Nicholas A. Charipar

United States Naval Research Laboratory, Washington, Washington, D.C., United States

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Publications (24)54.04 Total impact

  • Alberto Piqué, Heungsoo Kim, Nicholas A. Charipar, Michael Osofsky
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    ABSTRACT: Conventional metals with high carrier concentrations have served to date as the materials of choice for plasmonic and metamaterial devices. However, typical metals are not well suited for near IR (NIR) plasmonic applications because their associated plasma frequencies correspond to the visible and ultraviolet regions of the spectrum. On the other hand, materials with lower plasma frequencies such as conducting oxides like ZnO and VO2 are capable of more efficiently coupling the electromagnetic radiation for optical metamaterial and plasmonic applications in the NIR. Furthermore, unlike metals, the electrical transport properties of conductive oxides can be modulated intrinsically by doping or extrinsically by applying heat, light or an electrical bias, thus allowing tuning of their electro-optical behavior. At the Naval Research Laboratory (NRL), we have investigated the use of laser processing techniques for the deposition and processing of various types of conducting oxides, such as Al-doped ZnO and W-doped VO2, which can be optimized over a wide range of optical/electrical properties. This paper will describe the laser deposition of these oxide films and their electrical and optical characterization in the NIR.
    02/2014;
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    ABSTRACT: Additive manufacturing techniques such as 3D printing are able to generate reproductions of a part in free space without the use of molds; however, the objects produced lack electrical functionality from an applications perspective. At the same time, techniques such as inkjet and laser direct-write (LDW) can be used to print electronic components and connections onto already existing objects, but are not capable of generating a full object on their own. The approach missing to date is the combination of 3D printing processes with direct-write of electronic circuits. Among the numerous direct write techniques available, LDW offers unique advantages and capabilities given its compatibility with a wide range of materials, surface chemistries and surface morphologies. The Naval Research Laboratory (NRL) has developed various LDW processes ranging from the non-phase transformative direct printing of complex suspensions or inks to lase-and-place for embedding entire semiconductor devices. These processes have been demonstrated in digital manufacturing of a wide variety of microelectronic elements ranging from circuit components such as electrical interconnects and passives to antennas, sensors, actuators and power sources. At NRL we are investigating the combination of LDW with 3D printing to demonstrate the digital fabrication of functional parts, such as 3D circuits. Merging these techniques will make possible the development of a new generation of structures capable of detecting, processing, communicating and interacting with their surroundings in ways never imagined before. This paper shows the latest results achieved at NRL in this area, describing the various approaches developed for generating 3D printed electronics with LDW.
    02/2014;
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    ABSTRACT: High quality VO2 epitaxial thin films were deposited on sapphire single crystal substrates by pulsed laser deposition and their semiconductor-to-metal transitions (SMTs) were characterized as a function of film growth conditions. Varying the oxygen pressure during deposition affected the number of oxygen vacancies, which allowed tuning of the crystal structure and phase transition properties of the VO2 films. Films grown at optimized conditions exhibited a significant resistivity drop (>104 Ω-cm) across the SMT that is correlated with the strain due to oxygen vacancies. This resistivity drop is mainly accounted for by a large change in carrier density at the SMT.
    Applied Physics Letters 01/2014; 104(8):081913-081913-5. · 3.52 Impact Factor
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    ABSTRACT: Advanced fabrication technologies are poised to revolutionize the manufacturing environment. While the development of additive manufacturing technologies for mechanical components has been rapidly evolving, the application of these methods to the fabrication of RF and microwave components has been limited. Hybrid manufacturing processes, which combine distinct techniques such as fused deposition modeling (FDM), and laser micromachining, enable the creation of complex three-dimensional (3D) electromagnetic components. At NRL, we have investigated the combination of 3D printing techniques with direct-write processes that allow for the metallization, laser patterning and room temperature processing of electromagnetic patterns on 3D printed surfaces. The resolution and print volume achieved with these methods are well suited for the rapid prototyping of electromagnetic structures. Several example structures fabricated using these techniques will be presented.
