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High-power, flexible electronic devices require substrates that effectively dissipate heat while maintaining mechanical compliance. Nanocomposite substrates with ∼20 μm graphite nanoplatelets were ...

Printed electronics refers to an area of additive manufacturing (AM) that focuses specifically on using AM printing techniques, such as inkjet, aerosol jet, or extrusion printing, for electronic device applications. These types of technologies have emerged in the last several years as a new way to manufacture electronic elements and have found multiple application areas in both commercial industry and the defense arena. This chapter will focus on the technology and materials considerations for printed electronics and highlight aerospace application areas. Starting with materials considerations, we provide an overview of types of materials and inks being used for printed electronics, including materials challenges, such as material system compatibility and performance, post-processing techniques, and material characterization. We conclude with aerospace applications, specifically, an overview of select unmanned aerial vehicle antenna applications.

The effect of different substrates, inks and sintering methods on the breakdown of a printed conducting trace subjected to a single millisecond-range pulsed current was investigated. The breakdown current density (Jb) of a trace was found to be strongly dependent on substrate thermal diffusivity, which dictates the peak temperature and the cooling rate of the trace. As an example, a 102% increase in average Jb was observed in switching substrate from glass slide to sapphire. Different inks resulted in significant Jb deviation due to their distinct microstructure difference. Traces with dense microstructure exhibited an average Jb that is 42% higher than their porous counterpart. Different sintering methods also resulted in varying Jb. Traces thermally sintered on a hot plate demonstrated an average Jb that is 74% higher than their laser sintered counterpart. Finally, a simple concept that effectively dissipates heat from the trace was explored. It prevented breakdown when the traces were subjected to a single firing pulse used in detonation. Results from this work offer important considerations in printing conductive traces for high pulsed power applications.

This work explores additive manufacturing technology to fabricate hybrid circuits comprising of optical and electronic materials as photonic and electrical interconnects, respectively. Several polymeric optical materials have been investigated (including SU8, PDMS, UV15 and Norland adhesives) as waveguides directly printed on commercial circuit boards such as FR4 and Rogers TC600. An optical waveguide printed over RF (radio frequency) transmission lines and surface mount electronic components is demonstrated. As an application, the waveguide is used as an alternative to traditional electrical interconnects to control an RF switch for routing an RF signal from a single source to different locations. This work also investigates the feasibility of printed polymeric waveguides as a sensing platform for monitoring humidity and temperature changes in electronic circuits. Results show that the SU8 waveguide responds significantly to change in temperature and humidity and the response is appropriate for logistics applications such as cold chain supply.

A direct-write method to fabricate a strain sensor directly on a structure of interest is reported. In this method, a commercial graphene ink is printed as a square patch (6 mm square) on the structure. The patch is dried at 100 °C for 30 min to remove residual solvents but the printed graphene remains in an insulative state. By scanning a focused laser (830 nm, 100 mW), the graphene becomes electrically conductive and exhibits a piezoresistive effect and a low temperature coefficient of resistance of −0.0006 °C−1. Using this approach, the laser defines a strain sensor pattern on the printed graphene patch. To demonstrate the method, a strain sensor was directly fabricated on a 3D-printed test coupon made of ULTEM 9085 thermoplastic. The sensor exhibits a gauge factor of 3.58, which is significantly higher than that of commercial foil strain gauges made of constantan. This method is an attractive alternative when commercial strain sensors are difficult to employ due to the high porosity and surface roughness of the material structure under test.

The effects of atomic oxygen (AO) in low earth orbit and the physical effects of space launch on printed materials were studied for aerosol-jet printed Au and Ag through a 6 month exposure period on the Materials International Space Station Experiment (MISSE). RF and DC test platforms were designed for two printed electronics-compatible substrates (Rogers CLTE-XT and Ferro L8) to assess the amount of degradation caused by AO exposure in space. A passivation layer of CORIN-XLS applied over the printed metal traces was also studied for its effectiveness. Both bare and passivated test structures of printed Ag and Au traces were exposed to low earth orbit on the 10th MISSE mission. The effects of AO and the 6 month space exposure on the samples are reported here.

Direct printing technique has become indispensable in flexible electronics and low cost sensor applications. It has transformed into an enabling technology for many flexible devices. However, it is not very well explored for printing optical materials. In this work, a micro-dispense printer for printing polymeric optical waveguides was custom-built. It was employed to develop a simple method to couple light into printed optical interconnects. It was also used to apply a voltage bias during printing and drying of electro-optic polymer (SEO110) to pole the SEO110 in-situ with the goal of eliminating the need for traditional high temperature contact poling. With this in-situ poling method, electro-optic effect in SEO110 was demonstrated.

