Tactile Transducers Research Articles

Multimodal force and temperature tactile sensor based on a short-channel organic transistor with high sensitivity

In this manuscript, we report on a novel architecture for the fabrication of highly sensitive multimodal tactile transducers, for the simultaneous detection of temperature and force. Such devices are based on a flexible Organic Charge Modulated Field Effect Transistor (OCMFET) coupled with a pyro/piezoelectric element, namely a commercial film of poly-vinylene difluoride (PVDF). The reduction of the channel length, obtained by employing a low-resolution vertical channel architecture, allowed to maximize the ratio between the sensing area and the transistor’s channel area, a technological approach that allows to considerably enhance both temperature and force sensitivity, while at the same time minimize the sensor’s dimensions. Thanks to the employment of a straightforward, up-scalable, and highly reproducible fabrication process, this solution represents an interesting alternative for all those applications requiring high-density, high-sensitivity sensors such as robotics and biomedical applications.

Agar-based soft tactile transducer with embedded optical fiber specklegram sensor

Tactile transducers monitor physical variables like force and texture through direct contact, featuring indispensable in human–computer interaction and biomedical applications. This work proposes an optical fiber tactile sensor based on specklegram analysis. A soft matrix made of agar embeds a concatenated multimode/single-mode/multimode fiber structure. Forces exerted over the tactile surface disturb the probe mechanically, modulating the output speckle patterns for further processing through image correlation techniques. Experiments evaluated the sensor response as a function of the probe position and the agar matrix composition. Static and dynamic characterizations yielded average force and spatial resolutions of 0.006 N and 0.0008 mm, respectively, with a time response of 34.7 ms, exceeding most of the available optical fiber tactile devices. Compared with intensity and spectral approaches, the specklegram analysis provides high sensitivity (∼1.65 N−1) and relies on a straightforward interrogation system. Furthermore, as a biocompatible, degradable, and easy-to-manipulate material, the agar-based transducer shows perspectives for developing artificial skins and implantable sensors.

Design and evaluation of a digitally active drum

Despite the ever growing variety and popularity of commercially available electronic percussion (EP) instruments, there are still a significant number of active musicians who prefer to use acoustic drums. Digitally active drum (DAD) is an enhanced snare drum that provides sonic capabilities associated with digital musical instruments in the form of a traditional acoustic drum allowing full use of acoustic drumming gesture vocabulary. By using an in-built loud speaker and tactile sound transducers system, a Bela Cape and Beagle Bone Black, near field photoelectric sensors and a synthesis and effects patch built in Pure Data (PD), a prototype of a hybrid acoustic - electronic instrument has been made. This prototype has been evaluated by five expert drummers and two co-performers in both group and solo settings in order to determine its effectiveness and potential role in professional music making.

A User-Specific Approach for Comfortable Application of Advanced 3D CAD/CAM Technique in Dental Environments Using the Harmonic Series Noise Model

Recently, there has been a focus on improving the user’s emotional state by providing high-quality sound beyond noise reduction against industrial product noise. Three-dimensional computer aided design and computer-aided manufacturing (3D CAD/CAM) dental milling machines are a major source of industrial product noise in the dental environment. Here, we propose a noise-control method to improve the sound quality in the dental environment. Our main goals are to analyze the acoustic characteristics of the sounds generated from the dental milling machine, to control the noise by active noise control, and to improve the sound quality of the residual noise by synthesized new sound. In our previous study, we demonstrated noise reduction in dental milling machines through tactile transducers. To improve the sound quality on residual noise, we performed frequency analysis, and synthesized sound similarly as musical instruments, using the harmonic series noise model. Our data suggest that noise improvement through synthesis may prove to be a useful tool in the development of dental devices.

Condition Assessment of Foundation Piles and Utility Poles Based on Guided Wave Propagation Using a Network of Tactile Transducers and Support Vector Machines.

This paper presents a novel non-destructive testing and health monitoring system using a network of tactile transducers and accelerometers for the condition assessment and damage classification of foundation piles and utility poles. While in traditional pile integrity testing an impact hammer with broadband frequency excitation is typically used, the proposed testing system utilizes an innovative excitation system based on a network of tactile transducers to induce controlled narrow-band frequency stress waves. Thereby, the simultaneous excitation of multiple stress wave types and modes is avoided (or at least reduced), and targeted wave forms can be generated. The new testing system enables the testing and monitoring of foundation piles and utility poles where the top is inaccessible, making the new testing system suitable, for example, for the condition assessment of pile structures with obstructed heads and of poles with live wires. For system validation, the new system was experimentally tested on nine timber and concrete poles that were inflicted with several types of damage. The tactile transducers were excited with continuous sine wave signals of 1 kHz frequency. Support vector machines were employed together with advanced signal processing algorithms to distinguish recorded stress wave signals from pole structures with different types of damage. The results show that using fast Fourier transform signals, combined with principal component analysis as the input feature vector for support vector machine (SVM) classifiers with different kernel functions, can achieve damage classification with accuracies of 92.5% ± 7.5%.

Development of crystal matrix of tensoresistive pressure tactile transducers for robotics

The article presents the design of a silicon crystal matrix of the pressure of tensoresistive sensitive elements of the MIPD-32 for intelligent robotic systems having a function of tactile feel. The experimental data on the sensitivity of the tensoconverters were represented.

