Prolonged sitting inadequacies cause pressure ulcer to many individuals, especially to disadvantaged with reduced mobility. The measurement of distributed pressure and detection of irregular sitting postures is essential for preventing the risk of developing pressure ulcer. In this paper, a pressure sensing system capable of recognizing sitting postures by means of measuring interface pressure through printed pressure sensors is presented. A thin and flexible large area sensor is screen-printed using silver flake and carbon particle inks and comprises 16 sensing elements. For the evaluation of practical usability, the sensor characterization is carried out by conducting stability, repeatability, drift and bending tests. The performance of the sensor is checked under varying environmental conditions. Sitting posture detection accuracy above 80 % is achieved using a classification algorithm for four different sitting postures. Pressure distribution is monitored at a scanning rate of 10 Hz. A low power and small form factor of read-out electronics enables a compact packaging inside the seat cushion. The presented sensor design targets smart wheelchairs, but it is extendable to much larger areas, for example to be used in beds. The proposed sensing system would be of a great assistance for caregivers and health professionals.
In the biomedical sector, pressure sensors exhibit an important role towards monitoring and recognition of sitting posture for wheelchair users, which is helpful for pressure ulcer prevention and cure. In this paper, a flexible and inexpensive screen printed large area pressure sensing system is presented. The large area sensor comprise three layers, is able to cancel-out false pressure detection, and achieves a sitting classification accuracy over 80 percent. The sensor matrix contains 16 sensors distributed over an area of 23.5 cm × 21.5 cm and the pressure points are monitored at a scanning rate of 77 Hz. The sensor system provides wireless communication and a Windows based GUI is developed that allows real-time presentation of pressure data by means of a pressure map. The presented sensor design targets smart wheelchairs but is suitable for any low cost and high throughput pressure distribution monitoring systems.
The table is a result from cyclic strain test with 25 % and 50 % elongations of screen-printed stretchable conductive tracks on thermoplastic polyurethane.
This paper presents a posture recognition system aimed at detecting sitting postures of a wheelchair user. The main goals of the proposed system are to identify and inform irregular and improper posture to prevent sitting-related health issues such as pressure ulcers, with the potential that it could also be used for individuals without mobility issues. In the proposed monitoring system, an array of 16 screen printed pressure sensor units was employed to obtain pressure data, which are sampled and processed in real-time using read-out electronics. The posture recognition was performed for four sitting positions: right-, left-, forward- and backward leaning based on k-nearest neighbors (k-NN), support vector machines (SVM), random forest (RF), decision tree (DT) and LightGBM machine learning algorithms. As a result, a posture classification accuracy of up to 99.03 percent can be achieved. Experimental studies illustrate that the system can provide real-time pressure distribution value in the form of a pressure map on a standard PC and also on a raspberry pi system equipped with a touchscreen monitor. The stored pressure distribution data can later be shared with healthcare professionals so that abnormalities in sitting patterns can be identified by employing a post-processing unit. The proposed system could be used for risk assessments related to pressure ulcers. It may be served as a benchmark by recording and identifying individuals’ sitting patterns and the possibility of being realized as a lightweight portable health monitoring device.
The development of wearable health devices is an emerging technology, and pressure sensors have been widely used in several of these applications. Plenty of research within pressure sensors is focused on tactile sensing and artificial skin. In this paper, a highly flexible and stretchable pressure sensor is presented. The sensor comprises stretchable thermoplastic polyurethane (TPU) film as substrate and stretchable conductive inks as electrodes and sensing material. Screen printing is used to fabricate electrodes and pressure sensing components on TPU sheets. Electrical and mechanical properties of the fabricated sensors indicate good mechanical and electrical stability while retaining pressure sensing properties and marginal deterioration even after 100 elongation cycles. The findings show that the presented stretchable pressure sensor has a great potential for usage on surfaces where bending and stretching will occur while retaining nearly all of its electrical and mechanical capabilities. The proposed sensor may be employed as a wearable device to detect human movements.
Optical fiber duct installation requires blowing of cleaning sponges for dirt and moisture removal before blowing the fiber cables. The traditional method requires one operator that blows the sponge and one operator in the receiving end that manually evaluate the sponges until a dry sponge is received. The proposed system eliminates the need of a second operator by introducing a solution for automatic sponge detection and characterization of moisture in sponges at the receiving end. An optical sensor is used for detection and a capacitive sensor is developed to measure the sponge's wetness. Sensor data is automatically transmitted back to the operator at the feeding end via a mobile phone. The system is characterized to work with sponges ranging from saturated with wetness to what is deemed as dry.
