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Tactile Sensors and Sensing

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (30 September 2017) | Viewed by 233298

Special Issue Editor

Prof. Dr. Maurizio Valle

E-Mail Website
Guest Editor
Department of Electrical, Electronic and Telecommunications Engineering, and Naval Architecture, University of Genova, Via Opera Pia 11A, I16145 Genova, Italy
Interests: biomedical circuits and systems; electronic/artificial sensitive skin; tactile sensing systems for prosthetics and robotics; neuromorphic touch sensors; electronic and microelectronic systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The skin is one of the main organs of the human body and as such it implements many different and relevant functions, e.g. protection of the inner body organs, detection of cutaneous stimuli, etc. In particular, the skin implements tactile sensing which is one of the main functions through which humans can safely interact with the environment and explore their surroundings. Tactile sensing is a complex task which must be accomplished in an effective way (e.g. real-time response, light weight, low power consumption, etc.) all over the body surface. Tactile sensors are basically distributed sensors which translate mechanical variables (e.g. pressure, strain), temperature, humidity and pain stimuli into electrical variables. Contact information is further processed and conveyed to the “brain” (human or artificial). Tactile arrays must be mechanically flexible (i.e. conformable to the object it is to be applied on) and stretchable, e.g., to support joint movements; therefore tactile information processing must be implemented in real time to enable fast responses. Due to its complexity, the development of artificial tactile sensing is a very challenging goal which involves complementary research areas. The numerous application domains include humanoids and industrial robotics, artificial prosthetics, biomedical instrumentation, cyber physical systems, to name a few.

Since the early 1980s, tactile sensing has been a fast evolving research field involving a strong interdisciplinary effort from researchers in different fields, namely electronics, mechanics, material science, measurement methods, system engineering, robotics and bioengineering, etc. Furthermore, over the last decade, the research community has also been addressing the topic with a holistic approach putting not only transducers development into the equation, but also system integration and engineering issues.

In spite of the remarkable progress in tactile sensing systems and technologies, their effectiveness in addressing certain specific applications still requires further development. Technological and systems issues still require investigation and a coordinated and dedicated effort in interdisciplinary fields. Open issues involve, e.g., whole body awareness (i.e., large area skin), conformability and stretchability, structured design methodology, maintenance, calibration, system integration, interpretation of tactile data, reliability, fault tolerance and robustness, scalability, effective use of materials, small size and low power consumption, etc.

This Special Issue aims to provide an overview of current studies and achievements on tactile sensing, paving the way to effective applications in real world.

Prof. Dr. Maurizio Valle
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Smart sensing materials
  • Novel tactile sensors
  • Flexible and conformable sensors and arrays
  • Electronic interface
  • Artificial and electronic skin
  • Tactile data processing and interpretation
  • System integration
  • Touch-based human–robot interaction
  • Tactile sensing in prosthetics
  • Tactile sensing in neurorehabilitation
  • Tactile and visual sensing integration
  • Tactile sensing in neuroengineering
  • Tactile sensing in consumer goods
  • Tactile sensing and arts

Published Papers (24 papers)

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19 pages, 2407 KiB  
Article
Active Prior Tactile Knowledge Transfer for Learning Tactual Properties of New Objects
by Di Feng, Mohsen Kaboli and Gordon Cheng
Sensors 2018, 18(2), 634; https://doi.org/10.3390/s18020634 - 21 Feb 2018
Cited by 22 | Viewed by 5104
Abstract
Reusing the tactile knowledge of some previously-explored objects (prior objects) helps us to easily recognize the tactual properties of new objects. In this paper, we enable a robotic arm equipped with multi-modal artificial skin, like humans, to actively transfer the prior tactile exploratory [...] Read more.
Reusing the tactile knowledge of some previously-explored objects (prior objects) helps us to easily recognize the tactual properties of new objects. In this paper, we enable a robotic arm equipped with multi-modal artificial skin, like humans, to actively transfer the prior tactile exploratory action experiences when it learns the detailed physical properties of new objects. These experiences, or prior tactile knowledge, are built by the feature observations that the robot perceives from multiple sensory modalities, when it applies the pressing, sliding, and static contact movements on objects with different action parameters. We call our method Active Prior Tactile Knowledge Transfer (APTKT), and systematically evaluated its performance by several experiments. Results show that the robot improved the discrimination accuracy by around 10 % when it used only one training sample with the feature observations of prior objects. By further incorporating the predictions from the observation models of prior objects as auxiliary features, our method improved the discrimination accuracy by over 20 % . The results also show that the proposed method is robust against transferring irrelevant prior tactile knowledge (negative knowledge transfer). Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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19 pages, 6085 KiB  
Article
Modeling Electronic Skin Response to Normal Distributed Force
by Lucia Seminara
Sensors 2018, 18(2), 459; https://doi.org/10.3390/s18020459 - 3 Feb 2018
Cited by 4 | Viewed by 4534
Abstract
The reference electronic skin is a sensor array based on PVDF (Polyvinylidene fluoride) piezoelectric polymers, coupled to a rigid substrate and covered by an elastomer layer. It is first evaluated how a distributed normal force (Hertzian distribution) is transmitted to an extended PVDF [...] Read more.
