This research is sponsored by the US Defense Advanced Research Projects Agency under Centers in Integrated Photonics Engineering Research (CIPhER) program with Dr. J. Scott Rodgers as project manager. The information provided in this report does not necessarily reflect the position or the policy of the US Government and no official endorsement should be inferred.

1. PDMS Microsphere Preparation (Sphere I)
<ol>
	<li>Polydimethylsiloxane (PDMS) base and the curing agent are mixed with a volume ratio of 60:1.</li>
	<li>A strand of silica optical fiber, about 2 cm long, is first stripped of its plastic cladding using an optical stripper.</li>
	<li>One end of the fiber is heated and stretched to provide a stem end that is ~25-50 &mu;m in diameter at the tip.</li>
	<li>The stretched end of the fiber is submerged into the PDMS mixture by a length of approximately 2-4 mm and then is pulled out.</li>
	<li>Surface tension and weight of the PDMS mixture allow for the formation of a sphere at the tip of the silica fiber. The size of the sphere is controlled by the dipping length and extraction velocity. By varying these two parameters, sphere diameters in the range 100 &mu;m - 1,000 &mu;m can be obtained.</li>
	<li>The microsphere/stem assembly is then placed in an oven at ~90 &deg;C for 4 hr to allow for proper curing of the polymer material (to form cross-linked chains). Figure 1a is a schematic of Sphere I.</li>
</ol>
2. PDMS-based Triple Layer Sphere Preparation (Sphere II)
<ol>
	<li>A 60:1 PDMS microsphere is used as the inner core. The same steps described in 1) above is followed for this process.</li>
	<li>A mixture of barium titanate (BaTiO3) nano-particles and 60:1 PDMS is used as the middle layer. The PDMS mixture, prepared in the same way described in 1.1) above, is mixed with barium titanate nano-particles.</li>
	<li>The PDMS microsphere core described in 2.1) is then dipped into the PDMS- barium titanate mixture to coat it (with a layer nominal thickness of ~ 10 &mu;m).</li>
	<li>Next, the two-layer sphere is placed in an oven at ~ 90 &deg;C for 4 hr to allow for proper curing of the second layer.</li>
	<li>Once the two layer sphere is cured, it is again immersed in a mixture of 60:1 PDMS to provide an outer coating (third layer). This outermost layer serves as spherical optical guide (~10 &mu;m thickness). Figure 1b is a schematic of Sphere II.</li>
</ol>
3. Silica/PDMS Microsphere Preparation (Sphere III)
<ol>
	<li>A ~ 3 cm long section of a silica single mode optical fiber is first stripped of its buffer (plastic) coating and then its tip is melted using a micro-torch (together with the cladding and core). Surface tension and gravity work together to shape the melted tip into a sphere. Spheres with diameters ranging from 200 to 500 &mu;m can be obtained with this process.</li>
	<li>The silica microsphere is then immersed in a bath of PDMS base (without the curing agent) to cover it with a coat of ~ 50 &mu;m. This outer layer stays as a highly-viscous Bingham (yield-stress) fluid. Figure 1c is a schematic of Sphere III.</li>
</ol>
4. Optical Fiber Preparation
<ol>
	<li>A section of a single mode optical fiber is stripped of its plastic cladding using an optical stripper. Using a micro-torch the striped section of the fiber is heated until it is molten (both the cladding and fiber core).</li>
	<li>While the middle section is molten, one end of the optical fiber is pulled along its axis to form a tapered section of the fiber that is about 1 cm long. The duration of heating, the pulling speed and distance determine the diameter of the tapered section that ranges between 10 and 20 &mu;m. The light from the DFB laser is coupled into the sphere through the tapered section of the fiber. Figure 2 shows the sphere-fiber coupling.</li>
</ol>
5. Optoelectronic Setup
<ol>
	<li>The output of a tunable DFB laser is coupled into a single mode optical fiber on one end and terminated at a fast photodiode on the other end as shown in Figure 3.</li>
	<li>The photodiode output is digitized using an analog-to-digital converter (A/D) and stored on a personal computer (PC).</li>
	<li>Using a micro-translation stage the microsphere (Type I, II or III) is brought in contact with the tapered section of the optical fiber (Figures 2 and 3) to provide optical coupling between the two elements.</li>
	<li>The DFB laser is tuned by a laser controller. The laser controller, in turn is driven by a function generator which provides a saw-tooth voltage input.</li>
</ol>
6. Electric Field Generation
<ol>
	<li>Two square brass plates (2 x 2 cm) with thickness of 1 mm are used to generate the uniform electric field. The plates are connected to a voltage supply and the sphere sensors are placed in the gap between the two plates (Figure 4).</li>
	<li>In order to increase the measurement sensitivity, the spheres are first poled in an electric field of 1 MV/m for 2 hr.</li>
</ol>

