This work was supported by the National Science Foundation Grant No. 1531382 and MarTREC.

NOTE: All relevant material used in the following procedures are non-hazardous. Personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes) are still needed.
1. Preparation of bacteria solution
<ol>
	<li>Preparation of growth medium (NH4-YE medium) 
	NOTE: The components of growth media per liter of deionized water are: 20 g of yeast extract; 10 g of (NH4)2SO4; and 0.13 M Tris buffer (pH 9.0).
	<ol>
		<li>Autoclave ingredients separately.</li>
		<li>Dissolve 20 g of yeast extract, and 10 g of (NH4)2SO4 in 1 L of deionized water containing 0.13 M Tris buffer.</li>
		<li>Mix the components together using magnetic stirrer post-sterilization.</li>
	</ol>
	</li>
	<li>Propagation procedure of Sporosarcina pasteurii 
	NOTE: Use 50 mL centrifuge tubes in this experiment.
	<ol>
		<li>Thaw the frozen bacteria in a vial.</li>
		<li>Open the vial.</li>
		<li>Transfer 0.1 mL of bacteria suspension to a centrifuge tube with 10 mL of fresh growth medium. Mix well by hand (inoculation rate is 1:100). Repeat 5 more bacterial suspensions with growth medium. Prepare a control tube only with 10 of fresh growth medium inside. 
		NOTE: The cryoprotectant used in the freeze/drying procedure may inhibit growth in the primary tube. The lids of tubes were tightened loosely in order to maintain the aerobic condition.</li>
		<li>Incubate all tubes in a shaker at 200 rpm at 30 &#176;C for 48 to 72 hours. Stop the incubation if the growth medium becomes turbid after 48 h. Otherwise, extend the incubation to the maximum of 72 h.</li>
		<li>Centrifuge the tubes with bacteria and growth medium at 4,000 x g for 20 min.</li>
		<li>Remove the supernatant, replace with 25 mL of fresh growth medium, and mix well using a vortex machine.</li>
		<li>Repeat steps 1.2.3-1.2.6 twice to fully stimulate the activity of bacteria.</li>
		<li>Use the suspension from the tubes in step 1.2.7 to inoculate more tubes with 25 mL of growth medium to enhance the culture of bacteria (inoculation rate is 1:100).</li>
		<li>Incubate all tubes in a shaker at 200 rpm at 30 &#176;C for 48 hours.</li>
		<li>Centrifuge the tubes with bacteria and growth medium at 4,000 x g for 20 min.</li>
		<li>Remove the supernatant, replace with fresh growth medium, and mix well using a vortex machine.</li>
		<li>Adjust the bacteria concentration using fresh growth medium before the MICP experiments. Calculate the bacteria concentration by optical density of the suspension at 600 nm, which was measured using a spectrophotometer. The OD600 in this experiment was 0.6.</li>
	</ol>
	</li>
</ol>
2. Preparation of cementation media
NOTE: Cementation media is used to provide chemicals to induce the calcite precipitation during the MICP treatment. The urea-Ca2+ molar ratio is 1:1. The chemical components of cementation media is shown in Table 1. The following procedure is for 20 L of cementation media with 0.5 M Ca.
<ol>
	<li>Prepare 20 L of water in a plastic box.</li>
	<li>Dissolve 200 g of NH4Cl, 60 g of nutrient broth, 42.4 g of NaHCO3, 600 g of urea, and 1470 g of CaCl2&#8729;2H2O in the 20 L of distilled water. Mix well using stirring rod.</li>
</ol>
3. Preparation of molds
<ol>
	<li>Preparation of full contact flexible mold (FCFM) 
	NOTE: The full contact flexible mold is made of geotextile. The geotextile has a grab tensile strength of 1,689 N, a trapezoidal tear strength of 667 N, an apparent opening size of 0.15 mm, a water flow rate of 34 mm/s, a thickness of 1.51 mm, and a unit mass of 200 g/m2. The size of mold can be varied to prepare different sample sizes (for example, unconfined compression test sample or direct shear test sample).
