Epoxy resin mold and PDMS microfluidic devices through photopolymer flexographic printing plate

Photopolymer flexographic printing plate is a new photopolymeric material used for microdevices fabrication. This work demonstrates that a photopolymer flexographic master mold can be used for the fabrication of PDMS (polydimethylsiloxane) microdevices by a multi-step manufacturing process. The methodology entails three main fabrication steps: (1) a photopolymer flexographic printing plate mold (FMold) is generated by UV exposure through a transparent film, (2) an epoxy resin mold (ERmold) is fabricated by transferring the features of the photopolymer mold and (3) a PDMS microdevice is manufactured from the epoxy resin mold. The characterization of the manufactured PDMS microdevices was performed using scanning electron microscopy (SEM) and profilometry. Results showed high accuracy in the replication of the profiles. To show the feasibility of the fabrication process a microdevice for microdroplet generation was designed, manufactured and tested. Hence, the manufacturing process described in this work provides an easy, robust, and low-cost strategy that facilitates the scaling-up of microfluidic devices without requiring any sophisticated equipment.Fil: Olmos Carreno, Carol Maritza. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vaca Mora, Andrea Vanessa. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rosero, Gustavo. Universidad Tecnológica Nacional. Facultad Regional Haedo; ArgentinaFil: Peñaherrera Pazmiño, Ana Belén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Haedo; ArgentinaFil: Pérez Sosa, Camilo José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Haedo; ArgentinaFil: de Sá Carneiro, Igor. Universidad Tecnológica Nacional. Facultad Regional Haedo; ArgentinaFil: Vizuete, Karla. Universidad de Las Fuerzas Armadas Espe; EcuadorFil: Arroyo, Carlos R.. Universidad de Las Fuerzas Armadas; EcuadorFil: Debut, Alexis. Universidad de Las Fuerzas Armadas; EcuadorFil: Perez, Maximiliano Sebastian. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; ArgentinaFil: Cumbal, Luis. Universidad de Las Fuerzas Armadas; EcuadorFil: Lerner, Betiana. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentin

Resistances changes in printed conductive lines due to elongation during thermoforming

Abstract. In-Mold and structural electronics are an emerging field combining the processes of printed electronics thermoforming and injection-molding to create three dimensional parts. However, there is a lack of research when it comes to the behavior of printed circuits during and due to the thermoforming process. The research regarding the behavior of conductive inks undergoing deformation is so far focused on stretchable electronics, while research done with thermoforming of polymer films does not include printed circuits and their potential effect. In this thesis, the resistance changes in printed conductive lines due to the thermoforming process was investigated. Four different kinds of samples were prepared consisting of two different conductive inks formulated for thermoforming processes and two different widths for the printed conductive lines (0.3 mm and 0.6 mm). The measurements were done by elongating with a custom machine attempting to simulate thermoforming. The samples were characterized before and after elongation, and during the elongation process using multiple different measurement methods. Based on the measurements it was discovered that the formulation of the ink was one of the most important factors when it comes to how the printed conductors behave. It was also discovered that, for the inks used in the thesis, the heating process caused a decrease in resistance at low elongations. During the course of the research, several potential improvements for the measurements were identified, and the results should establish a starting point for future research.Resistanssin muutos printatuissa johtimissa lämpömuovauksen aiheuttaman venymän takia. Tiivistelmä. In-Mold ja rakenteellinen elektroniikka on aihealue, jonka suosio on nousussa. Se yhdistää printatun elektroniikan lämpömuovauksen ja ruiskuvalun kanssa luodakseen kolmiulotteisia osia. Printattujen piirien käytöstä lämpömuovauksen aikana ja sen takia on kuitenkin tutkittu hyvin vähän. Tutkimus deformaation aiheuttamiin muutoksiin printatuissa piireissä on tähän mennessä keskittynyt venyvään elektroniikkaan, kun taas muovikalvojen lämpömuovaukseen keskittynyt tutkimus ei sisällä printattuja piirejä ja niiden mahdollista vaikutusta. Tässä työssä tutkittiin lämpömuovauksesta johtuvia resistanssi muutoksia printatuissa johtimissa. Neljä erilaista näytettä valmistettiin, joissa käytettiin kahta erilaista johtavaa mustetta ja johtimen leveyttä (0.3 mm ja 0.6 mm). Mittauksissa käytettiin näytteiden vetämiseen mittatilaustyönä tehtyä laitetta, jolla oli tarkoitus simuloida lämpömuovausprosessia. Näytteitä karakterisoitiin ennen ja jälkeen venytyksen, sekä sen aikana käyttäen useita eri mittausmenetelmiä. Mittausten perusteella todettiin, että johtavien musteiden koostumuksella oli suurin vaikutus printattujen johtimien käytökseen. Huomattiin myös, että työssä käytettyjen musteiden osalta näytteen lämmitys aiheutti resistanssin laskun pienillä venymillä. Tutkielman teon aikana tunnistettiin useita potentiaalisia parannuksia mittauksiin, ja saadut tulokset luovat pohjan mahdolliselle tulevalle tutkimukselle

