Bare Fingertip Research Articles

A Robust Approach for Reproducing the Haptic Sensation of Sandpaper With Different Roughness During Bare Fingertip Interaction

When reproducing realistic virtual textures for bare finger interaction, an accelerometer attached to a fingernail is commonly used. This measurement depends on the dynamic conditions during the exploration action, and slight differences in roughness are difficult to acquire accurately because of masking by shivering, low-pass filtering by the finger tissue, and sensor accuracy. We propose a simpler yet robust approach based on the 3D measurement of the surface and compare it with the conventional approach. The 3D surface images of sandpaper with different degrees of roughness were captured using a 3D microscope, and the line roughness curve was transformed into an acceleration curve by quadratic differential transformation. The real-time acceleration and frictional force were measured by an accelerometer and force sensor for comparison. A haptic device replaying acceleration-based vibrations by two audio speakers and producing tangential force by a motor-controlled liner slide was developed for reproduction. We conducted experiments with participants to evaluate the reproduction approach. Experimental results showed that the conventional approach obtained sufficient discriminability with the assistance of force, whereas the proposed approach achieved higher reproducibility and discriminability by sole vibration. Thus, our approach provides a new reference for studies of bare finger interaction with rough surfaces.

Vibrotactile Feedback System From the Fingertip to the Temples for Perceptual Enhancement of Contracture Palpation.

Contractures are generally assessed by a physician or physical therapist through palpation. However, contracture palpation requires skill and experience. The frictional vibration, which has a pulse-like vibration due to sliding disturbances around the affected area during palpation, is important in assessing the degree of contracture progression. This paper aims to enhance the perceptual sensitivity of frictional vibration for contracture palpation using a vibrotactile feedback system. We previously proposed an evaluation system for palpation with a wearable skin vibration sensor that detects skin-propagated vibration, allowing touch with a bare fingertip. In this paper, we propose the vibrotactile feedback system that presents the tactile information of the fingertip detected by the wearable tactile sensor to the temples with a vibrotactile display. A stimulator that gives vibrations similar to those during the palpation, which include pulse-like vibration and small vibration, was assembled. Then, psychophysical experiments on the vibrotactile feedback system were conducted using this stimulator. The results showed that the detection sensitivity of the pulse-like vibration was significantly enhanced with the feedback.

UltraShiver: Lateral Force Feedback on a Bare Fingertip via Ultrasonic Oscillation and Electroadhesion

We propose a new lateral force feedback device, the UltraShiver, which employs a combination of in-plane ultrasonic oscillation (around 30 kHz) and out-of-plane electroadhesion. It can achieve a strong active lateral force (400 mN) on the bare fingertip while operating silently. The lateral force is a function of pressing force, lateral vibration velocity, and electroadhesive voltage, as well as the relative phase between the velocity and voltage. In this paper, we perform experiments to investigate characteristics of the UltraShiver and their influence on lateral force. A lumped-parameter model is developed to understand the physical underpinnings of these influences. The model with frequency-weighted electroadhesion forces shows good agreement with experimental results. In addition, a Gaussian-like potential well is rendered as an application of the UltraShiver.

Effects of Continuous Auditory Feedback on Drawing Trajectory-Based Finger Gestures

The well-known “fat finger” issue limits the interaction performance of trajectory-based finger gestures. To alleviate this issue, this work focuses on the possibility of using additional continuous auditory feedback to assist trajectory-based finger gestures. First, the experiment validated that, with the visual feedback only, the bare fingertip led to more errors in drawing of intersectional points, endpoints of closed gestures, and gestural length and shape variability compared to when the finger-attached pen was used. Then, we designed different types of auditory feedback (discrete beep, static, gradual) to provide additional information on the spatial relationship between finger-contact point and the endpoints or intersections of predefined gestures. An experiment that evaluates the effects of individual or combination of designed auditory feedback on trajectory-based finger gestures was conducted. These results show a few differences between them. However, a combination of gradual (amplitude and frequency) continuous sound and beep reached the highest drawing accuracy for trajectory-based finger gestures, which is similar to that of a finger-attached pen. This research offers insights and implications for the future design of continuous auditory feedback on small touchscreens.

Analysis of fingertip/fabric friction-induced vibration signals toward vibrotactile rendering

Recent publications on virtual reality and augmented reality have highlighted the possibility of inducing the tactile sensation of surface texture by exciting the fingertip skin with appropriate vibration. When fingertip and object surface are in contact with a relative motion, the sliding between the two surfaces generate vibrations, however, the link between friction-induced vibrations features and textile surface characteristics has not been fully investigated. This study will explore the dependence of different vibrational components on the constructional parameters of woven fabrics. This is achieved by measuring the friction-induced vibration with bare fingertip and analyzing the relationship of extracted vibration features with constructional details of woven fabrics. The results show that the yarn densities majorly affect the normal vibration intensity, the yarn fineness, and the weave pattern that determine the tangential components of vibration intensity, and the fundamental frequency of vibration spectrum characterizes the periodic surface textures of woven fabric. Generally, both normal and tangential components of friction-induced vibration signals represent the constructional specifications of woven fabrics, and they can be used to define objective indexes and reproducible stimuli of the perceived surface characteristics in vibrotactile rendering.