	<ol>
		<li>As the FCFM consists of an annular part, a bottom, and a cover, cut the geotextile into constituent parts of FCFM.</li>
		<li>Sew the three parts of FCFM together as shown in Figure 1.</li>
	</ol>
	</li>
	<li>Preparation of rigid full contact mold (RFCM) for bio-bricks 
	NOTE: The rigid full contact mold consists of a flexible layer and a rigid holder. The flexible layer is made of the same geotextile as the FCFM. The rigid holder is made of a polypropylene perforated sheet with 6.35 mm diameter staggered holes distributed on the polypropylene perforated sheet and the clearance distance between adjacent holes is 9.53 mm. One mold consist of three chambers and the size of each chamber is 177.8 mm in length, 76.2 mm in width and 38.1 mm in height. The size of RFCM can be varied to prepare different sample size. The holes in the rigid holder allow cementation media flow through the flexible layer freely.
	<ol>
		<li>Prepare the polypropylene perforated sheet for constituent pieces of the rigid holder.</li>
		<li>Assemble the pieces of rigid holder using plastic screws and nuts.</li>
		<li>Prepare the constituent parts of the geotextile flexible layer. The flexible layer consists of a bottom and a cover.</li>
		<li>Enclose the bottom of the flexible layer in the rigid holder.</li>
		<li>Once the sand is added into the mold, place the cover of flexible layer and fix by sewing on the top of the sand sample as shown in Figure 2.</li>
	</ol>
	</li>
	<li>Preparation of hollow brick mold 
	NOTE: The hollow brick mold includes a rigid holder, a flexible layer, and cardboard tubes. The size of the cardboard tube is 60 mm x 140 mm x 60 mm. Three chambers are included in one mold and the size of each mold chamber is 177.8 mm in length, 76.2 mm in width and 38.1 mm in height in this procedure.
	<ol>
		<li>Prepare the polypropylene perforated sheet for the constituent pieces of the rigid holder.</li>
		<li>Drill holes on the bottom of the rigid holder piece. The size of the holes is 61 mm in diameter. The location of holes in each chamber is shown in Figure 3a.</li>
		<li>Assemble the pieces of the rigid holder using plastic screws and nuts.</li>
		<li>Assemble the cardboard tubes in the drilled holes on the bottom of the rigid holder.</li>
		<li>Prepare the constituent parts of the geotextile flexible layer. The flexible layer consists of a bottom and a cover. Holes are also needed on the flexible layer at the same location of cardboard tubes.</li>
		<li>Once the sand is added into the mold, place the cover of flexible layer and fix by sewing on the top of the sand sample as shown in Figure 3b.</li>
	</ol>
	</li>
</ol>
4. Preparation of the batch reactor
NOTE: The reactor shown in Figure 4 consists of a plastic box, cementation media, a sample supported shelf, and air pumps. The soil samples can fully immerse into the cementation media while the cementation media can freely diffuse into the soil samples by this method. The air pump in the reactor provides oxygen for bacteria. To determine the effects of different oxygen supply on MICP treatment catalyzed by Sporosarcina pasteurii, Li et al. 201718 conducted contrast tests under three different conditions: an aerated condition, an air restricted condition, and an open-air condition. They found that a well-oxygenated condition is essential to improve MICP processes catalyzed by aerobic bacteria.
<ol>
	<li>Connect the air pump with air supply using a plastic hose.</li>
	<li>Place the air pump in the plastic box.</li>
	<li>Pour cementation media into the plastic box.</li>
</ol>
5. Preparation of soil samples
<ol>