The reference electronic skin is a sensor array based on PVDF (Polyvinylidene fluoride) piezoelectric polymers, coupled to a rigid substrate and covered by an elastomer layer. It is first evaluated how a distributed normal force (Hertzian distribution) is transmitted to an extended PVDF sensor through the elastomer layer. A simplified approach based on Boussinesq’s half-space assumption is used to get a qualitative picture and extensive FEM simulations allow determination of the quantitative response for the actual finite elastomer layer. The ultimate use of the present model is to estimate the electrical sensor output from a measure of a basic mechanical action at the skin surface. However this requires that the PVDF piezoelectric coefficient be known a-priori. This was not the case in the present investigation. However, the numerical model has been used to fit experimental data from a real skin prototype and to estimate the sensor piezoelectric coefficient. It turned out that this value depends on the preload and decreases as a result of PVDF aging and fatigue. This framework contains all the fundamental ingredients of a fully predictive model, suggesting a number of future developments potentially useful for skin design and validation of the fabrication technology. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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17 pages, 5519 KiB  
Article
Grasping Force Control for a Robotic Hand by Slip Detection Using Developed Micro Laser Doppler Velocimeter
by Nobutomo Morita, Hirofumi Nogami, Eiji Higurashi and Renshi Sawada
Sensors 2018, 18(2), 326; https://doi.org/10.3390/s18020326 - 23 Jan 2018
Cited by 30 | Viewed by 7457
Abstract
The purpose of this paper is to show the feasibility of grasping force control by feeding back signals of the developed micro-laser Doppler velocimeter (μ-LDV) and by discriminating whether a grasped object is slipping or not. LDV is well known as a high [...] Read more.
The purpose of this paper is to show the feasibility of grasping force control by feeding back signals of the developed micro-laser Doppler velocimeter (μ-LDV) and by discriminating whether a grasped object is slipping or not. LDV is well known as a high response surface velocity sensor which can measure various surfaces—such as metal, paper, film, and so on—thus suggesting the potential application of LDV as a slip sensor for grasping various objects. However, the use of LDV as a slip sensor has not yet been reported because the size of LDVs is too large to be installed on a robotic fingertip. We have solved the size problem and enabled the performance of a feasibility test with a few-millimeter-scale LDV referred to as micro-LDV (μ-LDV) by modifying the design which was adopted from MEMS (microelectromechanical systems) fabrication process. In this paper, by applying our developed μ-LDV as a slip sensor, we have successfully demonstrated grasping force control with three target objects—aluminum block, wood block, and white acrylic block—considering that various objects made of these materials can be found in homes and factories, without grasping force feedback. We provide proofs that LDV is a new promising candidate slip sensor for grasping force control to execute target grasping. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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2745 KiB  
Article
Marked Object Recognition Multitouch Screen Printed Touchpad for Interactive Applications
by Jivago Serrado Nunes, Nelson Castro, Sergio Gonçalves, Nélson Pereira, Vitor Correia and Senentxu Lanceros-Mendez
Sensors 2017, 17(12), 2786; https://doi.org/10.3390/s17122786 - 1 Dec 2017
Cited by 8 | Viewed by 4931
Abstract
The market for interactive platforms is rapidly growing, and touchscreens have been incorporated in an increasing number of devices. Thus, the area of smart objects and devices is strongly increasing by adding interactive touch and multimedia content, leading to new uses and capabilities. [...] Read more.
The market for interactive platforms is rapidly growing, and touchscreens have been incorporated in an increasing number of devices. Thus, the area of smart objects and devices is strongly increasing by adding interactive touch and multimedia content, leading to new uses and capabilities. In this work, a flexible screen printed sensor matrix is fabricated based on silver ink in a polyethylene terephthalate (PET) substrate. Diamond shaped capacitive electrodes coupled with conventional capacitive reading electronics enables fabrication of a highly functional capacitive touchpad, and also allows for the identification of marked objects. For the latter, the capacitive signatures are identified by intersecting points and distances between them. Thus, this work demonstrates the applicability of a low cost method using royalty-free geometries and technologies for the development of flexible multitouch touchpads for the implementation of interactive and object recognition applications. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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26800 KiB  
Article
GelSight: High-Resolution Robot Tactile Sensors for Estimating Geometry and Force
by Wenzhen Yuan, Siyuan Dong and Edward H. Adelson
Sensors 2017, 17(12), 2762; https://doi.org/10.3390/s17122762 - 29 Nov 2017
Cited by 510 | Viewed by 37100
Abstract
Tactile sensing is an important perception mode for robots, but the existing tactile technologies have multiple limitations. What kind of tactile information robots need, and how to use the information, remain open questions. We believe a soft sensor surface and high-resolution sensing of [...] Read more.
