The physical properties of objects cannot typically be adjusted post-fabrication to meet specific needs or preferences. While 3D printing offers the potential of design-time customization, manipulating object properties after the object has been printed remains challenging. We present a 3D printable bistable mechanism with an actuation force that can be quickly and repeatedly adjusted after fabrication by up to a factor of 5.25, enabling tunable monostable or bistable behavior. Our mechanism, printable on commodity low-cost 3D printers, incorporates off-the-shelf elastic threads to maintain robust operation when fabricated at different sizes. We present an evaluation of how manipulating geometric parameters influences the post-print behavior of our design and demonstrate its versatility in five functional objects.

Commercial touch input devices sense changes in capacitance (C), resistance (R), and inductance (L), but aggregate these into a single, complex quantity: impedance. Commercially available LCR meters, however, can report the individual elements of impedance. We use this capability to introduce Impedius, a signal-space multiplexing technique. With Impedius, we create and sense multiple static values and continuous changes in the R and C values within a single circuit by manipulating capacitance and resistance individually. Further, we explore 3D printing as a method to create predictable resistance and capacitance values via geometric and printer setting manipulation, and offer a software tool that generates components with desired R and C values. Based on 96 samples, our printed passive components have error μ = 4.63 pF, ο = 1.68 PF (capacitors) and μ = 13.85 kΩ, ο = 5.59 kΩ (resistors). We demonstrate multiple interactive example applications with our components, highlighting the opportunities for signal-space multiplexing.

Rapid prototyping is an important tool for designers, but many fabrication techniques are slow and create bulky components requiring multiple machines and processes to achieve desired device shape and electronic functionality. Prior work explored ways to ease fabricating shapes or designing electronics, but we focus on creating shape and electrical pathways at the same time from a single material and machine. LaCir leverages a three-layered, laser-cuttable material to incorporate circuits into the structural substrate of the design using laser cutters. Our substrate features a layer of conductive material sandwiched between thermoplastic sheets, allowing designers to cut electrical traces and assembleable, 3D object geometry in a single pass. We evaluate different composite materials, weighing their cuttability, ease of assembly, and conductivity; we also show using fully laser-cut joints as structural and electrical connections. We demonstrate LaCir’s flexibility through several example artifacts.

We introduce Rhapso, a 3D printing system designed to embed a diverse range of continuous fiber materials within 3D objects during the printing process. This approach enables integrating properties like tensile strength, force storage and transmission, or aesthetic and tactile characteristics, directly into low-cost thermoplastic 3D prints. These functional objects can have intricate actuation, self-assembly, and sensing capabilities with little to no manual intervention. To achieve this, we modify a low-cost Fused Filament Fabrication (FFF) 3D printer, adding a stepper motor-controlled fiber spool mechanism on a gear ring above the print bed. In addition to hardware, we provide parsing software for precise fiber placement, which generates G-code for printer operation. To illustrate the versatility of our system, we present applications that showcase its extensive design potential. Additionally, we offer comprehensive documentation and open designs, empowering others to replicate our system and explore its possibilities.

Touchscreens provide a platform for adaptable and versatile user interfaces making them a popular choice for modern smart devices. However, touchscreens lack physicality. Existing solutions to add tangible user interfaces to smart devices often require complicated assembly or occlude part of the touchscreen. We propose ClipWidgets: 3D-printed modular tangible UI extensions for smartphones. ClipWidgets uses a conical mirror and a custom phone case to redirect the field of view of the rear camera of a smartphone to the phone’s periphery. This allows the phone to optically sense input from modular passive 3D-printed widgets that are attached to the phone case. We developed three different widget types (button, dial and slider) that require minimal calibration and minimal assembly. To demonstrate the functionality of ClipWidgets we used it to prototype three different applications: a game controller, a music interface and an interactive graph tool.