<ol>
	<li>von Klitzing, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tunable+whispering+gallery+modes+for+spectroscopy+and+CQED+experiments.">Tunable whispering gallery modes for spectroscopy and CQED experiments.</a> New journal of physics. 3, 14.1-14.14 (2001).</li><li>Cai, M., Painter, O., Vahala, K. J., Sercel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fiber-coupled+microsphere+laser.">Fiber-coupled microsphere laser.</a> Optics letters. 25 (19), 1430-1432 (2000).</li><li>Tapalian, H. C., Laine, J. P., Lane, P. 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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wall+shear+stress+sensor+based+on+the+optical+resonances+of+dielectric+microspheres.">Wall shear stress sensor based on the optical resonances of dielectric microspheres.</a> Measurement science and technology. 22, 075203 (2011).</li><li>Ioppolo, T., Ayaz, U. K., &#214;t&#252;gen, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tuning+of+whispering+gallery+modes+of+spherical+resonators+using+an+external+electric+field.">Tuning of whispering gallery modes of spherical resonators using an external electric field.</a> Optics express. 17 (19), 16465-16479 (2009).</li><li>Ioppolo, T., Stubblefield, J., &#214;t&#252;gen, M. 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We have nothing to disclose.

The spheres are initially poled by connecting the electrodes to a DC high voltage supply. At the end of the poling duration, the electrode leads are disconnected from the DC voltage supply and connected to a function generator as indicated in Figure 4. The results presented in Figures 5 through 8 show that positive and negative electric fields (relative to direction of poling) lead to sphere elongation and compression, respectively. Sphere I, which is a single layer 60:1...

<table border="1">
 <tbody>
 <tr>
 <td></td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments (optional)</td>
 </tr>
 <tr>
 <td>PDMS</td>
 <td>Dow Corning</td>
 <td>Sylgard 184</td>
 <td></td>
 </tr>
 <tr>
 <td>Silica fiber</td>
 <td>Fiber Instrument Sales</td>
 <td>E-37AP15-FIS</td>
 <td></td>
 </tr>
 <tr>
 <td>Barium Titanate (BaTiO3) nanoparticles</td>
 <td>Sigma Aldrich</td>
 <td>467634-100G</td>
 <td></td>
 </tr>
 <tr>
 <td>Laser Controller</td>
 <td>ILX Lightwave</td>
 <td>LDC-3724B</td>
 <td></td>
 </tr>
 <tr>
 <td>DFB Laser</td>
 <td>Agere</td>
 <td>Agere 2300</td>
 <td>1.310 &mu;m central wavelength</td>
 </tr>
 <tr>
 <td>Photodiode</td>
 <td>Thorlabs</td>
 <td>PDA10CS</td>
 <td></td>
 </tr>
 <tr>
 <td>A/D Card</td>
 <td>National Instruments</td>
 <td>PXI 6115</td>
 <td></td>
 </tr>
 </tbody>
</table>

development of whispering gallery mode polymeric micro-optical electric field sensors