	<li>Preparation of MICP-treated soil sample 
	NOTE: Ottawa sand (99.7% quartz) is used in the experiments. The sand is uniform with a median particle size of 0.46 mm and no fines are included. It is classified as poorly graded sand based on the Unified Soil Classified System (USCS).
	<ol>
		<li>Add dry sand into molds by the air pluviation method (FCFM, RFCM, hollow brick mold) to reach a median dense condition (Dr in the range of approximately 42&#8211;55%, and dry density of sand in the range of 1.58&#8211;1.64 g/cm3). 
		NOTE: The weight of sand varies according to different kinds of molds: 145 &#177; 5 g sand for the UCS test sample, which is 38.6 mm in diameter and 76.2 mm in height.</li>
		<li>Place the cover on the top of samples and fix it by sewing.</li>
		<li>Pour the bacteria solution with a fixed optical density value through the permeable geotextile cover into the samples and make sure that they are saturated. 
		NOTE: The amount of bacteria solution varied according to different samples: 50 mL of bacteria solution for a UCS test sample, which is 38.6 mm in diameter and 76.2 mm in height.</li>
		<li>Place samples on the sample supported shelf as shown in Figure 5a.</li>
		<li>Immerse the entire shelf into the batch reactor filled with cementation media.</li>
		<li>Turn on the air supply and adjust the air output to keep 100% air saturation. Wait for 7 days of MICP reaction.</li>
		<li>Take out the samples from the reactor as shown in Figure 5b.</li>
		<li>Remove the samples by cutting the full contact flexible mold or demolding the rigid holder and then cutting the flexible layer.</li>
		<li>Wash the samples with water to remove the residual solution in the pore space.</li>
		<li>Place the samples in the 105 &#176;C oven for 48 h until their weights remain constant. The samples can be tested or treated additionally after the oven drying.</li>
	</ol>
	</li>
	<li>Preparation of fiber reinforced MICP-treated soil sample 
	NOTE: Synthetic fiber (see Table of Materials) and natural palm fiber as shown in Figure 6 are used in these procedures.
	<ol>
		<li>For the synthetic fiber, mix the proposed content of fibers and 900 g of dry sand in small increments by hand to obtain a uniform mixture. The fiber content in this experiment is fixed as 0.3% by weight of the dry sand.</li>
		<li>For the natural palm fiber, distribute 760 g of sand into four equal parts. Add these four parts of sand and three layers of fiber in RFCM at intervals.</li>
		<li>Repeat the same procedure as steps 5.1.2&#8212;5.1.10 to get the MICP-treated sample.</li>
	</ol>
	</li>
	<li>Preparation of cement-treated bricks with bio-surface treatment 
	NOTE: Portland cement (TYPE I/II) with specific gravity of 3.15 is used as the cementing agent for the cement-treated samples in this experiment. The early strength gain of this cement allowed the various curing times ranged from 7 to 21 days. The proportion of added cement in this procedure is 10% by weight of dry sand.
	<ol>
		<li>Mix 900 g of sand, 90 g of cement, and 200 mL of water to achieve a uniform mixture.</li>
		<li>Add the mixture to the rigid mold. The size of rigid mold is 177.8 mm in length, 76.2 mm in width and 38.1 mm in height.</li>
		<li>Cure for 7 days at a constant humidity of 100% and constant temperature of 25 &#176;C.</li>
		<li>Place samples in the 105 &#176;C oven for 48 hours until their weights remain constant.</li>
		<li>Repeat the same procedure as steps 5.1.3&#8212;5.1.8.</li>
		<li>Place samples in the 105 &#176;C oven for 48 hours until their weights remain constant. The samples can be tested or treated additionally after the oven drying.</li>
	</ol>
	</li>
</ol>