    NIP & Digital Fabrication Conference. 01/2014;
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    ABSTRACT: High-speed video (100 000 fps) is used to examine the behavior of silver nanoparticle suspensions ejected from a donor substrate during laser-induced forward transfer (LIFT) as a function of viscosity, donor film thickness, and voxel area. Both high-speed video and inspection of the post-transferred material indicate dramatic changes in the behavior of the fluid as the viscosity of the nano-suspensions increases from that of inks (∼0.01 Pa·s) to pastes (>100 Pa·s). Over a specific range of viscosities (90–150 Pa·s) and laser fluences (35–65 mJ/cm2), the ejected voxels precisely reproduce the size and shape of the laser spot. This LIFT regime is known as laser decal transfer or LDT. Analysis of the high-speed video indicates that the speeds of the voxels released by the LDT process do not exceed 1 m/s. Such transfer speeds are at least an order of magnitude lower than those associated with other LIFT processes, thus minimizing voxel deformation during flight and upon impact with the receiving substrate. Variation in the threshold fluence for initiating the LDT process is measured as a function of donor film thickness and transfer spot size. Overall, the congruent nature of the silver nanopaste voxels deposited by LDT is unique among non-contact digital printing techniques given its control of the voxel's size and shape, thus allowing partial parallelization of the direct-write process.
    Journal of Applied Physics 08/2013; 114(6). · 2.21 Impact Factor
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    ABSTRACT: The field of metamaterials has expanded to include more than four orders of magnitude of the electromagnetic spectrum, ranging from the microwave to the optical. While early metamaterials operated in the microwave region of the spectrum, where standard printed circuit board techniques could be applied, modern designs operating at shorter wavelengths require alternative manufacturing methods, including advanced semiconductor processes. Semiconductor manufacturing methods have proven successful for planar 2D geometries of limited scale. However, these methods are limited by material choice and the range of possible feature sizes, thus hindering the development of metamaterials due to manufacturing challenges. Furthermore, it is difficult to achieve the wide range of scales encountered in modern metamaterial designs with these methods alone. Laser direct-write processes can overcome these challenges while enabling new and exciting fabrication techniques. Laser processes such as micromachining and laser transfer are ideally suited for the development and optimization of 2D and 3D metamaterial structures. These laser processes are advantageous in that they have the ability to both transfer and remove material as well as the capacity to pattern non-traditional surfaces. This paper will present recent advances in laser processing of various types of metamaterial designs.
    03/2013
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    ABSTRACT: Laser forward transfer of arbitrary and complex configurable structures has recently been demonstrated using a spatial light modulator (SLM). The SLM allows the spatial distribution of the laser pulse, required by the laser transfer process, to be modified for each pulse. The programmable image on the SLM spatially modulates the intensity profile of the laser beam, which is then used to transfer a thin layer of material reproducing the same spatial pattern onto a substrate. The combination of laser direct write (LDW) with a SLM is unique since it enables LDW to operate not only in serial fashion like other direct write techniques but instead reach a level in parallel processing not possible with traditional digital fabrication methods. This paper describes the use of Digital Micromirror Devices or DMDs as SLMs in combination with visible (λ = 532 nm) nanosecond lasers. The parallel laser printing of arrayed structures with a single laser shot is demonstrated together with the full capabilities of SLMs for laser printing reconfigurable patterns of silver nano-inks Finally, an overview of the unique advantages and capabilities of laser forward transfer with SLMs is presented.
    Proc SPIE 03/2013;
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    ABSTRACT: The use of metamaterials structures has been the subject of extensive discussions given their wide range of applications. However, a large fraction of the work available to date has been limited to simulations and proof-of-principle demonstrations. One reason for the limited success inserting these structures into functioning systems and real-world applications is the high level of complexity involved in their fabrication. Direct-write processes are ideally suited for the fabrication of arbitrary periodic and aperiodic structures found in most metamaterial and plasmonic designs. For these applications, laser-based processes offer numerous advantages since they can be applied to virtually any surface over a wide range of scales. Furthermore, laser direct-write or LDW allows the precise deposition and/or removal of material thus enabling the fabrication of novel metamaterial designs. This presentation will show examples of metamaterial and plasmonic structures developed at the Naval Research Lab using LDW, and discuss the benefits of laser processing for these applications.
