Recent Advances in Printed Capacitive Sensors

In this review paper, we summarize the latest advances in the field of capacitive sensors fabricated by printing techniques. We first explain the main technologies used in printed electronics, pointing out their features and uses, and discuss their advantages and drawbacks. Then, we review the main types of capacitive sensors manufactured with different materials and techniques from physical to chemical detection, detailing the main substrates and additives utilized, as well as the measured ranges. The paper concludes with a short notice on status and perspectives in the field.H2020-MSCA-IF-2017-794885-SELFSEN

3 axis polymeric accelerometer and method of production

The present invention consists in a thermal accelerometer capable of detecting acceleration in multiple axes. The accelerometer is made of four microinjected polymeric parts (1, 2, 3, 4), which can be two identical top parts and two identical central parts or four different parts, which are assembled with active polymeric membranes (5, 6, 7) to construct the 3-axis acceleration sensing device. The microinjected parts provide mechanical support for the heater and temperature sensors that are placed on the membranes. The device operating gas medium is hermetically sealed by the polymer parts and electrical current applied to the heater causes the air to heat and external acceleration imposes a gradient of temperature sensed by the thermal sensing elements

Flexible electronics : materials and sensor fabrication

This dissertation demonstrates how to fabricate piezoelectric/pyroelectric thin films by using different printing techniques. These techniques could replace vacuum techniques for manufacturing piezoelectric/pyroelectric sensors. Ink-jet, screen and stencil printing techniques were developed to print these devices. This work outlines attempts to develop a solution processable conductive ink for ink-jet printing. It then details the printing of commercial conductive ink on flexible substrates employing the three printing methods. Raman spectroscopy and Fourier transform infrared spectroscopy, are both used to investigate the structure of the P(VDF-TrFE) films. Optical microscopy is used to investigate the thickness and uniformity of the deposited films. The formulation of P(VDF-TrFE) for printing is also described for the three printing methods. Piezoelectric accelerometers have been developed and demonstrated. The sensors are axial compression piezoelectric accelerometers which measure impacts in the direction perpendicular to the sensors themselves. When the sensors are moved downward the top electrode tends to move upward, inducing charge via the piezoelectric effect. The sensors were mounted on an electrodynamic shaker and tested with an input vibration up to 1.5 g s at 100 Hz. The test data show that the accelerometers track the frequency of the input vibration; the output increases with increasing input acceleration. A comparison of the three printing methods to fabricate sensors on flexible substrates with commercial conductive inks and formulated P(VDF-TrFE) ink specific to the print method with similar geometries produces the following conclusions: Excellent adhesion of the commercial silver ink for screen and stencil printing has been achieved. The stencil printed silver films are smoother and more uniform than the screen printed films. Adhesion of the commercial PEDOT/PSS ink-jettable was successful. However, smoothness and uniformity were issues that need to be resolved. Also, when the ink-jetted PDOT/PSS films were exposed to high temperatures the films tended to crack and adhesion was lost. Functional devices were fabricated with screen and stencil printing quickly. In a one day period, multiple sheets of functional devices were obtained with both printing methods. Ink-jet printing, on the other hand, required greater then twenty four hours to fabricate one sheet of sensors even when the sensor size was reduced. The cost of masks/cartridges was $0.75,$1.68 and $59 per layer for stencil, screen and ink-jet printing respectively. The ink-jet print system cartridges were manufactured for one time use, whereas the masks were reusable for both screen and stencil printing. The best stencil and screen printed accelerometers demonstrated a voltage sensitivity of 145 mV/g. It is believed that the performance of these sensors can be enhanced with an automated printing system that is equipped with optical vision and automated alignment systems. The successful development of printed devices demonstrates that these print methods will be beneficial to the future of flexible electronics

Inkjet-Printed Bandstop Filters for Interference Suppression in Multi-Standard Wireless Systems

This paper presents a highly compact inkjet printed microstrip bandstop filter (BSF) for interference suppression in multi-standard wireless applications. The structure is designed with strict specifications for inkjet printing such as the use of the Kapton substrate and its flexible polyimide film. The design was simulated based on Kapton substrate with a thickness of 50µm and dielectric constant of 3.4. The simulated results show a good narrowband response with good stopband attenuation of about 38 dB. When compared to other published BSFs, the proposed structure occupies the least normalized area and best return loss performance up to 10 GHz. This filter is then used to reject interference in a multi-standard wireless transmitter system with suppression of about 30 dB achieved with a great level of noise and spurious response reduction thereby improving the overall performance of the system. This type of filter will be very useful to eliminate undesired signals in next generation 4G LTE-Advanced and 5G mobile networks as well as being very attractive for modern day multi-standard wireless applications such as machine to machine (M2M) communications and internet of things (IoT)