At present, optical fiber microducts are joined together by mechanical type joints. Mechanical joints are bulky, require more space in multiple duct installations, and have poor water sealing capability. Optical fiber microducts are made of high-density polyethylene which is considered best for welding by remelting. Mechanical joints can be replaced with welded joints if the outer surface layer of the optical fiber microduct is remelted within one second and without thermal damage to the inner surface of the optical fiber duct. To fulfill these requirements, an electro-thermal model of Joule heat generation using a copper coil and heat propagation inside different layers of optical fiber microducts was developed and validated. The electro-thermal model is based on electro-thermal analogy that uses the electrical equivalent to thermal parameters. Depending upon the geometric shape and material properties of the high-density polyethylene, low-density polyethylene, and copper coil, the thermal resistance and thermal capacitance values were calculated and connected to the Cauer RC-ladder configuration. The power input to Joule heating coil and thermal convection resistance to surrounding air were also calculated and modelled. The calculated thermal model was then simulated in LTspice, and real measurements with 50 µm K-type thermocouples were conducted to check the validity of the model. Due to the non-linear transient thermal behavior of polyethylene and variations in the convection resistance values, the calculated thermal model was then optimized for best curve fitting. Optimizations were conducted for convection resistance and the power input model only. The calculated thermal parameters of the polyethylene layers were kept intact to preserve the thermal model to physical structure relationship. Simulation of the optimized electro-thermal model and actual measurements showed to be in good agreement.
Optical fiber microducts are joined together by mechanical joints. These mechanical joints are bulky, require more space per joint, and are prone to air pressure leakage and water seepage during service. A battery powered electrofusion welding system with a resistive-type joint has been recently developed to replace mechanical joints. These resistive-type electrofusion joints require physical connectors for power input. Due to a different installation environment, the power input connectors of resistive optical fiber microduct joints may corrode over time. This corrosion of connectors will eventually cause water seepage or air pressure leakage in the long run. Moreover, due to connector corrosion, resistive-type optical fiber microduct joints cannot be re-heated in future if the need arises. In this study, an inductively coupled electrofusion-type joint was proposed and investigated. This inductive-type electrofusion joint is not prone to long-term corrosion risk, due to the absence of power connectors. Inductive-type electrofusion joints can be re-heated again for resealing or removal in the long run, as no metal part is exposed to the environment. The battery powered inductive welding system can be easily powered with a 38 volts 160 watt-hour battery. The inductive-type electrofusion joint was welded within one second, and passed a 300-newton pull strength test and a 10-bar air pressure leakage test. It was demonstrated that the power input requirement for inductive electrofusion joints is 64% higher than that of resistive electrofusion joints. However, these inductive joints are relatively easy to manufacture, inexpensive, have no air leakage, and no water seepage risk in highly corrosive environments.
At present, optical fiber microducts are coupled together by mechanical types of joints. Mechanical joints are thick, require a large space, and reduce the installation distance in multi-microduct installation. They may leak or explode in the blown fiber installation process. Mechanical joints are subjected to time dependent deterioration under long service times beneath the earth's surface. It may start with a small leakage, followed by damage due to water freezing inside the optical fiber microduct. Optical fiber microducts are made up of high-density polyethylene, which is considered most suitable for thermoelectric welding. For thermoelectric welding of two optical fiber microducts, the welding time should be one second, and should not cause any damage to the inner structure of the microducts that are being coupled. To fulfill these requirements, an LTspice simulation model for the welding system was developed and validated. The developed LTspice model has two parts. The first part models the power input to joule heating wire and the second part models the heat propagation inside the different layers of the optical fiber microduct and surrounding joint by using electro-thermal analogy. In order to validate the simulation results, a battery powered prototype welding system was developed and tested. The prototype welding system consists of a custom-built electrofusion joint and a controller board. A 40 volt 4 ampere-hour Li-Ion battery was used to power the complete system. The power drawn from the battery was controlled by charging and discharging of a capacitor bank, which makes sure that the battery is not overloaded. After successful welding, a pull strength test and an air pressure leakage test were performed to ensure that the welded joints met the requirements set by the mechanical joints. The results show that this new kind of joint and welding system can effectively replace mechanical joints in future optical fiber duct installations.
