Publications
Origami-inspired manufacturing can produce complex structures and machines by folding two-dimensional composites into three-dimensional structures. This fabrication technique is potentially less expensive, faster, and easier to transport than more traditional machining methods, including 3-D printing. Self-folding enhances this method by minimizing the manual labor involved in folding, allowing for complex geometries and enabling remote or automated assembly. This paper demonstrates a novel method of self-folding hinges using shape memory polymers (SMPs), paper, and resistive circuits to achieve localized and individually addressable folding at low cost. A model for the torque exerted by these composites was developed and validated against experimental data, in order to determine design rules for selecting materials and designing hinges. Torque was shown to increase with SMP thickness, resistive circuit width, and supplied electrical current. This technique was shown to be capable of complex geometries, as well as locking assemblies with sequential folds. Its functionality and low cost make it an ideal basis for a new type of printable manufacturing based on two-dimensional fabrication techniques.
Abstract—Nature regularly uses self-folding as an efficient approach to automated fabrication. In engineered systems, however, the use of self-folding has been primarily restricted to the assembly of small structures using exotic materials and/or complex infrastructures. In this paper we present three approaches to the self-folding of structures using low-cost, rapid-prototyped shape memory laminates. These structures require minimal deployment infrastructure, and are activated by light, heat, or electricity. We compare the fabrication of a fundamental structure (a cube) using each approach, and test ways to control fold angles in each case. Finally, for each self-folding approach we present a unique structure that the approach is particularly suited to fold, and discuss the advantages and disadvantages of each approach.
This paper presents a methodology and validation of print-and-self-fold electric devices. For printing functional structures for robotic use, we realize electric circuitry based on metallic polyester film (MPF). By exploiting the unique material properties of MPF, we developed fundamental electric devices, namely a resistor, capacitor, and inductor. The developed polyvinyl chloride laminated MPF sheet shows reliable selffolding processes under a heat application, and it configures 3D electric devices. Due to the pre-resolved kinematic design, these devices feature elasticity, making them suitable as sensors and actuators in soft circuits. Here we testify to a self-assembled variable resistor and capacitive strain sensor. An actuation mechanism consisting of a folded contractible coil is also considered and shown. Finally, an RLC circuit obtained from the integration of all the developed devices is demonstrated, in which the coil based actuator is controlled by reading a variable capacitive strain sensor.
Self-folding is an approach used frequently in nature for the efficient fabrication of structures, but is seldom used in engineered systems. Here, self-folding origami are presented, which consist of shape memory composites that are activated with uniform heating in an oven. These composites are rapidly fabricated using inexpensive materials and tools. The folding mechanism based on the in-plane contraction of a sheet of shape memory polymer is modeled, and parameters for the design of composites that self-fold into target shapes are characterized. Four self-folding shapes are demonstrated: a cube, an icosahedron, a flower, and a Miura pattern; each of which is activated in an oven in less than 4 min. Self-sealing is also investigated using hot melt adhesive, and the resulting structures are found to bear up to twice the load of unsealed structures.
Abstract: This paper describes additive self-folding, an origami-inspired rapid fabrication approach for creating actuatable compliant structures. Recent work in 3-D printing and other rapid fabrication processes have mostly focused on rigid objects or objects that can achieve small deformations. In contrast, soft robots often require elastic materials and large amounts of movement. Additive self-folding is a process that involves cutting slices of a 3-D object in a long strip and then pleat folding them into a likeness of the original model. The zigzag pattern for folding enables large bending movements that can be actuated and controlled. Gaps between slices in the folded model can be designed to provide larger deformations or higher shape accuracy. We advance existing planar fabrication and self-folding techniques to automate the fabrication process, enabling highly compliant structures with complex 3-D geometries to be designed and fabricated within a few hours. We describe this process in this paper and provide algorithms for converting 3-D meshes into additive self-folding designs. The designs can be rapidly instrumented for global control using magnetic fields or tendon-driven for local bending. We also describe how the resulting structures can be modeled and their responses to tendon-driven control predicted. We test our design and fabrication methods on three models (a bunny, a tuna fish, and a starfish) and demonstrate the method’s potential for actuation by actuating the tuna fish and starfish models using tendons and magnetic control.
Abstract—Printing and folding are fast and inexpensive methods for prototyping complex machines. Self-assembly of the folding step would expand the possibilities of this method to include applications where external manipulation is costly, such as micro-assembly, mass production, and space applications. This paper presents a method for self-folding of printed robots from two-dimensional materials based on shape memory polymers actuated by joule heating using embedded circuits. This method was shown to be capable of sequential folding, angle-controlled folds, slot-and-tab assembly, and mountain and valley folds. An inchworm robot was designed to demonstrate the merits of this technique. Upon the application of sufficient current, the robot was able to fold into its functional form with fold angle deviations within six degrees. This printed robot demonstrated locomotion at a speed of two millimeters per second.