National MEMS Technology Roadmap - Markets, Applications and Devices

MEMS teknologiaa on jo pitkään käytetty lukuisien eri laitteiden valmistamiseen. Osa näistä laitteista on ollut markkinoilla jo useita vuosia, kun taas osa on vasta kehitysvaiheessa. Jotta tutkimus ja kehitystyötä osattaisiin jatkossa kohdistaa oikeille painopistealueille, on tärkeää tietää mihin suuntaan kehitys on menossa. Tämä työ on osa kansallista MEMS teknologioiden tiekartta -projektia ja sen tavoitteena oli selvittää MEMS laitteiden kehityksen suuntaa. Työ toteutettiin laajana kirjallisuustutkimuksena. Lisäksi tulosten tueksi haastateltiin asiantuntijoita Suomen MEMS teollisuudesta. Työssä tarkasteltiin lukuisia jo markkinoilta löytyviä ja vasta kehitteillä olevia MEMS laitteita ja analysoitiin niitä sekä teknisestä että kaupallisesta näkökulmasta. Tutkimuksen perusteella kävi ilmi, että MEMS markkinat ovat pitkään muodostuneet vakiintuneista laitteista kuten mustesuihkupäistä, kiihtyvyysantureista, paineantureista sekä RF suotimista. Lisäksi mikrofonit, gyroskoopit ja optiset laitteet ovat olleet kaupallisesti saatavilla jo pitkään. Markkinat ovat hiljattain alkaneet tehdä tilaa myös uusille MEMS laitteille, joita tulee ulos nopeaa vauhtia. Viimeisimpänä markkinoille tulleita laitteita ovat erilaiset mikrofluidistiikka laitteet, mikrobolometrit sekä yhdistelmäanturit. Pian kaupallisesti saatavia laitteita ovat magnetometrit, automaattitarkennuslaitteet sekä MEMS oskillaattorit. Näiden laitteiden lisäksi kehitteillä on monia uusia MEMS laitteita, jotka saattavat tarjota merkittäviä mahdollisuuksia tulevaisuudessa. Kehitteillä olevia laitteita ovat erilaiset lääketieteelliset laitteet, atomikellot, mikrojäähdyttimet, mikrokaiuttimet, energiantuottolaitteet sekä RFID-laitteet. Kaikki kehitteillä olevista laitteista eivät välttämättä tule menestymään kaupallisesti, mutta jatkuva tutkimustyö osoittaa, että monilla MEMS laitteilla on potentiaalia useissa eri sovelluksissa. Markkinanäkökulmasta tarkasteltuna suurin potentiaali piilee kuluttajaelektroniikka markkinoilla. Muita tulevaisuuden kannalta potentiaalisia markkinoita ovat lääketieteelliset ja teollisuusmarkkinat. Tutkimus osoitti että MEMS laitteiden tutkimukseen ja kehitykseen liittyy monia potentiaalisia painopistealueita tulevaisuudessa. Käyttömahdollisuuksien parantamiseksi monet jo vakiintuneet laitteet kaipaavat vielä parannuksia. Toisaalta, jo olemassa olevia laitteita voidaan hyödyntää uusissa sovelluksissa. Lisäksi monet uusista ja kehitteillä olevista MEMS laitteista vaativat vielä kehitystyötä.MEMS technology has long been applied to the fabrication of various devices from which some have already been in use for several years, whereas others are still under development. In order to find future focus areas in research and development activities in the industry, it is important to know where the development is going. This thesis was conducted as a part of National MEMS technology roadmap, and it aimed for determining the evolution of MEMS devices. The work was conducted as an extensive literature review. In addition, experts from the Finnish MEMS industry were interviewed in order obtain a broader insight to the results. In this thesis various existing and emerging MEMS devices were reviewed and analyzed from technological and commercial perspectives. The study showed that the MEMS market has long been composed of established devices, such as inkjet print-heads, pressure sensors, accelerometers and RF filters. Also gyroscopes, microphones and optical MEMS devices have already been on the market for a long time. Lately, many new devices have started to find their place in the markets. The most recently introduced commercial devices include microfluidic devices, micro bolometers, and combo sensors. There are also a few devices including magnetometers, MEMS oscillators, and auto-focus devices that are currently crossing the gap from R&D to commercialization. In addition to the already available devices, many new MEMS devices are under development, and might offer significant opportunities in the future. These emerging devices include various bioMEMS devices, atomic clocks, micro-coolers, micro speakers, power MEMS devices, and RFID devices. All of the emerging devices might not find commercial success, but the constant stream shows, that there are numerous applications, where MEMS devices could be applied in. From a market point of view, the greatest potential in the future lies in consumer electronics market. Other highly potential markets include medical and industrial markets. The results of the thesis indicate that there are many potential focus areas in the future related to MEMS devices, including improvements of the existing devices in order to gain better utilization, application of the existing devices in new areas, and development work among the emerging devices

Advanced Nanomanufacturing for Wearable Human Performance Monitoring Sensor Platforms

As part of the mini-symposium entitled Creating Devices for Personalized Health Monitoring, Dr. Morse discusses advances in transitioning nanofabrication processes for realizing sensors for personalized health monitoring, including the development of wearable microfluidic sensors for detection of biomarkers indicative of stress and fatigue. Examples from current projects include nanoparticle field effect transistor (FET) sensors, printed microfluidics, and replication of antimicrobial/anti-fouling surfaces via high throughput, roll-to-roll processes

Low weight additive manufacturing FBG accelerometer: design, characterization and testing

Structural Health Monitoring is considered the process of damage detection and structural characterization by any type of on-board sensors. Fibre Bragg Gratings (FBG) are increasing their popularity due to their many advantages like easy multiplexing, negligible weight and size, high sensitivity, inert to electromagnetic fields, etc. FBGs allow obtaining directly strain and temperature, and other magnitudes can also be measured by the adaptation of the Bragg condition. In particular, the acceleration is of special importance for dynamic analysis. In this work, a low weight accelerometer has been developed using a FBG. It consists in a hexagonal lattice hollow cylinder designed with a resonance frequency above 500 Hz. A Finite Element Model (FEM) was used to analyse dynamic behaviour of the sensor. Then, it was modelled in a CAD software and exported to additive manufacturing machines. Finally, a characterization test campaign was carried out obtaining a sensitivity of 19.65 pm/g. As a case study, this paper presents the experimental modal analysis of the wing of an Unmanned Aerial Vehicle. The measurements from piezoelectric, MEMS accelerometers, embedded FBGs sensors and the developed FBG accelerometer are compared.Ministerio de Economía y Competitividad BIA2013-43085-P y BIA2016-75042-C2-1-