Matrix Assisted Pulsed Laser Evaporation Direct Write Research Articles

Nanocomposite sensitive polymeric films for SAW sensors deposited by the MAPLE direct write technique

A matrix-assisted pulsed laser evaporation direct write (MAPLE-DW) deposition technique was used to improve the properties of sensitive layers used in surface acoustic wave (SAW) sensors. In contrast with conventional deposition methods, MAPLE-DW allows the synthesis of uniform nanocomposite layers based on nanoparticles, in a special configuration that significantly reduces the energy loss by wave scattering. Ethanol, methanol, and toluene vapor were used as the target gases. The study compared sensors with polyethylenimine sensitive films and nanocomposite polymeric films based on SiO 2/Si nanoparticles (deposited by spray coating), and nanocomposite layers based on SiO 2 nanoparticles (deposited by MAPLE-DW). The sensors made from sensitive layers deposited by MAPLE-DW exhibited 3–5 times the sensitivity and 10–40 times the detection limit of the sensors deposited by spray coating.

Transforming a Laser Micromachiner into a Direct-Write Tool for Electronic Materials

A conventional laser micromachining system is configured for use as a matrix-assisted pulsed laser evaporation direct-write (MAPLE-DW) system in a straightforward and cost-effective manner. The simplicity of the method is illustrated by highlighting the process for MAPLE-DW of polymer composites used in chemical gas sensor arrays. Important aspects are considered, including ribbon preparation, ribbon aging, and computerized process control for rapid prototyping.

Planar laser imaging and modeling of matrix-assisted pulsed-laser evaporation direct write in the bubble regime

A combination of planar laser imaging and theoretical modeling has been used to examine matrix-assisted pulsed-laser evaporation direct write (MAPLE-DW) in the bubble regime. MAPLE-DW is a method for patterning substrates via laser-initiated forward transfer of an organic fluid containing metallic particles and coated on a transparent support. For our conditions, best deposition of a silver-based, thick-film ink was found to occur when laser-initiated vaporization forces the ink outward as a bubble. Planar laser imaging was used to monitor bubble growth as a function of time for three different ink films with nominal thicknesses of 12, 25, and 50μm and two laser beam diameters of 30 and 60μm. From these measurements, correlations were developed for predicting the maximum height and velocity of bubbles via three known process variables: laser energy, ink thickness, and beam diameter. Further insight on the physics of the MAPLE-DW process was obtained by developing a theoretical model for bubble growth based on a simple force balance associating vapor-pocket pressure and viscous forces. Primary parameters specifying the subsequent differential equation were related to the above process variables. Numerical solutions to the differential equation were used to predict successfully bubble growth versus time for the conditions analyzed in the imaging experiments.

Direct Writing of Conventional Thick Film Inks Using MAPLE-DW Process

Matrix Assisted Pulsed Laser Evaporation – Direct Write (MAPLE-DW) was investigated for use with conventional thick-film (screen printable) inks. A layer of ink, coated onto a glass slide, was transferred to an alumina substrate after being irradiated with 1047-nm, 20-ns laser pulses in a forward transfer configuration. The effect of different parameters on this process was studied and optimized. The process was demonstrated to be capable of depositing 20-μm conducting lines with a high linear speed.

Three‐dimensional direct writing of B35 neuronal cells

We have demonstrated two-dimensional and three-dimensional transfer of B35 neuronal cells onto and within polymerized Matrigel substrates, using matrix-assisted pulsed laser evaporation-direct write (MDW). The B35 cells were transferred from a quartz ribbon to depths of up to 75 microm by systematically varying the fluence emitted from the ArF (lambda = 193 nm) laser source. MDW-transferred cells were examined using terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL), 4',6-diamidino-2-phenylindole (DAPI), and alpha-tubulin staining. Confocal microscopy has shown that the transferred B35 cells extended their axons outward in three dimensions within the polymerized Matrigel substrate. The B35 cells made axonal connections and formed a three-dimensional neural network within 72 h after MDW transfer. In addition, TUNEL staining demonstrated that only 3% of the B35 cells underwent apoptosis after being transferred using the MDW process. MDW and other emergent direct write processes may provide unique approaches for creating layered, heterogeneous, three-dimensional cell-seeded scaffolds for use in peripheral nerve repair.

