Giancarlo Canavese - Academia.edu (original) (raw)

Papers by Giancarlo Canavese

Journal of Physics D: Applied Physics, 2014

ABSTRACT The piezoresistive behaviour based on the quantum tunnelling conduction of a copper–poly... more ABSTRACT The piezoresistive behaviour based on the quantum tunnelling conduction of a copper–polydimethylsiloxane composite was studied by means of impedance spectroscopy and confirmed by the fitting with the tunnelling piezoresistance mathematical model. This investigation paves the way to the implementation of the impedance spectroscopy technique in the characterization of piezoresistive pressure sensors for robotic application.

Journal of Applied Polymer Science, 2014

ABSTRACT Among the wide variety of piezoelectric materials available, polymers offer an interesti... more ABSTRACT Among the wide variety of piezoelectric materials available, polymers offer an interesting solution because of their high mechanical flexibility, easy processing, and conformable features; they maintain good ferroelectric and piezoelectric properties. The most prominent examples of these are poly(vinylidene fluoride) (PVDF) and its copolymer, poly(vinylidene difluoride–trifluoroethylene) [P(VDF–TrFE)]. An attractive prospective consists of the preparation of nanostructured polymers. It has been shown that the dimensional confinement of such macromolecules down to the nanoscale can improve their piezoelectric properties because the tailoring of the chemical structure is performed at the molecular level. In this review, we show how nanostructured polymers can be obtained and discuss reports on the ferroelectric and piezoelectric properties of nanostructured PVDF and P(VDF–TrFE) materials. In particular, we show how dimensional confinement leads to piezoelectric nanostructures with relevant performances, with a focus on the macromolecular structural arrangement that enhances their behavior. Experimental results and applications are also reported to compare the performances of different nanostructuration processes and the polymer efficiencies as piezoelectric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41667.

Applied Mechanics and Materials, 2011

This work presents a comprehensive investigation of the piezoresistive response of a metal-polyme... more This work presents a comprehensive investigation of the piezoresistive response of a metal-polymer composite for robotic tactile sensor application. Composite samples, based on nickel nanostructured conductive filler in a polydimetihylsiloxane (PDMS) insulating elastomeric matrix, were prepared changing several process parameters like thickness, composition of the polymer and nickel filler content. A variation of electric resistance up to nine orders of magnitude under applied uniaxial load was measured in the fabricated samples. Cost efficient materials, simplicity of the process, large sensibility, and harsh environment compatibility make this quantum tunnelling composite adapted to be integrated as sensing coating in space robotic applications.

European Journal of Inorganic Chemistry, 2014

ABSTRACT Silver particles with spiky nanostructured morphologies have been obtained by two differ... more ABSTRACT Silver particles with spiky nanostructured morphologies have been obtained by two different wet-synthesis approaches. A detailed investigation was carried out into the synthesis parameters to tune the shape of the sample into desert-rose- and succulent-like particles. The first synthetic route was based on the reduction of silver nitrate by iron sulfate in the presence of maleic acid as anisotropic agent, whereas in the second method ascorbic acid was used as the reducing agent and citric acid as the anisotropic agent. A nucleation model is proposed to explain the growth mechanism and the effect of each parameter on the particle morphology. These Ag nanostructured spiky particles have been used as conductive fillers in polymeric piezoresistive composites, the working principle of which is based on the tunneling conduction mechanism. Composite samples were thus prepared and characterized, demonstrating the enhancing effect of the sharp protrusions on the tunneling phenomena upon a mechanical compressive strain.

The micro-and nano-technologies coupled with a deep knowledge of organic/inorganic interfaces gua... more The micro-and nano-technologies coupled with a deep knowledge of organic/inorganic interfaces guarantee an exceptional sensitivity and specificity of the sensor, while the lab-on-a-chip platform reduces assay times and limits sampling and/or sample preparation, providing compact and portable objects. Therefore, the development of innovative biosensors such as antibody-immobilized microcantilevers can overcome the evident limits of nowadays technologies, such as time consuming, expensiveness, difficult automation, low sensitivity, accuracy, and precision for quantitative methods. The present study proposes two device designs for the detection of food pathogens, exploiting an antibody-immobilized microcantilever biosensors, a novel class of mass detectors. For the first one, we integrated the mechanical sensors on a microfluidic platform (lab-on-a-chip) to perform online analysis, directly in liquid environment. We showed that our portable biosensors could easily detect the presence of pathogenic bacteria such as Salmonella enterica serotype enteritidis in concentration 10 5 cfu/mL in just 40 min, without any enrichment and/or sample preparation. To increase the mass sensitivity of our analysis, we also fabricated microstructures optimized for vibrating in vacuum environment. Using a dip-and-dry technique, we showed that, in such configuration, the experimental limit of detection is as low as 10 3 cfu/mL. Due to the extremely small volumes needed, our biosensors operating in vacuum have the potentiality of detecting the presence or absence of a single cell.