Tactile sensing is an important perception mode for robots, but the existing tactile technologies have multiple limitations. What kind of tactile information robots need, and how to use the information, remain open questions. We believe a soft sensor surface and high-resolution sensing of geometry should be important components of a competent tactile sensor. In this paper, we discuss the development of a vision-based optical tactile sensor, GelSight. Unlike the traditional tactile sensors which measure contact force, GelSight basically measures geometry, with very high spatial resolution. The sensor has a contact surface of soft elastomer, and it directly measures its deformation, both vertical and lateral, which corresponds to the exact object shape and the tension on the contact surface. The contact force, and slip can be inferred from the sensor’s deformation as well. Particularly, we focus on the hardware and software that support GelSight’s application on robot hands. This paper reviews the development of GelSight, with the emphasis in the sensing principle and sensor design. We introduce the design of the sensor’s optical system, the algorithm for shape, force and slip measurement, and the hardware designs and fabrication of different sensor versions. We also show the experimental evaluation on the GelSight’s performance on geometry and force measurement. With the high-resolution measurement of shape and contact force, the sensor has successfully assisted multiple robotic tasks, including material perception or recognition and in-hand localization for robot manipulation. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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2687 KiB  
Article
Tactile Perception of Roughness and Hardness to Discriminate Materials by Friction-Induced Vibration
by Shuyang Ding, Yunlu Pan, Mingsi Tong and Xuezeng Zhao
Sensors 2017, 17(12), 2748; https://doi.org/10.3390/s17122748 - 28 Nov 2017
Cited by 33 | Viewed by 7223
Abstract
The human fingertip is an exquisitely powerful bio-tactile sensor in perceiving different materials based on various highly-sensitive mechanoreceptors distributed all over the skin. The tactile perception of surface roughness and material hardness can be estimated by skin vibrations generated during a fingertip stroking [...] Read more.
The human fingertip is an exquisitely powerful bio-tactile sensor in perceiving different materials based on various highly-sensitive mechanoreceptors distributed all over the skin. The tactile perception of surface roughness and material hardness can be estimated by skin vibrations generated during a fingertip stroking of a surface instead of being maintained in a static position. Moreover, reciprocating sliding with increasing velocities and pressures are two common behaviors in humans to discriminate different materials, but the question remains as to what the correlation of the sliding velocity and normal load on the tactile perceptions of surface roughness and hardness is for material discrimination. In order to investigate this correlation, a finger-inspired crossed-I beam structure tactile tester has been designed to mimic the anthropic tactile discrimination behaviors. A novel method of characterizing the fast Fourier transform integral (FFT) slope of the vibration acceleration signal generated from fingertip rubbing on surfaces at increasing sliding velocity and normal load, respectively, are defined as kv and kw, and is proposed to discriminate the surface roughness and hardness of different materials. Over eight types of materials were tested, and they proved the capability and advantages of this high tactile-discriminating method. Our study may find applications in investigating humanoid robot perceptual abilities. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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16425 KiB  
Article
A Portable Stiffness Measurement System
by Onejae Sul, Eunsuk Choi and Seung-Beck Lee
Sensors 2017, 17(11), 2686; https://doi.org/10.3390/s17112686 - 21 Nov 2017
Cited by 8 | Viewed by 5609
Abstract
A new stiffness measurement method is proposed that utilizes the lateral deformation profile of an object under indentation. The system consists of a force measurement module between a pair of equidistant touch sensing modules. Unique feature of the method is that by adjusting [...] Read more.
A new stiffness measurement method is proposed that utilizes the lateral deformation profile of an object under indentation. The system consists of a force measurement module between a pair of equidistant touch sensing modules. Unique feature of the method is that by adjusting the touch module separation, indenter protrusion, and spring constant of the force sensing module, one can choose a desired sensing range for the force module. This feature helps to enhance the stiffness differentiation between objects of similar hardness and avoids measurement saturation. We devised a portable measurement system based on the method, and tested its performance with several materials including polymer foams and human skin. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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14407 KiB  
Article
Tactile Evaluation Feedback System for Multi-Layered Structure Inspired by Human Tactile Perception Mechanism
by Iza Husna Mohamad Hashim, Shogo Kumamoto, Kenjiro Takemura, Takashi Maeno, Shin Okuda and Yukio Mori
Sensors 2017, 17(11), 2601; https://doi.org/10.3390/s17112601 - 11 Nov 2017
Cited by 24 | Viewed by 6906
Abstract
Tactile sensation is one type of valuable feedback in evaluating a product. Conventionally, sensory evaluation is used to get direct subjective responses from the consumers, in order to improve the product’s quality. However, this method is a time-consuming and costly process. Therefore, this [...] Read more.
Tactile sensation is one type of valuable feedback in evaluating a product. Conventionally, sensory evaluation is used to get direct subjective responses from the consumers, in order to improve the product’s quality. However, this method is a time-consuming and costly process. Therefore, this paper proposes a novel tactile evaluation system that can give tactile feedback from a sensor’s output. The main concept of this system is hierarchically layering the tactile sensation, which is inspired by the flow of human perception. The tactile sensation is classified from low-order of tactile sensation (LTS) to high-order of tactile sensation (HTS), and also to preference. Here, LTS will be correlated with physical measures. Furthermore, the physical measures that are used to correlate with LTS are selected based on four main aspects of haptic information (roughness, compliance, coldness, and slipperiness), which are perceived through human tactile sensors. By using statistical analysis, the correlation between each hierarchy was obtained, and the preference was derived in terms of physical measures. A verification test was conducted by using unknown samples to determine the reliability of the system. The results showed that the system developed was capable of estimating preference with an accuracy of approximately 80%. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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9189 KiB  
Article
A Pneumatic Tactile Sensor for Co-Operative Robots
by Daoxiong Gong, Rui He, Jianjun Yu and Guoyu Zuo
Sensors 2017, 17(11), 2592; https://doi.org/10.3390/s17112592 - 10 Nov 2017
Cited by 41 | Viewed by 9050
Abstract
Tactile sensors of comprehensive functions are urgently needed for the advanced robot to co-exist and co-operate with human beings. Pneumatic tactile sensors based on air bladder possess some noticeable advantages for human-robot interaction application. In this paper, we construct a pneumatic tactile sensor [...] Read more.