In this article, a modified design of an RF Radio Frequency Electronic ArticleSurveillance (EAS) tag, used as a sensor platform, is manufactured and characterized. EAStags are passive devices consisting of a capacitor and coil, tuned to a resonance frequencyreadable by the detector equipment, in this case 8.2 MHz. They were originally used todetect whether merchandise was being moved through the detection gates at shop exits, inwhich case an alarm was triggered. If the capacitance is divided in two and a resistivesensor device inserted in between, the resonant Inductor-Capacitor (LC) circuit becomes anInductor-Capacitor-Capacitor-Resistor LCCR circuit and can be used as a sensor tag. Ahigh sensor resistance means that one capacitor is decoupled, leading to one resonancefrequency, while a low resistance will couple both capacitances into the circuit, resulting ina lower resonance frequency. Different types of resistive sensors exist that are able todetect properties such as pressure, moisture, light and temperature. The tag is manufacturedin Aluminum foil on a polyetylentereftalat (PET) substrate, resulting in a cost effectiveRF-platform for various resistive sensors. Two types of tags are designed andmanufactured, one with parallel plate capacitors and the other with interdigital capacitors.To test the tags, a resistive tilt sensor is mounted and the tags are characterized using anetwork analyzer. It is shown that for high resistance, the tags have a resonance frequencyof more than 10 MHz while for low values the frequency approaches 8.2 MHz.
Thin inkjet-printed tracks of silver nanoparticles have previously been observed to show a non-reversible decrease in resistance when exposed to a high degree of relative humidity and thus providing sensor functionality with a memory effect. This paper provides a more in-depth explanation of the observed humidity sensor effect that originates from inkjet-printed silver nanoparticle sensors on a paper substrate. It is shown that the geometry of the sensor has a large effect on the sensor's initial resistance, and therefore also on the sensor's resistive dynamic range. The importance of the sensor geometry is believed to be due to the amount of solvent from the ink interacting with the coating of the paper substrate, which in turn enables the diffusion of salts from the paper coating into the ink and thus affecting the silver ink.
Printed electronics is a rapidly developing field where many components can already be manufactured on flexible substrates by printing or by other high speed manufacturing methods. However, the functionality of even the most inexpensive microcontroller or other integrated circuit is, at the present time and for the foreseeable future, out of reach by means of fully printed components. Therefore, it is of interest to investigate hybrid printed electronics, where regular electrical components are mounted on flexible substrates to achieve high functionality at a low cost. Moreover, the use of paper as a substrate for printed electronics is of growing interest because it is an environmentally friendly and renewable material and is, additionally, the main material used for many packages in which electronics functionalities could be integrated. One of the challenges for such hybrid printed electronics is the mounting of the components and the interconnection between layers on flexible substrates with printed conductive tracks that should provide as low a resistance as possible while still being able to be used in a high speed manufacturing process. In this article, several conductive adhesives are evaluated as well as soldering for mounting surface mounted components on a paper circuit board with inkjet printed tracks and, in addition, a double sided Arduino compatible circuit board is manufactured and programmed.
In this paper an ink-jet printed write once read many (WORM) resistive memory fabricated on paper substrate is presented. The memory elements are programmed for different resistance states by printing triethylene glycol monoethyl ether on the substrate before the actual memory element is printed using silver nano particle ink. The resistance is thus able to be set to a broad range of values without changing the geometry of the elements. A memory card consisting of 16 elements is manufactured for which the elements are each programmed to one of four defined logic levels, providing a total of 4294 967 296 unique possible combinations. Using a readout circuit, originally developed for resistive sensors to avoid crosstalk between elements, a memory card reader is manufactured that is able to read the values of the memory card and transfer the data to a PC. Such printed memory cards can be used in various applications.
This paper describes mounting of standard surface mount component packages on a paper substrate using an industrial solder process with a low-temperature solder. The use of paper as a substrate for printed flexible electronics is becoming more and more widespread as an alternative to the more commonly used plastic substrates, such as polyethylene and polyimide. Paper has the benefits of being environmentally friendly, recyclable, and renewable, as well as inexpensive. It is shown that it is possible to mount standard surface mount device components on paper substrates using low-temperature solder in an industrial soldering process. The contact resistances obtained are mostly low, although the yield of functioning contacts is low. The reason is cracking of the substrate coating layer that goes through the printed silver tracks. It was observed that the cracks appear mostly close to the contact pads, the most likely cause is thermal mismatch between the coating layer and solder and also thermal expansion of the photo paper resin coating. The smallest component package size, 0201, resulted in the highest yield of >80% with decreasing yield for larger package sizes.
