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Special Issue "3D Printed Sensors"

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

Deadline for manuscript submissions: closed (15 February 2017).

Special Issue Editors

Prof. Dr. Jae-Won Choi
Website
Guest Editor
Department of Mechanical Engineering at the University of Akron (UA), OH, USA
Interests: 3D printed smart structures (sensors, actuators, and electronics); 3D printed bio structures; new 3D printing processes and materials
Prof. Dr. Erik D. Engeberg
Website
Co-Guest Editor
Department of Ocean and mechanical Engineering at Florida Atlantic University (FAU), FL, USA
Interests: robotics; control; sensor design; signal processing

Special Issue Information

Dear Colleagues,

Additive Manufacturing, also known as 3D Printing, has progressed greatly over the last 30 years. It is believed that one of the next generation 3D printing applications will be geometrically integrated three-dimensional smart structures, including sensors, actuators, and electronics. Although there are many mature 3D printing materials and systems that are commercially available, it is still difficult to realize 3D printing of smart structures using them. Recently, there have been several approaches for 3D printing sensors for various applications, where sensors have been hybrid 3D printed and/or assembled within 3D printed structures. In a practical view of 3D printing for sensors, there are many challenges, such as printing sensing elements, conductors, and insulators, as well as interconnecting external devices.

This Special Issue will be focused on recent breakthroughs in research and development of 3D printed sensors. New progress and measurement on 3D printing processes, materials, and applications are encouraged. Topics of interest include, but are not limited to:

  • Sensors for detecting pressure, humidity, temperature, gas, acceleration, displacement, force, and color, which are 3D printed and/or integrated within 3D printed structures.
  • New or hybrid 3D printing processes.
  • Novel 3D printable materials (polymers, metals, and composites).
  • Research on characterization of 3D printed sensors.
  • Use of commerical 3D printers for specialized sensing applications.
  • Review paper for 3D printed sensors.

Prof. Dr. Jae-Won Choi
Guest Editor

Prof. Dr. Erik D. Engeberg
Co-Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 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

  • Sensor
  • 3D printing
  • additive manufacturing
  • polymer
  • composite

Published Papers (9 papers)

