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.
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.
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 ...
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.
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.
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)
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.
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.
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.
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.
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.
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.
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 ...
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.
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.
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)
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.
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.
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.
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.
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Papers by Giancarlo Canavese