Researchers have developed various tools and techniques towards the vision of on-demand fabrication of custom, interactive devices. Recent work has 3D-printed artefacts like speakers, electromagnetic actuators, and hydraulic robots. However, these are non-trivial to instantiate as they require post-fabrication mechanical– or electronic assembly. We introduce AirLogic: a technique to create electronics-free, interactive objects by embedding pneumatic input, logic processing, and output widgets in 3D-printable models. AirLogic devices can perform basic computation on user inputs and create visible, audible, or haptic feedback; yet they do not require electronic circuits, physical assembly, or resetting between uses. Our library of 13 exemplar widgets can embed AirLogic-style computational capabilities in existing 3D models. We evaluate our widgets’ performance—quantifying the loss of airflow (1) in each widget type, (2) based on printing orientation, and (3) from internal object geometry. Finally, we present five applications that illustrate AirLogic’s potential.

Toolkits for shape-changing interfaces (SCIs) enable designers and researchers to easily explore the broad design space of SCIs. However, despite their utility, existing approaches are often limited in the number of shape-change features they can express. This paper introduces MorpheesPlug , a toolkit for creating SCIs that covers seven of the eleven shape-change features identified in the literature. MorpheesPlug is comprised of (1) a set of six standardized widgets that express the shape-change features with user-definable parameters; (2) software for 3D-modeling the widgets to create 3D-printable pneumatic SCIs; and (3) a hardware platform to control the widgets. To evaluate MorpheesPlug we carried out ten open-ended interviews with novice and expert designers who were asked to design a SCI using our software. Participants highlighted the ease of use and expressivity of the MorpheesPlug.

Using microgestures, prior work has successfully enabled gestural interactions while holding objects. Yet, these existing methods are prone to false activations caused by natural finger movements while holding or manipulating the object. We address this issue with SoloFinger, a novel concept that allows design of microgestures that are robust against movements that naturally occur during primary activities. Using a data-driven approach, we establish that single-finger movements are rare in everyday hand-object actions and infer a single-finger input technique resilient to false activation. We demonstrate this concept’s robustness using a white-box classifier on a pre-existing dataset comprising 36 everyday hand-object actions. Our findings validate that simple SoloFinger gestures can relieve the need for complex finger configurations or delimiting gestures and that SoloFinger is applicable to diverse hand-object actions. Finally, we demonstrate SoloFinger’s high performance on commodity hardware using random forest classifiers.

Assembling circuits is a challenging and time consuming activity for novice makers, frequently resulting in incorrect placements of wires and components into breadboards. This results in errors that are difficult to identify and debug, and delays that hinder creating, exploring or reconfiguring circuit layouts. This paper presents VirtualWire, a tool that allows users to rapidly design and modify circuits in software and have these changes instantiated in real-time as electrical connections on a physical breadboard. To achieve this, VirtualWire dynamically translates circuit design files into physical connections inside a hardware switching matrix, which handles wiring across breadboard rows and to/from an embedded Arduino. The user can interactively test, tune, and share different circuit layouts for an Arduino shield, and once satisfied, can fabricate the circuit on a permanent substrate. Quantitative and qualitative user studies demonstrate that VirtualWire significantly reduces the time taken for (by 37%), and the number of errors made during (by 53%) circuit assembly, while also supporting users in creating readable, space-efficient and flexible layouts.

3D printing technology can be used to rapidly prototype the look and feel of 3D objects. However, the objects produced are passive. There has been increasing interest in making these objects interactive, yet they often require assembling components or complex calibration. In this paper, we contribute AirTouch, a technique that enables designers to fabricate touch-sensitive objects with minimal assembly and calibration using pneumatic sensing. AirTouch-enabled objects are 3D printed as a single structure using a consumer-level 3D printer. AirTouch uses pre-trained machine learning models to identify interactions with fabricated objects, meaning that there is no calibration required once the object has completed printing. We evaluate our technique using fabricated objects with various geometries and touch sensitive locations, obtaining accuracies of at least 90% with 12 interactive locations.