Tactile sensors of comprehensive functions are urgently needed for the advanced robot to co-exist and co-operate with human beings. Pneumatic tactile sensors based on air bladder possess some noticeable advantages for human-robot interaction application. In this paper, we construct a pneumatic tactile sensor and apply it on the fingertip of robot hand to realize the sensing of force, vibration and slippage via the change of the pressure of the air bladder, and we utilize the sensor to perceive the object’s features such as softness and roughness. The pneumatic tactile sensor has good linearity, repeatability and low hysteresis and both its size and sensing range can be customized by using different material as well as different thicknesses of the air bladder. It is also simple and cheap to fabricate. Therefore, the pneumatic tactile sensor is suitable for the application of co-operative robots and can be widely utilized to improve the performance of service robots. We can apply it to the fingertip of the robot to endow the robotic hand with the ability to co-operate with humans and handle the fragile objects because of the inherent compliance of the air bladder. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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16343 KiB  
Article
Textile Pressure Mapping Sensor for Emotional Touch Detection in Human-Robot Interaction
by Bo Zhou, Carlos Andres Velez Altamirano, Heber Cruz Zurian, Seyed Reza Atefi, Erik Billing, Fernando Seoane Martinez and Paul Lukowicz
Sensors 2017, 17(11), 2585; https://doi.org/10.3390/s17112585 - 9 Nov 2017
Cited by 18 | Viewed by 9617
Abstract
In this paper, we developed a fully textile sensing fabric for tactile touch sensing as the robot skin to detect human-robot interactions. The sensor covers a 20-by-20 cm 2 area with 400 sensitive points and samples at 50 Hz per point. We defined [...] Read more.
In this paper, we developed a fully textile sensing fabric for tactile touch sensing as the robot skin to detect human-robot interactions. The sensor covers a 20-by-20 cm 2 area with 400 sensitive points and samples at 50 Hz per point. We defined seven gestures which are inspired by the social and emotional interactions of typical people to people or pet scenarios. We conducted two groups of mutually blinded experiments, involving 29 participants in total. The data processing algorithm first reduces the spatial complexity to frame descriptors, and temporal features are calculated through basic statistical representations and wavelet analysis. Various classifiers are evaluated and the feature calculation algorithms are analyzed in details to determine each stage and segments’ contribution. The best performing feature-classifier combination can recognize the gestures with a 93 . 3 % accuracy from a known group of participants, and 89 . 1 % from strangers. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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4481 KiB  
Article
Multifunctional Woven Structure Operating as Triboelectric Energy Harvester, Capacitive Tactile Sensor Array, and Piezoresistive Strain Sensor Array
by Kihong Kim, Giyoung Song, Cheolmin Park and Kwang-Seok Yun
Sensors 2017, 17(11), 2582; https://doi.org/10.3390/s17112582 - 9 Nov 2017
Cited by 47 | Viewed by 8360
Abstract
This paper presents a power-generating sensor array in a flexible and stretchable form. The proposed device is composed of resistive strain sensors, capacitive tactile sensors, and a triboelectric energy harvester in a single platform. The device is implemented in a woven textile structure [...] Read more.
This paper presents a power-generating sensor array in a flexible and stretchable form. The proposed device is composed of resistive strain sensors, capacitive tactile sensors, and a triboelectric energy harvester in a single platform. The device is implemented in a woven textile structure by using proposed functional threads. A single functional thread is composed of a flexible hollow tube coated with silver nanowires on the outer surface and a conductive silver thread inside the tube. The total size of the device is 60 × 60 mm2 having a 5 × 5 array of sensor cell. The touch force in the vertical direction can be sensed by measuring the capacitance between the warp and weft functional threads. In addition, because silver nanowire layers provide piezoresistivity, the strain applied in the lateral direction can be detected by measuring the resistance of each thread. Last, with regard to the energy harvester, the maximum power and power density were measured as 201 μW and 0.48 W/m2, respectively, when the device was pushed in the vertical direction. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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3164 KiB  
Article
Design Optimisation of a Magnetic Field Based Soft Tactile Sensor
by Gregory de Boer, Nicholas Raske, Hongbo Wang, Junwai Kow, Ali Alazmani, Mazdak Ghajari, Peter Culmer and Robert Hewson
Sensors 2017, 17(11), 2539; https://doi.org/10.3390/s17112539 - 3 Nov 2017
Cited by 23 | Viewed by 6253
Abstract
This paper investigates the design optimisation of a magnetic field based soft tactile sensor, comprised of a magnet and Hall effect module separated by an elastomer. The aim was to minimise sensitivity of the output force with respect to the input magnetic field; [...] Read more.