Laser-induced forward transfer for printed electronics applications

Laser-induced forward transfer (LIFT) is a printing technique based on the action of a laser pulse that is focused on a thin film of a precursor ink for getting the transfer of a droplet onto a receiver substrate. The experiments presented in this article aim to demonstrate the ability of LIFT to produce electronic circuits on paper, a substrate that is flexible, cheap and recyclable. Tests were conducted in order to study the printing of conductive tracks with an Ag ink. The printing of a suspension of carbon nanofibers (CNFs) was also studied in order to demonstrate the ability of LIFT for printing inks with particles with some microns in size that provoke inkjet nozzles to clog. As a proof-of-concept of the LIFT possibilities, both inks were used to print entirely by LIFT a functional humidity sensor on a piece of paper. All the LIFT experiments were performed with a Nd:YAG laser that delivers pulses of a few hundreds of ns in an attempt to approach the technique to laser systems that are already introduced in many production lines for marking and labeling

Rapid prototyping of electrochemical lateral flow devices: stencilled electrodes

A straightforward and very cost effective method is proposed to prototype electrodes using pressure sensitive adhesives (PSA) and a simple cutting technique. Two cutting methods, namely blade cutting and CO2 laser ablation, are compared and their respective merits are discussed. The proposed method consists of turning the protective liner on the adhesive into a stencil to apply screen-printing pastes. After the electrodes have been printed, the liner is removed and the PSA can be used as a backing material for standard lateral flow membranes. We present the fabrication of band electrodes down to 250 μm wide, and their characterization using microscopy techniques and cyclic voltammetry. The prototyping approach presented here facilitates the development of new electrochemical devices even if very limited fabrication resources are available. Here we demonstrate the fabrication of a simple lateral-flow device capable of determining glucose in blood. The prototyping approach presented here is highly suitable for the development of novel electroanalytical tools.This work has been funded by the Spanish Ministry of Economy through the DADDi2 project (Grant TEC2013-48506). MK acknowledges funding through the Beatriu de Pinós program (BP-DGR-2013), supported by the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia and the Cofund programme of the Marie Curie Actions of the 7th R&D Framework Programme of the European Union. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe

Fully Printed Electrolyte‐Gated Transistor Formed in a 3D Polymer Reservoir with Laser Printed Drain/Source Electrodes

In solution processed electronic devices it is crucial that the deposited inks are properly aligned and that all post-processing steps are compliant with each other. Moreover, shorter channel lengths are highly beneficial to increase the device performance. Herein, laser printing of metals and polymer reservoirs allows to print sub-micrometer sized channel lengths while confining functional inks into these small gaps. Therefore, a manufacturing concept and optimized material stack, suitable for combined inkjet and laser printing are proposed. A nanoparticulate indium oxide (In$_2$O$_3$) semiconductor is inkjet printed into and constrained by a 3D laser written polymer (pentaerythritol triacrylate, PETA) reservoir. Inside the 3D printed polymer reservoir, platinum (Pt) electrodes, that are further routed over the reservoir walls, are laser printed by a metal reduction process. The transistor fabrication is completed by a second inkjet printed layer of composite solid polymer electrolyte and an organic top-gate layer (PEDOT:PSS). This concept does not exceed annealing temperatures higher than 100°C, and is compatible with a range of substrates. The characterized electrolyte-gated field-effect transistor show a reasonable on/off-ratio in the range of 10$^4$ with negligible leakage currents. This materials and hybrid device manufacturing scheme has believed great potential for bioelectronics, lab-on-a-chip applications and others