Assembling circuits on breadboards using reference designs is a common activity among makers. While tools like Fritzing offer a simplified visualization of how components and wires are connected, such pictorial depictions of circuits are rare in formal educational materials and the vast bulk of online technical documentation. Electronic schematics are more common but are perceived as challenging and confusing by novice makers. To improve access to schematics, we propose SchemaBoard, a system for assisting makers in assembling and inspecting circuits on breadboards from schematic source materials. SchemaBoard uses an LED matrix integrated underneath a working breadboard to visualize via light patterns where and how components should be placed, or to highlight elements of circuit topology such as electrical nets and connected pins. This paper presents a formative study with 16 makers, the SchemaBoard system, and a summative evaluation with an additional 16 users. Results indicate that SchemaBoard is effective in reducing both the time and the number of errors associated with building a circuit based on a reference schematic, and for inspecting the circuit for correctness after its assembly.

Augmented fabrication is the practice of designing and fabricating an artifact to work with existing objects. Although common both in the wild and as an area for research tools, little is known about how novices approach the task of designing under the constraints of interfacing with real-world objects. In this paper, we report the results of a study of fifteen novice end users in an augmented fabrication design task. We discuss obstacles encountered in four contexts: capturing information about physical objects, transferring information to 3D~modeling software, digitally modeling a new object, and evaluating whether the new object will work when fabricated. Based on our findings, we suggest how future tools can better support augmented fabrication in each of these contexts.

While pressing can enable a wide variety of interesting applications, most press sensing techniques operate only at close distances and rely on fragile electronics. We present EchoTube, a robust, modular, simple, and inexpensive system for sensing low-resolution press events at a distance. EchoTube works by emitting ultrasonic pulses inside a flexible tube which acts as a waveguide and detecting reflections caused by deformations in the tube. EchoTube is deployable in a wide variety of situations: the flexibility of the tubes allows them to be wrapped around and affixed to irregular objects. Because the electronic elements are located at one end of the tube, EchoTube is robust, able to withstand crushing, impacts, water, and other adverse conditions. In this paper, we detail the design, implementation, and theory behind EchoTube; characterize its performance under different configurations; and present a variety of exemplar applications that illustrate its potential.

This paper provides resources and design recommendations for optimizing position input for pressure sensor matrices, a sensor design often used in eTextiles. Currently applications using pressure matrices for precise continuous position control are rare. One reason designers opt against using these sensors for continuous position control is that when the finger transitions from one sensing electrode to the next, jerky motion, jumps or other non-linear artifacts appear. We demonstrate that interdigitation can improve transition behavior and discuss interpolation algorithms to best leverage such designs. We provide software for reproducing our sensors and experiment, as well as a dataset consisting of 1122 swipe gestures performed on 17 sensors.

We present StackMold, a DIY molding technique to prototype multi-material and multi-colored objects with embedded electronics. The key concept of our approach is a novel multi-stage mold buildup in which casting operations are interleaved with the assembly of the mold to form independent compartments for casting different materials. To build multi-stage molds, we contribute novel algorithms that computationally design and optimize the mold and casting procedure. By default, the multi-stage mold is fabricated in slices using a laser cutter. For regions that require more surface detail, a high-fidelity 3D-printed mold subsection can be incorporated. StackMold is an integrated end-to-end system, supporting all stages of the process: it provides a UI to specify material and detail regions of a 3D~object; it generates fabrication files for the molds; and it produces a step-by-step casting instruction manual.

Three-dimensional design software is challenging for novices and non-experts; when working with objects that already exist, the task becomes even more difficult. We present Printy3D, a system that enables children to design customized containers for electronic modules using tangible interaction and spatially augmented reality feedback. Our system allows users to position physical objects in three dimensions relative to a virtual container, providing feedback on placement location and validity. We implemented two different interaction styles and conducted a user study with 26 participants, 23 of them children. We detail the results of our study and suggest implications for design as well as opportunities for future research for systems of this kind.