This paper investigates the design optimisation of a magnetic field based soft tactile sensor, comprised of a magnet and Hall effect module separated by an elastomer. The aim was to minimise sensitivity of the output force with respect to the input magnetic field; this was achieved by varying the geometry and material properties. Finite element simulations determined the magnetic field and structural behaviour under load. Genetic programming produced phenomenological expressions describing these responses. Optimisation studies constrained by a measurable force and stable loading conditions were conducted; these produced Pareto sets of designs from which the optimal sensor characteristics were selected. The optimisation demonstrated a compromise between sensitivity and the measurable force, a fabricated version of the optimised sensor validated the improvements made using this methodology. The approach presented can be applied in general for optimising soft tactile sensor designs over a range of applications and sensing modes. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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9707 KiB  
Article
High-Accuracy Readout Electronics for Piezoresistive Tactile Sensors
by José A. Hidalgo-López, Óscar Oballe-Peinado, Julián Castellanos-Ramos, José A. Sánchez-Durán, Raquel Fernández-Ramos and Fernando Vidal-Verdú
Sensors 2017, 17(11), 2513; https://doi.org/10.3390/s17112513 - 1 Nov 2017
Cited by 25 | Viewed by 6147
Abstract
The typical layout in a piezoresistive tactile sensor arranges individual sensors to form an array with M rows and N columns. While this layout reduces the wiring involved, it does not allow the values of the sensor resistors to be measured individually due [...] Read more.
The typical layout in a piezoresistive tactile sensor arranges individual sensors to form an array with M rows and N columns. While this layout reduces the wiring involved, it does not allow the values of the sensor resistors to be measured individually due to the appearance of crosstalk caused by the nonidealities of the array reading circuits. In this paper, two reading methods that minimize errors resulting from this phenomenon are assessed by designing an electronic system for array reading, and the results are compared to those obtained using the traditional method, obviating the nonidealities of the reading circuit. The different models were compared by testing the system with an array of discrete resistors. The system was later connected to a tactile sensor with 8 × 7 taxels. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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7013 KiB  
Article
Prostate Cancer Detection with a Tactile Resonance Sensor—Measurement Considerations and Clinical Setup
by Anders P. Åstrand, Britt M. Andersson, Ville Jalkanen, Börje Ljungberg, Anders Bergh and Olof A. Lindahl
Sensors 2017, 17(11), 2453; https://doi.org/10.3390/s17112453 - 26 Oct 2017
Cited by 14 | Viewed by 9274
Abstract
Tumors in the human prostate are usually stiffer compared to surrounding non-malignant glandular tissue, and tactile resonance sensors measuring stiffness can be used to detect prostate cancer. To explore this further, we used a tactile resonance sensor system combined with a rotatable sample [...] Read more.
Tumors in the human prostate are usually stiffer compared to surrounding non-malignant glandular tissue, and tactile resonance sensors measuring stiffness can be used to detect prostate cancer. To explore this further, we used a tactile resonance sensor system combined with a rotatable sample holder where whole surgically removed prostates could be attached to detect tumors on, and beneath, the surface ex vivo. Model studies on tissue phantoms made of silicone and porcine tissue were performed. Finally, two resected human prostate glands were studied. Embedded stiff silicone inclusions placed 4 mm under the surface could be detected in both the silicone and biological tissue models, with a sensor indentation of 0.6 mm. Areas with different amounts of prostate cancer (PCa) could be distinguished from normal tissue (p < 0.05), when the tumor was located in the anterior part, whereas small tumors located in the dorsal aspect were undetected. The study indicates that PCa may be detected in a whole resected prostate with an uneven surface and through its capsule. This is promising for the development of a clinically useful instrument to detect prostate cancer during surgery. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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6186 KiB  
Article
3-Axis Fully-Integrated Capacitive Tactile Sensor with Flip-Bonded CMOS on LTCC Interposer
by Sho Asano, Masanori Muroyama, Takahiro Nakayama, Yoshiyuki Hata, Yutaka Nonomura and Shuji Tanaka
Sensors 2017, 17(11), 2451; https://doi.org/10.3390/s17112451 - 25 Oct 2017
Cited by 30 | Viewed by 7326
Abstract
This paper reports a 3-axis fully integrated differential capacitive tactile sensor surface-mountable on a bus line. The sensor integrates a flip-bonded complementary metal-oxide semiconductor (CMOS) with capacitive sensing circuits on a low temperature cofired ceramic (LTCC) interposer with Au through vias by Au-Au [...] Read more.
