In this paper, we propose a novel tactile sensor with a “fingerprint” design, named due to its spiral shape and dimensions of 3.80 mm × 3.80 mm. The sensor is duplicated in a four-by-four array ...containing 16 tactile sensors to form a “SkinCell” pad of approximately 45 mm by 29 mm. The SkinCell was fabricated using a custom-built microfabrication platform called the NeXus which contains additive deposition tools and several robotic systems. We used the NeXus’ six-degrees-of-freedom robotic platform with two different inkjet printers to deposit a conductive silver ink sensor electrode as well as the organic piezoresistive polymer PEDOT:PSS-Poly (3,4-ethylene dioxythiophene)-poly(styrene sulfonate) of our tactile sensor. Printing deposition profiles of 100-micron- and 250-micron-thick layers were measured using microscopy. The resulting structure was sintered in an oven and laminated. The lamination consisted of two different sensor sheets placed back-to-back to create a half-Wheatstone-bridge configuration, doubling the sensitivity and accomplishing temperature compensation. The resulting sensor array was then sandwiched between two layers of silicone elastomer that had protrusions and inner cavities to concentrate stresses and strains and increase the detection resolution. Furthermore, the tactile sensor was characterized under static and dynamic force loading. Over 180,000 cycles of indentation were conducted to establish its durability and repeatability. The results demonstrate that the SkinCell has an average spatial resolution of 0.827 mm, an average sensitivity of 0.328 mΩ/Ω/N, expressed as the change in resistance per force in Newtons, an average sensitivity of 1.795 µV/N at a loading pressure of 2.365 PSI, and a dynamic response time constant of 63 ms which make it suitable for both large area skins and fingertip human–robot interaction applications.
In this article, we present the design, fabrication, integration, and performance evaluation of SkinCell sensors, a novel tactile array targeting human-robot interaction applications. A polyimide ...sheet is selected as the substrate of the sensor, and gold electrodes with circular interdigitated finger patterns are deposited through dc sputtering, creating a <inline-formula> <tex-math notation="LaTeX">4\times </tex-math></inline-formula> 4 sensor array with 16 tactile elements. Sensing elements are completed with a thin layer of spin-coated poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) organic polymer solution. Two individual sensor sheets are being laminated in a back-to-back fashion to create a half-Wheatstone-bridge configuration to reduce temperature coupling while improving sensitivity. The sensor array is then sandwiched between two layers of silicone elastomer with internal dimples and cavities to improve sensitivity, repeatability, and center of force detection resolution. A COMSOL simulation was performed to study the influence of adding the silicone encapsulation as well as design parameters to the sensor substrate. Our simulation results indicate an effective improvement of touch, i.e., voltage sensitivity by employing the featured encapsulation. Characterization experiments have been conducted to identify the sensitivity profile of each sensor on the array, which indicates an average sensitivity of <inline-formula> <tex-math notation="LaTeX">26.5~\mu </tex-math></inline-formula> V/N. In subsequent experiments, the calibration profiles are used to identify the resultant force during pressing, as well as the location of the center of pressure (COP) on the SkinCell sensor. Finally, SkinCell sensors have been integrated into the OctoCan, a structural electronic device that can acquire squeezing pressure data during physical human-robot interaction (pHRI).
This paper presents the NeXus, a precision robotic platform with additive manufacturing capabilities that can be used to prototype strain gauge-based tactile sensors – SkinCells - on flexible ...substrates. An Aerosol Inkjet printer was employed to print the strain gauge structures of the SkinCell sensor. The design of this sensor combines curvilinear geometries representing both a radial shape structure and an arc shape structure, which have opposite gauge responses when the force is applied to the center of the sensor. The fabrication process of the SkinCell sensor is predicated on a parametric kinematic calibration of the NeXus to identify features on the sensor substrate and align them to the printing and metrology tools. Several strain gauge SkinCell sensor samples were printed on pre-fabricated flexible substrates using the NeXus. Results indicate a calibration precision of approximately 36 microns with 100 microns line-width features. This precision is sufficient to ensure that all printed gauges are electrically connected to the prefabricated contacts. Furthermore, the printing errors accumulating during a continuous four-sensor array print also fall within the contact tolerance.
In Nigerian universities, enrolment into any engineering undergraduate program requires that the minimum entry criteria established by the National Universities Commission (NUC) must be satisfied. ...Candidates seeking admission to study engineering discipline must have reached a predetermined entry age and met the cut-off marks set for Senior School Certificate Examination (SSCE), Unified Tertiary Matriculation Examination (UTME), and the post-UTME screening. However, limited effort has been made to show that these entry requirements eventually guarantee successful academic performance in engineering programs because the data required for such validation are not readily available. In this data article, a comprehensive dataset for empirical evaluation of entry requirements into engineering undergraduate programs in a Nigerian university is presented and carefully analyzed. A total sample of 1445 undergraduates that were admitted between 2005 and 2009 to study Chemical Engineering (CHE), Civil Engineering (CVE), Computer Engineering (CEN), Electrical and Electronics Engineering (EEE), Information and Communication Engineering (ICE), Mechanical Engineering (MEE), and Petroleum Engineering (PET) at Covenant University, Nigeria were randomly selected. Entry age, SSCE aggregate, UTME score, Covenant University Scholastic Aptitude Screening (CUSAS) score, and the Cumulative Grade Point Average (CGPA) of the undergraduates were obtained from the Student Records and Academic Affairs unit. In order to facilitate evidence-based evaluation, the robust dataset is made publicly available in a Microsoft Excel spreadsheet file. On yearly basis, first-order descriptive statistics of the dataset are presented in tables. Box plot representations, frequency distribution plots, and scatter plots of the dataset are provided to enrich its value. Furthermore, correlation and linear regression analyses are performed to understand the relationship between the entry requirements and the corresponding academic performance in engineering programs. The data provided in this article will help Nigerian universities, the NUC, engineering regulatory bodies, and relevant stakeholders to objectively evaluate and subsequently improve the quality of engineering education in the country.
