Artificial Roughness Encoding with a Bio-inspired MEMS- based Tactile Sensor Array

A compliant 2×2 tactile sensor array was developed and investigated for roughness encoding. State of the art cross shape 3D MEMS sensors were integrated with polymeric packaging providing in total 16 sensitive elements to external mechanical stimuli in an area of about 20 mm2, similarly to the SA1 innervation density in humans. Experimental analysis of the bio-inspired tactile sensor array was performed by using ridged surfaces, with spatial periods from 2.6 mm to 4.1 mm, which were indented with regulated 1N normal force and stroked at constant sliding velocity from 15 mm/s to 48 mm/s. A repeatable and expected frequency shift of the sensor outputs depending on the applied stimulus and on its scanning velocity was observed between 3.66 Hz and 18.46 Hz with an overall maximum error of 1.7%. The tactile sensor could also perform contact imaging during static stimulus indentation. The experiments demonstrated the suitability of this approach for the design of a roughness encoding tactile sensor for an artificial fingerpad

A Polymer-Based Capacitive Sensing Array for Normal and Shear Force Measurement

In this work, we present the development of a polymer-based capacitive sensing array. The proposed device is capable of measuring normal and shear forces, and can be easily realized by using micromachining techniques and flexible printed circuit board (FPCB) technologies. The sensing array consists of a polydimethlysiloxane (PDMS) structure and a FPCB. Each shear sensing element comprises four capacitive sensing cells arranged in a 2 × 2 array, and each capacitive sensing cell has two sensing electrodes and a common floating electrode. The sensing electrodes as well as the metal interconnect for signal scanning are implemented on the FPCB, while the floating electrodes are patterned on the PDMS structure. This design can effectively reduce the complexity of the capacitive structures, and thus makes the device highly manufacturable. The characteristics of the devices with different dimensions were measured and discussed. A scanning circuit was also designed and implemented. The measured maximum sensitivity is 1.67%/mN. The minimum resolvable force is 26 mN measured by the scanning circuit. The capacitance distributions induced by normal and shear forces were also successfully captured by the sensing array

Roughness Encoding in Human and Biomimetic Artificial Touch: Spatiotemporal Frequency Modulation and Structural Anisotropy of Fingerprints

The influence of fingerprints and their curvature in tactile sensing performance is investigated by comparative analysis of different design parameters in a biomimetic artificial fingertip, having straight or curved fingerprints. The strength in the encoding of the principal spatial period of ridged tactile stimuli (gratings) is evaluated by indenting and sliding the surfaces at controlled normal contact force and tangential sliding velocity, as a function of fingertip rotation along the indentation axis. Curved fingerprints guaranteed higher directional isotropy than straight fingerprints in the encoding of the principal frequency resulting from the ratio between the sliding velocity and the spatial periodicity of the grating. In parallel, human microneurography experiments were performed and a selection of results is included in this work in order to support the significance of the biorobotic study with the artificial tactile system

Microfabricated tactile sensors for biomedical applications: a review

During the last decades, tactile sensors based on different sensing principles have been developed due to the growing interest in robotics and, mainly, in medical applications. Several technological solutions have been employed to design tactile sensors; in particular, solutions based on microfabrication present several attractive features. Microfabrication technologies allow for developing miniaturized sensors with good performance in terms of metrological properties (e.g., accuracy, sensitivity, low power consumption, and frequency response). Small size and good metrological properties heighten the potential role of tactile sensors in medicine, making them especially attractive to be integrated in smart interfaces and microsurgical tools. This paper provides an overview of microfabricated tactile sensors, focusing on the mean principles of sensing, i.e., piezoresistive, piezoelectric and capacitive sensors. These sensors are employed for measuring contact properties, in particular force and pressure, in three main medical fields, i.e., prosthetics and artificial skin, minimal access surgery and smart interfaces for biomechanical analysis. The working principles and the metrological properties of the most promising tactile, microfabricated sensors are analyzed, together with their application in medicine. Finally, the new emerging technologies in these fields are briefly described

Friction Induced Vibration Based Pattern Detection On An Artificial Skin By Preload Control

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2012Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2012Bu çalışma, kayma hızı, önyükleme kuvveti ve tip çapı gibi farklı tasarım parametreleri altında, yapay olarak yapılan yüzeyin deseninin algılanmasını ve sürtünme özelliklerini ortaya koymaktadır. İsteğe göre yapılmış olan yarı otonom sürtünme deney düzeneğinde, düz şeffaf polimer kullanılarak yapılan sürtünme testlerinin neticesinde, düzenek gerçeklenmiş ve uygun çalışma şartları belirlenmiştir. Desen algılama deneyleri, kayma sırasında yüzeye uygulanan önyükleme kuvveti, kuvvet geribesleme kontrolcüsü tarafından sabit tutulurken, sert cam tipe karşı sürtülen, eşit aralıklarla dağıtılmış tümsekleri olan yapay deri üzerinde gerçekleştirilmiştir. Yüzey taraması esnasında oluşan sürtünmenin yol açtığı titreşimler, yapay derinin desenine ait olan ve taranan yüzeyin tümseklerinin yükseklik ve dalgaboyu gibi bilgisini taşıyan frekansın algılanmasına olanak tanımıştır. Bu arada test sonuçlarına göre önyükleme kuvveti, düşük kayma hızı ve yüksek kuvvet altında minimum hata yüzdesiyle sabit kalmaktadır. Buna ek olarak, önyükleme kuvvet hatasının azaltılmasında ve sinyal harmoniklerinin filtrelenmesinde tip çapının etkisi de gözlemlenmiştir.This study exhibits pattern detection and frictional properties of the artificially made surface under different design parameters such as sliding velocity, preload, and tip diameter. In consequence of frictional tests on the custom built semi-autonomous friction set-up using flat soft polymer, the set-up is validated, and proper working conditions are determined. The pattern detection experiments are realized on an artificial skin with evenly distributed ridges rubbed against a rigid glass tip while the preload applied to the surface is kept constant during sliding by the force-feedback controller. The friction induced vibrations occurred during surface scanning allowed to detect the frequency belonging to the pattern of the artificial skin, and carrying the information of the scanned surface like height and wavelength of ridges. Meanwhile, according to the results of the tests, the preload remains consistent with a minimum percentage of error at low sliding velocity and under high preload value. In addition, tip diameter effect on reducing the preload error, and filtering harmonics of the signal is also observed.Yüksek LisansM.Sc

