77 research outputs found
Shear-Force Sensors on Flexible Substrates Using Inkjet Printing
Printing techniques are a promising way of fabricating low-cost electronics without the need for masking and etching. In recent years, additive printing techniques, such as inkjet and screen printing, have been adopted to fabricate low-cost and large-area electronics on flexible substrates. In this work, a three-axial normal and shear force sensor was designed and printed that consists of four miniaturized, printed capacitors. The partially overlapping electrodes are arranged in a manner, so that force sensitivity in orthogonal directions is achieved. A silicone rubber is used as an elastic dielectric and spacer between the two electrodes. The base unit of this sensor has been fabricated using inkjet printing and characterized for normal and shear forces. The force response was investigated in a force range from 0.1 N to 8 N, the normal-force sensitivity was determined to be Sz=5.2 fF/N, and the shear-force sensitivity was Sy=13.1 fF/N. Due to its sensing range, this sensor could be applicable in tactile sensing systems like wearables and artificial electronic skins
A Facile and Efficient Protocol for Preparing Residual-Free Single-Walled Carbon Nanotube Films for Stable Sensing Applications
In this article, we report on an efficient post-treatment protocol for the manufacturing of
pristine single-walled carbon nanotube (SWCNT) films. To produce an ink for the deposition, the
SWCNTs are dispersed in an aqueous solution with the aid of a carboxymethyl cellulose (CMC)
derivative as the dispersing agent. On the basis of this SWCNT-ink, ultra-thin and uniform films are
then fabricated by spray-deposition using a commercial and fully automated robot. By means of X-ray
photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and scanning
electron microscopy (SEM), we show that the CMC matrix covering the CNTs can be fully removed
by an immersion treatment in HNO3 followed by thermal annealing at a moderate temperature
of 100 ºC, in the ambient air. We propose that the presented protocols for the ink preparation
and the post-deposition treatments can in future serve as a facile and efficient platform for the
fabrication of high-quality and residual-free SWCNT films. The purity of SWCNT films is of particular
importance for sensing applications, where residual-induced doping and dedoping processes distort
the contributions from the sensing specimen. To study the usability of the presented films for practical
applications, gas sensors are fabricated and characterized with the CNT-films as the sensing material,
screen printed silver-based films for the interdigitated electrode (IDE) structure, and polyimide as a
flexible and robust substrate. The sensors show a high and stable response of 11% to an ammonia
(NH3) test gas, at a concentration of 10 ppm.The authors thank the Deutsche Forschungsgemeinschaft (DFG) and the Natural Sciences and
Engineering Research Council (NSERC) for financial support of the Alberta/Technische Universität München
Graduate School for Functional Hybrid Materials ATUMS (IRTG2022, NSERC CREATE), as well as the TUM
Graduate School, the Nanosystems Initiative Munich (NIM), and the TUM International Graduate School of
Science and Engineering (IGSSE)
Screen-Printed Chipless Wireless Temperature Sensor
A chipless wireless sensor for temperature monitoring is described in this work. The sensor is fabricated by screen printing of an RLC circuit on a flexible substrate. The sensing element is a resistive carbon paste with positive temperature coefficient placed in a small area in the interconnection between the inductor and the capacitor. This sensing layer modifies the resonance frequency of the circuit when the temperature varies. We also show the influence of the sensor sensitivity with respect to the reading distance
UHF Printed Sensor for Force Detection
In this contribution, we show the advances in the direction of designing Radiofrequency Identification (RFID) antennas with sensing capabilities. In this particular case, we have integrated a force/pressure sensor made of a silicon-based organic polymer in one of the arms of a dipole antenna made of silver paste. The sensor response to external forces modifies the resonance frequency of the dipole antenna that can be detected by an external RFID reader, building up a wireless force sensor system.Pervasive Electronics Advanced Research Laboratory(PEARL), Department of Electronics and Computer Technology, University of Granada
Institute for Nanoelectronics, Technical University of Munic
Optimization of a Handwriting Method by an Automated Ink Pen for Cost-Effective and Sustainable Sensors
In this work, we present a do-it-yourself (DIY) approach for the environmental-friendly
fabrication of printed electronic devices and sensors. The setup consists only of an automated
handwriting robot and pens filled with silver conductive inks. Here, we thoroughly studied the
fabrication technique and different optimized parameters. The best-achieved results were 300 mΩ/sq
as sheet resistance with a printing resolution of 200 µm. The optimized parameters were used
to manufacture fully functional electronics devices: a capacitive sensor and a RFID tag, essential
for the remote reading of the measurements. This technique for printed electronics represents an
alternative for fast-prototyping and ultra-low-cost fabrication because of both the cheap equipment
required and the minimal waste of materials, which is especially interesting for the development of
cost-effective sensors.TUM Graduate School and by the European Commission
through the fellowship H2020-MSCA-IF-2017-794885-SELFSEN
Screen Printable Electrochemical Capacitors on Flexible Substrates
