Endoscopic Tactile Capsule for Non-Polypoid Colorectal Tumour Detection

An endoscopic tactile robotic capsule, embedding miniaturized MEMS force sensors, is presented. The capsule is conceived to provide automatic palpation of non-polypoid colorectal tumours during colonoscopy, since it is characterized by high degree of dysplasia, higher invasiveness and lower detection rates with respect to polyps. A first test was performed employing a silicone phantom that embedded inclusions with variable hardness and curvature. A hardness-based classification was implemented, demonstrating detection robustness to curvature variation. By comparing a set of supervised classification algorithms, a weighted 3-nearest neighbor classifier was selected. A bias force normalization model was introduced in order to make different acquisition sets consistent. Parameters of this model were chosen through a particle swarm optimization method. Additionally, an ex-vivo test was performed to assess the capsule detection performance when magnetically-driven along a colonic tissue. Lumps were identified as voltage peaks with a prominence depending on the total magnetic force applied to the capsule. Accuracy of 94 % in hardness classification was achieved, while a 100 % accuracy is obtained for the lump detection within a tolerance of 5 mm from the central path described by the capsule. In real application scenario, we foresee our device aiding physicians to detect tumorous tissues

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

A Biomimetic MEMS-based Tactile Sensor Array with Fingerprints integrated in a Robotic Fingertip for Artificial Roughness Encoding

This work shows the accomplishment of a full integration of a biomimetic 2 à 2 tactile array and related electronics in an artificial fingertip. The technological approach is based on merging 3D MEMS sensors and skin-like artificial materials that are moulded mimicking human epidermal ridges. Experimental results using a mechatronic tactile stimulator for indenting periodic gratings (spatial periodicity from 400 ¿m to 1900 ¿m) and sliding them at constant speeds (from 5 mm/s to 40 mm/s) under regulated normal contact forces (between 100 mN and 400 mN) show that the developed sensing technology is suitable for fine roughness encoding: a frequency shift of the principal spectral component arising from sensor outputs was observed coherently with the spatial periodicity of the used ridged stimuli and their sliding velocity. Such phenomenon is pointed out with fine gratings particularly when the stimulation is operated along the proximal-distal direction of the finger (i.e. with sliding motion of the ridges of the stimulus across the ridges of the packaging) showing a more marked frequency locked behavior if compared to the radial-ulnar stimulation (i.e. with sliding motion of the ridges of the grating along the ridges of the packaging)

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