This paper reports the first known investigation of power dissipation and electrical breakdown in aerosol-jet-printed (AJP) graphene interconnects. The electrical performance of aerosol-jet printed (AJP) graphene was characterized using the Transmission Line Method (TLM). The electrical resistance decreased with increasing printing pass number (n); the lowest sheet resistance measured was 1.5 kΩ/sq. for n = 50. The role of thermal resistance (RTH) in power dissipation was studied using a combination of electrical breakdown thermometry and infrared (IR) imaging. A simple lumped thermal model ($${\boldsymbol{\Delta }}{\bf{T}}={\bf{P}}{\boldsymbol{\times }}{{\bf{R}}}_{{\bf{TH}}}$$ Δ T = P × R TH ) and COMSOL Multiphysics was used to extract the total RTH, including interfaces. The RTH of AJP graphene on Kapton is ~27 times greater than that of AJP graphene on Al2O3 with a corresponding breakdown current density 10 times less on Kapton versus Al2O3.

Much work has been done developing and utilizing biomaterials over the last decade. Biomaterials not only includes deoxyribonucleic acid (DNA), but nucleobases and silk. These materials are abundant, inexpensive, non-fossil fuel-based and green. Researchers have demonstrated their potential to enhance the performance of organic and inorganic electronic and photonic devices, such as light emitting diodes, thin film transistors, capacitors, electromagnetic interference shielding and electro-optic modulators. Starting around the year 2000, with only a hand full of researchers, including researchers at the Air Force Research Laboratory (AFRL) and researchers at the Chitose Institute of Technology (CIST), it has grown into a large US, Asia and European consortium, producing over 3400 papers, three books, many book chapters and multiple patents. Presented here is a short overview of the progress in this exciting field of nano bio-engineering.

Electrical resistivity, electron and hole barrier heights and interfaces can significantly affect the efficiency of electric field poling of non-linear optic (NLO) polymers. A combination of uniformity of the electric field distribution, charge carrier blocking and behavior of NLO chromophores can be optimized by introducing buffer layers and/or charge carrier blocking layers between the NLO polymer core layer and the anode and cathode electrodes, maximizing the poling field, chromophore alignment, nonlinearity or electro-optic (EO) coefficient, r33, and yield of the poled NLO polymers.

In our previous work we introduced charge carrier blocking layers to realize an increase in the poling field and, hence, an increase in the nonlinearity, or electro-optic (EO) coefficient, r33, of the nonlinear optic (NLO) polymer disperse red 1:polymethylmethacrylate (DR1:PMMA). In addition, we not only achieved higher poling voltages, which resulted in higher r33s at these higher poling voltages, but we also observed higher r33s when both the samples with and without the charge carrier blocking layers were poled at the same poling voltage. We attributed that primarily to a decrease in the surface resistance. Here we provide a more detailed analysis and propose that the increase may be attributed not only to surface resistance but a combination of lower surface resistance, more uniform electric field distribution and charge carrier blocking, provided by the charge carrier blocking layers.

A multilayer polymeric photodetector fabricated on a paper substrate by inkjet and aerosol jet printing has been demonstrated. It employs a poly(3-hexylthiophene) and C61-butyric acid methyl ester blend (P3HT:PCBM) as a photoactive layer sandwiched between a silver bottom electrode and a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) top electrode. A deoxyribonucleic acid biopolymer interlayer between P3HT:PCBM and PEDOT:PSS top electrode enables the printing of the PEDOT:PSS on P3HT:PCBM. The printed photodetector exhibits a photoresponse when photoexcited by four different light emitting diodes with center wavelengths of 405, 465, 525, and 635 nm. The highest responsivity was observed at 405 nm. The responsivity to pulsed light reveals a strong frequency dependence from 25 to 1000 Hz.

The performance of a printable, ultraviolet (UV) photoconducting biopolymer is investigated for UV photodetectors of varying layer thicknesses. The biopolymer is formed from deoxyribonucleic acid (DNA) with the addition of the Clevios P formulation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulphonate) (PEDOT:PSS) and hexadecyltrimethyl-ammonium chloride (CTMA); it is then combined with phenyl-C61-butyric acid methyl (PCBM) to make a printable, UV photoconducting material. The highest measured responsivity of the photodetectors is 1.2 mA/W at 20 V bias using a 260 nm source.