All-Printed, Stretchable Zn-Ag2O Rechargeable Battery via Hyperelastic Binder for Self-Powering Wearable Electronics

While several stretchable batteries utilizing either deterministic or random composite architectures have been described, none have been fabricated using inexpensive printing technologies. In this study, the authors printed a highly stretchable, zinc-silver oxide (Zn-Ag2O) battery by incorporating polystyrene-block-polyisoprene-block-polystyrene (SIS) as a hyperelastic binder for custom-made printable inks. The remarkable mechanical properties of the SIS binder lead to an all-printed, stretchable Zn-Ag2O rechargeable battery with a ≈2.5 mA h cm−2 reversible capacity density even after multiple iterations of 100% stretching. This battery offers the highest reversible capacity and discharge current density for intrinsically stretchable batteries reported to date. The electrochemical and mechanical properties are characterized under different strain conditions. The new stress-enduring printable inks pave ways for further developing stretchable electronics for the wide range of wearable applications

Passive UHF RFID Tag with Multiple Sensing Capabilities

This work presents the design, fabrication, and characterization of a printed radio frequency identification tag in the ultra-high frequency band with multiple sensing capabilities. This passive tag is directly screen printed on a cardboard box with the aim of monitoring the packaging conditions during the different stages of the supply chain. This tag includes a commercial force sensor and a printed opening detector. Hence, the force applied to the package can be measured as well as the opening of the box can be detected. The architecture presented is a passive single-chip RFID tag. An electronic switch has been implemented to be able to measure both sensor magnitudes in the same access without including a microcontroller or battery. Moreover, the chip used here integrates a temperature sensor and, therefore, this tag provides three different parameters in every reading.This work was partially funded by the Ministerio de Educación y Ciencia under Projects CTQ2009-14428-C02-01 and CTQ2009-14428-C02-02 and the Junta de Andalucía (Proyecto de Excelencia P10-TIC-5997), Spain. This project was partially supported by European Regional Development Funds (ERDF)

An Automated Room Temperature Flip-Chip Mounting Process for Hybrid Printed Electronics

Printing technology and mounting technology enable the novel field of hybrid printed electronics. To establish a hybrid printed system, one challenge is that the applied mounting process meets the requirements of functional inks and substrates. One of the most common requirements is low process temperature. Many functional inks and substrates cannot withstand the high temperatures required by traditional mounting processes. In this work, a standardized interconnection and an automated bump-less flip-chip mounting process using a room temperature curing conductive adhesive are realised. With the proposed process, the conductive adhesive selected for the standardized interconnection can be dispensed uniformly, despite its increase of viscosity already during pot time. Electrical and mechanical performance of the interconnection are characterized by four terminal resistance measurement and shear test. The herein proposed automated process allows for fabrication of hybrid printed devices in larger batch sizes than manual assembly processes used beforehand and thus, more comprehensive evaluation of device parameters. This is successfully demonstrated in a first application, a novel hybrid printed security device. The room temperature mounting process eliminates any potentially damaging thermal influence on the performance of the printed circuits that might result from other assembly techniques like soldering

Hall Effect Modeling in FEM Simulators and Comparison to Experimental Results in Silicon and Printed Sensors

Finite element method simulation models for thin-film semiconductor-based Hall sensors were developed using secondary data in order to understand their behavior under strong magnetic fields. Given a device geometry and charge carrier density and mobility, the models accurately calculated sensor resistance, Hall voltage under a normally-incident constant magnetic field, and expected offset from a population of Hall devices. The model was successfully matched against data from integrated chip Hall sensors from St. Jude Medical. Additionally, the feasibility of creating Hall effect devices with common carbon ink was explored experimentally. The material properties obtained from testing these ink-based devices through the Van der Pauw method were added to the simulation model to analyze validity of the collected data