    03/2013;
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    ABSTRACT: The ability to manufacture and assemble complex three-dimensional (3D) systems via traditional photolithographic techniques has attracted increasing attention. However, most of the work to date still utilizes the traditional patterning and etching processes designed for the semiconductor industry where 2D structures are first fabricated, followed by some alternative technique for releasing these structures out-of-plane. Here we present a novel technique called Laser Origami, which has demonstrated the ability to generate 3D microstructures through the controlled out-of-plane folding of 2D patterns. This non-lithographic, and non silicon-based process is capable of microfabricating 3D structures of arbitrary shape and geometric complexity on a variety of substrates. The Laser Origami technique allows for the design and fabrication of arrays of 3D microstructures, where each microstructure can be made to fold independently of the others. Application of these folded micro-assemblies might make possible the development of highly complex and interconnected electrical, optical and mechanical 3D systems. This article will describe the unique advantages and capabilities of Laser Origami, discuss its applications and explore its role for the assembly and generation of 3D microstructures.
    Proc SPIE 02/2012;
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    ABSTRACT: The opportunities presented by the use of metamaterials have been the subject of extensive discussions. However, a large fraction of the work available to date has been limited to simulations and proof-of-principle demonstrations. One reason for the limited success inserting these structures into functioning systems and real-world applications is the high level of complexity involved in their fabrication. Most approaches to the realization of metamaterial structures utilize traditional lithographic processing techniques to pattern the required geometries and then rely on separate steps to assemble the final design. Obviously, composite structures with arbitrary and/or 3-D geometries present a challenge for their implementation with these approaches. Non-lithographic processes are ideally suited for the fabrication of arbitrary periodic and aperiodic structures needed to implement many of the metamaterial designs being proposed. Furthermore, non-lithographic techniques are true enablers for the development of conformal or 3-D metamaterial designs. This article will show examples of metamaterial structures developed at the Naval Research Laboratory using non-lithographic processes. These processes have been applied successfully to the fabrication of complex 2-D and 3-D structures comprising different types of materials.
    Proc SPIE 01/2012;
  • Article: SPIE LASE
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    ABSTRACT: Digital microfabrication processes are non-lithographic techniques ideally capable of directly generating patterns and structures of functional materials for the rapid prototyping of electronic, optical and sensor devices. Laser Direct-Write is an example of digital microfabrication that offers unique advantages and capabilities. A key advantage of laser directwrite techniques is their compatibility with a wide range of materials, surface chemistries and surface morphologies. These processes have been demonstrated in the fabrication of a wide variety of microelectronic elements such as interconnects, passives, antennas, sensors, power sources and embedded circuits. Recently, a novel laser direct-write technique able to digitally microfabricate thin film-like structures has been developed at the Naval Research Laboratory. This technique, known as Laser Decal Transfer, is capable of generating patterns with excellent lateral resolution and thickness uniformity using high viscosity metallic nano-inks. The high degree of control in size and shape achievable has been applied to the digital microfabrication of 3-dimensional stacked assemblies, MEMS-like structures and freestanding interconnects. Overall, laser forward transfer is perhaps the most flexible digital microfabrication process available in terms of materials versatility, substrate compatibility and range of speed, scale and resolution. This paper will describe the unique advantages and capabilities of laser decal transfer, discuss its applications and explore its role in the future of digital microfabrication.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
    02/2011;
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    ABSTRACT: Digital microfabrication processes are non-lithographic techniques ideally capable of directly generating patterns and structures of functional materials for the rapid prototyping of electronic, optical and sensor devices. Laser Direct-Write is an example of digital microfabrication that offers unique advantages and capabilities. A key advantage of laser directwrite techniques is their compatibility with a wide range of materials, surface chemistries and surface morphologies. These processes have been demonstrated in the fabrication of a wide variety of microelectronic elements such as interconnects, passives, antennas, sensors, power sources and embedded circuits. Recently, a novel laser direct-write technique able to digitally microfabricate thin film-like structures has been developed at the Naval Research Laboratory. This technique, known as Laser Decal Transfer, is capable of generating patterns with excellent lateral resolution and thickness uniformity using high viscosity metallic nano-inks. The high degree of control in size and shape achievable has been applied to the digital microfabrication of 3-dimensional stacked assemblies, MEMS-like structures and freestanding interconnects. Overall, laser forward transfer is perhaps the most flexible digital microfabrication process available in terms of materials versatility, substrate compatibility and range of speed, scale and resolution. This paper will describe the unique advantages and capabilities of laser decal transfer, discuss its applications and explore its role in the future of digital microfabrication.