Deoxyribonucleic acid (DNA) biopolymer films are fabricated with varying amounts of hexadecyltrimethylammonium chloride (CTMA), which is a surfactant necessary to produce a DNA complex that is soluble in organic solvents. The dielectric constant (κ) of these films at microwave frequencies as a function of applied static electric field (E DC) is investigated. Results show that the dependence of κ on E DC, which is referred to as the dielectric tunability, is influenced by the amount of CTMA in the complex. Dielectric tunability is suppressed when the amount of CTMA is insufficient and improved when more CTMA is added. However, excessive amounts of CTMA also result in a very rough film surface that causes shorting problems when used in a capacitive structure. A varactor employing a 1-μm-thick DNA biopolymer film as the dielectric is demonstrated. Under 5 V DC bias, which generates E DC = 5 V/μm, its capacitance at 15 GHz changes by 0.04 pF. This change corresponds to a relative dielectric tunability of 6.6%. A simple application of this varactor for modulation of the power transmitted through a microwave transmission line is also demonstrated.

In our previous work we demonstrated a 3X increase in the nonlinearity, or electro-optic (EO) coefficient of the nonlinear optic (NLO) polymer disperse red 1:Polymethylmethacrylate (DR1: PMMA) by introducing a thin guanine nucleobase interfacial buffer layer, deposited between the NLO polymer and the cathode and a thin bathocuproine (BCP) interfacial buffer layer, deposited between the NLO polymer and the anode, being poled at 100 V/μm. In addition, we observed a 40% increase in EO coefficient by depositing either a thin sol-gel derived titanium dioxide layer or a thin guanine layer on either the anode or cathode side of the structure, poling at 100 V/μm. This paper addresses our analysis of these differences and is based on surface resistance.

Here we demonstrate a 3X - 6X increase in the nonlinearity, or electro-optic (EO) coefficient, and a 40% - 85% increase in working device yield, of the nonlinear optic (NLO) polymer disperse red 1:polymethylmethacrylate (DR1:PMMA) by introducing a thin guanine nucleobase interfacial buffer layer, deposited between the NLO polymer and the cathode and a thin bathocuproine (BCP) interfacial buffer layer, deposited between the NLO polymer and the anode. This has the potential to realize significantly higher EO coefficients without the need to synthesize new NLO polymer materials, as well as an increase in device yield due to less failure during poling.

An aerosol jet printer is used to precisely control the deposition in 25 nm increments of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on an oxygen plasma-treated Ni (O2-Ni) electrode to modify its work function. As revealed by Kelvin probe measurements, the effective work function of the O2-Ni electrode is dependent on the thickness of the PEDOT:PSS coating. By precisely controlling the coating thickness, the effective work function of metal electrodes in polymer-based photodetectors can be tailored for improved device performance. This is verified by demonstrating a threefold increase in the photoresponse of a polymer-based Schottky barrier infrared photodetector.

An approach for printing micron-scale electronic devices built from two-dimensional materials is presented. Experimental phage display techniques and computational atomistic simulation approaches were used to identify a peptide molecule that effectively anchors to the basal plane surface of two-dimensional (2D) MoS2 to SiO2 surfaces. This peptide was suspended in water to develop an ink suitable for aerosol jet printing. The printed substrates were then dip coated with a suspension of liquid phase exfoliated 2D MoS2 particles. Strong adhesion of physically continuous lines of these particles was observed only on regions of the substrate patterned with the peptide-based ink, thereby enabling aerosol jet printing as a template for devices based on 2D materials. Graphene was also bound to SiO2 via a similar approach, but with a different peptide known from prior work to selectively adhere to the basal plane of graphene. Fundamental peptide-surface interactions for MoS2, graphene, and SiO2 were explored via simulation and experiment. This printing method is proposed as a route towards large-scale, low temperature patterning of 2D materials and devices. The electrical properties of continuous lines of MoS2 particles printed in a single pass of peptide ink printing were measured via transmission line measurements. The results indicate that this molecular attachment approach to printing possesses several advantages such as overcoming nozzle clogging due to nanomaterial aggregation, decoupling of particle size from any dimensions associated with the printer, and single-pass printing of electrically continuous films.An approach for printing micron-scale electronic devices built from two-dimensional materials is presented. Experimental phage display techniques and computational atomistic simulation approaches were used to identify a peptide molecule that effectively anchors to the basal plane surface of two-dimensional (2D) MoS2 to SiO2 surfaces. This peptide was suspended in water to develop an ink suitable for aerosol jet printing. The printed substrates were then dip coated with a suspension of liquid phase exfoliated 2D MoS2 particles. Strong adhesion of physically continuous lines of these particles was observed only on regions of the substrate patterned with the peptide-based ink, thereby enabling aerosol jet printing as a template for devices based on 2D materials. Graphene was also bound to SiO2 via a similar approach, but with a different peptide known from prior work to selectively adhere to the basal plane of graphene. Fundamental peptide-surface interactions for MoS2, graphene, and SiO2 were explored via s...