Journal of Petroleum Science and Engineering, 2015

Pipeline pigging for in-line inspection is a fundamental practice in the oil and gas industry. Ye... more Pipeline pigging for in-line inspection is a fundamental practice in the oil and gas industry. Yet, the socalled "smart pigs" used for this purpose are expensive and delicate and the risk related to their possible blocking inside the pipeline is non-negligible, hence their deployment is rather infrequent (generally, just once in several years). In this paper, we present a new, low-cost and low-risk foam pig with inspection capabilities similar to those of a multi-channel caliper pig (i.e. able to detect, locate and size inner diameter changes and deformations) together with additional features that allow to detect internal roughness changes (e.g. due to corrosion) and perform some pH/salinity determinations, also useful for corrosion assessment purposes. One implementation of the new tool makes use of a foam pig "carrier", providing the required push with a good capability to surpass restrictions, equipped with specialized sensors and modules for data acquisition and storage. Another implementation, called "skeleton caliper pig" and suitable to prevent the massive displacement of condensates from gas lines, deploys the light plastic system without any foam pig carrier, pushed by the gas velocity alone. In the paper we will discuss the design, construction and field testing of this new low-risk inspection pig.

2013 IEEE SENSORS, 2013

ABSTRACT The feedback of the foot plantar pressure is important in gait and posture application f... more ABSTRACT The feedback of the foot plantar pressure is important in gait and posture application for diagnosing lower limb problems, injury prevention and motor relearning therapy as well as for footwear design and sport biomechanics. Tracking the pressure that acts between the foot and the support surface during everyday locomotor activities is clinically imperative to evaluate the foot function and in particular to assist patients with musculoskeletal and neurological diseases in the development of normal gait functionality. Here a flexible piezoresistive insole with dedicated electronics was developed to measure both the pressure distribution under 64 nodes arranged in the main plantar regions and the mean plantar pressure during walking activity with a sampling frequency of 20 Hz. This study reports on the easy and cost effective approach used to fabricate the conformable insole based on a piezoresistive material composed by copper spiky microparticles dispersed into silicon rubber. The entire insole was prepared in a single step by casting technique, and then completed with a patterned metalized polyimide films as bottom and top electrodes. The insole was then connected to a dedicated electronics to register the dynamic resistance variation under the plantar pressure. A connected personal computer was used for data analysis and visualization through a developed pressure imaging 3D software. The confidence on the obtained data allows the use of such piezoresisitve insole as a therapeutic or rehabilitative tool.

ABSTRACT Microbial Fuel Cells (MFCs) are energy sources which generate electrical charge thanks t... more ABSTRACT Microbial Fuel Cells (MFCs) are energy sources which generate electrical charge thanks to bacteria metabolism. Although functionally similar to chemical fuel cells (both including reactants and two electrodes, and anode and cathode), they have substantial ...

Key Engineering Materials, 2014

ABSTRACT The feedback in the motor relearning therapy is essential and helpful for hemiplegic pat... more ABSTRACT The feedback in the motor relearning therapy is essential and helpful for hemiplegic patient training. Tracking plantar pressure is clinically imperative to evaluate the foot function and in particular to assist patients with musculoskeletal and neurological diseases in the development of normal gait functionality. A flexible piezoresistive insole with dedicated electronics was developed to measure both the pressure distribution under 64 nodes arranged in the main plantar regions and the mean plantar pressure during walking activity with a sampling frequency of 20 Hz. This study reports on the easy and cost effective approach used to fabricate the flexible insole based on a piezoresistive material composed by copper spiky microparticles dispersed into silicon rubber. The entire insole was fabricated by single step casting technique, and then completed with a patterned metalized polyimide films as bottom electrode, while the top electrode was directly sputtered on the sample.