Two-dimensional differential adherence and alignment of C2C12 myoblasts

Surface microstructure is a critical parameter for scaffolds used in skeletal muscle tissue engineering. We have developed micromachined surfaces using matrix assisted pulsed laser evaporation-direct write (MAPLE-DW) that demonstrate differential adherence of C2C12 myoblast cells. The 60–400 μm diameter channels were micromachined onto 2% agarose surfaces using an ArF excimer laser and lined with Matrigel ® basement membrane matrix solution. Suspensions containing C2C12 myoblast cells were then placed on the surface of these micromachined channels. The C2C12 myoblast cells aligned themselves parallel to the 60–150 μm channels. Live/dead assays over 72 h demonstrated that cell number, cell size, and number of nuclei per cell increased within these channels. In addition, some of the myoblasts fused and differentiated into multinucleated myotubes. These results provide the basis for the development of direct-write scaffolds for skeletal muscle tissue engineering.

Laser transfer of biomaterials: Matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE Direct Write

Two techniques for transferring biomaterial using a pulsed laser beam were developed: matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE direct write (MDW). MAPLE is a large-area vacuum based technique suitable for coatings, i.e., antibiofouling, and MDW is a localized deposition technique capable of fast prototyping of devices, i.e., protein or tissue arrays. Both techniques have demonstrated the capability of transferring large (mol wt>100 kDa) molecules in different forms, e.g., liquid and gel, and preserving their functions. They can deposit patterned films with spatial accuracy and resolution of tens of μm and layering on a variety of substrate materials and geometries. MDW can dispense volumes less than 100 pl, transfer solid tissues, fabricate a complete device, and is computed aided design/computer aided manufacturing compatible. They are noncontact techniques and can be integrated with other sterile processes. These attributes are substantiated by films and arrays of biomaterials, e.g., polymers, enzymes, proteins, eucaryotic cells, and tissue, and a dopamine sensor. These examples, the instrumentation, basic mechanisms, a comparison with other techniques, and future developments are discussed.

Plume and jetting regimes in a laser based forward transfer process as observed by time-resolved optical microscopy

Matrix-assisted pulsed laser evaporation direct-write was investigated by ultra high-speed optical microscopy. A layer of viscous fluid was irradiated with 355 nm, 30 ns laser pulses in a laser forward transfer configuration. The fluid response as a function of fluence was studied, and several distinct regimes of behavior were observed: plume, jetting and sub-threshold. This work emphasizes the fundamental differences between laser forward transfer of solid-state materials and rheological fluids.

Ferroelectric Capacitors Made by a Laser Forward Transfer Technique

Ferroelectric capacitors have been fabricated using a novel laser based transfer technique called Matrix Assisted Pulsed Laser Evaporation-Direct Write (MAPLE-DW) with the dielectric films thermally processed by selective laser sintering. MAPLE-DW is a versatile direct writing technique capable of writing a wide variety of materials on virtually any substrate under ambient conditions. Lead magnesium niobate (PMN) based dielectric films were deposited by MAPLE-DW on metallized alumina and kapton substrates under ambient conditions. Infrared CW CO2 ( u = 10.6 w m) laser was used for thermal processing of the dielectric films. Electrical characteristics of these MAPLE-DW deposited capacitors were studied over a wide frequency range (1 MHz to 1.8 GHz).

The deposition, structure, pattern deposition, and activity of biomaterial thin-films by matrix-assisted pulsed-laser evaporation (MAPLE) and MAPLE direct write

Two techniques, Matrix-Assisted Pulsed-Laser Evaporation (MAPLE) and MAPLE Direct Write (MDW) were developed to deposit biomaterial thin-films. MAPLE involves dissolving or suspending the biomaterial in a volatile solvent, freezing the mixture to create a solid target, and using a low fluence pulsed laser to evaporate the target for deposition of the solute inside a vacuum system. Using simple shadow masks, i.e. lines, dots and arrays, pattern features with length scales as small as 20 μm can be deposited using multiple materials on different types of substrates. MDW uses pulsed laser to directly transfer material from a ribbon to a substrate. Patterns with a spatial resolution of ∼10 μm can be written directly. Biomaterials ranging from polyethylene glycol to eukaryotic cells, i.e. Chinese hamster ovaries, were deposited with no measurable damage to their structures or genotype. Deposits of immobilized horseradish peroxidase, an enzyme, in the form of a polymer composite with a protective coating, i.e. polyurethane, retained their enzymatic functions. A dopamine electrochemical sensor was fabricated by MDW using a natural tissues/graphite composite. These examples and the unique features of MAPLE and MDW for biosensor fabrication have been discussed.

