Name: a high performance impedance-based platform for evaporation rate detection
Uploaded: 2016-10-17T15:00:00
Description: Watch this Scientific Journal Video about A High Performance Impedance-based Platform for Evaporation Rate Detection at JoVE.com

This work was sponsored by the Ministry of Science and Technology, Taiwan, under grant numbers MOST 104-2221-E-241-001-MY3 and MOST 105-2627-B-005-002.

1. Experimental Chip Module
<ol>
	<li>Fabricate the indium tin oxide (ITO) electrode chip by photolithography and chemical wet etching processes
	<ol>
		<li>Obtain an ITO substrate (370 mm x 480 mm x 0.5 mm (L x W x H)) with a 2,600 &#197; ITO layer commercially (See Materials List). Slice the ITO substrate to the dimensions of 90 mm x 90 mm x 0.5 mm with a glass cutter for the ITO electrode patterning process in a 4 inch aligner.</li>
		<li>Use an ultrasonic cleaner to clean the ITO glass with acetone...

<ol>
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Acta. 184, 233-238 (2015).</li><li>Olejnik, A., Goscianska, J., Zielinska, A., Nowak, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stability+determination+of+the+formulations+containing+hyaluronic+acid.">Stability determination of the formulations containing hyaluronic acid.</a> Int. J. Cosmetic Sci. 37, 401-407 (2015).</li><li>Marcellin, E., Steen, J. A., Nielsen, L. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insight+into+hyaluronic+acid+molecular+weight+control.">Insight into hyaluronic acid molecular weight control.</a> Appl. Microbiol. Biotechnol. 98, 6947-6956 (2014).</li><li>Laurent, T. C., Laurent, U. B. G., Fraser, J. R. 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S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+real-time+impedance-sensing+chip+for+the+detection+of+emulsion+phase+separation.">A real-time impedance-sensing chip for the detection of emulsion phase separation.</a> Electrophoresis. 34 (12), 1743-1748 (2013).</li><li>Lin, Y. S., Chen, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+evaporation+detection+system+using+an+impedance+sensing+chip.">A novel evaporation detection system using an impedance sensing chip.</a> Analyst. 139 (22), 5781-5784 (2014).</li><li>Tseng, S. 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The critical step for evaporation measurement in this impedance-based detection is the preparation of the tested solutions. Deionized water cannot be used due to its enormous impedance. Instead, tap water containing conductive ions was used to prepare hyaluronic acid solutions for experiments. However, the electrical properties of tap water were not constant for use. Therefore, normalization, such as the relative evaporation rate to water in this study, was adopted as an alternative index for...

Evaporation is a type of liquid vaporization and occurs along the gas-liquid interface of a collective body of water. The water molecules near the surface become capable of escaping from the liquid due to collision of water molecules. The evaporation rate is an important key factor during the process of evaporation. Generally, a balance or volumetric tube1-3 is widely-used to detect the evaporation of solutions. However, it takes a long time to measure the evaporation rate due to the precision limitation of a balance or a volumetric tube. For this reason, a responsive and high-sensitivity instrument must be developed to probe into the details of the evaporation process.
Electrochemical impedance spectroscopy (EIS) is a fast-response, sensitive and effective experimental means in terms of in-situ impedance detection for electrochemical system characterization4. Therefore, EIS can be applied in various fields, such as recent studies on cellular behavior5, bioanalytical sensing6-7, electrolysis8, conducting polymers9, and electrochemical extraction10. Even though EIS systems had successfully been applied in a wide variety of disciplines, there exist an extremely small number of publications on its application to evaporation research.
Hyaluronic acid, a high molecular weight polysaccharide with strong water-binding potential, is a well-known humectant for cosmetic applications. One hyaluronic acid molecule can bind up to 500 water molecules11 and reach 1,000 times its original volume12. An extremely small amount of hyaluronic acid can possess moisturizing function13-14. Due to the high moisture retention, hyaluronic acid has become an important component of cosmetic humectant products with high commercial value worldwide15.
This study presents the method of a novel impedance-based apparatus featuring high speed detection, small volume sample requirement, and multiple sample measurements16-19. It is presented with a focus on the relative evaporation rate comparison among solutions as a way to validate the superiority of the innovative detection mechanism over a conventional weighing manner.