A novel dual-band circularly polarized MIMO wearable antenna is screen-printed on a cotton polyester fabric to operate at 2.45 and 5.8 GHz wireless body area network communications. The MIMO fabric antenna is realized with two circularly polarized wearable antennas arranged in orthogonal directions, which provides a less than -10 dB bandwidth of 400 MHz from 2.2 to 2.6 GHz and 800 MHz from 5.3 to 6.1 GHz, with impedance bandwidth of 17 and 14% for lower and higher bands, respectively. The antenna provides an axial ratio bandwidth (below 3 dB) of 3% from 2.4 to 2.47 GHz and 8% from 5.45 to 5.94 GHz. The proposed MIMO antenna is integrated with an artificial magnetic conductor, which helps to create isolation between the human body and antenna, which also minimizes the specific absorption rate (SAR). The antenna SAR performance is tested on the HUGO model, which gives 0.025, 0.035 W/Kg for 1g tissue at 2.45 and 5.8 GHz. Furthermore, the antenna provides good MIMO characteristics such as envelope correlation coefficient, diversity gain, and channel capacity. The antenna is suitable for flexible wearable applications due to fabric substrate, screen printing, low SAR, and lightweight.
This article presents the design, manufacturing, and measurements of antennas on paper, realized using ink-jet printing of conductive inks based on nano-silver particles (nSPs). The extraction of the substrate characteristics such as the dielectric constant and dielectric loss is performed using a printed ring resonator technique. The characterization of the nSPs conductive inks assesses different parameters as sintering time and temperature. Two antennas are realized corresponding to the most common needs for wireless sensor networks in Trains Environment. The first one is a patch antenna characterized by a broadside radiation pattern and suited for operation on metallic structures. The second one is a quasi-yagi antenna, with an end fire radiation pattern and higher directivity, without requiring a metallic ground plane. Both antennas present a good matching (S11 < -20 dB and S11 < -30 dB, respectively) and acceptable efficiency (55% and 45%, respectively) for the paper substrate used at the center frequency of 2.4 GHz, corresponding to the first channel of the IEEE 802.15.4 band.
Fragment-type etch patterns are proposed and designed on ultra-wideband planar antenna to acquire sharp roll-off band notch. Multi-objective evolutionary algorithm is applied to achieve the optimization searching of the best fragment-type etch pattern by setting multiple objectives to acquire the exact notched band and challenge the roll-off criterion (ROC) of band notch. Efficiency of the design can be improved by properly presetting slits on the patch radiator. For demonstration, designs with different slit presetting are implemented and tested. With single slit preset, band notch of ROC=0.72 at the WLAN band ranging from 5.15 GHz to 5.85GHz is acquired.
By specifying objective functions defining the two bands to be notched with high roll-off criteria (ROCs), optimization searching for the best fragment-type etch pattern on ultra-wideband (UWB) antenna is implemented by using multi-objective optimization. The optimization with too many objective functions requires special treatment to improve the searching efficiency. In this design, two slits are preset on appropriate positions on different sides of the UWB radiator to constrain the decision space for etch pattern searching and yield two initial notched bands to speed up the optimization. For demonstration, a UWB patch antenna is designed with dual-band notches of ROC = 0.63 at WiMAX band and ROC = 0.65 at WLAN band. Both the simulation and measurement results indicate that there is significant improvement of the selectivity of the dual-band notches.
I dagens samhälle blir det allt viktigare att fortbilda sig under hela sitt yrkesverksamma liv. För att möta efterfrågan på det livslånga lärandet har Mittuniversitetet utvecklat och genomfört ett antal kurser som riktar sig mot yrkesverksamma ingenjörer. Detta arbete presenterar våra erfarenheter av att ge dessa kurser, med en tyngdpunkt på studenternas upplevelser. Syftet med detta är att bygga upp en vetenskaplig bas för vad vi gör som är bra, men även vad som kan förbättras och förändras. Målsättningen är att göra dessa specialanpassade kurser riktade mot yrkesverksamma ingenjörer så givande och flexibla som möjligt. Våra initiala resultat visar bland annat att studenternas negativa upplevelser ofta var kopplade till antagningsförfarandet och det praktiska genomförandet av kurserna. Man hade svårigheter med att hitta hur man skulle registrera sig på kursen och att tidsramen för registrering kunde vara ett problem. Läroplattformen uppfattades som svår att överblicka och det förekom även viss otydlighet gällande var undervisningen skulle äga rum. Den positiva responsen i utvärderingarna gällde främst det faktiska kursinnehållet, då man ansåg att uppgifter och kursmaterial var givande. Vidare uppskattades kursupplägget, att man kunde kombinera studierna med arbete. Framledes kommer vi att fortsätta med dessa utvärderingar i takt med att kurserna ges, och därefter anpassa vårt mottagande och kommunikationen med studenterna. Även kursupplägget ses över kontinuerligt via den återkoppling vi mottar.
