moreover, due to the different adhesions, the superhydrophobic and superhydrophilic surfaces can be used for microdroplet transportation and water storage devices. This bio-inspired approach provides a new generic route for fabrication of Janus-paper for potential multifunctional applications.

There is an increasing demand for soft actuators because of their importance in soft robotics, artificial muscles, biomimetic devices, and beyond. However, the development of soft actuators capable of low-voltage operation, powerful actuation, and programmable shape-changing is still challenging. In this work, we propose programmable bilayer actuators that operate based on the large hygroscopic contraction of the copy paper and simultaneously large thermal expansion of the polypropylene film upon increasing the temperature. The electrothermally activated bending actuators can function with low voltages (≤ 8 V), low input electric power per area (P ≤ 0.14 W cm–2), and low temperature changes (≤ 35 °C). They exhibit reversible shape-changing behavior with curvature radii up to 1.07 cm–1 and bending angle of 360°, accompanied by powerful actuation. Besides the electrical activation, they can be powered by humidity or light irradiation. We finally demonstrate the use of our paper actuators as a soft gripper r...

Recently, actuating materials based on carbon nanotubes or graphene have been widely studied. However, present carbon-based actuating materials are mostly driven by a single stimulus (humidity, light, electricity, etc.), respectively, which means that the application conditions are limited. Here, a new kind of multiresponsive actuating material which can be driven by humidity, light, and electricity is proposed, so it can be used in various conditions. The fabrication is based on the simplest pencil-on-paper method, in which the pencil and paper are both low-cost and easily obtained daily materials. The actuation effect is more remarkable due to a dual-mode actuation mechanism, which leads to an ultralarge actuation (bending curvature up to 2.6 cm−1). Elaborately designed, the actuator can further exhibit a bidirectional bending actuation, which is a significant improvement compared with previous reported thermal actuators. What is more, a colorful biomimetic flower and a smart curtain are also fabricated, fully utilizing the printable characteristic of the paper and multiresponsive characteristic of the actuator. It is assumed that the newly designed actuating material has great potential in the fields of lab-on-paper devices, artificial muscles, robotics, biomimics, and smart household materials.

This paper presents an application of a customized linear programming (LP) based model predictive control strategy to the paper machine cross direction (CD) control problem. The objective of CD control is to maintain flat profiles of variables of interest by minimizing worst case deviations from setpoints (defects). These control problems can have as many as 200 actuators (inputs) and 400 sensor measurements (outputs). This large size coupled with the stringent real-time requirement of computing a control move in a few seconds poses a very challenging control problem. Computational results that demonstrate the effectiveness of this strategy will be presented. For typical disturbances this algorithm can compute provably optimal control moves for a 400 input ×400 output control problem in approximately 5 s versus approximately 90 s for a generic LP algorithm on a HP 9000/770 workstation.

We present a printed paper actuator as a low cost, reversible and electrical actuation and sensing method. This is a novel but easily accessible enabling technology that expands upon the library of actuation-sensing materials in HCI. By integrating three physical phenomena, including the bilayer bending actuation, the shape memory effect of the thermoplastic and the current-driven joule heating via conductive printing filament, we developed the actuator by simply printing a single layer conductive Polylactide (PLA) on a piece of copy paper via a desktop fused deposition modeling (FDM) 3D printer. This paper describes the fabrication process, the material mechanism, and the transformation primitives, followed by the electronic sensing and control methods. A software tool that assists the design, simulation and printing toolpath generation is introduced. Finally, we explored applications under four contexts: robotics, interactive art, entertainment and home environment.

Electro-active polymer (EAP) actuators, such as electronic, ionic and electrothermal (ET) actuators, have become an important branch of next-generation soft actuators in bionic robotics. However, most reported EAP actuators could realize only simple movements, being restricted by the small area of flexible electrodes and simple designs. We prepared large-area flexible electrodes of high anisotropy, made of oriented carbon nanotube (CNT) paper, and carried out artful graphic designs and processing on the electrodes to make functional ET bimorph actuators which can realize large bending deformations (over 220°, curvature > 1.5 cm−1) and bionic movements driven by electricity. The anisotropy of CNT paper benefits electrode designs and multiform actuations for complex actuators. Based on the large-area CNT paper, more interesting and functional actuators can be designed and prepared which will have practical applications in the fields of artificial muscles, complicated actuations, and soft and bionic robotics.

We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and ability to form hybrid nanocomposites. The mechanical, electrical, and chemical characterizations of the cellulose-based electro-active paper and its hybrid composites such as blends or coatings with synthetic polymers, biopolymers, carbon nanotubes, chitosan, and metal oxides, are explained. In addition, the integration of cellulose electro-active paper is highlighted to form various functional devices including but not limited to bending actuators, flexible speaker, strain sensors, energy harvesting transducers, biosensors, chemical sensors and transistors for electronic applications. The frontiers in cellulose paper devices are reviewed together with the strategies and perspectives of cellulose electro-active paper and cellulose nanocomposite research and applications.