This work presents a novel approach for the fabrication of Electrochemical Capacitors (ECs) based on the screen-printing of a commercial carbon-based conductive ink on flexible substrates. This technique enables the fast and cost-effective production of ECs with high flexibility and outstanding performance over bending states and voltage cycling, as demonstrated by means of cyclic voltammetry and galvanometric charge-discharge measurements. Despite the fact that the specific areal capacitances achieved are lower than the ones obtained using other carbon-based materials (~22 μF/cm2), the results show that, as soon as new screen-printable carbon-based pastes become available, this fabrication method will enable the mass production of ECs that can be attached to any surface as a conformal patch, as it is being required by a large number of the emerging technological applications.This work has been partially supported by the Spanish Ministry of Education, Culture and Sport (MECD) and the European Union through the pre-doctoral grant FPU16/01451, and its mobility program, the project TEC2017-89955-P and fellowship H2020-MSCA-IF-2017794885-SELFSENS
How Metal/Insulator Interfaces Enable the Enhancement of the Hydrogen Evolution Reaction Kinetics in Two Ways
Laterally nanostructured surfaces give rise to a new dimension of
understanding and improving electrochemical reactions. In this study, we
present a peculiar mechanism appearing at a metal/insulator interface, which
can significantly enhance the Hydrogen Evolution Reaction (HER) from water
reduction by altering the local reaction conditions in two ways: facilitated
adsorption of hydrogen on the metal catalyst surface and improved transfer of
ions through the double layer. The mechanism is uncovered using electrodes
consisting of well-defined nanometer-sized metal arrays (Au, Cu, Pt) embedded
in an insulator layer (silicon nitride), varying various parameters of both the
electrode (size of the metal patches, catalyst material) and the electrolyte
(cationic species, cation concentration, pH). In addition, simulations of the
electrochemical double layer are carried out, which support the elaborated
mechanism. Knowledge of this mechanism will enable new design principles for
novel composite electrocatalytic systems
Over-Stretching Tolerant Conductors on Rubber Films by Inkjet-Printing Silver Nanoparticles for Wearables
The necessity to place sensors far away from the processing unit in smart clothes or artificial
skins for robots may require conductive wirings on stretchable materials at very low-cost. In this
work, we present an easy method to produce wires using only commercially available materials.
A consumer grade inkjet printer was used to print a wire of silver nanoparticles with a sheet resistance
below 1 W/sq. on a non-pre-strained sheet of elastic silicone. This wire was stretched more than
10,000 times and was still conductive afterwards. The viscoelastic behavior of the substrate results in
a temporarily increased resistance that decreases to almost the original value. After over-stretching,
the wire is conductive within less than a second. We analyze the swelling of the silicone due to the
ink’s solvent and the nanoparticle film on top by microscope and SEM images. Finally, a 60 mm long
stretchable conductor was integrated onto wearables, and showed that it can bear strains of up to
300% and recover to a conductivity that allows the operation of an assembled LED assembled at only
1.8 V. These self-healing wires can serve as wiring and binary strain or pressure sensors in sportswear,
compression underwear, and in robotic applications.This work has been partially supported the TUM Graduate School (TUM GS), and the European Union
through the fellowship H2020-MSCA-IF-2017 794885-SELFSENS. Additionally, this work was supported by the
German Research Foundation (DFG) and the Technical University of Munich within the Open Access Publishing
Funding Programme
Screen Printed Security-Button for Radio Frequency Identification Tags
Radio frequency identi cation (RFID) security is a relevant matter. The wide spread of RFID
applications in the general society and the persistent attempts to safeguard it con rm it, especially since its
use involves payments and the store or transmission of sensitive information. In this contribution, we present
an innovative solution for improving the security of RFID passive tags through the use of a screen printed
button, that allows the reception and transmission only when a certain level of physical pressure normal to
its plane is applied. The materials and fabrication technology used demonstrate an easy to implement and
cost-effective system, valuable in several scenarios where the user has straight contact with the tags and
where its usage is direct and intentional.This work was supported by the fellowship under Grant 2020-MSCA-IF-2017-794885-SELFSENS
Enabling Logic Computation Between Ta/CoFeB/MgO Nanomagnets
Dipolar coupled magnets proved to have the potential to be capable of successfully performing digital computation in a highly parallel way. For that, nanomagnet-based computation requires precise control of the domain wall nucleation from a well-localized region of the magnet. Co/Pt and Co/Ni multilayer stacks were successfully used to demonstrate a variety of computing devices. However, Ta/CoFeB/MgO appears more promising, thanks to the lower switching field required to achieve a full magnetization reversal, reduced thickness (less than 10 nm), and its compatibility with magnetic tunnel junctions. In this work, the switch of the information is achieved through the application of a magnetic field, which allows to scale more the nanomagnets with respect to current-driven magnetization reversal-based devices and to go toward 3-D structures. We experimentally demonstrate that Ga ions can be used to tune the energy landscape of the structured magnets to provide signal directionality and achieve a distinct logic computation. We prove that it is possible to define the artificial nucleation center (ANC) in different structures with two irradiation steps and that this approach can enable logic computation in ultrathin films by dipolar interaction. Moreover, different from previous studies, the results coming from the irradiation analysis are then used for real logic devices. We present the experimental demonstration of a set of fully working planar inverters, showing that it is possible to reach a coupling field between the input and the output, which is strong enough to reliably implement logic operations. Micromagnetic simulations are used to study the nucleation center's effectiveness with respect to its position in the magnet and to support the experiments. Our results open the path to the development of more efficient nanomagnet-based logic circuits
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