    Proc SPIE 02/2011;
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    ABSTRACT: We report the first demonstration of laser forward transfer using a real-time reconfigurable mask based on a spatial light modulator. The ability to dynamically change the projected beam shape and size of a coherent light source, in this case a 355-nm pulsed UV laser, represents a significant technological advancement in laser direct-write processing. The application of laser transfer techniques with adaptive control of the laser beam pattern is unique and represents a paradigm shift in non-lithographic processing. This work describes how the size and shape of an incident laser beam can be dynamically controlled in real time with the use of a digital micromirror device (DMD), resulting in laser-printed functional nanomaterials with geometries identical to those of the projected beam. For applications requiring additive non-lithographic techniques, this novel combination, which relies on the laser forward transfer of variable, structured voxels, represents a dramatic improvement in the capabilities and throughput of laser direct-write processes.
    Applied Physics A 01/2011; 102(1):21-26. · 1.69 Impact Factor
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    ABSTRACT: A laser printing technique was used to fabricate split-ring resonators (SRRs) on Si substrates for terahertz (THz) metamaterials and their resonance behavior evaluated by THz time-domain spectroscopy. The laser-printed Ag SRRs exhibited sharp edge definition and excellent thickness uniformity, which resulted in an electromagnetic response similar to that from identical Au SRR structures prepared by conventional photolithography. These results demonstrate that laser printing is a practical alternative to conventional photolithography for fabricating metamaterial structures at terahertz frequencies, since it allows their design to be easily modified and optimized.
    Optics Letters 12/2010; 35(23):4039-41. · 3.39 Impact Factor
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    ABSTRACT: Detection of explosives is important for public safety. A recently developed low-temperature plasma (LTP) probe for desorption and ionization of samples in the ambient environment ( Anal. Chem. 2008 , 80 , 9097 ) is applied in a comprehensive evaluation of analytical performance for rapid detection of 13 explosives and explosives-related compounds. The selected chemicals [pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), cyclo-1,3,5-trimethylenetrinitramine (RDX), tetryl, cyclo-1,3,5,7-tetramethylenetetranitrate (HMX), hexamethylene triperoxide diamine (HMTD), 2,4-dinitrotoluene, 1,3-dinitrobenzene, 1,3,5-trinitrobenzene, 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,6-dinitrotoluene, and 4-nitrotoluene) were tested at levels in the range 1 pg-10 ng. Most showed remarkable sensitivity in the negative-ion mode, yielding limits of detection in the low picogram range, particularly when analyzed from a glass substrate heated to 120 °C. Ions typically formed from these molecules (M) by LTP include [M + NO(2)](-), [M](-), and [M - NO(2)](-). The LTP-mass spectrometry methodology displayed a linear signal response over three orders of magnitude of analyte amount for the studied explosives. In addition, the effects of synthetic matrices and different types of surfaces were evaluated. The data obtained demonstrate that LTP-MS allows detection of ultratrace amounts of explosives and confirmation of their identity. Tandem mass spectrometry (MS/MS) was used to confirm the presence of selected explosives at low levels; for example, TNT was confirmed at absolute levels as low as 0.6 pg. Linearity and intra- and interday precision were also evaluated, yielding results that demonstrate the potential usefulness and ruggedness of LTP-MS for the detection of explosives of different classes. The use of ion/molecule reactions to form adducts with particular explosives such as RDX and HMX was shown to enhance the selectivity and specificity. This was accomplished by merging the discharge gas with an appropriate reagent headspace vapor (e.g., from a 0.2% trifluoracetic acid solution).