This letter presents a printed UHF RFID sensor solution that indicates if a passive RFID tag has been exposed to a certain degree of moisture. The printed sensor operates as a write-once-read-many (WORM) resistive memory device as it permanently changes its resistance from about 10 to 10 after exposure to moisture or water. A printed coupling loop with an embedded WORM sensor is horizontally placed just above the surface of an ordinary UHF RFID tag. Electromagnetic coupling is used to modulate the properties of the tag antenna by changing its input impedance and introducing ohmic losses in proportion to the embedded sensor values. The passive RFID tag can change state from readable to unreadable when the WORM bit is set, i.e., is put in a low-resistance state. The proposed concept verifies that commercial RFID tags can be used as sensor tags by simply adding an electromagnetically coupled sensor as a sticker or by similar means, without the need for ohmic contacts between the sensor and the original RFID tag. © 2006 IEEE.
This paper presents an analytical model for electromagnetically coupled UHF RFID sensor tags where a coupling loop with an embedded sensor is attached to an ordinary UHF RFID tag with a small gap. Electromagnetic coupling is used, in this case, to modulate the properties of the tag antenna in proportion to the values of the embedded sensor. The antenna together with the coupling loop are represented as an equivalent circuit and the analysis of the sensor tag becomes a circuit-level calculation after extracting parameters from full-wave simulations for, respectively, the separated dipole antenna and coupling loop. The results calculated from the equivalent circuit model are compared with the results from full-wave simulations and show good agreement. The presented model can thus be used for analyzing and predicting the behavior of electromagnetically coupled sensor tags. Based on the analysis with the presented model, the methods for optimizing the sensory performance of this kind of RFID sensor tags are also presented in this paper.
High speed manufacturing processes are commonly associated with high mechanical tolerances. For RFID antennas, mechanical manufacturing tolerances imply uncertainties in the antennas outer dimensions as well as in the surface- and line-roughness of the antennas geometry. Rough edges can for example be caused by high speed dry patterning processes. This work investigates the impact that rough patterns along the edges of an antenna structure have on UHF RFID tags' communication capabilities. The work characterizes the negative influence that edge roughness of different levels has on standard RFID dipoles. Results show that, as expected, the performance degradation for an RFID tag antenna increases with increased edge roughness amplitude. The results also show that the performance degradation due to edge roughness is almost identical for the investigated antennas' different line widths when the roughness level is normalized to its specific antenna line width, i.e., an antenna with a wider line width is more robust and can withstand a higher degree of edge roughness.
This paper presents a printed UHF RFID sensor solution that indicates whether a passive RFID tag has been exposed to a certain degree of humidity. The printed sensor operates as a Write Once Read Many (WORM) resistive memory as it permanently changes its resistance from about 2 kÙ to less than 50 Ù after exposure to humidity or water. The change of the sensor resistance is used to modulate the properties of a UHF RFID tag antenna by changing antenna input impedance and also introducing or removing ohmic losses in the antenna structure. The final result is reflected in the change of the minimum transmit power required to power-up the RFID tag. Both the sensor and the tag antenna are printed horizontally on a paper substrate. Different geometric combinations of sensor and antenna structures are investigated. Typical applications include non-invasive methods for detecting wetness or humidity levels in hidden locations such as within construction structures. The sensor setup can also serve to provide information as to whether a package sent over a supply chain has exceeded a certain level of humidity during its route.
The development of printed electronics on flexible substrates is increasing rapidly, where the main benefit is large area and low cost. However, the functionality and performance of printed circuits cannot compete with standard silicon based microprocessors or integrated circuits, though the functionality and performance of printed circuits are increasing. Therefore, in this work we investigate the possibilities of using Sn42/Bi57.6/Ag0.4 low-temperature solder paste together with a reflow solder oven and hot air solder iron to mount regular SMD components on screen-printed silver tracks. It was found that it is possible to solder standard Si SMD pack-ages onto screen-printed Ag ink tracks on paper substrate, however, the component bonding strength to Polyimide were not satisfactory. The resistance of the solder joints was found to be no more than 240 mΩ. The bond strength was found to be higher using the manual hot air sol-der iron than the reflow solder oven. Bending tests show that the bonding strength is higher for the hot air soldered components. Reference samples on FR-4 based copper PCB show a bond strength ~10 times higher but we conclude that it is possible to solder regular Si SMD components onto Ag-printed conductors on paper substrate with good results. The process could be used to fabricate hybrid printed electronics on a standard solder process line.