<table border="0" cellpadding="0" cellspacing="0" width="848">
	<tbody>
		<tr height="28">
			<td height="28" style="height:28px;width:143px;">95 % ethanol</td>
			<td style="width:292px;">Echo Chemical Co., Ltd., Miaoli, Taiwan</td>
			<td style="width:155px;">484000001103C-00EC</td>
			<td style="width:259px;"></td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:143px;">Acetone</td>
			<td style="width:292px;">Avantor Performance Materials Inc., Center Valley, PA, USA</td>
			<td style="width:155px;">JTB-9005-68</td>
			<td></td>
		</tr>
		<tr height="30">
			<td height="30" style="height:30px;width:143px;">Development solution</td>
			<td style="width:292px;">Kemitek Industrial Crop., Hsinchu, Taiwan</td>
			<td style="width:155px;">12F01031</td>
			<td style="width:259px;">KTD-1</td>
		</tr>
		<tr height="30">
			<td height="30" style="height:30px;width:143px;">Etching solution</td>
			<td style="width:292px;">eSolv Technology Co., Taipei, Taiwan</td>
			<td style="width:155px;"></td>
			<td style="width:259px;">EG-462</td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:143px;">Hyaluronic acid</td>
			<td style="width:292px;">Shandong Freda Biopharm Co., Ltd., Jinan, China</td>
			<td style="width:155px;">1010212</td>
			<td>Molecular weight 980k, Cosmetic Grade</td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:143px;">Photoresist solution</td>
			<td style="width:292px;">AZ Electronic Materials Taiwan Co., Ltd., Hsinchu, Taiwan</td>
			<td style="width:155px;">65101M19</td>
			<td style="width:259px;">AZ6112</td>
		</tr>
		<tr height="47">
			<td height="47" style="height:47px;width:143px;">8-well silicone array</td>
			<td style="width:292px;">Greiner bio-one Inc., Frickenhausen, Baden-W&#252;rttemberg, Germany</td>
			<td style="width:155px;">FlexiPERM</td>
			<td></td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:143px;">ITO glass</td>
			<td style="width:292px;">GemTech Optoelectronics Co., Taoyuan, Taiwan</td>
			<td style="width:155px;"></td>
			<td></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:143px;">Vial&#160;</td>
			<td style="width:292px;">Sigma-Aldrich Co. LLC., St. Louis, MO, USA</td>
			<td style="width:155px;">854190</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:143px;">Film photomask</td>
			<td style="width:292px;">Taiwan Mesh Co., Ltd, Taoyuan, Taiwan</td>
			<td style="width:155px;"></td>
			<td></td>
		</tr>
		<tr height="46">
			<td height="46" style="height:46px;width:143px;">Lock-in amplifier</td>
			<td style="width:292px;">Stanford Research Systems, Inc., Palo Alto, CA, USA</td>
			<td style="width:155px;">SR830</td>
			<td></td>
		</tr>
		<tr height="66">
			<td height="66" style="height:66px;width:143px;">Switch relay</td>
			<td style="width:292px;">Instrument Technology Research Center, National Applied Research Laboratories, Hsinchu, Taiwan</td>
			<td style="width:155px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:143px;">Electronic balance machine</td>
			<td style="width:292px;">Precisa Co., Dietikon, Switzerland</td>
			<td>XS225A</td>
			<td></td>
		</tr>
	</tbody>
</table>

a high performance impedance-based platform for evaporation rate detection

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

During the evaporation process, the conductive ions in the tested solution became concentrated with the decreasing solution volume, and the impedance of this solution decreased. The rates of weight loss and impedance decrease in the evaporation progress for each tested solution were measured. For comparison purposes, the data in the rates of weight loss and impedance decrease were normalized to water and then plotted together in Figure 5. As illustrated in Figure 5, the weight loss demon...

Watch this Scientific Journal Video about A High Performance Impedance-based Platform for Evaporation Rate Detection at JoVE.com

A High Performance Impedance-based Platform for Evaporation Rate Detection

This paper presents an impedance-based apparatus for evaporation rate detection of solutions. It offers clear advantages over a conventional weight loss approach: a fast response, high-sensitivity detection, a small sample requirement, multiple sample measurements, and easy disassembly for cleaning and reuse purposes.