This paper reports a 3-axis fully integrated differential capacitive tactile sensor surface-mountable on a bus line. The sensor integrates a flip-bonded complementary metal-oxide semiconductor (CMOS) with capacitive sensing circuits on a low temperature cofired ceramic (LTCC) interposer with Au through vias by Au-Au thermo-compression bonding. The CMOS circuit and bonding pads on the sensor backside were electrically connected through Au bumps and the LTCC interposer, and the differential capacitive gap was formed by an Au sealing frame. A diaphragm for sensing 3-axis force was formed in the CMOS substrate. The dimensions of the completed sensor are 2.5 mm in width, 2.5 mm in length, and 0.66 mm in thickness. The fabricated sensor output coded 3-axis capacitive sensing data according to applied 3-axis force by three-dimensional (3D)-printed pins. The measured sensitivity was as high as over 34 Count/mN for normal force and 14 to 15 Count/mN for shear force with small noise, which corresponds to less than 1 mN. The hysteresis and the average cross-sensitivity were also found to be less than 2% full scale and 11%, respectively. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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1512 KiB  
Article
Fingertip Fiber Optical Tactile Array with Two-Level Spring Structure
by Jelizaveta Konstantinova, Agostino Stilli and Kaspar Althoefer
Sensors 2017, 17(10), 2337; https://doi.org/10.3390/s17102337 - 13 Oct 2017
Cited by 23 | Viewed by 7069
Abstract
Tactile perception is a feature benefiting reliable grasping and manipulation. This paper presents the design of an integrated fingertip force sensor employing an optical fiber based approach where applied forces modulate light intensity. The proposed sensor system is developed to support grasping of [...] Read more.
Tactile perception is a feature benefiting reliable grasping and manipulation. This paper presents the design of an integrated fingertip force sensor employing an optical fiber based approach where applied forces modulate light intensity. The proposed sensor system is developed to support grasping of a broad range of objects, including those that are hard as well those that are soft. The sensor system is comprised of four sensing elements forming a tactile array integrated with the tip of a finger. We investigate the design configuration of a separate force sensing element with the aim to improve its measurement range. The force measurement of a single tactile element is based on a two-level displacement that is achieved thanks to a hybrid sensing structure made up of a stiff linear and flexible ortho-planar spring. An important outcome of this paper is a miniature tactile fingertip sensor that is capable of perceiving light contact, typically occurring during the initial stages of a grasp, as well as measuring higher forces, commonly present during tight grasps. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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1244 KiB  
Article
Analysis of Multi-Level Simultaneous Driving Technique for Capacitive Touch Sensors
by Jong Kang Park, Chang-Ju Lee and Jong Tae Kim
Sensors 2017, 17(9), 2016; https://doi.org/10.3390/s17092016 - 2 Sep 2017
Cited by 6 | Viewed by 5874
Abstract
The signal-to-noise ratio (SNR) and driving levels of capacitive touch sensors determine the applicability of these sensors to thinner displays and sensor-integrated modules. The simultaneous driving technique has been widely applied to capacitive touch sensors to cope with various types of environmental noise. [...] Read more.
The signal-to-noise ratio (SNR) and driving levels of capacitive touch sensors determine the applicability of these sensors to thinner displays and sensor-integrated modules. The simultaneous driving technique has been widely applied to capacitive touch sensors to cope with various types of environmental noise. A Hadamard matrix has been used to determine the driving code and multiplex capacitive signals required to increase the SNR and responsivity of touch sensors. Using multi-level Hadamard matrices, a new driving technique for sensing concurrent capacitive elements across multiple rows of a touch panel was developed. The technique provides more effective design choices than the existing bipolar driving method by supporting a variety of orders of matrices and regular capacity. The required TX voltage can be reduced by applying the Kronecker product for higher orders of simultaneous driving. A system model is presented for multiplexing capacitive signals to extract the SNR of the existing Hadamard matrices as well as one of the proposed multi-level sequences. In addition, the corresponding multi-level drivers and receivers were implemented to verify the theoretical expectations and simulation results of the proposed technique. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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4513 KiB  
Article
A Tactile Sensor Network System Using a Multiple Sensor Platform with a Dedicated CMOS-LSI for Robot Applications
by Chenzhong Shao, Shuji Tanaka, Takahiro Nakayama, Yoshiyuki Hata, Travis Bartley, Yutaka Nonomura and Masanori Muroyama
Sensors 2017, 17(9), 1974; https://doi.org/10.3390/s17091974 - 28 Aug 2017
Cited by 18 | Viewed by 6320
Abstract
Robot tactile sensation can enhance human–robot communication in terms of safety, reliability and accuracy. The final goal of our project is to widely cover a robot body with a large number of tactile sensors, which has significant advantages such as accurate object recognition, [...] Read more.