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The optical modes are frequently referred to as "whispering gallery modes" (WGM) or "morphology dependent resonances" (MDR) and exhibit high optical quality factors. Some proposed applications of micro-cavity optical resonators are in spectroscopy1, micro-cavity laser technology2, optical communications3-6 as well as sensor technology. The WGM-based sensor applications include those in biology7, trace gas detection8, and impurity detection in liquids9. Mechanical sensors based on microsphere resonators have also been proposed, including those for force10,11, pressure12, acceleration13 and wall shear stress14. In the present, we demonstrate a WGM-based electric field sensor, which builds on our previous studies15,16. A candidate application of this sensor is in the detection of neuronal action potential.
The electric field sensor is based on polymeric multi-layered dielectric microspheres. The external electric field induces surface and body forces on the spheres (electrostriction effect) leading to elastic deformation. This change in the morphology of the spheres, leads to shifts in the WGM. The electric field-induced WGM shifts are interrogated by exciting the optical modes of the spheres by laser light. Light from a distributed feedback (DFB) laser (nominal wavelength of ~ 1.3 &mu;m) is side-coupled into the microspheres using a tapered section of a single mode optical fiber. The base material of the spheres is polydimethylsiloxane (PDMS). Three microsphere geometries are used: (1) PDMS sphere with a 60:1 volumetric ratio of base-to-curing agent mixture, (2) multi layer sphere with 60:1 PDMS core, in order to increase the dielectric constant of the sphere, a middle layer of 60:1 PDMS that is mixed with varying amounts (2% to 10% by volume) of barium titanate and an outer layer of 60:1 PDMS and (3) solid silica sphere coated with a thin layer of uncured PDMS base. In each type of sensor, laser light from the tapered fiber is coupled into the outermost layer that provides high optical quality factor WGM (Q ~ 106). The microspheres are poled for several hours at electric fields of ~ 1 MV/m to increase their sensitivity to electric field.

An optical mode (WGM) of the sphere is excited by the laser light when optical path length traveled by the light is a multiple integer of the laser wavelength. For the arrangement shown in Figure 3, the optical path length is 2&pi;rn, where n and r are the refractive index and radius of the sphere, respectively. Using geometric optics approximation, a WGM condition is satisfied when 2&pi;rn = l&lambda; wherel is an integer and &lambda; is the laser's ...

Watch this Scientific Journal Video about Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors at JoVE.com

Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors

A high-sensitivity photonic micro sensor was developed for electric field detection. The sensor exploits the optical modes of a dielectric sphere. Changes in the external electric field perturb the sphere morphology leading to shifts in its optical modes. The electric field strength is measured by monitoring these optical shifts.

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The ...

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13.0K Views.  Southern Methodist University. A high-sensitivity photonic micro sensor was developed for electric field detection. The sensor exploits the optical modes of a dielectric sphere. Changes in the external electric field perturb the sphere morphology leading to shifts in its optical modes. The electric field strength is measured by monitoring these optical shifts.

Video: Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency.

The customized techniques developed in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators are presented. The protocols to obtain and characterize these resonators are detailed, and an explanation of some of their applications in microwave photonics is given.

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various ...

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

Characterization of Anisotropic Leaky Mode Modulators for Holovideo

Holovideo displays are based on light-bending spatial light modulators. One such spatial light modulator is the anisotropic leaky mode modulator. This modulator is particularly well suited for holographic video experimentation as it is relatively simple and inexpensive to fabricate1-3. Some additional advantages of leaky mode devices include: large aggregate bandwidth, polarization separation of signal light from noise, large angular deflection and frequency control of color1. In order to realize these advantages, it is necessary to be able to adequately characterize these devices as their operation is strongly dependent on waveguide and transducer parameters4. To characterize the modulators, the authors use a commercial prism coupler as well as a custom characterization apparatus to identify guided modes, calculate waveguide thickness and finally to map the device's frequency input and angular output of leaky mode modulators. This work gives a detailed description of the measurement and characterization of leaky mode modulators suitable for full-color holographic video.

This work describes fabrication and characterization of anisotropic leaky mode modulators for holographic video.

Holovideo displays are based on light-bending spatial light modulators.  One such spatial light modulator is the anisotropic leaky mode modulator.  This ...

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap.

Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS).

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres ...

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists chiefly of velocity and temperature readings, both ideally having high spatial and temporal resolution to facilitate rigorous code validation. While high resolution velocity data is readily obtained through optical measurement techniques such as particle image velocimetry, it has proven difficult to obtain temperature data with similar resolution. Traditional sensors such as thermocouples cannot fill this role, but the recent development of distributed sensing based on Rayleigh scattering and swept-wave interferometry offers resolution suitable for CFD code validation work. Thousands of temperature measurements can be generated along a single thin optical fiber at hundreds of Hertz. Sensors function over large temperature ranges and within opaque fluids where optical techniques are unsuitable. But this type of sensor is sensitive to strain and humidity as well as temperature and so accuracy is affected by handling, vibration, and shifts in relative humidity. Such behavior is quite unlike traditional sensors and so unconventional installation and operating procedures are necessary to ensure accurate measurements. This paper demonstrates implementation of a Rayleigh scattering-type distributed temperature sensor in a thermal mixing experiment involving two air jets at 25 and 45 &#176;C. We present criteria to guide selection of optical fiber for the sensor and describe installation setup for a jet mixing experiment. We illustrate sensor baselining, which links readings to an absolute temperature standard, and discuss practical issues such as errors due to flow-induced vibration. This material can aid those interested in temperature measurements having high data density and bandwidth for fluid dynamics experiments and similar applications. We highlight pitfalls specific to these sensors for consideration in experiment design and operation.

