Velocity and size measurement of droplets from an ultrasonic spray coater using Photon Correlation Spectroscopy and Turbidimetry

We have developed a combination of light scattering techniques to study and characterize droplets of a ultrasonic spray printer or coater in flight. For this economically relevant printer there is so far no reliable technique to systematically adjust the experimental parameters. We have combined photon correlation spectroscopy and turbidimetry to determine size and speed of the droplets depending on parameters of the printing process as viscosity, concentration and speed of the driving shroud gas. Our method allows to predetermine these parameters to control the properties of the printed films as e.g. thickness from tens of nanometers to micrometers

MICROWAVE ANNEALING, A PROMISING STEP IN THE ROLL-TO-ROLL PROCESSING OF ORGANIC ELECTRONICS

In recent years, organic printable electronics has gained more and more attention [1]. The development and characterization of new printing techniques and functional inks is vital to accomplish solution processable, large area organic electronic devices e.g.: organic photovoltaics (OPV) [2], organic light-emitting diodes (OLEDs)[3].  In this study a systematic comparison is made between hotplate annealing and microwave annealing of (screen) printed Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layers. PEDOT:PSS films treated with both techniques were characterized and compared by their thin film morphology, their electronic properties and their annealing time. It is shown that no difference in the thin film morphology and final sheet resistance was observed for microwave annealed compared to the hotplate annealed samples. Above that the annealing time is decreased up to a factor 6. These results show that microwave annealing is a feasible fast annealing technique for PEDOT:PSS thin films and can therefor reduce the total processing time of organic and PEDOT:PSS based electronic applications

Charge-discharge characteristics of textile energy storage devices having different PEDOT:PSS ratios and conductive Yarns configuration

Conductive polymer PEDOT:PSS, sandwiched between two conductive yarns, has been proven to have capacitive behavior in our textile energy storage devices. Full understanding of its underlying mechanism is still intriguing. The effect of the PEDOT to PSS ratio and the configuration of the electrode yarns are the focus of this study. Three commercial PEDOT:PSS yarns, Clevios P-VP-AI-4083, Ossila AI 4083, and Orgacon ICP 1050, as well as stainless steel and silver-coated polybenzoxazole (Ag/PBO) yarns, in various combinations, were used as solid electrolytes and electrodes, respectively. Analyses with NMR, ICP-OES, TGA, and resistivity measurement were employed to characterize the PEDOT:PSS. The device charge-discharge performance was measured by the Arduino microcontroller. Clevios and Ossila were found to have identical characteristics with a similar ratio, that is, 1:5.26, hence a higher resistivity of 1000 Ω.cm, while Orgacon had a lower PEDOT to PSS ratio, that is, 1:4.65, with a lower resistivity of 0.25⁻1 Ω.cm. The thermal stability of PEDOT:PSS up to 250 °C was proven. Devices with PEDOT:PSS having lower conductivity, such as Clevios P-VP-AI-4083 or Ossila AI 4083, showed capacitive behavior. For a better charge-discharge profile, it is also suggested that the PEDOT to electrode resistance should be low. These results led to a conclusion that a larger ratio of PEDOT to PSS, having higher resistivity, is more desirable, but further research is needed

A Model-based Sensor Fusion Approach for Force and Shape Estimation in Soft Robotics

International audienceIn this paper, we address the challenge of sensor fusion in Soft Robotics for estimating forces and deformations. In the context of intrinsic sensing, we propose the use of a soft capacitive sensor to find a contact's location, and the use of pneumatic sensing to estimate the force intensity and the deformation. Using a FEM-based numerical approach, we integrate both sensing streams and model two Soft Robotics devices we have conceived. These devices are a Soft Pad and a Soft Finger. We show in an evaluation that external forces on the Soft Pad can be estimated and that the shape of the Soft Finger can be reconstructed

Fabrication Approaches to Interconnect Based Devices for Stretchable Electronics: A Review

Stretchable electronics promise to naturalize the way that we are surrounded by and interact with our devices. Sensors that can stretch and bend furthermore have become increasingly relevant as the technology behind them matures rapidly from lab-based workflows to industrially applicable production principles. Regardless of the specific materials used, creating stretchable conductors involves either the implementation of strain reliefs through insightful geometric patterning, the dispersion of stiff conductive filler in an elastomeric matrix, or the employment of intrinsically stretchable conductive materials. These basic principles however have spawned a myriad of materials systems wherein future application engineers need to find their way. This paper reports a literature study on the spectrum of different approaches towards stretchable electronics, discusses standardization of characteristic tests together with their reports and estimates matureness for industry. Patterned copper foils that are embedded in elastomeric sheets, which are closest to conventional electronic circuits processing, make up one end of the spectrum. Furthest from industry are the more recent circuits based on intrinsically stretchable liquid metals. These show extremely promising results, however, as a technology, liquid metal is not mature enough to be adapted. Printing makes up the transition between both ends, and is also well established on an industrial level, but traditionally not linked to creating electronics. Even though a certain level of maturity was found amongst the approaches that are reviewed herein, industrial adaptation for consumer electronics remains unpredictable without a designated break-through commercial application