2013 IEEE SENSORS, 2013

ABSTRACT We have prepared a novel pH sensor consisting in single ZnO micro-wire (MW) aligned on g... more ABSTRACT We have prepared a novel pH sensor consisting in single ZnO micro-wire (MW) aligned on gold-electrode array prepared by electromigrating eight parallel gold wires on silicon wafer with a custom electronic system, leading to nano-sized gap. We also anchored to the ZnO MW surface organic functional molecules rich of amine (-NH2) groups, thus ZnO-NH The MWs were then deposited from solution and oreinted through dielectrophoresis, resulting in eight single MWs aligned across the electromigrated gold electrodes. Therefore each single silicon chip is composed by eight separated pH sensors. We measured the I-V characteristic and secondly the ZnO MW Field Effect Transistor (MW-FET) to evaluate the sensitivity of both amine-functionalized and unfunctionalized ZnO-gold junctions upon a pH variation to both acidic and basic values of the solution environmentWe show the superiority in pH response of the ZnO-NH junctions, with an increase of one order of magnitude of the current during the pH reduction, with respect to the bare ZnO ones. In particular a strong sensitivity enhancement was measured by MW-FET with respect to conventional I-V characteristics.

Smart Materials and Structures, 2013

ABSTRACT A highly mechanically flexible tactile device based on a metal–elastomer composite mater... more ABSTRACT A highly mechanically flexible tactile device based on a metal–elastomer composite material was prepared by an efficient and simple process. The microcasting fabrication technique, used for the preparation of a selfstanding sheet of functional material, gives the possibility of easily fabricating complex-shaped structures suitable for integration on robot surfaces for tactile sensing applications. Under the action of a compressive stress the composite material exhibits a giant piezoresistive effect, varying its electrical resistance by several orders of magnitude. This phenomenon can be tuned by changing the material composition parameters, which directly modify the sensitivity of the sensor. After a comprehensive characterization of the functional properties of the material, an 8 × 8 pressure sensor matrix with dedicated electronics was fabricated and tested. (Some figures may appear in colour only in the online journal)

Sensors and Actuators A: Physical, 2012

ABSTRACT A high flexible and easy conformable piezoresistive composite material was used and test... more ABSTRACT A high flexible and easy conformable piezoresistive composite material was used and tested to fit in complex-shaped structures and to be suitably integrated onto the robot surface for tactile sensing. In order to obtain the functional material in the form of self standing multilayer thin samples, two process flows based on microcasting and hot embossing techniques were optimized. The influence of different composition parameters on the functional performances was investigated and a huge variation of the electrical resistance, up to nine orders of magnitude, was registered when a mechanical pressure was applied to the prepared samples.

Sensors, 2014

The large expansion of the robotic field in the last decades has created a growing interest in th... more The large expansion of the robotic field in the last decades has created a growing interest in the research and development of tactile sensing solutions for robot hand and body integration. Piezoresistive composites are one of the most widely employed materials for this purpose, combining simple and low cost preparation with high flexibility and conformability to surfaces, low power consumption, and the use of simple read-out electronics. This work provides a review on the different type of composite materials, classified according to the conduction mechanism and analyzing the physics behind it. In particular piezoresistors, strain gauges, percolative and quantum tunnelling devices are reviewed here, with a perspective overview on the most used filler types and polymeric matrices. A description of the state-of-the-art of the tactile sensor solutions from the point of view of the architecture, the design and the performance is also reviewed, with a perspective outlook on the main promising applications.

Procedia Engineering, 2012

ABSTRACT A low cost and highly mechanically flexible 8x8 pressure matrix sensor with dedicated el... more ABSTRACT A low cost and highly mechanically flexible 8x8 pressure matrix sensor with dedicated electronics has been fabricated with an innovative metal-elastomer composite material. Under the action of a compressive stress the material exhibits a giant piezoresistive effect varying its electrical resistance of several orders of magnitude. This phenomenon can be tuned by changing the material composition parameters, directly modifying the sensitivity of the sensor. The micro casting fabrication technique, used for the preparation of self standing sheet of functional material, gives the possibility of easily fabricating complex-shaped structure suitable for integration on robot surface for tactile sensing. The sensor has been tested with a customized electronic circuit after an exhaustive characterization of the functional properties of the material.

A new cost-effective setup for silicon bulk micromachining is presented which makes use of a poly... more A new cost-effective setup for silicon bulk micromachining is presented which makes use of a polymeric protective coating, ProTEK R B2 coating, instead of a conventional hardmask. Different concentrations of KOH and bath conditions (pure, with surfactant, with stirrer, with both surfactant and stirrer) have been considered. ProTEK R B2 coating exhibits good adhesion to Si substrates, no degradation, etching rates and surface roughness comparable to literature data, and etching times greater than 180 min without damaging front side microstructures. Microcantilevers have also been fabricated using two different process flows in order to demonstrate the suitability of such a protective coating in microelectromechanical system (MEMS) technology.