RF electronics commonly incorporate PCB-materials with low loss tangents, which limits its use for large-area applications due to its high cost. This work verifies one alternative solution how non-conventional flexible circuit materials can be used to manufacture large functional surfaces for RF-based applications. Laminated Al foils are used for conducting layers and a flexible foam material is used for substrate. An RFID reader system has been developed to demonstrate the functionality, comprising of eight microstrip antenna elements arranged in a SP4T switching structure covering an area of 1.2 m × 0.6 m. Each antenna element is individually addressable with aid of distributed digital and analogue multiplexer circuitry and it is shown how these components can be soldered directly onto the Al conductors. The constructed system shows good RF performance, both with regards to the materials and to the interconnections with the distributed multiplexer circuitry. It can perform far-field RFID tag reading above its surface without dead zones and the system characterization implies that the concept can be further expanded to cover geometrical areas up to 1000 square meters.
RFID readers serve the obvious role of extracting information from RFID tagged objects. Objects without RFID tags or objects with tags that for some reason are unreadable will not be noted at all when positioned within an RFID reader antenna's interrogation zone. In this paper, we investigate how UHF RFID reader systems for smart shelf applications could also be used for classification and distance estimation of non RFID tagged objects, if the reader modules provide access to antenna S-parameters. The investigation is performed with an inset fed microstrip antenna where objects of different materials are positioned at different heights above the antenna. It is shown how objects are detected and classified in terms of their materialistic properties through S-parameter analysis and how the distance from the antenna to the object could be estimated.
Electronic textiles, integrating functional electronics circuits into fabric materials, are emerging as an important branch of flexible circuits. In this paper, we introduce a novel material combination for electronic textiles that can be used in implementing hybrid electronics. This type of circuits is fabricated by laminating patterned aluminum foils onto a nonwoven substrate in a high-speed roll-to-roll method. An isotropic conductive adhesive and an anisotropic conductive adhesive are used to assemble standard surface mount device components onto the fabricated circuits. The surface mount techniques are characterized by means of contact resistance measurements, component bonding strength tests, circuit bending tests, and scanning electron microscopy. An NFC tag with relative humidity sensing functionality is fabricated to evaluate the fabricated circuits to an electronic system level.
Implementing electronics systems on paper is an important area of flexible circuit technologies. One of the approaches is to print conductive inks onto paper substrates, on which silicon-based surface mount device components are mounted. However, one of the problems is that the printed conductors have unneglectable resistivity. In this paper, we present paper-based flexible circuits, using copper and aluminium conductors that are laminated onto paper substrates using a high-speed roll-to-roll method. Edge roughness inspections and repeated two-point bending tests are carried out to evaluate the manufactured flexible circuits. Three surface mount techniques are used to assemble standard surface mount device components onto the flexible circuits, including an isotropic conductive adhesive, an anisotropic conductive adhesive, and a low-temperature solder paste. Several characterizations are performed to the surface mount techniques, including contact resistance measurements, component bonding strength tests, assembled circuit bending tests, and scanning electron microscopy. The results of the characterizations suggest that flexible circuits made from Cu with paper substrate achieve satisfactory results for mechanical reliability, all surface mount techniques, and have the potential to be used on automatic component assembly lines. In order to test whether such flexible circuits and surface mount techniques can be used in implementing electronics systems, passive NFC tags with relative humidity sensing functionality are made, which are interrogated by an NFC equipped mobile phone.
Screen printing is a stencil process where conductive inks are patterned onto substrates through a fine mesh of threads. Nowadays, screen printing can be used to print RFID antenna structures onto flexible and ultra-low-cost substrates such as pa-per. In this manuscript, we present an HF RFID reader antenna system, operating at 13.56 MHz, using screen printed Ag particle ink as conductor and using HP photo paper as substrate. The proposed antenna system comprises four loop antenna elements, matched to 50 Ω, and one I2C addressed SP4T multiplexer circuitry, controlled through an exterior embedded system. The geometries, designs and characterizations of the antenna system are described in the manuscript in details. Measurement results show that the antenna system has low power reflections and a suitable Q factor. It has a maximum 11.1 cm RFID tag read range at an antenna system input power of 33 dBm. 2D RFID tag positioning can be enabled by utilizing the RFID tag interrogation zones formed by the four loop antenna elements. In addition, a parametric study is carried out to investigate the effect of loop antenna element DC resistance on the antenna element performance. It can be concluded that the proposed method can be used to create low-cost and large-area HF RFID reader antenna systems.