Low stiffness tactile transducers based on AlN thin film and polyimide

In this paper, we propose a flexible piezoelectric MEMS transducer based on aluminum nitride thin film grown on polyimide soft substrate and developed for tactile sensing purposes. The proposed device consists of circular micro-cells, with a radius of 350 μm, made of polycrystalline c-axis textured AlN. The release of compressive stress by crystalline layers over polymer substrate allows an enhanced transduction response when the cell is patterned in circular dome-shaped geometries. The fabricated cells show an electromechanical response within the full scale range of 80 mN (≃200 kPa) both for dynamic and static load. The device is able to detect dynamic forces by exploiting both piezoelectric and flexoelectric capabilities of the aluminum nitride cells in a combined and synergistic sensing that occurs as voltage generation. No additional power supply is required to provide the electrical readout signals, making this technology suitable candidate when low power consumption is demanding. Moreover a capacitance variation under constant stress is observed, allowing the detection of static forces. The sensing ability of the AlN-based cells has been tested using an ad hoc setup, measuring both the applied load and the generated voltage and capacitance variation.

Inverse analysis for the recovery of forces applied to photoelastic tactile transducers

Inverse analysis for the recovery of forces applied to photoelastic tactile transducers

Inverse analysis for the recovery of forces applied to photoelastic tactile transducers

In this paper, the forward and inverse analyses of one- and two-layer photoelastic tactile transducers are presented. For such transducers, an applied force profile generates stresses in the photoelastic layer, making it birefringent. Consequently, circularly polarized light input to the transducer becomes elliptically polarized at the output because of the introduction of a phase-lead distribution. Herein, the forward and inverse analyses of a one-layer photoelastic tactile transducer, under ideal conditions, are first presented. The transducer is modeled using closed form equations based on the theories of elasticity and photoelasticity, which allow the calculation of the light intensity distribution corresponding to an applied force profile. However, to recover the force profile from a light intensity distribution (i.e., the inverse problem), the phase-lead distribution must be determined first. A novel technique is described for this purpose. In the second part of the paper, we consider the forward and inverse analyses of a two-layer transducer, under nonideal conditions, where the light-intensity distribution is no longer noise-free. In the forward analysis, the calculation of the stress distribution in the transducer is implemented by finite-element analysis. The recovery of the phase-lead distribution under noisy conditions, however, constitutes an ill-posed inverse problem. A novel algorithm that accurately and effectively determines the phase-lead distribution from a noisy light-intensity distribution is presented. © 1998 John Wiley & Sons, Inc.

Method and apparatus for performing ultrasonic assisted surgical procedures

Ultrasonic sensing systems are incorporated into surgical instruments to monitor operational fields defined by distal ends of the instruments. The instruments include proximal ends for their activation typically including one or a pair of handles which a surgeon grasps and operates, for example by squeezing the handles together or by pivotally moving a trigger portion of the handle relative to a fixed portion of the handle. Circuitry for performing ultrasonic sensing preferably is enclosed in housings defined within the handles of the proximal ends of the instruments. Wiring, preferably running through the instruments, connects the circuitry to transducers formed in or mounted on the distal ends of the surgical instruments. The transducers direct ultrasonic energy to the operational fields defined by the distal ends of the instruments and receive ultrasonic energy reflected from the operational fields. The direction for transmission and receipt of ultrasonic energy is determined by acoustic lenses, angularly oriented transducer mounts or a combination of the two. Signals representative of the tissue or contents of the operational fields of surgical instruments drive audible signal generators or preferably tactile transducers to inform the surgeon of the contents. Tactile transducers are mounted for access by the surgeon, preferably on the handles of the surgical instruments.

Effects of number of channels on speech perception with tactile aids

Although there is considerable evidence that multichannel tactile aids for the hearing impaired provide more information about the speech signal to the wearer than do single‐channel tactile aids, it has not been determined how many channels are necessary for optimal transmission of speech information. In the present study, the 5‐channel Tactaid V (Audiological Engineering Corporation) and the 16‐channel Queen's University tactile vocoder were evaluated in a series of phoneme identification and connected speech tasks, to determine whether the additional channels present in the 16‐channel design lead to better speech perception performance. Results showed that, in relatively simple tasks, such as minimal pairs phoneme discrimination, subjects performed at similar levels with both devices. However, in more complex tasks, such as integration with lipreading, the 16‐channel device yielded significantly higher levels of performance. In connected discourse tracking, both devices showed significantly higher levels of performance in conjunction with lipreading than were found under lipreading alone conditions. Results are discussed with respect to the benefits provided by a tactile aid relative to the practical limitations of tactile aids that employ a large number of tactile transducers. [Work supported by NIH and NSF.]

Observed temporal summation effects for lingual vibrotactile threshold measurements

Investigations using mechanical stimulation to measure lingual threshold sensitivity have resulted in conflicting assumptions concerning the nature of underlying neural transducers. A basic question concerns whether or not exteroceptive touch receptors in the lingual surface summate energy in response to displacement of tissues. This study tested the hypothesis that these receptors would demonstrate temporal summation as a function of pulse duration time. The stimulus unit included an audio oscillator, frequency counter, electronic switch, interval timer, amplifier, and electromagnetic vibrator. The measurement unit consisted of an accelerometer, cathode follower, microphone amplifier, and vacuum‐tube volt‐meter. Vibrotactile lingual thresholds for 250 Hz were obtained for four groups of normal speaking adult subjects using respective pulse duration times of 50, 100, 200, and 400 msec. Peak values were recorded in millivolts and converted to dB re one micron rms. Temporal summation was observed up to 200 msec reaching an asymptote around 400 msec. Findings supported the position that tactile transducers in mucous tissues respond to vibratory displacements in the same ways as pressure receptors in other cutaneous tissues.