The metal-insulator transition in vanadium dioxide thin films implanted with O + ions was studied. Ion implantation lowered the metal-insulator transition temperature of the VO 2 films by 12 °C compared to the unimplanted ones, as measured both optically and electrically. The lowering of the transition temperature was accomplished without significantly reducing the mid-wave infrared optical transmission in the insulating state for wavelengths > 4.3 μm. Raman spectroscopy was used to examine changes to the crystalline structure of the implanted films. The Raman spectra indicate that ion implantation effects are not annealed out for temperatures up to 120 °C.

An ultraviolet (UV) photodetector utilizing an inkjet printable , UV photoconducting biopolymer was fabricated and the performance of the photodetector was characterized for varying thickness layers of the biopolymer. The biopolymer was formed of deoxyribonucleic acid (DNA), the Clevios P formulation of poly(3,4-ethylenedioxythiophene)- poly(styrenesulfonate) (PEDOT:PSS), and hexadecyltrimethyl-ammonium chloride (CTMA); this was then combined with phenyl-C61-butyric acid methyl (PCBM) to form the printable, UV photoconducting biopolymer. Using a 260-nm source, the highest measured responsivity of the photodetectors is 1.2 mA/W at 20 V bias.

Here we demonstrate a 40% increase in the nonlinearity, or electro-optic (EO) coefficient, of the nonlinear optic (NLO) polymer SEO100 with the addition of a thin guanine nucleobase buffer layer deposited between the NLO polymer and the cathode electrode. We suggest that the high lowest unoccupied molecular orbital of guanine flattens the field distribution at the high injection barrier reducing leakage current during poling. This has the potential to realize higher EO coefficients without the need to synthesize new NLO polymer materials, as well as an increase in device yield due to less failure during poling.

Purified deoxyribonucleic acid (DNA) derived from salmon and scallop sperm has demonstrated excellent passive and active optical properties. Characterization of the optical and electromagnetic properties of DNA suggests suitability for photonic applications. One of interesting features of DNA we discovered was an intercalation of aromatic compounds into stacked layers within the double helix of DNA molecules. We found that various optical dyes inserted into the double helix of DNA molecules rendered active optical waveguide materials with excellent nonlinear optical properties. Our research included the investigation of DNA for use as an optical waveguide material as well as intercalation of fluorescent dyes, photochromic dyes, nonlinear optic chromophores, two photon dyes and rare earth compounds into DNA for use as a nonlinear optical material.

Deoxyribonucleic acid (DNA)-based polymer thin-films are characterized at microwave frequencies. The dielectric properties of the films are extracted from comparison of the propagation constants of the co-planar waveguide (CPW) lines on bare MgO substrates and the DNA-based films on MgO substrates. The insertion loss introduced by an undoped DNA-based polymer film is only 0.1 dB at 10 GHz and 0.5 dB at 30 GHz. A red-dye-doped DNA polymer film exhibited higher losses. The relative dielectric constant of the undoped DNA-based film averages to 4 at microwave frequencies, and the loss-tangent is below 0.1 up to 30 GHz. The dielectric properties of a 5% red-dye-doped DNA polymer film is compared to that of the pure DNA film. The DR1 doped DNA film exhibits 0.4-dB higher loss at 10 GHz and 0.9-dB higher loss at 30 GHz. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 278–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20965

Our research in nonlinear optic (NLO) polymer-based electro-optic (EO) modulators has centered on optimizing device performance through the using of polymer cladding layers with higher relative conductivities than the NLO core material. We have demonstrated as much as a 10 times increase in the effective EO coefficient of electrode poled, guest/host NLO polymers, compared to using passive polymer claddings. We have achieved the lowest poling voltage to date for maximum EO coefficient, 300 V, for a two-layer waveguide structure consisting of a 2 μm thick NLO polymer layer and 2 μm thick conductive cladding layer. Optimized polymer cladding materials posessing the desired optical and electromagnetic properties we find need to be balanced with materials processability. In addition to the conventional polymer materials under investigation, a novel material, deoxyribonucleic acid (DNA), derived from salmon sperm, has shown promise in providing both the desired optical and electromagnetic properties, as well as...