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was ...

The overall goal of this experiment is to measure the evaporation rates of solutions, using an impedance-based system. This method can help answer key questions in the analytical chemistry fields such as moisturizing competitive of cosmetics. The main advantage of this technique are faster detection response, small sample size, high sensitivities, management of multiple samples, and easy disassembly for cleaning and reuse.This method can provide insight into the evaporation process. It can also be applied to other laces such as biomolecular dissection and cellular behavior. We first had the idea for the method when we found the time-consuming nature of the standard way those measurements system to be troublesome.To begin building the experimental chip module, use a glass cutter to cut an indium tin oxide-coated glass substrate to the appropriate dimensions. Sonicate the ITO glass in acetone. And then in deionized water for 15 minutes each.Then dry the ITO glass with dry air. Apply five milliliters of positive photoresist liquid to the ITO glass and spin-coat the glass for 30 seconds. Keep the glass at 90 degrees Celsius for five minutes.Then cover the glass with a film photo mask and expose the glass to 14 milliwatts of 436-nanometer ultraviolet light for 3.1 seconds. Allow the glass to cool to room temperature. Then develop the glass in developer solution for 30 seconds.Heat the developed glass on a hot plate at 120 degrees Celsius for 10 minutes. Allow the glass to cool to 80 degrees Celsius. Place the glass in etching solution at 80 degrees for three minutes.Then place the glass in acetone for one minute to remove residual photoresist material. Using a glass cutter, trim the excess ITO glass from the chip. Next, sonicate an 8-well silicone array and the ITO chip in detergent, deionized water, 95%ethanol, and deonized water again for 15 minutes each.Dry the array and chip with dry air. Carefully place the clean, dry silicone array on the surface of the ITO chip so the electrode fingers on the chip are all within the wells of the silicone array. Finally, press the silicone array onto the ITO chip to form the experimental chip module.To begin preparation for the experiment, connect a lock-in amplifier to a computer. Then connect a switch relay circuit to the lock-in amplifier. Insert the experimental chip module into the switch relay circuit socket.In the software, set the signal frequency, the sample well numbers, the execution cycle, and the name of the file. Then prepare 4-milliliter solutions of varying concentrations of hyaluronic acid in tap water. Transfer 2.5 milliliters of each solution to a small vial.To begin the experiment, for each sample transfer 0.5 milliliters to a well of the experimental chip module. Then weigh each sample vial with a precision balance and record the weights. In the software, begin collecting resistance and signal phase data.Record the weights of the vials at regular time intervals throughout the evaporation experiment. Continue collecting data until the evaporation rate can be accurately determined by the change in weight of the sample vials. The rate of evaporation of hyaluronic acid solutions relative to water could be calculated from the impedance data after an hour of data collection.The weighing method required half a day of data collection to determine the rate of evaporation. The impedance data, when normalized and converted to rate of weight loss, indicated that the evaporation rate of the solution of 0.05 weight to volume percent hyaluronic acid is 12%lower relative to water. The conventional weighing method displayed the same trend of decreased relative evaporation rate.But the sensitivity of the precision balance was less than that of the impedance detector. Once mastered, this technique can be done in a hour if it is performed properly. After its development, this technique pave the way for researchers in the field of biomedicine to improve biomedication detection and cellular behavior using a constant microchip.

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JoVE Journal

Engineering

Research and Development of High-performance Explosives

Developmental testing of high explosives for military applications involves small-scale formulation, safety testing, and finally detonation performance tests to verify theoretical calculations. For newly developed formulations, the process begins with small-scale mixes, thermal testing, and impact and friction sensitivity. Only then do subsequent larger scale formulations proceed to detonation testing, which will be covered in this paper. Recent advances in characterization techniques have led to unparalleled precision in the characterization of early-time evolution of detonations. The new technique of Photonic Doppler Velocimetry (PDV) for the measurement of detonation pressure will be shared and compared with traditional fiber-optic detonation velocity and plate-dent calculation of detonation pressure. In particular, the role of aluminum in explosive formulations will be discussed. Recent developments led to the development of explosive formulations that result in reaction of aluminum very early in the detonation product expansion. This enhanced reaction leads to changes in the detonation velocity and pressure due to reaction of the aluminum with oxygen in the expanding gas products.