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Research

Open AccessArticle
3D Printing-Based Integrated Water Quality Sensing System
Sensors 2017, 17(6), 1336; https://doi.org/10.3390/s17061336 - 08 Jun 2017
Cited by 10
Abstract
The online and accurate monitoring of drinking water supply networks is critically in demand to rapidly detect the accidental or deliberate contamination of drinking water. At present, miniaturized water quality monitoring sensors developed in the laboratories are usually tested under ambient pressure and [...] Read more.
The online and accurate monitoring of drinking water supply networks is critically in demand to rapidly detect the accidental or deliberate contamination of drinking water. At present, miniaturized water quality monitoring sensors developed in the laboratories are usually tested under ambient pressure and steady-state flow conditions; however, in Water Distribution Systems (WDS), both the pressure and the flowrate fluctuate. In this paper, an interface is designed and fabricated using additive manufacturing or 3D printing technology—material extrusion (Trade Name: fused deposition modeling, FDM) and material jetting—to provide a conduit for miniaturized sensors for continuous online water quality monitoring. The interface is designed to meet two main criteria: low pressure at the inlet of the sensors and a low flowrate to minimize the water bled (i.e., leakage), despite varying pressure from WDS. To meet the above criteria, a two-dimensional computational fluid dynamics model was used to optimize the geometry of the channel. The 3D printed interface, with the embedded miniaturized pH and conductivity sensors, was then tested at different temperatures and flowrates. The results show that the response of the pH sensor is independent of the flowrate and temperature. As for the conductivity sensor, the flowrate and temperature affect only the readings at a very low conductivity (4 µS/cm) and high flowrates (30 mL/min), and a very high conductivity (460 µS/cm), respectively. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessArticle
Inkjet-Printed Membrane for a Capacitive Acoustic Sensor: Development and Characterization Using Laser Vibrometer
Sensors 2017, 17(5), 1056; https://doi.org/10.3390/s17051056 - 06 May 2017
Cited by 7
Abstract
This paper describes the fabrication process and the method to determine the membrane tension and defects of an inkjet-printed circular diaphragm. The membrane tension is an important parameter to design and fabricate an acoustic sensor and resonator with the highest sensitivity and selectivity [...] Read more.
This paper describes the fabrication process and the method to determine the membrane tension and defects of an inkjet-printed circular diaphragm. The membrane tension is an important parameter to design and fabricate an acoustic sensor and resonator with the highest sensitivity and selectivity over a determined range of frequency. During this work, the diaphragms are fabricated by inkjet printing of conductive silver ink on pre-strained Mylar thin films, and the membrane tension is determined using the resonant frequency obtained from its measured surface velocity response to an acoustic excitation. The membrane is excited by an acoustic pressure generated by a loudspeaker, and its displacement (response) is acquired using a laser Doppler vibrometer (LDV). The response of the fabricated membrane demonstrates good correlation with the numerical result. However, the inkjet-printed membrane exhibits undesired peaks, which appeared to be due to defects at their boundaries as observed from the scanning mode of LDV. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessArticle
Microfluidic EBG Sensor Based on Phase-Shift Method Realized Using 3D Printing Technology
Sensors 2017, 17(4), 892; https://doi.org/10.3390/s17040892 - 18 Apr 2017
Cited by 12
Abstract
In this article, we propose a novel microfluidic microstrip electromagnetic band gap (EBG) sensor realized using cost-effective 3D printing technology. Microstrip sensor allows monitoring of the fluid properties flowing in the microchannel embedded between the microstrip line and ground plane. The sensor’s operating [...] Read more.
In this article, we propose a novel microfluidic microstrip electromagnetic band gap (EBG) sensor realized using cost-effective 3D printing technology. Microstrip sensor allows monitoring of the fluid properties flowing in the microchannel embedded between the microstrip line and ground plane. The sensor’s operating principle is based on the phase-shift method, which allows the characterization at a single operating frequency of 6 GHz. The defected electromagnetic band gap (EBG) structure is realized as a pattern in the microstrip ground plane to improve sensor sensitivity. The designed microfluidic channel is fabricated using a fused deposition modelling (FDM) 3D printing process without additional supporting layers, while the conductive layers are realized using sticky aluminium tape. The measurement results show that the change of permittivity of the fluid in the microfluidic channel from 1 to 80 results in the phase-shift difference of almost 90°. The potential application is demonstrated through the implementation of a proposed sensor for the detection of toluene concentration in toluene–methanol mixture where various concentrations of toluene were analysed. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessFeature PaperArticle
Measurement of Pressure Fluctuations inside a Model Thrust Bearing Using PVDF Sensors
Sensors 2017, 17(4), 878; https://doi.org/10.3390/s17040878 - 16 Apr 2017
Cited by 7
Abstract
Thrust bearings play a vital role in propulsion systems. They rely on a thin layer of oil being trapped between rotating surfaces to produce a low friction interface. The “quality” of this bearing affects many things from noise transmission to the ultimate catastrophic [...] Read more.