Detection of forest wildfires at early stages can significantly improve the success of fire fighting and thus it contributes to the damage and cost reduction. Surface deployed sensor networks linked to global nets are often regarded as technically simple options to achieve forest fire detection and progress monitoring. Straightforward solutions with sensor nodes continuously supplying telemetric information demand heavy duty power supplies and periodic service. They are relatively expensive and commonly not environmentally friendly. We have suggested and currently develop an early warning forest fire detection system based on inexpensive, dormant fire-activated detecting sensors and a number of monitoring nodes in a network configuration. Small deploy-and-forget type sensors contain a radio transmitter with recorded identity number, together with an inactive power element. When activated by high temperature of a developing wildfire, this element produces enough power to support the transmitter, broadcasting the unique identity code until the sensor is completely burnt. Monitoring nodes of such system stand by for sensor activation and forward the alarm information along the monitoring nodes network. Implementation of anti-collision transmission protocols in the sensors allows the monitoring nodes to keep track of fire development and progress. Monitoring nodes and nodes linking the forest fire detection and monitoring net to public networks can be made using conventional technology and utilizing existing communication networks. Thus significant efforts have been directed to the design of the primary sensors, designing them to be cost efficient and minimizing their environmental impact. Cellulose-based materials are widely used in the sensor construction to decrease its environmental impact and cost. The core of the sensor power element is made of laminated and screen-printed cellulose- based substrates. The power element is activated by a small amount of water, trapped in crystal hydrate salts in storage and released by elevated temperatures of the fire. These salt-based sensors can be manufactured in a rollto- roll manner, making them cost effective. Absence of any liquids or gels in the sensor construction will guarantee a good shelf time. © 2012 WIT Press.
A horizontal printed Write Once Read Many (WORM) resistive memory has been developed for use in wireless sensortags targeting single event detection in smart packaging applications. The WORM memory can be programmed using a 1.5 V printedbattery. An alternative programming method is to use chemical sintering which allows the development of exposure-time triggeredsingle event tags that can be accessed wirelessly. The new WORM memory has very low losses in the ON-state which allows directintegration into antenna structures.A sensor tag that utilizes the WORM memory functionality and the well established Electronic Article Surveillance (EAS)communication standard has been outlined. Both active and fully passive sensor tag solutions have been proposed.The role of printed electronics in smart packaging applications has been reviewed and discussed. Important enabling factors forthe future development have been highlighted, such as the need for hierarchical design and test tools, better printed interconnecttechnologies as well as better components that allow communication with existing information and communication technology (ICT)standards. This is illustrated and underlined by the presented smart packaging concept demonstrators.
The current work addresses the challenge of measuring urine volume in diapers primarily targeting geriatric care applications. There are number of incontinence alarm innovations suggested and described in patents and scientific reports. However, there are hardly any reports of such systems in permanent use in the hospital care market. One reason might be the challenging system requirements of such applications. According to our own experiences and requirements reported in the literature those are truly demanding. We need meter long communication range, passive sensor functionality, robust and safe measurement, unobtrusive sensor device design (patient) and a convenient reader and user interface (care personal). The list of specifications can be added to, a very low price adding only a small fraction to the over all diaper cost. Finally the system should improve the comfort of the patient and increase diaper management efficiency, reducing the costs of the care provider. The recent progress and usage of RFID technology have reduced the cost levels for inlays and readers. Thus, standard RFID inlays may be a candidate providing the targeted functionality in a smart diaper. In this work we evaluate the possibility to use the RFID antenna as the sensor element when detecting when a diaper has reached a certain degree of urine saturation. The evaluation has been done in a laboratory setup, with real test persons providing authentic readout scenarios. © 2011 IEEE.
The present invention relates to a sensor arrangement (100) suitable for determining a condition, for example moisture, comprising a first RFID-unit 5 (110) and a second RFID-unit (120) being subjected to said condition. The sensor arrangement is characterized in that the second RFID-unit (120) is at least partly provided with a degradation means (130) having such properties that, when subjected to said condition, the second RFID-unit (120) is functionally degraded to a greater extent than the first RFID-unit (110). The 10 invention also relates to a sensor arrangement product (199) comprising at least one sensor arrangement.
Antennas in RFID tags have often been designed in a single layer with copper as conductor and plastic foils as substrate. There is currently a large interest in roll to roll production of RFID tags and silver based inks have been developed for use in printed RFID antennas. Silver ink based single layer antennas works well and is providing 70% to 80% of the reading range compared to copper solutions. However, more advanced antennas are needed to provide less sensitivity to the environment of RFID tags .i.e. need for placing tags on metal or near water. In this work we present a study of multilayered antennas so called patch antennas, for 2.45 GHz RFID tags. The advantage of the patch antenna is that it can be applied to any kind of material, reflecting or lossy material, and still provide good antenna function. However, the patch antenna efficiency is strongly dependent on the material used. For low cost RFID tags in logistics there is a need to manufacture the antenna as a part of the packaging process. In the current work we have investigated the possibility to manufacture printed patch antennas of common packaging materials.