This manuscript presents the design and fabrication process of an additively manufactured multilayer antenna. The antenna reported herein is an x-band 32 element patch array and is fabricated on a multi-curved surface that is typical of what one might find on an airborne platform. In this design all of the substrate materials and conductive elements (except the ground plane) are fully printed including the via fills. Peak gain for the antenna is greater than 15 dBi at 10.4 GHz and showed close adherence to modeling results.

A complex of salmon milt deoxyribonucleic acid (DNA) and the cationic surfactant cetyltrimethylammonium (CTMA) forms an organic-soluble biomaterial that can be readily incorporated within an organically modified silane-based xerogel. The photoluminescence (PL) intensity and excited-state luminescence lifetime of tris(4,7′-diphenyl-1, 10′-phenanathroline) ruthenium(II) [(Ru(dpp)3]2+, a common O2 responsive luminophore, increases in the presence of DNA-CTMA within the xerogel. The increase in the [Ru(dpp)3]2+ excited-state lifetime in the presence of DNA-CTMA arises from DNA intercalation that attenuates one or more non-radiative processes, leading to an increase in the [Ru(dpp)3]2+ excited-state lifetime. Prospects for the use of these materials in an oxygen sensor are demonstrated.

This paper is a review of the recent research in bio-based materials for photonics and electronics applications. Materials that we have been working with include: deoxyribonucleic acid (DNA)-based biopolymers and nucleobases. We will highlight work on increasing the ionic conductivity of DNA-based membranes, enhancing the direct (DC) current and photoconductivity of DNA-based biopolymers, crosslinking of DNA-based biopolymers and promising applications for DNA nucleobases. Key

A graphene-based biopolymer is developed which exhibits saturable absorption and optical limiting behavior in the femtosecond and nanosecond regime respectively. Further this composite film when irradiated with nanosecond pulses indicates a damage threshold >50 J/cm2.

Deoxyribonucleic acid (DNA) based polymer thin-films were characterized at microwave frequencies for the first time. The dielectric properties of the film were extracted from comparison of the propagation constants of the co-planar waveguide (CPW) lines on bare MgO substrates and the DNA based films on MgO substrates. The insertion loss introduced by the DNA film is only 0.1 dB at 10 GHz and 0.5 dB at 30 GHz. The relative dielectric constant of the DNA based film averages to four at microwave frequencies, and the loss-tangent was below 0.1 up to 30 GHz.

This study highlights some of the effects of UV crosslinking of DNA-CTMA on its electrical and optical characteristics. The crosslinking of DNA-CTMA occurs via the photodimerization of attached coumarin moieties under UV irradiation. An exposure time of 30 min to UV light with an output power of 166 mW/cm 2 is needed to complete the crosslinking process. The UV-crosslinked films show a significant increase in the electrical resistivity (decrease in leakage current) and a markedly lower dielectric constant. This paper, originally published on 1 October 2013, was replaced with a corrected/revised version on 25 October 2013. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.

An in situ technique that uses a stylus profilometer has been developed for studying current-induced thermal expansion in printed conductive traces and for investigating the effects of expansion on trace resistance and power handling. It was employed to study printed silver traces (50–100 μm linewidths) subjected to a pulsed, millisecond-range current. The traces were aerosol jet printed on a glass substrate using a commercial nanoparticle-based ink. At low peak current densities (J p < 5 × 104 A mm−2), trace expansion is reversible with no permanent resistance increase. At J p ≥ 5 × 104 A mm−2 the expansion becomes irreversible, resulting in reduced power handling and a permanent resistance increase of up to 50%. Since the irreversible expansion decreases density and weakens nanoparticle connectivity, further expansion easily distends the material to the point of forming a void. This is one breakdown mechanism of printed nanoparticle-based silver at high pulsed current.

Biopolymers such as DNA can be used as a host material for nonlinear optical dyes for photonic applications. In previous work by Heckman et al. (Proc. SPIE 6401, 640108-2), the chromophore Disperse Red 1 (DR1) was combined with CTMA-DNA (a water-insoluble DNA/surfactant complex) to produce an electro-optic waveguide modulator. However, DR1 does not bind strongly to DNA and has a low first hyperpolarizability (β). We have used theory-aided design to develop and synthesize a novel chromophore with strong affinity for DNA and higher β than DR1. We have also developed a surfactant containing a photocrosslinkable moiety that can be used to harden thin films of the DNA/surfactant/dye composite under ultraviolet light. The optical and thermal properties of these materials and outlook for device applications will be discussed.