Thrust bearings play a vital role in propulsion systems. They rely on a thin layer of oil being trapped between rotating surfaces to produce a low friction interface. The “quality” of this bearing affects many things from noise transmission to the ultimate catastrophic failure of the bearing itself. As a result, the direct measure of the forces and vibrations within the oil filled interface would be very desirable and would give an indication of the condition of the bearing in situ. The thickness of the oil film is, however, very small and conventional vibration sensors are too cumbersome to use in this confined space. This paper solves this problem by using a piezoelectric polymer film made from Polyvinylidine Fluoride (PVDF). These films are very thin (50 m) and flexible and easy to install in awkward spaces such as the inside of a thrust bearing. A model thrust bearing was constructed using a 3D printer and PVDF films inserted into the base of the bearing. In doing so, it was possible to directly measure the force fluctuations due to the rotating pads and investigate various properties of the thrust bearing itself. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessArticle
A Two-Axis Goniometric Sensor for Tracking Finger Motion
Sensors 2017, 17(4), 770; https://doi.org/10.3390/s17040770 - 05 Apr 2017
Cited by 12
Abstract
The study of finger kinematics has developed into an important research area. Various hand tracking systems are currently available; however, they all have limited functionality. Generally, the most commonly adopted sensors are limited to measurements with one degree of freedom, i.e., flexion/extension of [...] Read more.
The study of finger kinematics has developed into an important research area. Various hand tracking systems are currently available; however, they all have limited functionality. Generally, the most commonly adopted sensors are limited to measurements with one degree of freedom, i.e., flexion/extension of fingers. More advanced measurements including finger abduction, adduction, and circumduction are much more difficult to achieve. To overcome these limitations, we propose a two-axis 3D printed optical sensor with a compact configuration for tracking finger motion. Based on Malus’ law, this sensor detects the angular changes by analyzing the attenuation of light transmitted through polarizing film. The sensor consists of two orthogonal axes each containing two pathways. The two readings from each axis are fused using a weighted average approach, enabling a measurement range up to 180 and an improvement in sensitivity. The sensor demonstrates high accuracy (±0.3 ), high repeatability, and low hysteresis error. Attaching the sensor to the index finger’s metacarpophalangeal joint, real-time movements consisting of flexion/extension, abduction/adduction and circumduction have been successfully recorded. The proposed two-axis sensor has demonstrated its capability for measuring finger movements with two degrees of freedom and can be potentially used to monitor other types of body motion. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessArticle
Flexible Piezoresistive Sensors Embedded in 3D Printed Tires
Sensors 2017, 17(3), 656; https://doi.org/10.3390/s17030656 - 22 Mar 2017
Cited by 22
Abstract
In this article, we report the development of a flexible, 3D printable piezoresistive pressure sensor capable of measuring force and detecting the location of the force. The multilayer sensor comprises of an ionic liquid-based piezoresistive intermediate layer in between carbon nanotube (CNT)-based stretchable [...] Read more.
In this article, we report the development of a flexible, 3D printable piezoresistive pressure sensor capable of measuring force and detecting the location of the force. The multilayer sensor comprises of an ionic liquid-based piezoresistive intermediate layer in between carbon nanotube (CNT)-based stretchable electrodes. A sensor containing an array of different sensing units was embedded on the inner liner surface of a 3D printed tire to provide with force information at different points of contact between the tire and road. Four scaled tires, as well as wheels, were 3D printed using a flexible and a rigid material, respectively, which were later assembled with a 3D-printed chassis. Only one tire was equipped with a sensor and the chassis was driven through a motorized linear stage at different speeds and load conditions to evaluate the sensor performance. The sensor was fabricated via molding and screen printing processes using a commercially available 3D-printable photopolymer as 3D printing is our target manufacturing technique to fabricate the entire tire assembly with the sensor. Results show that the proposed sensors, inserted in the 3D printed tire assembly, could detect forces, as well as their locations, properly. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessArticle
Bismuth Infusion of ABS Enables Additive Manufacturing of Complex Radiological Phantoms and Shielding Equipment
Sensors 2017, 17(3), 459; https://doi.org/10.3390/s17030459 - 24 Feb 2017
Cited by 20
Abstract
Radiopacity is a critical property of materials that are used for a range of radiological applications, including the development of phantom devices that emulate the radiodensity of native tissues and the production of protective equipment for personnel handling radioactive materials. Three-dimensional (3D) printing [...] Read more.