How tactor size and density of normal indentation tactile displays affects grating discrimination tasks.

Tactile fingertip devices of vertically moving tactors have two important design parameters that significantly affect physical feedback and human tactile perception: tactor size and tactor density. However, there are a limited number of research studies that have evaluated the effect of these parameters on human tactile perception. This paper investigated the influence and interaction of these two parameters on a discrimination task. The task consisted of discriminating the spatial-period of sinusoidal gratings through the use of passive-guided touch. In two complementary experiments 40 participants performed the discrimination task under two different tactile conditions: (I) using direct bare fingertip sensing (baseline condition), and (II) using tactile displays with different tactor spacings and diameters. In both experiments differences between and within subjects were considered for Condition II, and for all test conditions the spatial-period Weber fraction for each participant was measured. Results from both experiments were consistent in indicating that tactile performance improves as tactor spacing is decreased and tactor diameter is increased. However, tactor spacings below 1.1 mm might not result in any significant further improvement. The findings of this study might help designers to choose design parameters for tactile displays based upon the cost-benefit of tactor density versus perceptual performance.

A role for “air writing” in second-language learners’ acquisition of Japanese in the age of the word processor

Abstract This article addresses the pedagogical implications of kūsho ( ; literally “air writing”), that is, the spontaneous manual tracing of Sino-Japanese characters (kanji) in the air with a bare fingertip, by learners of Japanese. I describe the phenomenon of kūsho, then review research indicating that it is common (if under-recognized) during kanji learning and recall and, moreover, is associated with a small but statistically significant advantage over conventional paper-andpencil copying as a technique for memorizing the shapes of kanji. I propose that teachers of Japanese explicitly sanction kūsho and encourage students to selfconsciously incorporate it into their repertoire of techniques for memorizing or recalling kanji. The issue is particularly salient in the context of the ongoing cultural shift away from writing by hand to computerized word processing, which in this generation is reshaping the psycholinguistics of literacy in Japanese. Practice of kūsho may secure a kinesthetic basis for facility with kanji among learners for whom keyboard-based typing is rapidly displacing manual writing.

CONTAMINATION OF THE SURGEON'S BARE AND GLOVED FINGERTIPS IN CARDIAC OPERATIONS

SUMMARY The surgeon's bare fingertips and the external surface of gloved fingertips were examined for contamination by bacteria during the course of 27 cardiac surgical operations. Following the surgical scrub, positive colony counts were obtained in 20 (74%) of bare fingertip impressions (median colony count 4 [inter‐quartile range, IQR, 0‐9)], while at the conclusion of surgery positive counts were obtained in 15 (55.6%) fingertip impressions (median count 1 [IQR 0‐6]; range 0‐247; paired Wilcoxon test p=NS). Furthermore, positive colony counts at the start of the operation were obtained in none of the gloved fingertip impressions and at conclusion of surgery in 17 (62.9%) of the gloved fingertip impressions (median count 2 [IQR 0‐6] p=0.0002). There was no significant relationship between the total colony count on gloved fingertip impressions and the length of surgery (Pearson's r=0.17, p=NS). Contrary to expectations there was no significant increase in the colony count on the bare fingertips at the conclusion of surgery. Although there was an increase in the bacterial count on the surgeon's. gloved fingertips, this increase did not correlate with the length of surgery.

Colour 3-D electronic imaging of the surface of the human body

The NRC laboratories have developed a laser scanning technique to digitize shapes and colours in registration. The technique, known as synchronized scanning, is capable of digitizing topography as small as the relief of a bare finger tip, showing a clear picture of the skin structure (essentially a clean fingerprint without distortion), as well as the shape and size of body components such as hands, face, and feet, and the full body of one or more subjects simultaneously. The laser scanner uses a RGB laser, coupled to an optical fibre, which is projected in the field of view. The three-dimensional colour measurements are made by optical triangulation to a resolution of 10 μm for finger tip scans and a resolution of 1 mm for whole body scans. Experimental results are presented and discussed. Potential applications of this technology in the field of identification and inspection of humans include face recognition, finger, foot and teeth print identification, and 3-D mugshots that can be rapidly broadcast through satellite communication. One of the unique properties of this technology is that absolute measurements, not only appearance and relative position of features, can be used for identification purposes.