We demonstrate use of a fiber optic distributed sensor for mapping the temperature field of mixing air jets. The Rayleigh scattering-based sensor generates thousands of data points along a single fiber to provide exceptional spatial resolution that is unattainable with traditional sensors such as thermocouples.

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists ...

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high external quantum efficiencies (EQE) and spans the whole visible spectrum. It has been recently reported that the UV excited luminescence of partially Li-exchanged sodium Linde type A zeolites [LTA(Na)] containing luminescent silver clusters can be controlled by adjusting the water content of the zeolite. These samples showed a dynamic change in their emission color from blue to green and yellow upon an increase of the hydration level of the zeolite, showing the great potential that these materials can have as luminescence-based humidity sensors at the macro and micro scale. Here, we describe the detailed procedure to fabricate a humidity sensor prototype using silver-exchanged zeolite composites. The sensor is produced by suspending the luminescent Ag-zeolites in an aqueous solution of polyethylenimine (PEI) to subsequently deposit a film of the material onto a quartz plate. The coated plate is subjected to several hydration/dehydration cycles to show the functionality of the sensing film.

A protocol for the synthesis of moisture-responsive luminescent Ag-zeolite composites is described in this report.

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high ...

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape method or individual WS2 nanotubes by dispersing the suspension of WS2 nanotubes. The selected samples have been fabricated into devices by the use of the electron beam lithography and electrolyte is put on the devices. We have characterized the electronic properties of the devices under applying the gate voltage. In the small gate voltage region, ions in the electrolyte are accumulated on the surface of the samples which leads to the large electric potential drop and resultant electrostatic carrier doping at the interface. Ambipolar transfer curve has been observed in this electrostatic doping region. When the gate voltage is further increased, we met another drastic increase of source-drain current which implies that ions are intercalated into layers of WS2 and electrochemical carrier doping is realized. In such electrochemical doping region, superconductivity has been observed. The focused technique provides a powerful strategy for achieving the electric-filed-induced quantum phase transition.

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

Here, we present a protocol to control the carrier number in solids by using the electrolyte.

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape ...

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 (STO) Single-crystal Substrates

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF) magnetron sputtering. LSMO nanoparticles were deposited with diameters from 10 to 20 nm and heights between 20 and 50 nm. At the same time, (Gd) Ba2Cu3O7&#8722;&#948; ((Gd) BCO) films were fabricated on both undecorated and LSMO nanoparticle decorated STO substrates using RF magnetron sputtering. This report also describes the properties of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 quasi-bilayer films structures (e.g., crystalline phase, morphology, chemical composition); magnetization, magneto-transport, and superconducting transport properties were also evaluated.

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7ÃƒÂ¢Ã‹â€ &#039;ÃƒÅ½ ´/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 STO Single-crystal Substrates

Here, we present a protocol to grow LSMO nanoparticles and (Gd) BCO films on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF)-sputtering.

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio ...

Hybrid Printing for the Fabrication of Smart Sensors

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, three substrates (acrylate, ceramics, and copper) are prepared. To determine the resulting material properties of these substrates, profilometer, contact angle, scanning electron microscope (SEM), and focused ion beam (FIB) measurements are done. The achievable printing resolution and suitable drop volume for each substrate are, then, found through the drop size tests. Then, layers of insulating and conductive ink are inkjet printed alternately to fabricate the target sensor structures. After each printing step, the respective layers are individually treated by photonic curing. The parameters used for the curing of each layer are adapted depending on the printed ink, as well as on the surface properties of the respective substrate. To confirm the resulting conductivity and to determine the quality of the printed surface, four-point probe and profilometer measurements are done. Finally, a measurement set-up and results achieved by such an all-printed sensor system are shown to demonstrate the achievable quality.

Here we present a protocol for the fabrication of inkjet-printed multilayer sensor structures on additively manufactured substrates and foil.

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, ...