Abstract: We propose pouch motors, a new family of printable soft actuators integrated with computational design. The pouch motor consists of one or more inflatable gas-tight bladders made of sheet materials. This printable actuator is designed and fabricated in a planar fashion. It allows both easy prototyping and mass fabrication of affordable robotic systems. We provide theoretical models of the actuators compared with the experimental data. The measured maximum stroke and tension of the linear pouch motor are up to 28% and 100 N, respectively. The measured maximum range of motion and torque of the angular pouch motor are up to 80 and 0.2 N, respectively. We also develop an algorithm that automatically generates the patterns of the pouches and their fluidic channels. A custom-built fabrication machine streamlines the automated process from design to fabrication. We demonstrate a computer-generated life-sized hand that can hold a foam ball and perform gestures with 12 pouch motors, which can be fabricated in 15 min. [DOI: 10.1089/soro.2014.0023]
This paper describes a novel self-assembling, self-reconfiguring cubic robot that uses angular momentum to change its intended geometry through pivoting.
Abstract: Origami-based design methods enable complex devices to be fabricated quickly in plane and then folded into their final 3-D shapes. So far, these folded structures have been designed manually. This paper presents a geometric approach to automatic composition of folded surfaces, which will allow existing designs to be combined and complex functionality to be produced with minimal human input. We show that given two surfaces in 3-D and their 2-D unfoldings, a surface consisting of the two originals joined along an arbitrary edge can always be achieved by connecting the two original unfoldings with some additional linking material, and we provide an algorithm to generate this composite unfolding. The algorithm is verified using various surfaces, as well as a walking and gripping robot design.
Abstract: The process of designing and programming a new robot requires expert knowledge and design skills that are often acquired over the course of many years. This makes design of new robots difficult for non-experienced users. In addition to design, physical realization of a robot is also time and labor intensive. We propose a new fabrication process for mechanical robots, called 3D print and fold, which combines 3D printing with origami fabrication methods. In our technique, robots are 3D printed as flat faces connected at joints and are then folded into their final shape. To help casual users design ground robots using our 3D print and fold technique, we present our Interactive Robogami system. The system leverages a database of examples created by expert roboticists. A composition tool allows users to create new designs by composing parts from the robots in this database. The system automatically ensures that the assembled robot is fabricable and that it can locomote forward while still giving creative freedom to users. [DOI: 10.1145/2785585.2792556]
Abstract: This paper describes a method for manufacturing complex three-dimensional curved structures by self-folding layered materials. Our main focus is to first show that the material can cope with curved crease self-folding and then to utilize the curvature to predict the folding angles. The self-folding process employs uniform heat to induce self-folding of the material and shows the successful generation of several types of propellers as a proof of concept. We further show the resulting device is functional by demonstrating its levitation in the presence of a magnetic field applied remotely. [DOI: 10.1115/1.4029548]
Abstract: Print-and-fold manufacturing has the potential to democratize access to robots with robots that are easier to fabricate using materials that are easier to procure. Unfortunately, a lack of understanding about how motion can be achieved by folding hinders the scope of print-and-fold robots. In this paper, we show how the basic joints used in robots can be constructed using print-and-fold. Our patterns are parameterized so that users not only get the desired degrees of freedom but can also specify the joint’s range of motion. The joints can be combined with each other to achieve higher degrees of freedom or with rigid bodies to produce foldable linkages. We have folded our basic joints and measured their force–displacement curves. We have composed them into joints with higher degrees of freedom and into foldable mechanisms and found that they achieve the expected kinematics. We have also added actuators and control circuitry to our joints and mechanisms, showing that it is possible to print and fold entire robots with many different kinematics using a uniform process. [DOI: 10.1115/1.4029490]
Abstract: Print-and-fold manufacturing has the potential to democratize access to robots with robots that are easier to fabricate using materials that are easier to procure. Unfortunately, a lack of understanding about how motion can be achieved by folding hinders the scope of print-and-fold robots. While hinge joints can easily be included in folded structures, joints with other degrees of freedom have yet to be designed. In this paper, we show how all the basic joints used in robots can be constructed using print-and-fold. Our patterns are parameterized so that users not only get the desired degrees of freedom but can also specify the joint's range of motion. The joints can be combined with each other to achieve higher degrees of freedom or with rigid bodies to produce foldable linkages. We folded several of our basic and combined joints, as well as a composed foldable mechanisms. We also add actuation and control circuitry to our joints and mechanisms, showing that it possible to create a print-and fold robot with many dierent kinematics using a uniform process.