Developmental testing of high explosives for military applications involves small-scale formulation, safety testing, and finally detonation performance tests to verify theoretical calculations. This paper will share typical development tests associated with the measurement of detonation velocity and detonation pressure.

Developmental testing of high explosives for military applications involves small-scale formulation, safety testing, and finally detonation performance ...

Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

Here a seedless and template-free technique is demonstrated to scalably grow bismuth nanowires, through thermal evaporation in high vacuum at RT. Conventionally reserved for the fabrication of metal thin films, thermal evaporation deposits bismuth into an array of vertical single crystalline nanowires over a flat thin film of vanadium held at RT, which is freshly deposited by magnetron sputtering or thermal evaporation. By controlling the temperature of the growth substrate the length and width of the nanowires can be tuned over a wide range. Responsible for this novel technique is a previously unknown nanowire growth mechanism that roots in the mild porosity of the vanadium thin film. Infiltrated into the vanadium pores, the bismuth domains (~ 1 nm) carry excessive surface energy that suppresses their melting point and continuously expels them out of the vanadium matrix to form nanowires. This discovery demonstrates the feasibility of scalable vapor phase synthesis of high purity nanomaterials without using any catalysts.

A protocol for seedless and high yield growth of bismuth nanowire arrays through vacuum thermal evaporation technique is presented.

Here a seedless and template-free technique is demonstrated to scalably grow bismuth nanowires, through thermal evaporation in high vacuum at RT. ...

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing technology is used to fabricate particles with slender arms connected at a common center. Shapes explored are crosses (two perpendicular rods), jacks (three perpendicular rods), triads (three rods in triangular planar symmetry), and tetrads (four arms in tetrahedral symmetry). Methods for producing on the order of 10,000 fluorescently dyed particles are described. Time-resolved measurements of their orientation and solid-body rotation rate are obtained from four synchronized videos of their motion in a turbulent flow between oscillating grids with R&#955; = 91. In this relatively low-Reynolds number flow, the advected particles are small enough that they approximate ellipsoidal tracer particles. We present results of time-resolved 3D trajectories of position and orientation of the particles as well as measurements of their rotation rates.

We use 3D printing to fabricate anisotropic particles in the shapes of jacks, crosses, tetrads, and triads, whose alignments and rotations in turbulent fluid flow can be measured from multiple simultaneous video images.

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing ...

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

This paper reports an array-designed C84-embedded Si substrate fabricated using a controlled self-assembly method in an ultra-high vacuum chamber. The characteristics of the C84-embedded Si surface, such as atomic resolution topography, local electronic density of states, band gap energy, field emission properties, nanomechanical stiffness, and surface magnetism, were examined using a variety of surface analysis techniques under ultra, high vacuum (UHV) conditions as well as in an atmospheric system. Experimental results demonstrate the high uniformity of the C84-embedded Si surface fabricated using a controlled self-assembly nanotechnology mechanism, represents an important development in the application of field emission display (FED), optoelectronic device fabrication, MEMS cutting tools, and in efforts to find a suitable replacement for carbide semiconductors. Molecular dynamics (MD) method with semi-empirical potential can be used to study the nanoindentation of C84-embedded Si substrate. A detailed description for performing MD simulation is presented here. Details for a comprehensive study on mechanical analysis of MD simulation such as indentation force, Young&#39;s modulus, surface stiffness, atomic stress, and atomic strain are included. The atomic stress and von-Mises strain distributions of the indentation model can be calculated to monitor deformation mechanism with time evaluation in atomistic level.

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

This paper reports the nanomaterial fabrication of a fullerene Si substrate inspected and verified by nanomeasurements and molecular dynamic simulation.

This paper reports an array-designed C84-embedded Si substrate fabricated using a controlled self-assembly method in an ultra-high vacuum chamber. The ...

