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Capillary and surface effects at the interface between two media enhance adhesion in wet environments. This phenomenon, called wet adhesion, is exploited in nature by some insects and amphibians to stand or walk over wet substrates. Since surface effects are generally voltage-sensitive, as demonstrated, for example, by electrowetting phenomena, one may expect that the strength of wet adhesion could be adjusted by using electric means. Indeed, in this paper, we show that the liquid-mediated adhesion between a flat and a grooved surface, the latter equipped with interdigitated electrodes deposited beneath it, can be reduced by more than 80 %, when a 90 V DC voltage is applied. The described technique points out the possibility of realizing surfaces with tunable adhesive properties, when in contact with wet substrates, which may be useful for several applications, including the development of propulsion systems for autonomous endoscopic robots and the fabrication of microgrippers for the manipulation of small objects.

Invasive interfaces with the Peripheral Nervous System (PNS), which currently rely on electric means for both nerves stimulation and signals recording, are needed in a number of applications, including prosthetics and assistive technologies. Recent studies showed that the quality of the signal-to-noise ratio of the afferent channel might be negatively affected by physiological reactions, including fibrosis. In this paper we propose a novel approach to the development of implantable neural interfaces, where the PNS is excited electromagnetically and in situ, while electrical means are used only for neural signals recording. Electromagnetic (EM) waves, capable of overcoming fibrotic capsules, are generated by microfabricated coils. Stimulation coils and registration electrodes are deposited on the same flexible substrate, also provided with a bio-absorbable coating, which releases anti-fibrotic drugs and neurons-specific functionalized magnetic nanoparticles (NPs). The NPs are intended to improve the capability of local EM waves to elicit membranes depolarization, thus enhancing selectivity. This paper details the concept of the proposed technology and provides a preliminary in silico feasibility study.

Slip sensing is important in robotic dexterous manipulation and in advanced upper limb prosthetics because it provides useful information for conveniently adapting manipulation forces. In this paper the physical phenomena involved in slip occurrence are briefly examined, as well as the physiological bases of the human “sense of slip.” Transduction principles and technological approaches, exploited over the years for reproducing the “artificial sense of slip,” are analyzed, with the final aim of identifying the most relevant open issues, as well as research trends.

Fiber Bragg Grating (FBG) technology is very attractive to develop sensors for the measurement of thermal and mechanical parameters in biological applications, particularly in presence of electromagnetic interferences. This work presents the design, working principle and experimental characterization of a force sensor based on two FBGs, with the feature of being compatible with Magnetic Resonance. Two prototypes based on different designs are considered and characterized: 1) the fiber with the FBGs is encapsulated in a polydimethylsiloxane (PDMS) sheet; 2) the fiber with the FBGs is free without the employment of any polymeric layer. Results show that the prototype which adopts the polymeric sheet has a wider range of measurement (4200 mN vs 250 mN) and good linearity; although it has lower sensitivity (≈0.1 nm-N1 vs 7 nm-N1). The sensor without polymeric layer is also characterized by employing a differential configuration which allows neglecting the influence of temperature. This solution improves the linearity of the sensor, on the other hand the sensitivity decreases. The resulting good metrological properties of the prototypes here tested make them attractive for the intended application and in general for force measurement during biomedical applications in presence of electromagnetic interferences. © 2014 IEEE.

Fiber optic-based mechanical sensors, thanks to their reduced sensitivity to external electromagnetic fields, are promising in the development of biomechatronic systems able to work in demanding environments, such as MRI chambers. In this chapter we report on the working principle, design, and experimental characterization of a micro-opto-mechanical displacement sensor, which exploits the light modulation induced by the relative displacement of two overlapped micro-fabricated gratings. The gratings are obtained by photo patterning a Pt layer (45 nm thick), sputtered on a Pyrex substrate, into an array of stripes, 150 μm wide and with a 525 μm period. The calibration was carried out up to 525 μm displacement. The sensor showed high and constant sensitivity in the ranges from 30 to 140 μm and from 360 to 490 μm. The experimental data, together with the known advantages of fiber optic-based sensors, encourage further studies for the development of sensors exploiting the proposed measurement principle.