Journal of Materials Science, 2013

This paper deals with the preparation and characterization of nanocomposite (NC) materials, compa... more This paper deals with the preparation and characterization of nanocomposite (NC) materials, comparing different technologies for sample fabrication, in view of their possible application as piezoelectric sensors. Those NCs consist on BaTiO 3 nanoparticles embedded into a polyvinylidene fluoride matrix, where both the ceramic and the polymeric phases could exhibit ferroelectricity. In particular, we compare the properties of samples prepared through three different methods, i.e., solvent casting, enabling a fast realization, spin-coating, which allows to realize thin flexible films particularly interesting for large area sensors, and hot embossing, which is exploited to modify the residual porosity in the thick films. The influence of the fabrication techniques on the physical and chemical properties is investigated. Different electrode materials have been tested and compared, ranging from sputtered Pt to an engineered thermally evaporated Ti/Au bilayer. Leakage current, polarization, displacement curves, and piezoelectric coefficient d 33 are evaluated by small signal indirect measurements, comparing the properties of different materials and understanding how processing technologies influence the sensor performances by acting on the functional materials.

IEEE Sensors Journal, 2000

The effect of micro and nanostructuration on the piezoelectric properties of polymeric samples wa... more The effect of micro and nanostructuration on the piezoelectric properties of polymeric samples was studied in the present work. We prepared micro-sized pillars and nano-wires (thus one-dimensional structures) of a piezoelectric polymer Poly(VinyliDene Fluoride-Tri FluoroEthylene) PVDF-TrFE and we compared their structural and piezoelectrical properties with a thin film (thus two-dimensional) of the same material. X-ray diffraction and infrared spectroscopy measurements showed that the crystallization of the polymer into the ferroelectric β-phase is affected by the size of the confinement. The piezoelectric characterization of the three polymeric structures showed important improvements as far as the nanostructuration is reached. Application as tactile sensor devices is therefore under development.

Chemistry - A European Journal, 2013

Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain de... more Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain dense arrays of vertically oriented nanostructures with high aspect ratio. Herein we present a systematic study of the different synthesis parameters that influence the ZnO seed layer and thus the resulting morphological features of the free-standing vertically oriented ZnO nanowires. We obtained a homogeneous coverage of transparent conductive substrates with high-aspect-ratio nanowire arrays (length/diameter ratio of up to 52). Such nanostructured vertical arrays were examined to assess their electric and piezoelectric properties, and showed an electric charge generation upon mechanical compressive stress. The principle of energy harvesting with these nanostructured ZnO arrays was demonstrated by connecting them to an electronic charge amplifier and storing the generated charge in a series of capacitors. We found that the generated charge and the electrical behavior of the ZnO nanowires are strictly dependent on the nanowire length. We have shown the importance of controlling the morphological properties of such ZnO nanostructures for optimizing a nanogenerator device.

Carbon, 2009

A simple and low cost method based on slurry coating was used to produce silicon carbide, titaniu... more A simple and low cost method based on slurry coating was used to produce silicon carbide, titanium carbide and glass-ceramic coatings on low density carbon/carbon composites in order to improve their erosion resistance. Microstructural analyses were performed for substrate and coatings by optical microscopy, and scanning and transmission electron microscopy. As-received and coated composites were submitted to erosion tests using a sandblasting machine according to ASTM G76-95. The best results were obtained with a silica-alumina-yttria based glass-ceramic coating.

Biosensors and Bioelectronics, 2010

Microcantilever based oscillators have shown the possibility of highly sensitive label-free detec... more Microcantilever based oscillators have shown the possibility of highly sensitive label-free detection by allowing the transduction of a target mass into a resonant frequency shift. Most of such measurements were performed in air or vacuum environment, since immersion in liquid dramatically deteriorates the mechanical response of the sensor. Besides, the integration of microcantilever detection in a microfluidic platform appears a highly performing technological solution to exploit real time monitoring of biomolecular interactions, while limiting sample handling and promoting portability and automation of routine diagnostic tests (Point-Of-Care devices). In the present paper, we report on the realization and optimization of a microcantilever-based Lab-on-Chip, showing that microplates rather than microbeams exhibit largest mass sensitivity in liquid, while pirex rather than polymers represents the best choice for microfluidic channels. Maximum Q factor achieved was 140 (for fifth resonance mode of Pirex prototype), as our knowledge the highest value reported in literature for cantilever biosensors resonating in liquid environment without electronic feedback. Then, we proved the successfully detection of Angiopoietin-1 (a putative marker in tumor progression), showing that the related frequency shifts coming from non-specific interactions (negative controls) are roughly one order of magnitude lower than typical variations due to specific protein binding. Furthermore, we monitored the formation of antibody-antigen complex on MC surface in real-time. The proposed tool could be extremely useful for the comprehension of complex biological systems such as angiogenic machinery and cancer progression.