In this work we present a simple printed moisture sensor fabricated using electronic inks on a multilayer paper structure. The sensor is based on a Carbon-Zinc type energy cell and provides power to a readout electronic circuit when activated by moisture. The sensors are based on a number of our filed patents according to which the sensor is used for both event detection and as a power source for the processing electronics. Typical applications are moisture and leakage detection in buildings, water pipe lines, smart packages and health care systems such as smart incontinence sensors. As the detector is triggered, it powers up an electronic circuit (polymer based or silicon based) that starts communication with the alarm server. In the simplest systems a sound or a light alarm is started to alert the user. In this work we present a characterization of some critical parameters of the sensor such as power driving capability, linearity, internal memory effects and saturation. In addition, we examine a specific application, when sensor is used as defrosting alarm for surveillance of frozen articles during transport.
A system integration scheme relevant for smart packaging applications is presented. Recent advances in printed electronics, radio frequency identification tag production, and standardization of communication protocols are factors that increase the design freedom for new applications. As in all new technology fields, the first products are expected to appear in the high-cost segment attracting early adopters in the form of niche products. A reasonable assumption is that these products will come from hybridization of different types of technologies. Such a scenario is likely since no technology solution available can provide all features that these types of applications demand. There is a need of standard solutions for hybridization of silicon devices and printed (or foil-type) components. Conductive ink technology is a powerful tool for hybridization and customization of large-area electronics, providing 3-D integration and large-area customization. However, high-performance communication and advanced processing demand the use of silicon. Smart hybridization solutions allow combination of the best from both worlds. This paper analyzes the requirements on hybridization technologies suitable for smart packaging applications and provides design examples on integration of intrusion surveillance solutions for cellulose-based packaging applications. It shows that even though the current hybridization technologies are far from optimal, they can provide a considerable design freedom and system performance. © 2011-2012 IEEE.
Is it possible to produce a planar dipole-like antenna with a reduced conductive area without any loss in either robustness or performance? The objective is to reduce the amount of expensive conductor to be used when applying a meshing technique to the printing of antennas. In this context, robustness means that the characteristics are maintained when the antenna is damaged, for example if it is scratched. This is particularly important for radio frequency identification tags in logistic systems. A general antenna robustness evaluation methodology, based on numerical simulations of a large number of randomly damaged antennas, is used for the antenna comparisons. The antenna performance degradation, based on the return loss (S11) at 868MHz, is monitored for some basic planar antennas. Finally, we show that it is possible to produce robust low-cost antennas using wire replacements for the solid planar antennas and thus, provided that the robustness requirement is moderate, replace the solid antenna with a thin conductor analogue.
Antennas in some military applications can be expected to suffer from physical damage of the antenna structure itself. Examples are intelligent munitions when rammed into the gun barrel and vehicle mounted conformal antennas harmed by various types of mechanical impact. Another example is extremely low cost antenna applications. A Radio Frequency IDentification (RFID) system consists of a more or less advanced reader and a very simple tag that can be fastened onto a variety of surfaces. The tag incorporates a transceiver and can carry one or more sensing devices and report findings back to the reader. To keep costs down, low-cost standardized antennas will be used even when the tag is deployed in harsh environments. For the kind of antennas described above, a predictable graceful degradation of performance is appealing. A partial damage of the antenna must not lead to a system breakdown. An essential part of the antenna design must be to ensure robust communication even when the antenna is partially damaged. What performance can be expected from an antenna when part of its structure has been removed? In this paper this issue is examined for a bow-tie antenna when part of its structure has been removed. The structural deformation has been inflicted by removing stripes of the outer part of one of the antenna arms. The investigation was undertaken by simulations in a commercial Finite Integration (FI) program and by verifying measurements.
We address the question of robustness of damaged microstrip antennas, the damage being either penetrating, caused by fragment impact, or floating, caused by manufacturing imperfections. A simple analytic expression is derived to facilitate the prediction of robustness. To verify this expression a Monte Carlo method, based on a general 3D electromagnetic solver, is used to evaluate the robustness of the antennas. The simulations are verified by measurements and supplementary simulations in an alternative electromagnetic solver, using the finite difference time domain method (FDTD). The agreement between the simulated results and the analytic expression is found to be good in a qualitative comparison.