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We have nothing to disclose.

The MICP technique by immersion was presented in this paper. Soil samples were immersed into the batch reactor to get fully penetrated by cementation media in the MICP process. In this method, a full contact flexible mold, a rigid full contact mold, and a cored brick mold were applied to prepare MICP-treated samples.
Different molds can be designed for different geometry requirements. The fibrous structure of geotextile increased the contact area between sand and cementation media, which effec...

As a biological ground improvement technology, microbially induced calcite precipitation (MICP) is capable of improving engineering properties of soil. It has been used to enhance the strength, stiffness, and permeability of soil. The MICP technique has gained much attention for soil improvement worldwide1,2,3,4. Carbonate precipitation naturally happens and can be induced by nonpathogenic organisms that are native to the soil environment5. The MICP biogeochemical reaction is driven by the existence of ureolytic bacteria, urea and a calcium-rich solution5,6. Sporosarcina pasteurii is a highly active urease enzyme that catalyzes the reaction network towards precipitation of calcite7,8. The urea hydrolysis process produces dissolved ammonium (NH4+) and inorganic carbonate (CO32-). The carbonate ions react with calcium ions to precipitate as calcium carbonate crystals. The urea hydrolysis reactions are shown here:
<img alt="Equation 1" src="/files/ftp_upload/60059/60059equ01.jpg" />
<img alt="Equation 2" src="/files/ftp_upload/60059/60059equ02.jpg" />
The precipitated CaCO3 can bond the sand particles together to improve the engineering properties of MICP-treated soil. The MICP technique has been applied in various applications, such as improvement of strength and stiffness of soil, repair of concrete, and environmental remediation9,10,11,12,13,14,15.
Zhao et al.16 developed an immersion method to prepare MICP-treated samples. A full contact flexible mold made of geotextile was used in this method. The precipitated CaCO3 distributed uniformly throughout their MICP-treated samples. Bu et al.17 developed a rigid full contact mold to prepare MICP-treated beam samples by an immersion method. The MICP-treated sample prepared by this method using a rigid full contact mold can form the suitable beam shape. The MICP-treated sample was divided into four and the CaCO3 contents were measured. The CaCO3 content ranged from 8.4 &#177; 1.5% to 9.4 &#177; 1.2% by weight, which indicated that the CaCO3 distributed uniformly in the MICP-treated samples by the immersion method. These MICP-treated samples also achieved better mechanical properties. These MICP-treated bio-specimens reached a 950 kPa flexure strength, which was similar to that of 20- 25% cement-treated samples (600- 1300 kPa). Li et al.10 added randomly distributed discrete fiber into the sandy soil and treated the soil by the MICP immersion method. They found that the shear strength, ductility, and failure strain of MICP-treated soil were enhanced obviously by adding appropriate fiber.
The immersion method for MICP has been continually improved10,16,17. This method can be used to prepare MICP-treated soil samples and MICP-treated prefabricated building materials, such as bricks and beams. Different geometry dimensions of sample preparation mold were developed. Fibers were added in the MICP-treated samples to enhance their properties. This detailed protocol was intended to document the immersion methods for MICP treatment.

<table>
	<tbody>
		<tr>
			<td>Ammonium Chloride, &#62;99%</td>
			<td>Bio-world</td>
			<td>40100196-3 (705033)</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium Sulfate</td>
			<td>Bio-world</td>
			<td>30635330-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium Chloride Dihydrate, &#62;99%</td>
			<td>Bio-world</td>
			<td>40300016-3 (705111)</td>
			<td></td>
		</tr>
		<tr>
			<td>Nutrient Broth</td>
			<td>Bio-world</td>
			<td>30620056-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate, &#62;99%</td>
			<td>Bio-world</td>
			<td>41900068-3 (705727)</td>
			<td></td>
		</tr>
		<tr>
			<td>Sporosarcina pasteurii</td>
			<td>American Type Culture Collection</td>
			<td>ATCC 11859</td>
			<td></td>
		</tr>
		<tr>
			<td>Synthetic fiber</td>
			<td>FIBERMESH</td>
			<td>Fibermesh 150e3</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris-Base, Biotechnology Grade, &#62;99.7%</td>
			<td>Bio-world</td>
			<td>42020309-2 (730205)</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea, USP Grade, &#62;99%</td>
			<td>Bio-world</td>
			<td>42100008-2 (705986)</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Extract</td>
			<td>Bio-world</td>
			<td>30620096-3 (760095)</td>
			<td></td>
		</tr>
	</tbody>
</table>

sandy soil improvement through microbially induced calcite precipitation (micp) by immersion

The goal of this article is to develop an immersion method to improve the microbially induced calcite precipitation (MICP) treated samples. A batch reactor was assembled to immerse soil samples into cementation media. The cementation media can freely diffuse into the soil samples in the batch reactor instead of cementation media being injected. A full contact flexible mold, a rigid full contact mold, and a cored brick mold were used to prepare different soil sample holders. Synthetic fibers and natural fibers were selected to reinforce the MICP-treated soil samples. The precipitated CaCO3 in different areas of the MICP-treated samples was measured. The CaCO3 distribution results demonstrated that the precipitated CaCO3 was distributed uniformly in the soil sample by the immersion method.

Figure 7 shows the distribution of precipitated CaCO3 throughout the MICP-treated sample. The MICP-treated sample was divided into three different areas. The CaCO3 content in each area was tested by the acid washing method. To dissolve precipitated carbonates, the dry MICP-treated samples were washed in a HCl solution (0.1 M), then rinsed, drained, and oven-dried for 48 hours. The difference value between the masses of samples before and after acid washing was considere...

Watch this Scientific Journal Video about Sandy Soil Improvement through Microbially Induced Calcite Precipitation MICP by Immersion at JoVE.com

Sandy Soil Improvement through Microbially Induced Calcite Precipitation MICP by Immersion

Here, microbially induced calcite precipitation (MICP) technology is presented to improve soil properties by immersion.