Journal of Physics D: Applied Physics, 2014

ABSTRACT The piezoresistive behaviour based on the quantum tunnelling conduction of a copper–poly... more ABSTRACT The piezoresistive behaviour based on the quantum tunnelling conduction of a copper–polydimethylsiloxane composite was studied by means of impedance spectroscopy and confirmed by the fitting with the tunnelling piezoresistance mathematical model. This investigation paves the way to the implementation of the impedance spectroscopy technique in the characterization of piezoresistive pressure sensors for robotic application.

Journal of Applied Polymer Science, 2014

ABSTRACT Among the wide variety of piezoelectric materials available, polymers offer an interesti... more ABSTRACT Among the wide variety of piezoelectric materials available, polymers offer an interesting solution because of their high mechanical flexibility, easy processing, and conformable features; they maintain good ferroelectric and piezoelectric properties. The most prominent examples of these are poly(vinylidene fluoride) (PVDF) and its copolymer, poly(vinylidene difluoride–trifluoroethylene) [P(VDF–TrFE)]. An attractive prospective consists of the preparation of nanostructured polymers. It has been shown that the dimensional confinement of such macromolecules down to the nanoscale can improve their piezoelectric properties because the tailoring of the chemical structure is performed at the molecular level. In this review, we show how nanostructured polymers can be obtained and discuss reports on the ferroelectric and piezoelectric properties of nanostructured PVDF and P(VDF–TrFE) materials. In particular, we show how dimensional confinement leads to piezoelectric nanostructures with relevant performances, with a focus on the macromolecular structural arrangement that enhances their behavior. Experimental results and applications are also reported to compare the performances of different nanostructuration processes and the polymer efficiencies as piezoelectric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41667.

Applied Mechanics and Materials, 2011

This work presents a comprehensive investigation of the piezoresistive response of a metal-polyme... more This work presents a comprehensive investigation of the piezoresistive response of a metal-polymer composite for robotic tactile sensor application. Composite samples, based on nickel nanostructured conductive filler in a polydimetihylsiloxane (PDMS) insulating elastomeric matrix, were prepared changing several process parameters like thickness, composition of the polymer and nickel filler content. A variation of electric resistance up to nine orders of magnitude under applied uniaxial load was measured in the fabricated samples. Cost efficient materials, simplicity of the process, large sensibility, and harsh environment compatibility make this quantum tunnelling composite adapted to be integrated as sensing coating in space robotic applications.

European Journal of Inorganic Chemistry, 2014

ABSTRACT Silver particles with spiky nanostructured morphologies have been obtained by two differ... more ABSTRACT Silver particles with spiky nanostructured morphologies have been obtained by two different wet-synthesis approaches. A detailed investigation was carried out into the synthesis parameters to tune the shape of the sample into desert-rose- and succulent-like particles. The first synthetic route was based on the reduction of silver nitrate by iron sulfate in the presence of maleic acid as anisotropic agent, whereas in the second method ascorbic acid was used as the reducing agent and citric acid as the anisotropic agent. A nucleation model is proposed to explain the growth mechanism and the effect of each parameter on the particle morphology. These Ag nanostructured spiky particles have been used as conductive fillers in polymeric piezoresistive composites, the working principle of which is based on the tunneling conduction mechanism. Composite samples were thus prepared and characterized, demonstrating the enhancing effect of the sharp protrusions on the tunneling phenomena upon a mechanical compressive strain.

The micro-and nano-technologies coupled with a deep knowledge of organic/inorganic interfaces gua... more The micro-and nano-technologies coupled with a deep knowledge of organic/inorganic interfaces guarantee an exceptional sensitivity and specificity of the sensor, while the lab-on-a-chip platform reduces assay times and limits sampling and/or sample preparation, providing compact and portable objects. Therefore, the development of innovative biosensors such as antibody-immobilized microcantilevers can overcome the evident limits of nowadays technologies, such as time consuming, expensiveness, difficult automation, low sensitivity, accuracy, and precision for quantitative methods. The present study proposes two device designs for the detection of food pathogens, exploiting an antibody-immobilized microcantilever biosensors, a novel class of mass detectors. For the first one, we integrated the mechanical sensors on a microfluidic platform (lab-on-a-chip) to perform online analysis, directly in liquid environment. We showed that our portable biosensors could easily detect the presence of pathogenic bacteria such as Salmonella enterica serotype enteritidis in concentration 10 5 cfu/mL in just 40 min, without any enrichment and/or sample preparation. To increase the mass sensitivity of our analysis, we also fabricated microstructures optimized for vibrating in vacuum environment. Using a dip-and-dry technique, we showed that, in such configuration, the experimental limit of detection is as low as 10 3 cfu/mL. Due to the extremely small volumes needed, our biosensors operating in vacuum have the potentiality of detecting the presence or absence of a single cell.

