Craig D. Shultz

Exploring affective communication through variable-friction surface haptics

This paper explores the use of variable friction surface haptics enabled by the TPad Tablet to support affective communication between pairs of users. We introduce three haptic applications for the TPad Tablet (text messaging, image sharing, and virtual touch) and evaluate the applications with 24 users, including intimate couples and strangers. Participants used haptics to communicate literal texture, denote action within a scene, convey emotional information, highlight content, express and engage in physical playfulness, and to provide ones partner with an experience or sensation. We conclude that users readily associate haptics with emotional expression and that the intimacy of touch in the contexts we study is best suited for communications with close social partners.

Surface haptics via electroadhesion: Expanding electrovibration with Johnsen and Rahbek

This work aims to demonstrate and explain a nearly century old electrostatic haptic effect in human fingertips, which has since gone unreported. This effect, based on the original work of Johnsen and Rahbek [1], as well as research on electrostatic chucking devices [2], is capable of producing electrostatic forces on the finger an order of magnitude greater than those previously reported in literature. It is also capable of working with DC excitation, an aspect which stands out against previous reports which utilize purely AC excitation. This work also proposes a unified force model for this effect, drawn from electrostatic chuck research, and resolves this model with those in previous reports. We briefly discuss the background and specifics of the Johnsen-Rahbek effect, and include measurements made with our own electroadhesive surface and experimental apparatus. Finally, we discuss how this model fits in with previous observations, and its implications going forward.

Surface haptic interactions with a TPad tablet

A TPad Tablet is a tablet computer with a variable friction touchscreen. It can create the perception of force, shape, and texture on a fingertip, enabling unique and novel haptic interactions on a flat touchscreen surface. We have created an affordable and easy to use variable friction device and have made it available through the open-hardware TPad Tablet Project. We present this device as a potential research platform as well as demonstrate two applications: remote touch communication and rapid haptic sketching.

OS-level surface haptics for touch-screen accessibility

The TPad Tablet combines an Android tablet with a variable friction haptic touch-screen and offers many novel interaction possibilities. For example, unique textures may be associated with different user interface elements, such as text boxes and buttons. This paper presents an Android AccessibilityService that was created to give operating system-wide (OS) access to haptic effects. Prior to this work, the haptic feedback of the TPad could be controlled only from within specific applications. With the new implementation, all applications and primary user interfaces (e.g. home screen) will have access to the TPad. Rather than focus on specific elements or applications, we seek to provide a high fidelity haptic experience that elevates the TPads accessibility to the standard of Talkback and Voiceover, Androids and Apples accessibility programs respectively. The code for the application is available on our website.

Designing Wearable Haptic Information Displays for People with Vision Impairments

With the ubiquity of wearable computing, an important and emerging challenge is to understand how to design wearable information displays for non-visual, non-auditory interaction. This is particularly relevant to the design of accessible technologies for people with vision impairments. Working towards this aim, we developed a smartwatch prototype that uses variable friction surface haptics to test initial design concepts. Through interviews and iterative prototyping with seven blind users, we identified three key use cases for a haptic smartwatch as well as embodied conceptual models for presenting haptic information. We found that a physical clock face, compass, and numerical keypad are productive representations for presenting information haptically, and these models build on existing tactile and spatial understandings of our target user group.

The application of tactile, audible, and ultrasonic forces to human fingertips using broadband electroadhesion

We report an approach to controlling friction forces on sliding human fingertips in order to produce simultaneous vibrations across an exceedingly broad range of tactile, audible, and ultrasonic frequencies. Vibrations in the skin can be felt directly by the fingertip, and vibrations in the air can be heard emanating from the proximity of the finger. We introduce and detail an experimental apparatus capable of recording friction forces up to a frequency of 6 kHz, and describe a custom designed electroadhesive amplifier and system with a flat current to force magnitude response throughout this entire measurement range. Recordings with a MEMS microphone confirm the existence of ultrasonic forces applied to the finger and further reveal the ultra wideband capability of broadband electroadhesion. Implications for the design of surface haptic and general audio-haptic displays are discussed.

The Application of Tactile, Audible, and Ultrasonic Forces to Human Fingertips Using Broadband Electroadhesion

We report an electroadhesive approach to controlling friction forces on sliding fingertips which is capable of producing vibrations across an exceedingly broad range of tactile, audible, and ultrasonic frequencies. Vibrations on the skin can be felt directly, and vibrations in the air can be heard emanating from the finger. Additionally, we report evidence from an investigation of the electrical dynamics of the system suggesting that an air gap at the skin/surface interface is primarily responsible for the induced electrostatic attraction underlying the electroadhesion effect. We developed an experimental apparatus capable of recording friction forces up to a frequency of 6 kHz, and used it to characterize two different electroadhesive systems, both of which exhibit flat force magnitude responses throughout the measurement range. These systems use custom electrical hardware to modulate a high frequency current and apply surprisingly low distortion, broadband forces to the skin. Recordings of skin vibrations with a laser Doppler vibrometer demonstrate the tactile capabilities of the system, while recordings of vibrations in the air with a MEMS microphone quantify the audible response and reveal the existence of ultrasonic forces applied to the skin via electronic friction modulation. Implications for surface haptic and audio-haptic displays are briefly discussed.

[D96] Variable friction and multi-actuator vibrotactile haptics on a tablet computer

Variable friction and multi-actuator vibrotactile haptic effects have been demonstrated separately from each other in the past. In this application, a TPad Tablet, containing a variable friction screen, has been combined with four independently controlled vibrotactile actuators to create a device which can render both types of effects. Users can receive localized lateral force information as their finger glides across the screen, and they can feel directional vibration information through their hand holding the device. Directionality with the vibrotactile actuators is achieved through the use of apparent haptic movement and phantom sensation. An example application has been developed in which users interact with a virtual ball on the surface of the tablet. Users can indirectly feel the ball interact with its environment as it rolls across the screen or bumps into obstacles. They can also interact with the ball directly to feel collision forces right at their fingertip.

[D98] TPad watch

The small size of touchscreen smart watches presents a unique interaction challenge. While the “fat-finger problem” is present on tablets and smartphones, it is exacerbated on smart watches, potentially occluding up to half of the display at a time. Haptic feedback can potentially be used to fill this information gap by aiding in location identification and in discriminating between fine selections. We have developed a miniaturized ultrasonic variable friction display integrated with a smart watch. We demonstrate the TPad Watch (Tactile Pattern Display) with two prototypical navigation elements- distinctly textured buttons, and closely spaced menu items in a list.