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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.

This article describes a process of fabricating highly porous paper from cellulosic fibers and carbon black (CB) with tunable conductivity. By embossing such paper, its porosity decreases while its conductivity increases. Tuning the porosity of composite paper alters the magnitude and trend of conductivity over a spectrum of concentrations of conductive particles. The largest increase in conductivity from 8.38 × 10–6 to 2.5 × 10–3 S/m by a factor of ∼300 occurred at a percolation threshold of 3.8 wt % (or 0.36 vol %) with the composite paper plastically compressed by 410 MPa, which caused a decrease of porosity from 88% to 42% on average. Our composite paper showed stable piezoresistive responses within a broad pressure range from 1 kPa up to 5.5 MPa for 800 cycles. The piezoresistive sensitivities of the composite paper were dependent on concentration and decreased with pressure. Composite paper with 7.5 wt % CB had sensitivities of −0.514 kPa–1 over applied pressures ranging from 1 to 50 kPa and −0.215 kPa–1 from 1 to 250 kPa. This piezoresistive paper with embossed patterns enabled touch sensing and detection of damage from darts and punches. Understanding the percolation behavior of three-phase composites (cellulosic fibers/conductive particles/air) and their response to damage, pressure, and processing conditions has the potential to enable scalable applications in prosthetics and robotics, haptic feedback, or structural health monitoring on expansive surfaces of buildings and vehicles.

This article presents a sensor for detecting the distribution of forces on a surface. The device with nine buttons consisted of an elastomer-based layer as a touch interface resting on a substrate of patterned metallized paper. The elastomer-based layer included a three-by-three array of deformable, hemispherical elements/reliefs, facing down toward an array of interdigitated capacitive sensing units on patterned metallized paper. Each hemispherical element is 20 mm in diameter and 8 mm in height. When a user applied pressure to the elastomer-based layer, the contact area between the hemispherical elements and the interdigitated capacitive sensing units increased with the deformation of the hemispherical elements. To enhance the sensitivity of the sensors, embedded particles of hydrogel in the elastomer-based layer increased the measured electrical responses. The measured capacitance increased because the effective dielectric permittivity of the hydrogel was greater than that of air. Electromechanical characterization verified that the hydrogel-filled elastomer was more sensitive to force at a low range of loads (23.4 pF/N) than elastomer alone without embedded hydrogel (3.4 pF/N), as the hydrogel reduced the effective elastic modulus of the composite material by a factor of seven. A simple demonstration suggests that the force-sensing array has the potential to contribute to wearable and soft robotic devices.

user interface. In other words, increasing resolution or adding sites for the detection of touch, generally requires augmenting the number of interconnects. With the exception of using a single electrode-based sensing technique to make natural and inanimate objects become user interfaces, there has been a lack of effort in the reduction of the number of wired leads required for scalable sensing of touch. [9] In contrast to electronic touch sensors, skin on humans/vertebrates uses hierarchical neural networks to transmit the relative spatial detection and intensity of force on fleshy surfaces to the brain. [10] These neural networks do not depend on having a pair of running wires for each location. Instead, they have developed mechanisms for sending spatial information about touch along the spinal cord. Inspired by this concept, Tee et al. presented a skininspired organic digital mechanoreceptor, which converted force-based stimuli into digital signals with varied frequencies to mimic the communication between biological mechanoreceptors and the brain. [11] Similarly, there are opportunities to build electrical networks to reduce the number of wired leads required for spatial detection of touch on synthetic electronic skins.The advancements in skin-like sensing with flexible electronics have moved toward the design and fabrication of active electronic components arrayed on flexible sheets with surface areas less than 10 cm in diameter. [12][13][14][15][16] For example, Someya and co-workers demonstrated an application of thin-film transistors in skin-like sensors capable of measuring distributed pressures over a 9 cm × 9 cm footprint. [12] The size of the sensors is typically dependent on the method of fabrication, and current skin-like sensors often cover small areas (i.e., much less area than that of human skin) because of the limited size of semiconductor-based wafers. As mentioned previously, the number of wired leads in conventional arrays of skin-like sensors increases with the square root of the number of buttons. While this scaling may appear favorable, there are still difficulties with making large sensing grids, as a larger quantity of traces requires more space for wired connections and multiplexed measurements.In this work, we present an approach to passive sensing for skin-like sensors consisting of tunable resistive networks and This work presents a unique approach to the design, fabrication, and characterization of paper-based, skin-like sensors that use patterned resistive networks for passive, scalable sensing with a reduced number of interconnects. When touched or wetted with water, the sensors in the resistive networks detect significant changes in electrical impedance. Fabricating these resistive networks and sensors in a single sheet of metallized paper reduces the number of distinct inputs/outputs to the arrayed sensors. For human-electrode interactions, circuit-based models guide the design/material processing of the resistive networks and selection of operating frequencies-typically ranging...