Journal of Petroleum Science and Engineering, 2015

Pipeline pigging for in-line inspection is a fundamental practice in the oil and gas industry. Ye... more Pipeline pigging for in-line inspection is a fundamental practice in the oil and gas industry. Yet, the socalled "smart pigs" used for this purpose are expensive and delicate and the risk related to their possible blocking inside the pipeline is non-negligible, hence their deployment is rather infrequent (generally, just once in several years). In this paper, we present a new, low-cost and low-risk foam pig with inspection capabilities similar to those of a multi-channel caliper pig (i.e. able to detect, locate and size inner diameter changes and deformations) together with additional features that allow to detect internal roughness changes (e.g. due to corrosion) and perform some pH/salinity determinations, also useful for corrosion assessment purposes. One implementation of the new tool makes use of a foam pig "carrier", providing the required push with a good capability to surpass restrictions, equipped with specialized sensors and modules for data acquisition and storage. Another implementation, called "skeleton caliper pig" and suitable to prevent the massive displacement of condensates from gas lines, deploys the light plastic system without any foam pig carrier, pushed by the gas velocity alone. In the paper we will discuss the design, construction and field testing of this new low-risk inspection pig.

2013 IEEE SENSORS, 2013

ABSTRACT The feedback of the foot plantar pressure is important in gait and posture application f... more ABSTRACT The feedback of the foot plantar pressure is important in gait and posture application for diagnosing lower limb problems, injury prevention and motor relearning therapy as well as for footwear design and sport biomechanics. Tracking the pressure that acts between the foot and the support surface during everyday locomotor activities is clinically imperative to evaluate the foot function and in particular to assist patients with musculoskeletal and neurological diseases in the development of normal gait functionality. Here a flexible piezoresistive insole with dedicated electronics was developed to measure both the pressure distribution under 64 nodes arranged in the main plantar regions and the mean plantar pressure during walking activity with a sampling frequency of 20 Hz. This study reports on the easy and cost effective approach used to fabricate the conformable insole based on a piezoresistive material composed by copper spiky microparticles dispersed into silicon rubber. The entire insole was prepared in a single step by casting technique, and then completed with a patterned metalized polyimide films as bottom and top electrodes. The insole was then connected to a dedicated electronics to register the dynamic resistance variation under the plantar pressure. A connected personal computer was used for data analysis and visualization through a developed pressure imaging 3D software. The confidence on the obtained data allows the use of such piezoresisitve insole as a therapeutic or rehabilitative tool.

ABSTRACT Microbial Fuel Cells (MFCs) are energy sources which generate electrical charge thanks t... more ABSTRACT Microbial Fuel Cells (MFCs) are energy sources which generate electrical charge thanks to bacteria metabolism. Although functionally similar to chemical fuel cells (both including reactants and two electrodes, and anode and cathode), they have substantial ...

Key Engineering Materials, 2014

ABSTRACT The feedback in the motor relearning therapy is essential and helpful for hemiplegic pat... more ABSTRACT The feedback in the motor relearning therapy is essential and helpful for hemiplegic patient training. Tracking plantar pressure is clinically imperative to evaluate the foot function and in particular to assist patients with musculoskeletal and neurological diseases in the development of normal gait functionality. A flexible piezoresistive insole with dedicated electronics was developed to measure both the pressure distribution under 64 nodes arranged in the main plantar regions and the mean plantar pressure during walking activity with a sampling frequency of 20 Hz. This study reports on the easy and cost effective approach used to fabricate the flexible insole based on a piezoresistive material composed by copper spiky microparticles dispersed into silicon rubber. The entire insole was fabricated by single step casting technique, and then completed with a patterned metalized polyimide films as bottom electrode, while the top electrode was directly sputtered on the sample.