Radiopacity is a critical property of materials that are used for a range of radiological applications, including the development of phantom devices that emulate the radiodensity of native tissues and the production of protective equipment for personnel handling radioactive materials. Three-dimensional (3D) printing is a fabrication platform that is well suited to creating complex anatomical replicas or custom labware to accomplish these radiological purposes. We created and tested multiple ABS (Acrylonitrile butadiene styrene) filaments infused with varied concentrations of bismuth (1.2–2.7 g/cm3), a radiopaque metal that is compatible with plastic infusion, to address the poor gamma radiation attenuation of many mainstream 3D printing materials. X-ray computed tomography (CT) experiments of these filaments indicated that a density of 1.2 g/cm3 of bismuth-infused ABS emulates bone radiopacity during X-ray CT imaging on preclinical and clinical scanners. ABS-bismuth filaments along with ABS were 3D printed to create an embedded human nasocranial anatomical phantom that mimicked radiological properties of native bone and soft tissue. Increasing the bismuth content in the filaments to 2.7 g/cm3 created a stable material that could attenuate 50% of 99mTechnetium gamma emission when printed with a 2.0 mm wall thickness. A shielded test tube rack was printed to attenuate source radiation as a protective measure for lab personnel. We demonstrated the utility of novel filaments to serve multiple radiological purposes, including the creation of anthropomorphic phantoms and safety labware, by tuning the level of radiation attenuation through material customization. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessArticle
Temperature Mapping of 3D Printed Polymer Plates: Experimental and Numerical Study
Sensors 2017, 17(3), 456; https://doi.org/10.3390/s17030456 - 24 Feb 2017
Cited by 16
Abstract
In Fused Deposition Modeling (FDM), which is a common thermoplastic Additive Manufacturing (AM) method, the polymer model material that is in the form of a flexible filament is heated above its glass transition temperature (Tg) to a semi-molten state in the [...] Read more.
In Fused Deposition Modeling (FDM), which is a common thermoplastic Additive Manufacturing (AM) method, the polymer model material that is in the form of a flexible filament is heated above its glass transition temperature (Tg) to a semi-molten state in the head’s liquefier. The heated material is extruded in a rastering configuration onto the building platform where it rapidly cools and solidifies with the adjoining material. The heating and rapid cooling cycles of the work materials exhibited during the FDM process provoke non-uniform thermal gradients and cause stress build-up that consequently result in part distortions, dimensional inaccuracy and even possible part fabrication failure. Within the purpose of optimizing the FDM technique by eliminating the presence of such undesirable effects, real-time monitoring is essential for the evaluation and control of the final parts’ quality. The present work investigates the temperature distributions developed during the FDM building process of multilayered thin plates and on this basis a numerical study is also presented. The recordings of temperature changes were achieved by embedding temperature measuring sensors at various locations into the middle-plane of the printed structures. The experimental results, mapping the temperature variations within the samples, were compared to the corresponding ones obtained by finite element modeling, exhibiting good correlation. Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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Open AccessArticle
Proof of Concept of Integrated Load Measurement in 3D Printed Structures
Sensors 2017, 17(2), 328; https://doi.org/10.3390/s17020328 - 09 Feb 2017
Cited by 4
Abstract
Currently, research on structural health monitoring systems is focused on direct integration of the system into a component or structure. The latter results in a so-called smart structure. One example of a smart structure is a component with integrated strain sensing for continuous [...] Read more.
Currently, research on structural health monitoring systems is focused on direct integration of the system into a component or structure. The latter results in a so-called smart structure. One example of a smart structure is a component with integrated strain sensing for continuous load monitoring. Additive manufacturing, or 3D printing, now also enables such integration of functions inside components. As a proof-of-concept, the Fused Deposition Modeling (FDM) technique was used to integrate a strain sensing element inside polymer (ABS) tensile test samples. The strain sensing element consisted of a closed capillary filled with a fluid and connected to an externally mounted pressure sensor. The volumetric deformation of the integrated capillary resulted in pressure changes in the fluid. The obtained pressure measurements during tensile testing are reported in this paper and compared to state-of-the-art extensometer measurements. The sensitivity of the 3D printed pressure-based strain sensor is primarily a function of the compressibility of the capillary fluid. Air- and watertightness are of critical importance for the proper functioning of the 3D printed pressure-based strain sensor. Therefore, the best after-treatment procedure was selected on basis of a comparative analysis. The obtained pressure measurements are linear with respect to the extensometer readings, and the uncertainty on the strain measurement of a capillary filled with water (incompressible fluid) is ±3.1 µstrain, which is approximately three times less sensitive than conventional strain gauges (±1 µstrain), but 32 times more sensitive than the same sensor based on air (compressible fluid) (±101 µstrain). Full article
(This article belongs to the Special Issue 3D Printed Sensors)
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