Sandy Soil Improvement through Microbially Induced Calcite Precipitation (MICP) by Immersion

The goal of this article is to develop an immersion method to improve the microbially induced calcite precipitation (MICP) treated samples. A batch ...

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9.3K Views.  Jackson State University. Here, microbially induced calcite precipitation (MICP) technology is presented to improve soil properties by immersion.

Video: Sandy Soil Improvement through Microbially Induced Calcite Precipitation MICP by Immersion

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11.
Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps).
Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators.

An experimental method to examine the early plasma evolution induced by ultrashort laser pulses is described. Using this method, high quality images of early plasma are obtained with high temporal and spatial resolutions. A novel integrated atomistic model is used to simulate and explain the mechanisms of early plasma.

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

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 ...

Visible-light Induced Reduction of Graphene Oxide Using Plasmonic Nanoparticle

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using visible light irradiation with plasmonic nanoparticles. The plasmonic nanoparticle is used to improve the reduction efficiency of GO. It only takes 30 min&#160;at RT by illuminating the solutions with Xe-lamp, the r-GO solutions can be obtained by completely removing gold nanoparticles through simple centrifugation step. The spherical gold nanoparticles (AuNPs) as compared to the other nanostructures is the most suitable plasmonic nanostructure for r-GO preparation. The reduced graphene oxide prepared using visible light and AuNPs was equally qualitative as chemically reduced graphene oxide, which was supported by various analytical techniques such as UV-Vis spectroscopy, Raman spectroscopy, powder XRD and XPS. The reduced graphene oxide prepared with visible light shows excellent quenching properties over the fluorescent molecules modified on ssDNA and excellent fluorescence recovery for target DNA detection. The r-GO prepared by recycled AuNPs is found to be of same quality with that of chemically reduced r-GO. The use of visible light with plasmonic nanoparticle demonstrates the good alternative method for r-GO synthesis.

A simple protocol for the preparation of reduced graphene oxide using visible light and plasmonic nanoparticle is described.

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints.

A straightforward procedure for ultrasonic welding of thermoplastic composite coupons for basic mechanical testing is described. Key characteristics of this ultrasonic welding process are the use of flat energy directors for simplified process preparation and the use of process data for the fast definition of optimum processing conditions.

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Laser-induced Forward Transfer of Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

We demonstrate the use of the Laser-induced forward transfer technique (LIFT) for the printing of high-viscosity Ag paste. This technique offers a simple, low temperature, robust process for non-lithographically printing microscale 2D and 3D structures.

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of ...

Magnetically Induced Rotating Rayleigh-Taylor Instability

Classical techniques for investigating the Rayleigh-Taylor instability include using compressed gasses1, rocketry2 or linear electric motors3 to reverse the effective direction of gravity, and accelerate the lighter fluid toward the denser fluid. Other authorse.g. 4,5,6 have separated a gravitationally unstable stratification with a barrier that is removed to initiate the flow. However, the parabolic initial interface in the case of a rotating stratification imposes significant technical difficulties experimentally. We wish to be able to spin-up the stratification into solid-body rotation and only then initiate the flow in order to investigate the effects of rotation upon the Rayleigh-Taylor instability. The approach we have adopted here is to use the magnetic field of a superconducting magnet to manipulate the effective weight of the two liquids to initiate the flow. We create a gravitationally stable two-layer stratification using standard flotation techniques. The upper layer is less dense than the lower layer and so the system is Rayleigh-Taylor stable. This stratification is then spun-up until both layers are in solid-body rotation and a parabolic interface is observed. These experiments use fluids with low magnetic susceptibility, |&#967;| ~ 10-6 - 10-5, compared to a ferrofluids. The dominant effect of the magnetic field applies a body-force to each layer changing the effective weight. The upper layer is weakly paramagnetic while the lower layer is weakly diamagnetic. When the magnetic field is applied, the lower layer is repelled from the magnet while the upper layer is attracted towards the magnet. A Rayleigh-Taylor instability is achieved with application of a high gradient magnetic field. We further observed that increasing the dynamic viscosity of the fluid in each layer, increases the length-scale of the instability.

We present a protocol for preparing a two-layer density-stratified liquid that can be spun-up into solid body rotation and subsequently induced into Rayleigh-Taylor instability by applying a gradient magnetic field.

Classical techniques for investigating the Rayleigh-Taylor instability include using compressed gasses1, rocketry2 or linear electric motors3 to reverse ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...