2013 IEEE SENSORS, 2013

ABSTRACT We have prepared a novel pH sensor consisting in single ZnO micro-wire (MW) aligned on g... more ABSTRACT We have prepared a novel pH sensor consisting in single ZnO micro-wire (MW) aligned on gold-electrode array prepared by electromigrating eight parallel gold wires on silicon wafer with a custom electronic system, leading to nano-sized gap. We also anchored to the ZnO MW surface organic functional molecules rich of amine (-NH2) groups, thus ZnO-NH The MWs were then deposited from solution and oreinted through dielectrophoresis, resulting in eight single MWs aligned across the electromigrated gold electrodes. Therefore each single silicon chip is composed by eight separated pH sensors. We measured the I-V characteristic and secondly the ZnO MW Field Effect Transistor (MW-FET) to evaluate the sensitivity of both amine-functionalized and unfunctionalized ZnO-gold junctions upon a pH variation to both acidic and basic values of the solution environmentWe show the superiority in pH response of the ZnO-NH junctions, with an increase of one order of magnitude of the current during the pH reduction, with respect to the bare ZnO ones. In particular a strong sensitivity enhancement was measured by MW-FET with respect to conventional I-V characteristics.

Smart Materials and Structures, 2013

ABSTRACT A highly mechanically flexible tactile device based on a metal–elastomer composite mater... more ABSTRACT A highly mechanically flexible tactile device based on a metal–elastomer composite material was prepared by an efficient and simple process. The microcasting fabrication technique, used for the preparation of a selfstanding sheet of functional material, gives the possibility of easily fabricating complex-shaped structures suitable for integration on robot surfaces for tactile sensing applications. Under the action of a compressive stress the composite material exhibits a giant piezoresistive effect, varying its electrical resistance by several orders of magnitude. This phenomenon can be tuned by changing the material composition parameters, which directly modify the sensitivity of the sensor. After a comprehensive characterization of the functional properties of the material, an 8 × 8 pressure sensor matrix with dedicated electronics was fabricated and tested. (Some figures may appear in colour only in the online journal)

Sensors and Actuators A: Physical, 2012

ABSTRACT A high flexible and easy conformable piezoresistive composite material was used and test... more ABSTRACT A high flexible and easy conformable piezoresistive composite material was used and tested to fit in complex-shaped structures and to be suitably integrated onto the robot surface for tactile sensing. In order to obtain the functional material in the form of self standing multilayer thin samples, two process flows based on microcasting and hot embossing techniques were optimized. The influence of different composition parameters on the functional performances was investigated and a huge variation of the electrical resistance, up to nine orders of magnitude, was registered when a mechanical pressure was applied to the prepared samples.

Sensors, 2014

The large expansion of the robotic field in the last decades has created a growing interest in th... more The large expansion of the robotic field in the last decades has created a growing interest in the research and development of tactile sensing solutions for robot hand and body integration. Piezoresistive composites are one of the most widely employed materials for this purpose, combining simple and low cost preparation with high flexibility and conformability to surfaces, low power consumption, and the use of simple read-out electronics. This work provides a review on the different type of composite materials, classified according to the conduction mechanism and analyzing the physics behind it. In particular piezoresistors, strain gauges, percolative and quantum tunnelling devices are reviewed here, with a perspective overview on the most used filler types and polymeric matrices. A description of the state-of-the-art of the tactile sensor solutions from the point of view of the architecture, the design and the performance is also reviewed, with a perspective outlook on the main promising applications.

Procedia Engineering, 2012

ABSTRACT A low cost and highly mechanically flexible 8x8 pressure matrix sensor with dedicated el... more ABSTRACT A low cost and highly mechanically flexible 8x8 pressure matrix sensor with dedicated electronics has been fabricated with an innovative metal-elastomer composite material. Under the action of a compressive stress the material exhibits a giant piezoresistive effect varying its electrical resistance of several orders of magnitude. This phenomenon can be tuned by changing the material composition parameters, directly modifying the sensitivity of the sensor. The micro casting fabrication technique, used for the preparation of self standing sheet of functional material, gives the possibility of easily fabricating complex-shaped structure suitable for integration on robot surface for tactile sensing. The sensor has been tested with a customized electronic circuit after an exhaustive characterization of the functional properties of the material.

A new cost-effective setup for silicon bulk micromachining is presented which makes use of a poly... more A new cost-effective setup for silicon bulk micromachining is presented which makes use of a polymeric protective coating, ProTEK R B2 coating, instead of a conventional hardmask. Different concentrations of KOH and bath conditions (pure, with surfactant, with stirrer, with both surfactant and stirrer) have been considered. ProTEK R B2 coating exhibits good adhesion to Si substrates, no degradation, etching rates and surface roughness comparable to literature data, and etching times greater than 180 min without damaging front side microstructures. Microcantilevers have also been fabricated using two different process flows in order to demonstrate the suitability of such a protective coating in microelectromechanical system (MEMS) technology.