Biomimétoca Neuronal del Sistema Sensorial Periférico de las Vibrisas de la Rata

Este trabajo de tesis está basado en un importante know-how de procedimientos electrofisiológicos para el estudio del sistema vibrisal de la rata, los cuales incluyen estudios de conducción nerviosa para comprender los mecanismos fisiológicos del sistema y estudios conductuales. Estos estudios fueron dirigidos a una de las capacidades sensoriales más sobresalientes de la rata: la capacidad de discriminar objetos de diferentes texturas. Se pusieron en evidencia estrategias conductuales que permitirían a los roedores mejorar la percepción de la información táctil y la existencia de patrones temporales en los aferentes primarios relacionados a la rugosidad de las superficies palpadas.Estos hallazgos electrofisiológicos condujeron, naturalmente, a preguntas tales como: ¿qué característica física de la superficie de rozamiento está siendo codificada por el sistema vibrisal en determinadas condiciones?, ¿Cómo se trasmite esa información? y ¿todas las vibrisas transmiten de igual forma la información?Para comenzar a responder estas preguntas, fue necesario abordar el estudio de las características morfológicas relevantes de las superficies de rozamiento, desarrollar técnicas de procesamiento de la información de las señales electrofisiológicas, modelar el sistema y estudiar posibles diferencias funcionales entre las vibrisas. Así quedaron planteados los objetivos de la tesis.En el desarrollo de este trabajo de tesis se propuso una herramienta estadística, basada en la teoría de la información, que nos permitió cuantificar la información táctil presente en la actividad eléctrica de las fibras nerviosas que inervan las vibrisas; se modeló matemáticamente el comportamiento eléctrico del nervio vibrisal lo que permitió interpretar mejor el significado/motivo por el cual los potenciales evocados del registro se presentan con diferentes formas, amplitud y duración; se realizaron registros electrofisiológicos en la innervación de varias vibrisas en forma simultánea cuando estas eran estimuladas con superficies de diferente rugosidad para revelar y caracterizar los códigos neuronales involucrados en la integración sensorial. Además, se hizo un análisis de respuesta en frecuencia de varias vibrisas que demostró qué, aunque todos los senos foliculares son anatómicamente similares, funcionalmente son muy diferentes. Cada folículo está preparado para tener mayor sensibilidad para un estímulo de frecuencia específico, que a su vez está en sintonía con su vibrisa, cuya frecuencia de resonancia depende exclusivamente de sus características físicas.Por último, considerando los parámetros generales del proceso de transducción determinados en el transcurso de la tesis tales como linealidad, sensibilidad y capacidad de adaptación a diferentes modalidades del estímulo, se plantearon los criterios para una futura implementación en sistemas tecnológicos multisensoriales biomiméticos lo cual representa el mayor aporte de la tesis al conocimiento científico y tecnológico.Fil: Pizá, Alvaro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentin

Creating tactile feedback with intelligent electrical stimulation to compensate for sensory impairment.

Performing daily life activities can be more challenging as a result of peripheral neuropathy in the feet and can lead to an increased risk of falls and injuries. Biofeedback, in the form of electrocutaneous stimulation, can be used as a means to transmit information about the force and pressure applied to the feet, and this can help people determine their body position in relation to the ground and the amount of sway movements. The motivation for the present work was to explore whether a wearable electrotactile feedback system (EFS) could improve life quality by supporting people with balance instability as a result of this condition. In this study a wearable EFS was designed to estimate the magnitude of pressure applied to the feet during standing and walking. The study also aimed to determine whether the EFS had an effect on posture control in standing and confidence in walking among individuals suffering from peripheral neuropathy. A wearable EFS has been developed in this work including the hardware design for an electrocutaneous stimulation and a processing unit to compute the sensor data. The EFS uses a sensor system with piezoresitive force sensors that has been developed and tested beforehand. The proposed system considers aspects of safety and portability, as well as meeting individual parameters. The latter one was assured by implementing and testing a novel calibration method for the detection of sensory thresholds and device parameters. A software for magnitude estimation and force and pressure feedback based on the centre of pressure (COP) movement was programmed and a psychophysical transfer function involving sensory thresholds and sensor system variables was implemented. A pilot study with 11 participants was carried out to evaluate the suitability of the EFS for magnitude estimation. Magnitude estimation with the EFS showed high accuracy and sensitivity and it was found that the design proposed in this work is beneficial over other solutions. The upper leg was identified as a suitable location for electrotactile feedback. A proof of concept study was undertaken among 14 individuals suffering with peripheral neuropathy and five controls in a clinical environment, testing the effects of the EFS on balancing and walking in different scenarios. It was shown that, when used by patients with neuropathy, the EFS helped improving posture control in certain scenarios and did not hinder patients during walking. A longer learning period might be necessary so that users can fully benefit from the EFS. The findings of the study contribute to the understanding of electrotactile feedback and are valuable for further developments of wearable EFS to compensate for sensory impairment and improve activities of daily life for people with sensation loss in their feet