Inkjet printing for fabricating microstructures has gained popularity during the last decade, making it possible to realize complex electronic circuits, components, and devices previously ...manufactured using 2D lithographic processes. Aerosol jet printing enables the deposition of feature sizes in the micron-scale order. Investigated in this work, is a tactile sensor featuring a strain gauge in a circular pattern and using aerosol inkjet printing delivered from the NeXus, a custom-built microfabrication platform that can deposit silver ink on a flexible printed circuit (FPC) substrate. Also presented is the finite element analysis (FEA) to evaluate the performance of the tactile sensor, packaged in between cover and bedding created with elastomer to fit the tactile sensor. The elastomer covering and bedding contains a dimple and cavity complying with external deformation, which concentrates the applied indented force. Simulation was used to optimize the configuration of the dimple size, cover, and bedding design required to improve the sensor performance. The fabrication method for creating 10mm diameter circular strain gauge tactile sensors include an annealing process using the oven, developed by comparing different curing time. Finally, experimental indentation tests were carried out under varying curing schedules, evaluated by loading packaged sensors with increasing weight, and indented force profile from 0.5-2.0N. Results show a 67% decrease in resistance from 2-20 hours of oven cure and about a 0.08% increase in sensitivity.
This paper presents the NeXus, a precision robotic platform with additive manufacturing capabilities that can be used to prototype strain gauge-based tactile sensors - SkinCells - on flexible ...substrates. An Aerosol Inkjet printer was employed to print the strain gauge structure of the SkinCell sensor. The design of this sensor combines curvilinear geometries representing both a radial shape structure and an arc shape structure, which have opposite gauge responses when the force is applied to the center of the sensor. The fabrication process of the SkinCell sensor is predicated on a parametric kinematic calibration of the NeXus to identify features on the sensor substrate and align them to the printing and metrology tools. Several strain gauge SkinCell sensor samples were printed on pre-fabricated flexible substrates using the NeXus. Results indicate a calibration precision of approximately 170 microns with 60 microns line-width features. This precision is sufficient to ensure that all printed gauges are electrically connected to the pre-fabricated contacts.
Aerosol Jet Printed Tactile Sensor on Flexible Substrate Olowo, Olalekan O.; Zhang, Ruoshi; Wei, Danming ...
2022 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS),
2022-July-10
Conference Proceeding
Inkjet printing for fabricating microstructures has gained popularity during the last decade, making it possible to realize complex electronic circuits, components, and devices previously ...manufactured using 2D lithographic processes. In this work, we use aerosol inkjet printing delivered from the NeXus, a custom-built microfabrication platform that can deposit silver ink on a flexible printed circuit (FPC) substrate. We present the fabrication method of a 10mm diameter circular strain gauge tactile sensor, which is annealed using oven curing or intense pulse light (IPL) process. The resulting sensor performance under varying curing schedules is evaluated by loading packaged sensors with increasing weight, reporting a measured resistance in the 300Ω-1.2kΩ range.
Robot skin sensors are being developed to improve the tactile perception that comes with physical touch. This is desired as it enhances the interaction between robots and humans. In this publication, ...we present a process for improving the deposition of PEDOT: PSS using Aerosol jet printing technology. Previously, we deposited PEDOT: PSS with the MEMS fabrication techniques in the cleanroom. The PEDOT: PSS, an organic polymer that gives the robot skin sensors their piezoresistive ability, is deposited on the designated microfabricated sensor electrodes, significantly cutting down the manufacturing time. Testing of the robot skin sensors is done on an automated testing station having a force plunger and an integrated circuit. The results display the resistance values measured across the sensors and their tactile responses to applied strain.
A fast emerging source of knowledge acquisition through inference from available data is analytics. The convergence of maturity, ubiquity and ease of deployment of Internet of Things (IoT) enabling ...technologies has engendered this possibility. The need to leverage on available data from credible sources to develop sustainable systems within the smart and connected communities (SCC) paradigm cannot be overemphasized. In this paper, the architecture of an IoT-enabled smart micro-grid system is proposed to harness the potentials of emerging independent power projects in sub-Saharan Africa. As a case study, this paper examines the interrelation between the economy and electric power consumption in Nigeria, Africa's energy giant and most populous nation, from 1981 to 2014 using the off-the-shelf IBM Watson analytics software. The predictive analytics tool provided an in-depth analysis of the determinants of energy-driven economic growth, as a basis for developing a sustainable smart energy system in Nigeria. Insights gained from this predictive analytics afford private investors, policy makers, consumers and other stakeholders an opportunity to work together to meet the increasing demand for energy production in sub-Saharan Africa.
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