Robot tactile sensation can enhance human–robot communication in terms of safety, reliability and accuracy. The final goal of our project is to widely cover a robot body with a large number of tactile sensors, which has significant advantages such as accurate object recognition, high sensitivity and high redundancy. In this study, we developed a multi-sensor system with dedicated Complementary Metal-Oxide-Semiconductor (CMOS) Large-Scale Integration (LSI) circuit chips (referred to as “sensor platform LSI”) as a framework of a serial bus-based tactile sensor network system. The sensor platform LSI supports three types of sensors: an on-chip temperature sensor, off-chip capacitive and resistive tactile sensors, and communicates with a relay node via a bus line. The multi-sensor system was first constructed on a printed circuit board to evaluate basic functions of the sensor platform LSI, such as capacitance-to-digital and resistance-to-digital conversion. Then, two kinds of external sensors, nine sensors in total, were connected to two sensor platform LSIs, and temperature, capacitive and resistive sensing data were acquired simultaneously. Moreover, we fabricated flexible printed circuit cables to demonstrate the multi-sensor system with 15 sensor platform LSIs operating simultaneously, which showed a more realistic implementation in robots. In conclusion, the multi-sensor system with up to 15 sensor platform LSIs on a bus line supporting temperature, capacitive and resistive sensing was successfully demonstrated. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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1985 KiB  
Article
Slippage Detection with Piezoresistive Tactile Sensors
by Rocco A. Romeo, Calogero M. Oddo, Maria Chiara Carrozza, Eugenio Guglielmelli and Loredana Zollo
Sensors 2017, 17(8), 1844; https://doi.org/10.3390/s17081844 - 10 Aug 2017
Cited by 37 | Viewed by 7467
Abstract
One of the crucial actions to be performed during a grasping task is to avoid slippage. The human hand can rapidly correct applied forces and prevent a grasped object from falling, thanks to its advanced tactile sensing. The same capability is hard to [...] Read more.
One of the crucial actions to be performed during a grasping task is to avoid slippage. The human hand can rapidly correct applied forces and prevent a grasped object from falling, thanks to its advanced tactile sensing. The same capability is hard to reproduce in artificial systems, such as robotic or prosthetic hands, where sensory motor coordination for force and slippage control is very limited. In this paper, a novel algorithm for slippage detection is presented. Based on fast, easy-to-perform processing, the proposed algorithm generates an ON/OFF signal relating to the presence/absence of slippage. The method can be applied either on the raw output of a force sensor or to its calibrated force signal, and yields comparable results if applied to both normal or tangential components. A biomimetic fingertip that integrates piezoresistive MEMS sensors was employed for evaluating the method performance. Each sensor had four units, thus providing 16 mono-axial signals for the analysis. A mechatronic platform was used to produce relative movement between the finger and the test surfaces (tactile stimuli). Three surfaces with submillimetric periods were adopted for the method evaluation, and 10 experimental trials were performed per each surface. Results are illustrated in terms of slippage events detection and of latency between the slippage itself and its onset. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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Review

Jump to: Research

29 pages, 9188 KiB  
Review
Recent Progress in Technologies for Tactile Sensors
by Cheng Chi, Xuguang Sun, Ning Xue, Tong Li and Chang Liu
Sensors 2018, 18(4), 948; https://doi.org/10.3390/s18040948 - 22 Mar 2018
Cited by 172 | Viewed by 15221
Abstract
Over the last two decades, considerable scientific and technological efforts have been devoted to developing tactile sensing based on a variety of transducing mechanisms, with prospective applications in many fields such as human–machine interaction, intelligent robot tactile control and feedback, and tactile sensorized [...] Read more.
Over the last two decades, considerable scientific and technological efforts have been devoted to developing tactile sensing based on a variety of transducing mechanisms, with prospective applications in many fields such as human–machine interaction, intelligent robot tactile control and feedback, and tactile sensorized minimally invasive surgery. This paper starts with an introduction of human tactile systems, followed by a presentation of the basic demands of tactile sensors. State-of-the-art tactile sensors are reviewed in terms of their diverse sensing mechanisms, design consideration, and material selection. Subsequently, typical performances of the sensors, along with their advantages and disadvantages, are compared and analyzed. Two major potential applications of tactile sensing systems are discussed in detail. Lastly, we propose prospective research directions and market trends of tactile sensing systems. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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16 pages, 3481 KiB  
Review
Tactile-Sensing Based on Flexible PVDF Nanofibers via Electrospinning: A Review
by Xiaomei Wang, Fazhe Sun, Guangchao Yin, Yuting Wang, Bo Liu and Mingdong Dong
Sensors 2018, 18(2), 330; https://doi.org/10.3390/s18020330 - 24 Jan 2018
Cited by 187 | Viewed by 16690
Abstract
The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical [...] Read more.
The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical performance have been widely utilized as functional materials in flexible tactile sensors. Polymer nanomaterials, representing the most promising materials, especially polyvinylidene fluoride (PVDF), PVDF co-polymer and their nanocomposites with ultra-sensitivity, high deformability, outstanding chemical resistance, high thermal stability and low permittivity, can meet the flexibility requirements for dynamic tactile sensing in wearable electronics. Electrospinning has been recognized as an excellent straightforward and versatile technique for preparing nanofiber materials. This review will present a brief overview of the recent advances in PVDF nanofibers by electrospinning for flexible tactile sensor applications. PVDF, PVDF co-polymers and their nanocomposites have been successfully formed as ultrafine nanofibers, even as randomly oriented PVDF nanofibers by electrospinning. These nanofibers used as the functional layers in flexible tactile sensors have been reviewed briefly in this paper. The β-phase content, which is the strongest polar moment contributing to piezoelectric properties among all the crystalline phases of PVDF, can be improved by adjusting the technical parameters in electrospun PVDF process. The piezoelectric properties and the sensibility for the pressure sensor are improved greatly when the PVDF fibers become more oriented. The tactile performance of PVDF composite nanofibers can be further promoted by doping with nanofillers and nanoclay. Electrospun P(VDF-TrFE) nanofiber mats used for the 3D pressure sensor achieved excellent sensitivity, even at 0.1 Pa. The most significant enhancement is that the aligned electrospun core-shell P(VDF-TrFE) nanofibers exhibited almost 40 times higher sensitivity than that of pressure sensor based on thin-film PVDF. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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1690 KiB  
Review
Novel Tactile Sensor Technology and Smart Tactile Sensing Systems: A Review
by Liang Zou, Chang Ge, Z. Jane Wang, Edmond Cretu and Xiaoou Li
Sensors 2017, 17(11), 2653; https://doi.org/10.3390/s17112653 - 17 Nov 2017
Cited by 193 | Viewed by 19381
Abstract
During the last decades, smart tactile sensing systems based on different sensing techniques have been developed due to their high potential in industry and biomedical engineering. However, smart tactile sensing technologies and systems are still in their infancy, as many technological and system [...] Read more.