Direct writing of polymer thick film resistors using a novel laser transfer technique

Polymer thick film (PTF) resistors were fabricated using a new laser-based transfer technique called matrix-assisted pulsed laser evaporation direct write (MAPLE-DW). MAPLE-DW is a versatile direct writing technique capable of writing a wide variety of materials on virtually any substrate in air and at room temperature. Epoxy-based PTF resistors spanning four decades of sheet resistances (10 Ω/sq. to 100 kΩ/sq.) were deposited on alumina substrates under ambient conditions. Electrical characteristics of these MAPLE-DW deposited resistors were studied at a wide frequency range (1 MHz to 1.8 GHz), and the results were explained through an equivalent circuit model and impedance spectroscopy. Temperature coefficient of resistance measurements for the PTF resistors were performed between 25 and 125 °C. The results based on the percolation theory were used to explain the temperature dependence of the resistance behavior of the PTF resistors.

Dielectric properties of oxide structures by a laser-based direct-writing method

Matrix-assisted pulsed laser evaporation direct-write (MAPLE-DW) is a laser-based method of directly writing mesoscopic patterns of electronic materials. Patterns of composite BaTiO3/SiO2/TiO2 dielectric material were written onto Pt/Au interdigitated-electrode test structures, with precise control over final dielectric properties. Scanning electron microscopy indicates random close-packed structures of BaTiO3 and SiO3 particles, with interstitial spaces partially filled with titania. Depending on the BaTiO3:silica ratio, the dielectric constant ranged from 5 to 55 and followed a 4-component logarithmic rule of mixing. This work demonstrates that the transfer process and the final material properties of MAPLE-DW oxide materials are largely decoupled.

Laser Direct Writing of Hydrous Ruthenium Dioxide Micro-Pseudocapacitors

ABSTRACTWe are using a laser engineering approach to develop and optimize hydrous ruthenium dioxide (RuOxHyor RuO2·0.5 H2O) pseudocapacitors. We employ a novel laser forward transfer process, Matrix Assisted Pulsed Laser Evaporation Direct Write (MAPLE-DW), in combination with UV laser machining, to fabricate mesoscale pseudocapacitors and microbatteries under ambient temperature and atmospheric conditions. Thin films with the desired high surface area morphology are obtained without compromising their electrochemical performance. The highest capacitance structures are achieved by depositing mixtures of sulfuric acid with the RuO2·0.5 H2O electrode material. Our pseudocapacitors exhibit linear discharge behavior and their properties scale proportionately when assembled in parallel and series configurations.

Maple direct write: A new approach to fabricate ferroelectric thin film devices in air at room temperature

MAPLE Direct Write or MAPLE DW is a new direct writing technique which combines some of the major positive advantages of laser induced forward transfer and matrix assisted pulsed laser evaporation (MAPLE). This novel laser driven direct writing technique has demonstrated the deposition of metal, ceramic, and polymer materials in air and at room temperature and with sub-10 micron resolution for active and passive prototype circuit elements on planar and nonplanar substrates. Here, we have used MAPLE DW to synthesize ferroelectric devices for tunable microwave device applications. For ferroelectrics and the other functional materials, MAPLE DW can be used to investigate directly the properties of powder materials as a function of grain size, doping, and processing technique. The best properties obtained for Ba0.5Sr0.5TiO3 and BaTiO3 films were dielectric constants of 40, with loss tangents of about 0.025 with ∽ 1% tuning.

Deposition of Ceramic Materials Using Powder and Precursor Vehicles Via Direct Write Processing

ABSTRACTDry powder and sol gel ceramic films were deposited using a Matrix Assisted Pulsed Laser Evaporation Direct Write (MAPLE-DW) technique developed at NRL for optical and electrical device applications. The MAPLE-DW technique uses a high-energy focussed photon source in combination with a “ribbon” to fabricate materials onto a range of substrates at room temperature without material degradation. Two different classes of materials were processed in this research, (1) ceramic dry powder materials and (2) sot gel precursor materials. Cathodoluminescent measurements demonstrated that the efficiencies of the transferred phosphor materials were not degraded during the laser transfer process. Scanning electron microscopy and 3-D surface profilometry of the ribbon after the MAPLE-DW process revealed a 90–95% transfer efficiency for the dry powders. Scanning electron microscopy and energy dispersive spectroscopy revealed that the sol gel materials also transferred with an efficiency in the 90-95% range. Three distinct regions were identified on the so gel ribbon after the laser transfer process. The regions suggest that the matrix absorbing layer and the sol gel materials are completely removed for the areas irradiated by the laser pulse, and in a second so-called “heat affected region,” only the sol gel material is ejected from the ribbon.