A micro opto-mechanical displacement sensor is here presented. It is constituted by a sensing element based on two overlapped micro-diffraction gratings (MDGs). They present a platinum layer (45 nm of thick) on a glass substrate, a period of 525 μm constituted by a width of 150 μm of platinum separated (71.4% duty cycle). The working principle is based on the modulation of light intensity induced by the relative displacement between the MDGs: when a laser light perpendicularly hits the MDGs, the intensity of the transmitted light is a periodic function of the relative displacement between the two MDGs. A fiber optic is used to transport the transmitted light to a photodetector in order to avoid concerns related to the alignment between the optical components. The sensor's output is the ratio between the light intensity measured by the photodetector during the displacement of the MDGs and largest light intensity values measured in the whole range of measurement, therefore, it is lower than 1. The proposed sensor allows to discriminate displacement lower than 10 μm, using a cost effective micro-fabrication process implemented by the technique of Lift-Off. It shows a good linear behaviour in two ranges covering about one half of the MDGs period. Within the linear ranges it shows high sensitivity (about 0.5%/μm) and good accuracy (lower than 4 % in the whole range of calibration); furthermore, the results show that a design with a duty cycle of 50 % overcomes the marked decrease of sensitivity in a range of measurement corresponding to a grating period.

Tactile sensors are needed for effectively controlling the interaction between a robotic hand and the environment, e.g., during manipulation of objects, or for the tactile exploration of unstructured environments, especially when other sensing modalities, such as vision or audition, become ineffective. In the case of hand prostheses, mainly intended for dexterous manipulation of daily living objects, the possibility of quickly detecting slip occurrence, thus avoiding inadvertent falling of the objects, is prodromal to any manipulation task. In this paper we report on a slip sensor with no-moving parts, based on thermo-electrical phenomena, fabricated on a flexible substrate and suitable for integration on curved surfaces, such as robotic finger pads. Experiments performed using a custom made test bench, which is capable of generating controlled slip velocities, show that the sensor detects slip events in less than 50 ms. This response time is short enough for enabling future applications in the field of hand prosthetics.

Slip sensors are useful in robotics and prosthetics to improve the precision of force control during manipulation tasks. This work describes the design and fabrication of a flexible slip microsensor with no-moving parts, based on thermo-electrical phenomena. The sensor has been tested on a purposively developed test bench capable of producing a repeatable and controllable slip velocity. Experimental results are reported, demonstrating microsensor capability of discriminating slip events. The flexibility of the sensor makes it suitable for its integration on curved or deformable surfaces, such as robotic finger pads.

Fully implantable Cochlear Implants (CIs) would represent a tremendous advancement in terms of quality of life, comfort and cosmetics, for patients with profound sensorineural deafness. One of the main challenges involved in the development of such implants consists of finding a power supply means which does not require recharging. To this aim an inertial Energy Harvester (EH), exploiting the kinetic energy produced by vertical movements of the head during walking, has been investigated. Compared to existing devices, the EH needs to exploit very low frequency vibrations (

During manipulation tasks it is important to maintain a precise and safe control of the grasping force. Slip detection plays a key role to assure an adequate adaptation of the grasping force, without object damaging. Several approaches to slip detection are currently under investigation. In particular, thermal slip sensors use a detection strategy similar to the one employed in hot wire anemometry, using a microfabricated thermal probe for detecting the convective heat flux associated to the movement of the touched object. This paper reports on the model-based optimization of a thermal slip sensor, intended for robotic prosthesis. In particular, an analytical thermal model has been developed, by merging FEM and dimensional analysis. A sensitivity analysis, performed on the parameters appearing in the model, has been performed for optimizing both sensor's geometry and materials in order to increase the heat flux and thereby to obtain a reduction of response times in the identification of slip. Simulations on the proposed design indicate an expected increase of the thermal dissipated power of about 400%.

This paper describes an intensity-modulated fiber optic sensor for strain measurements. The sensing element is a polydimetilsiloxane (PDMS) micro-diffraction grating, 15 mm long, 2 mm thick, with channels 150 µm wide, spaced apart 200 µm. The working principle of the sensor can be summarized as follows: when the sensing element is strained perpendicularly to the grating plane, light passing through the grating undergoes a modulation caused by the phenomenon of diffraction. Since the grating is interposed between a laser source and a fiber optic, the coupled radiation intensity between these two optical elements can be considered as an indirect measure of strain. A static calibration of the measuring system has been performed, showing that the device, with measuring range of about 0.04, is capable to discriminate strain of 0.005 and it presents a sensitivity increase with strain in the whole range of measurements.