During the last decades, smart tactile sensing systems based on different sensing techniques have been developed due to their high potential in industry and biomedical engineering. However, smart tactile sensing technologies and systems are still in their infancy, as many technological and system issues remain unresolved and require strong interdisciplinary efforts to address them. This paper provides an overview of smart tactile sensing systems, with a focus on signal processing technologies used to interpret the measured information from tactile sensors and/or sensors for other sensory modalities. The tactile sensing transduction and principles, fabrication and structures are also discussed with their merits and demerits. Finally, the challenges that tactile sensing technology needs to overcome are highlighted. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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5456 KiB  
Review
Review of Recent Inkjet-Printed Capacitive Tactile Sensors
by Ahmed Salim and Sungjoon Lim
Sensors 2017, 17(11), 2593; https://doi.org/10.3390/s17112593 - 10 Nov 2017
Cited by 78 | Viewed by 12653
Abstract
Inkjet printing is an advanced printing technology that has been used to develop conducting layers, interconnects and other features on a variety of substrates. It is an additive manufacturing process that offers cost-effective, lightweight designs and simplifies the fabrication process with little effort. [...] Read more.
Inkjet printing is an advanced printing technology that has been used to develop conducting layers, interconnects and other features on a variety of substrates. It is an additive manufacturing process that offers cost-effective, lightweight designs and simplifies the fabrication process with little effort. There is hardly sufficient research on tactile sensors and inkjet printing. Advancements in materials science and inkjet printing greatly facilitate the realization of sophisticated tactile sensors. Starting from the concept of capacitive sensing, a brief comparison of printing techniques, the essential requirements of inkjet-printing and the attractive features of state-of-the art inkjet-printed tactile sensors developed on diverse substrates (paper, polymer, glass and textile) are presented in this comprehensive review. Recent trends in inkjet-printed wearable/flexible and foldable tactile sensors are evaluated, paving the way for future research. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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1404 KiB  
Review
Human Thalamic Somatosensory Nucleus (Ventral Caudal, Vc) as a Locus for Stimulation by INPUTS from Tactile, Noxious and Thermal Sensors on an Active Prosthesis
by Jui Hong Chien, Anna Korzeniewska, Luana Colloca, Claudia Campbell, Patrick Dougherty and Frederick Lenz
Sensors 2017, 17(6), 1197; https://doi.org/10.3390/s17061197 - 24 May 2017
Cited by 9 | Viewed by 5357
Abstract
The forebrain somatic sensory locus for input from sensors on the surface of an active prosthesis is an important component of the Brain Machine Interface. We now review the neuronal responses to controlled cutaneous stimuli and the sensations produced by Threshold Stimulation at [...] Read more.
The forebrain somatic sensory locus for input from sensors on the surface of an active prosthesis is an important component of the Brain Machine Interface. We now review the neuronal responses to controlled cutaneous stimuli and the sensations produced by Threshold Stimulation at Microampere current levels (TMIS) in such a locus, the human thalamic Ventral Caudal nucleus (Vc). The responses of these neurons to tactile stimuli mirror those for the corresponding class of tactile mechanoreceptor fiber in the peripheral nerve, and TMIS can evoke sensations like those produced by the stimuli that optimally activate each class. These neuronal responses show a somatotopic arrangement from lateral to medial in the sequence: leg, arm, face and intraoral structures. TMIS evoked sensations show a much more detailed organization into anterior posteriorly oriented rods, approximately 300 microns diameter, that represent smaller parts of the body, such as parts of individual digits. Neurons responding to painful and thermal stimuli are most dense around the posterior inferior border of Vc, and TMIS evoked pain sensations occur in one of two patterns: (i) pain evoked regardless of the frequency or number of spikes in a burst of TMIS; and (ii) the description and intensity of the sensation changes with increasing frequencies and numbers. In patients with major injuries leading to loss of somatic sensory input, TMIS often evokes sensations in the representation of parts of the body with loss of sensory input, e.g., the phantom after amputation. Some patients with these injuries have ongoing pain and pain evoked by TMIS of the representation in those parts of the body. Therefore, thalamic TMIS may produce useful patterned somatotopic feedback to the CNS from sensors on an active prosthesis that is sometimes complicated by TMIS evoked pain in the representation of those parts of the body. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing)
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