The e-NABLE community is a global, distributed, loosely coordinated effort to design, produce, and deliver upper-limb assistive technology to those in need. e-NABLE's volunteers are often 3D-printing enthusiasts who are driven to use their skills to improve the lives of others. Volunteers provide the devices they produce to recipients around the world; these recipients are mainly children, but some are adults as well. While e-NABLE and its participants have received much attention from the media, little has been written about the experiences of the e-NABLE device users themselves. In this paper, we document the experiences of one user of an e-NABLE hand, detailing in a first-person account the journey from a recipient to an active participant and advocate for self-efficacy.

We present the results of a study of e-NABLE, a distributed, collaborative volunteer effort to design and fabricate upper-limb assistive technology devices for limb-different users. Informed by interviews with 14 stakeholders in e-NABLE, including volunteers and clinicians, we discuss differences and synergies among each group with respect to motivations, skills, and perceptions of risks inherent in the project. We found that both groups are motivated to be involved in e-NABLE by the ability to use their skills to help others, and that their skill sets are complementary, but that their different perceptions of risk may result in uneven outcomes or missed expectations for end users. We offer four opportunities for design and technology to enhance the stakeholders' abilities to work together.

Textiles are an old and well developed technology that have many desirable characteristics. They can be easily folded, twisted, deformed, or cut; some can be stretched; many are soft. Textiles can maintain their shape when placed under tension and can even be engineered with variable stretching ability. Conversely, 3D printing is a relatively new technology that can precisely produce functional, rigid objects with custom geometry. Combining 3D printing and textiles opens up new opportunities for rapidly creating rigid objects with embedded flexibility as well as soft materials imbued with additional functionality. In this paper, we introduce a suite of techniques for integrating 3D printing with textiles during the printing process, opening up a new design space that takes inspiration from both fields. We demonstrate how the malleability, stretchability and aesthetic qualities of textiles can enhance rigid printed objects, and how textiles can be augmented with functional properties enabled by 3D printing.

We present Bitey, a subtle, wearable device for enabling input via tooth clicks. Based on a bone-conduction microphone worn just above the ears, Bitey recognizes the click sounds from up to five different pairs of teeth, allowing fully hands-free interface control. We explore the space of tooth input and show that Bitey allows for a high degree of accuracy in distinguishing between different tooth clicks, with up to 94% accuracy under laboratory conditions for five different tooth pairs. Finally, we illustrate Bitey's potential through two demonstration applications: a list navigation and selection interface and a keyboard input method.

We introduce AirLink, a novel technique for sharing files between multiple devices. By waving a hand from one device towards another, users can directly transfer files between them. The system utilizes the devices' built-in speakers and microphones to enable easy file sharing between phones, tablets and laptops. We evaluate our system in an 11-participant study with 96.8% accuracy, showing the feasibility of using AirLink in a multiple-device environment. We also implemented a real-time system and demonstrate the capability of AirLink in various applications.

We present Facet, a multi-display wrist worn system consisting of multiple independent touch-sensitive segments joined into a bracelet. Facet automatically determines the pose of the system as a whole and of each segment individually. It further supports multi-segment touch, yielding a rich set of touch input techniques. Our work builds on these two primitives to allow the user to control how applications use segments alone and in coordination. Applications can expand to use more segments, collapses to encompass fewer, and be swapped with other segments. We also explore how the concepts from Facet could apply to other devices in this design space.

We present Nenya, a new input device in the shape of a finger ring. Nenya provides an input mechanism that is always available, fast to access, and allows analog input, while remaining socially acceptable by being embodied in commonly worn items. Users make selections by twisting the ring and "click" by sliding it along the finger. The ring - the size of a regular wedding band - is magnetic, and is tracked by a wrist-worn sensor. Nenya's tiny size, eyes-free usability, and physical form indistinguishable from a regular ring make its use subtle and socially acceptable. We present two user studies (one- and two-handed) in which we studied sighted and eyes-free use, finding that even with no visual feedback users were able to select from eight targets.