    Analytical Chemistry 12/2010; 83(3):1084-92. · 5.82 Impact Factor
  • Advanced Materials 10/2010; 22(40):4462-6. · 14.83 Impact Factor
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    ABSTRACT: The discontinuous atmospheric pressure interface (DAPI) has allowed the transfer of ions from atmospheric pressure ionization sources to an ion trap mass analyzer in hand-held mass spectrometers with miniature pumping systems at transfer efficiencies high enough for proper chemical analysis. The DAPI potentially would allow a significant enhancement to the mass analysis efficiency of laboratory-scale mass spectrometers, which have pumping systems of much larger capacities. A laboratory-scale mass spectrometer with a DAPI-RIT (rectilinear ion trap)-DAPI configuration has been developed to explore this possibility. The gas dynamic effects on ion trapping and mass analysis have been studied at various conditions. A pulsed nanoelectrospray ionization source synchronized with the DAPI has been implemented to improve the sample usage efficiency as well as to adjust the number of ions to be trapped for MS analysis, so that space charge effects can be avoided. Single-scan spectra of peptides were recorded with an ionization time as short as 1 micros, corresponding to an analyte consumption of several attomoles. The simplicity of application of the DAPI for performing ion/molecule and ion/ion reactions has also been demonstrated with proton transfer and electron transfer dissociation reactions with peptides.
    Analytical Chemistry 08/2010; 82(15):6584-92. · 5.82 Impact Factor
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    ABSTRACT: Low-temperature plasma (LTP) permits direct ambient ionization and mass analysis of samples in their native environment with minimal or no prior preparation. LTP utilizes dielectric barrier discharges (DBDs) to create a low power plasma which is guided by gas flow onto the sample from which analytes are desorbed and ionized. In this study, the potential of LTP-MS for the detection of pesticide residues in food is demonstrated. Thirteen multi-class agricultural chemicals were studied (ametryn, amitraz, atrazine, buprofezin, DEET, diphenylamine, ethoxyquin, imazalil, isofenphos-methyl, isoproturon, malathion, parathion-ethyl and terbuthylazine). To evaluate the potential of the proposed approach, LTP-MS experiments were performed directly on fruit peels as well as on fruit/vegetable extracts. Most of the agrochemicals examined displayed remarkable sensitivity in the positive ion mode, giving limits of detection (LOD) for the direct measurement in the low picogram range. Tandem mass spectrometry (MS/MS) was used to confirm identification of selected pesticides by using for these experiments spiked fruit/vegetable extracts (QuEChERS, a standard sample treatment protocol) at levels as low as 1 pg, absolute, for some of the analytes. Comparisons of the data obtained by direct LTP-MS were made with the slower but more accurate conventional LC-MS/MS procedure. Herbicides spiked in aqueous solutions were detectable at LODs as low as 0.5 microg L(-1) without the need for any sample preparation. The results demonstrate that ambient LTP-MS can be applied for the detection and confirmation of traces of agrochemicals in actual market-purchased produce and in natural water samples. Quantitative analysis was also performed in a few selected cases and displayed a relatively high degree of linearity over four orders of magnitude.
    The Analyst 05/2010; 135(5):971-9. · 4.23 Impact Factor
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    ABSTRACT: A laser forward transfer technique for the simultaneous printing of polymer/metal stacked micro-laminates is introduced. Several different material combinations as well as stacking architectures are presented including single laser pulse deposited dual layer capacitors, three-layer stacks for potentially printing organic thin-film transistors (OTFTs), and photo-definable polymer/metal laminates and free-standing membranes for MEMS based sensors.
    Applied Physics A 01/2010; 99(4):711-716. · 1.69 Impact Factor
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    Rapid Communications in Mass Spectrometry 10/2009; 23(21):3492. · 2.51 Impact Factor