Scalable Solution-processed Fabrication Strategy for High-performance, Flexible, Transparent Electrodes with Embedded Metal Mesh

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a polymer film. This paper also presents a low-cost, vacuum-free fabrication method for this novel TE; the approach combines lithography, electroplating, and imprint transfer (LEIT) processing. The embedded nature of the EMTEs offers many advantages, such as high surface smoothness, which is essential for organic electronic device production; superior mechanical stability during bending; favorable resistance to chemicals and moisture; and strong adhesion with plastic film. LEIT fabrication features an electroplating process for vacuum-free metal deposition and is favorable for industrial mass production. Furthermore, LEIT allows for the fabrication of metal mesh with a high aspect ratio (i.e., thickness to linewidth), significantly enhancing its electrical conductance without adversely losing optical transmittance. We demonstrate several prototypes of flexible EMTEs, with sheet resistances lower than 1 &#937;/sq and transmittances greater than 90%, resulting in very high figures of merit (FoM) &#8211; up to 1.5 x 104 &#8211; which are amongst the best values in the published literature.

This protocol describes a solution-based fabrication strategy for high-performance, flexible, transparent electrodes with fully-embedded, thick metal mesh. Flexible transparent electrodes fabricated by this process demonstrate among the highest reported performances, including ultra-low sheet resistance, high optical transmittance, mechanical stability under bending, strong substrate adhesion, surface smoothness, and environmental stability.

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...

Developing High Performance GaP/Si Heterojunction Solar Cells

To improve the efficiency of Si-based solar cells beyond their Shockley-Queisser limit, the optimal path is to integrate them with III-V-based solar cells. In this work, we present high performance GaP/Si heterojunction solar cells with a high Si minority-carrier lifetime and high crystal quality of epitaxial GaP layers. It is shown that by applying phosphorus (P)-diffusion layers into the Si substrate and a SiNx layer, the Si minority-carrier lifetime can be well-maintained during the GaP growth in the molecular beam epitaxy (MBE). By controlling the growth conditions, the high crystal quality of GaP was grown on the P-rich Si surface. The film quality is characterized by atomic force microscopy and high-resolution x-ray diffraction. In addition, MoOx was implemented as a hole-selective contact that led to a significant increase in the short-circuit current density. The achieved high device performance of the GaP/Si heterojunction solar cells establishes a path for further enhancement of the performance of Si-based photovoltaic devices.

Here, we present a protocol to develop high-performance GaP/Si heterojunction solar cells with a high Si minority-carrier lifetime.

To improve the efficiency of Si-based solar cells beyond their Shockley-Queisser limit, the optimal path is to integrate them with III-V-based solar ...

A Silicon-tipped Fiber-optic Sensing Platform with High Resolution and Fast Response

In this article, we introduce an innovative and practically promising fiber-optic sensing platform (FOSP) that we proposed and demonstrated recently. This FOSP relies on a silicon Fabry-Perot interferometer (FPI) attached to the fiber end, referred to as Si-FOSP in this work. The Si-FOSP generates an interferogram determined by the optical path length (OPL) of the silicon cavity. Measurand alters the OPL and thus shifts the interferogram. Due to the unique optical and thermal properties of the silicon material, this Si-FOSP exhibits an advantageous performance in terms of sensitivity and speed. Furthermore, the mature silicon fabrication industry endows the Si-FOSP with excellent reproducibility and low cost toward practical applications. Depending on the specific applications, either a low-finesse or high-finesse version will be utilized, and two different data demodulation methods will be adopted accordingly. Detailed protocols for fabricating both versions of the Si-FOSP will be provided. Three representative applications and their according results will be shown. The first one is a prototype underwater thermometer for profiling the ocean thermoclines, the second one is a flow meter to measure flow speed in the ocean, and the last one is a bolometer used for monitoring exhaust radiation from magnetically confined high-temperature plasma.

This work reports an innovative silicon-tipped fiber-optic sensing platform (Si-FOSP) for high-resolution and fast-response measurement of a variety of physical parameters, such as temperature, flow, and radiation. Applications of this Si-FOSP span from oceanographic research, mechanical industry, to fusion energy research.

In this article, we introduce an innovative and practically promising fiber-optic sensing platform (FOSP) that we proposed and demonstrated recently. This ...