Journal of Materials Science, 2013

This paper deals with the preparation and characterization of nanocomposite (NC) materials, compa... more This paper deals with the preparation and characterization of nanocomposite (NC) materials, comparing different technologies for sample fabrication, in view of their possible application as piezoelectric sensors. Those NCs consist on BaTiO 3 nanoparticles embedded into a polyvinylidene fluoride matrix, where both the ceramic and the polymeric phases could exhibit ferroelectricity. In particular, we compare the properties of samples prepared through three different methods, i.e., solvent casting, enabling a fast realization, spin-coating, which allows to realize thin flexible films particularly interesting for large area sensors, and hot embossing, which is exploited to modify the residual porosity in the thick films. The influence of the fabrication techniques on the physical and chemical properties is investigated. Different electrode materials have been tested and compared, ranging from sputtered Pt to an engineered thermally evaporated Ti/Au bilayer. Leakage current, polarization, displacement curves, and piezoelectric coefficient d 33 are evaluated by small signal indirect measurements, comparing the properties of different materials and understanding how processing technologies influence the sensor performances by acting on the functional materials.

IEEE Sensors Journal, 2000

The effect of micro and nanostructuration on the piezoelectric properties of polymeric samples wa... more The effect of micro and nanostructuration on the piezoelectric properties of polymeric samples was studied in the present work. We prepared micro-sized pillars and nano-wires (thus one-dimensional structures) of a piezoelectric polymer Poly(VinyliDene Fluoride-Tri FluoroEthylene) PVDF-TrFE and we compared their structural and piezoelectrical properties with a thin film (thus two-dimensional) of the same material. X-ray diffraction and infrared spectroscopy measurements showed that the crystallization of the polymer into the ferroelectric β-phase is affected by the size of the confinement. The piezoelectric characterization of the three polymeric structures showed important improvements as far as the nanostructuration is reached. Application as tactile sensor devices is therefore under development.

Chemistry - A European Journal, 2013

Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain de... more Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain dense arrays of vertically oriented nanostructures with high aspect ratio. Herein we present a systematic study of the different synthesis parameters that influence the ZnO seed layer and thus the resulting morphological features of the free-standing vertically oriented ZnO nanowires. We obtained a homogeneous coverage of transparent conductive substrates with high-aspect-ratio nanowire arrays (length/diameter ratio of up to 52). Such nanostructured vertical arrays were examined to assess their electric and piezoelectric properties, and showed an electric charge generation upon mechanical compressive stress. The principle of energy harvesting with these nanostructured ZnO arrays was demonstrated by connecting them to an electronic charge amplifier and storing the generated charge in a series of capacitors. We found that the generated charge and the electrical behavior of the ZnO nanowires are strictly dependent on the nanowire length. We have shown the importance of controlling the morphological properties of such ZnO nanostructures for optimizing a nanogenerator device.

Carbon, 2009

A simple and low cost method based on slurry coating was used to produce silicon carbide, titaniu... more A simple and low cost method based on slurry coating was used to produce silicon carbide, titanium carbide and glass-ceramic coatings on low density carbon/carbon composites in order to improve their erosion resistance. Microstructural analyses were performed for substrate and coatings by optical microscopy, and scanning and transmission electron microscopy. As-received and coated composites were submitted to erosion tests using a sandblasting machine according to ASTM G76-95. The best results were obtained with a silica-alumina-yttria based glass-ceramic coating.

Biosensors and Bioelectronics, 2010

Microcantilever based oscillators have shown the possibility of highly sensitive label-free detec... more Microcantilever based oscillators have shown the possibility of highly sensitive label-free detection by allowing the transduction of a target mass into a resonant frequency shift. Most of such measurements were performed in air or vacuum environment, since immersion in liquid dramatically deteriorates the mechanical response of the sensor. Besides, the integration of microcantilever detection in a microfluidic platform appears a highly performing technological solution to exploit real time monitoring of biomolecular interactions, while limiting sample handling and promoting portability and automation of routine diagnostic tests (Point-Of-Care devices). In the present paper, we report on the realization and optimization of a microcantilever-based Lab-on-Chip, showing that microplates rather than microbeams exhibit largest mass sensitivity in liquid, while pirex rather than polymers represents the best choice for microfluidic channels. Maximum Q factor achieved was 140 (for fifth resonance mode of Pirex prototype), as our knowledge the highest value reported in literature for cantilever biosensors resonating in liquid environment without electronic feedback. Then, we proved the successfully detection of Angiopoietin-1 (a putative marker in tumor progression), showing that the related frequency shifts coming from non-specific interactions (negative controls) are roughly one order of magnitude lower than typical variations due to specific protein binding. Furthermore, we monitored the formation of antibody-antigen complex on MC surface in real-time. The proposed tool could be extremely useful for the comprehension of complex biological systems such as angiogenic machinery and cancer progression.