False positives are a common problem for interfaces that rely on gesture recognition. Often a gesture can seem fine in development but is found to trigger accidentally during an initial deployment of the interface, restarting development and increasing expense. In this work we introduce MAGIC 2.0, a technique for false positive prediction and prevention that can be used interactively during the interface design process. To ground our research, we implement MAGIC 2.0 as a web service and develop gesture interfaces using sensors on common Android mobile phone platforms. We use iSAX (indexable Symbolic Aggregate approXimation) to enable interactive searching (;1,500,000 sec) of everyday user movements on a standard workstation to determine if a candidate gesture will trigger accidentally during use of an interface. We perform a user-independent study that suggests that the number of matches to this Everyday Gesture Library (EGL) database is indeed predictive of a candidate gesture's suitability. We compare iSAX to hidden Markov models (HMMs) and nearest neighbor with respect to accuracy and speed for the EGL search. Using iSAX on the EGL, we also develop a “garbage” class and show that including this class in recognition reduces errors.

We present RhythmLink, a system that improves the wireless pairing user experience. Users can link devices such as phones and headsets together by tapping a known rhythm on each device. In contrast to current solutions, RhythmLink does not require user interaction with the host device during the pairing process; and it only requires binary input on the peripheral, making it appropriate for small devices with minimal physical affordances. We describe the challenges in enabling this user experience and our solution, an algorithm that allows two devices to compare imprecisely-entered tap sequences while maintaining the secrecy of those sequences. We also discuss our prototype implementation of RhythmLink and review the results of initial user tests.

Devices capable of gestural interaction through motion sensing are increasingly becoming available to consumers; however, motion gesture control has yet to appear outside of game consoles. Interaction designers are frequently not expert in pattern recognition, which may be one reason for this lack of availability. Another issue is how to effectively test gestures to ensure that they are not unintentionally activated by a user's normal movements during everyday usage. We present MAGIC, a gesture design tool that addresses both of these issues, and detail the results of an evaluation.

With the continuing miniaturization of powerful computation into mobile devices, there exists an opportunity for re-envisioning how we interact with our personal technology.In addition to a core computational/interaction component such as a mobile phone, there could be substantial benefit to a user by offering an ensemble of multiple mobile devices that can be used together. Such devices could provide novel input or output capabilities, or distribute user interactions in a more effective way. Our goal with this proposed workshop is to foster discussion about what possibilities such collections of devices might offer.

We investigate the effect of placement and user mobility on the time required to access an on-body interface. In our study, a wrist-mounted system was significantly faster to access than a device stored in the pocket or mounted on the hip. In the latter two conditions, 78% of the time it took to access the device was spent retrieving the device from its holder. As mobile devices are beginning to include peripherals (for example, Bluetooth headsets and watches connected to a mobile phone stored in the pocket), these results may help guide interface designers with respect to distributing functions across the body between peripherals.

The wristwatch is a device that is quick to access, but is currently under-utilized as a platform for interaction. We investigate interaction on a circular touchscreen wristwatch, empirically determining the error rate for variously-sized buttons placed around the rim. We consider three types of inter-target movements, and derive a mathematical model for error rate given a movement type and angular and radial button widths.

In this paper, we explore the concept of dual-purpose speech: speech that is socially appropriate in the context of a human-to-human conversation which also provides meaningful input to a computer. We motivate the use of dual-purpose speech and explore issues of privacy and technological challenges related to mobile speech recognition. We present three applications that utilize dual-purpose speech to assist a user in conversational tasks: the Calendar Navigator Agent, DialogTabs, and Speech Courier. The Calendar Navigator Agent navigates a user's calendar based on socially appropriate speech used while scheduling appointments. DialogTabs allows a user to postpone cognitive processing of conversational material by proving short-term capture of transient information. Finally, Speech Courier allows asynchronous delivery of relevant conversational information to a third party.