Abstract: Origami-based design methods enable complex devices to be fabricated quickly in plane and then folded into their final 3D shapes. So far, these folded structures have been designed manually. This paper presents a geometric approach to automatic composition of folded surfaces, which will allow existing designs to be combined and complex functionality to be produced with minimal human input. We show that given two surfaces in 3D and their 2D unfoldings, a surface consisting of the two originals joined along an arbitrary edge can always be achieved by connecting the two original unfoldings with some additional linking material, and we provide a polynomial-time algorithm to generate this composite unfolding. The algorithm is verified using various surfaces, as well as a walking and gripping robot design. [DOI: 10.1115/1.4025378]
We propose a data-driven method for designing 3D models that can be fabricated. First, our approach converts a collection of expert-created designs to a dataset of parameterized design templates that includes all information necessary for fabrication. The templates are then used in an interactive design system to create new fabricable models in a design-by-example manner. A simple interface allows novice users to choose template parts from the database, change their parameters, and combine them to create new models. Using the information in the template database, the system can automatically position, align, and connect parts: the system accomplishes this by adjusting parameters, adding appropriate constraints, and assigning connectors. This process ensures that the created models can be fabricated, saves the user from many tedious but necessary tasks, and makes it possible for non-experts to design and create actual physical objects. To demonstrate our data-driven method, we present several examples of complex functional objects that we designed and manufactured using our system.
Smooth motion is critical to some robotic applications such as haptics or those requiring high precision force control. These systems are often direct-drive, so any torque ripple in the motor output must be minimal. Unfortunately, low inherent torque ripple motors are expensive. Low cost brushless DC motors are becoming more prevalent, especially from the hobby RC community. These motors often have the required high torque density; however, they also have significant torque ripple. This paper presents a system that is low cost using a method for anticogging - the compensation of cogging torque in low cost, high torque motors. While other methods exist to compensate for current-based torque ripple (mutual or reluctance torque), none have addressed cogging torque, except by adding expensive force sensors. This paper presents two methods that use a position sensor (already present for servo motors) to map cogging torque to rotor position. The map is played back according to position reported from the sensor to cancel the cogging torque. The design and testing of a low cost haptic arm using anticogging shows validation; however, the approach is much broader, and can be applied to any precision force application. Test results on eleven different motors show an average removal of 69% of torque ripple with no added cost in robotic servo applications.
Abstract: A miniature robotic device that can fold-up on the spot, accomplish tasks, and disappear by degradation into the environment promises a range of medical applications but has so far been a challenge in engineering. This work presents a sheet that can self-fold into a functional 3D robot, actuate immediately for untethered walking and swimming, and subsequently dissolve in liquid. The developed sheet weighs 0.31 g, spans 1.7 cm square in size, features a cubic neodymium magnet, and can be thermally activated to self-fold. Since the robot has asymmetric body balance along the sagittal axis, the robot can walk at a speed of 3.8 body-length/s being remotely controlled by an alternating external magnetic field. We further show that the robot is capable of conducting basic tasks and behaviors, including swimming, delivering/carrying blocks, climbing a slope, and digging. The developed models include an acetone-degradable version, which allows the entire robot’s body to vanish in a liquid. We thus experimentally demonstrate the complete life cycle of our robot: self-folding, actuation, and degrading.
We prove that every simple polygon can be made as a (2D) pop-up card/book that opens to any desired angle between 0 and 360°. More precisely, given a simple polygon attached to the two walls of the open pop-up, our polynomial-time algorithm subdivides the polygon into a single-degree-of-freedom linkage structure, such that closing the pop-up flattens the linkage without collision. This result solves an open problem of Hara and Sugihara from 2009. We also show how to obtain a more efficient construction for the special case of orthogonal polygons, and how to make 3D orthogonal polyhedra, from pop-ups that open to 90°, 180°, 270°, or 360°.
<p> Printing and folding are fast and inexpensive methods for prototyping complex machines. Self-assembly of the folding step would expand the possibilities of this method to include applications where external manipulation is costly, such as micro-assembly, mass production, and space applications. This project investigates a method for self-folding of printed robots from two-dimensional materials based on shape memory polymers actuated by joule heating using embedded circuits. This method was shown to be capable of sequential folding, angle-controlled folds, slot-and-tab assembly, and mountain and valley folds. These features, in turn, can be combined to create complex structures and dynamic linkages, and all necessary components for the folding process can be embedded in the machine, enabling autonomous assembly. We can also include additional functional layers such as magnetic sheets and copper pads to create planar sensors that are compatible with the self-folding fabrication process.
Origami can turn a sheet of paper into complex three-dimensional shapes, and similar folding techniques can produce structures and mechanisms. To demonstrate the application of these techniques to the fabrication of machines, we developed a crawling robot that folds itself. The robot starts as a flat sheet with embedded electronics, and transforms autonomously into a functional machine. To accomplish this, we have developed shape memory composites that fold themselves along embedded hinges. We use these composites to recreate fundamental folded patterns, derived from computational origami, which can be extrapolated to a wide range of geometries and mechanisms. This origami-inspired robot can fold itself in four minutes and walk away without human intervention, demonstrating the potential both for complex self-folding machines and autonomous, self-controlled assembly.