Aside from salmon DNA, other DNA sources were explored namely, herring and onion, to prepare DNAsurfactant complex, which will be used as a template for dyes undergoing Forster Resonance Energy Transfer (FRET). Also, salmon DNA of low and high molecular weight were compared. This study aims to assess the effect of using different DNA sources and molecular weight on the efficiency of energy transfer between the dyes, coumarin 480 (Cm 480) and 4-[4-(dimethylamino)styryl]-1-docosyl-pyridinium bromide (Hemi 22 and to understand the fundamental properties of DNA-CTMA as a supporting matrix for optoelectronics applications.

In this paper we present our current research in exploring a DNA biopolymer for photonics applications. A new processing technique has been adopted that employs a modified soxhlet-dialysis (SD) rinsing technique to completely remove excess ionic contaminants from the DNA biopolymer, resulting in a material with greater mechanical stability and enhanced performance reproducibility. This newly processed material has been shown to be an excellent material for cladding layers in poled polymer electro-optic (EO) waveguide modulator applications. Thin film poling results are reported for materials using the DNA biopolymer as a cladding layer, as are results for beam steering devices also using the DNA biopolymer. Finally, progress on fabrication of a Mach Zehnder EO modulator with DNA biopolymer claddings using nanoimprint lithography techniques is reported.

We study the effect on the microwave S-parameters of adding a conjugated polymer layer to a deoxyribonucleic acid-based (DNA-based) biopolymer within a variable capacitor (varactor) using a capacitive test structure. The conjugated polymer we are using in this work is poly(3-hexylthiophene-2,5-diyl) (P3HT) and the DNA-based biopolymer is DNA-CTMA. The results are compared to both the baseline DNA-based biopolymer and the conjugated polymer layer added to a layer of polyvinyl alcohol. The addition of the conjugated polymer layer underneath the DNA-based biopolymer is found to most significantly improve the stability and dielectric tuning of the DNA-based biopolymer.

The potential of bio-dielectrics for thin film transistor applications was explored via the incorporation of titanium dioxide (TiO2) nanoparticles, rutile form, a high dielectric constant (ε) ceramic, in the deoxyribonucleic acid (DNA) bio-polymer. The DNA-ceramic hybrid films were fabricated from stable suspensions of the TiO2 nanoparticles in viscous, aqueous DNA solutions. Dielectric characterization revealed that the incorporation of TiO2 in DNA resulted in enhanced dielectric constant (14.3 at 1 kHz for 40 wt % TiO2) relative to that of DNA in the entire frequency range of 1 kHz-1 MHz. Variable temperature dielectric measurements, in the 20-80°C range, of the DNA-TiO2 films revealed that the ceramic additive stabilizes DNA against large temperature dependent variations in both ε and the dielectric loss factor tan δ. The bulk resistivity of the DNA-TiO2 hybrid films was measured to be two to three orders of magnitude higher than that of the control DNA films, indicating their potential for utilization as insulating dielectrics in transistor and capacitor applications.

DNA-CTMA is an attractive material to explore for reconfigurable optical and electronic devices. Its dielectric constant at microwave frequencies can be tuned by applying a DC electric field. In this work, the origin of dielectric tunability and other ferroelectric-like behavior observed in DNA-CTMA films is investigated. Results suggest that the dominant polarization mechanism is ionic in nature and is caused by intentionally retaining excess ions in the DNA-CTMA precipitate during processing.

The potential of using a DNA biopolymer in an electro-optic device is presented. A complex of DNA with the cationic surfactant cetyltrimethylammonium-chloride (CTMA) was used to obtain an organic-soluble DNA material (DNA-CTMA). Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) was added to the DNACTMA to increase the electrical conductivity of the biopolymer. The CW absorbance and time-resolved photoluminescence of the resulting DNA-CTMA and DNA-CTMA-PEDOT:PSS were investigated. Both DNA materials have absorbance peaks at ~260 nm and a broad, Stokes shifted, photoluminescence peak around 470nm. The photoluminescence lifetime of the materials was observed to decrease with increasing UV excitation. Specifically, excitation with a high power ultrafast (~150fs) UV (266nm) laser pulse resulted in a drastic decrease in the photoluminescence lifetime decreases after a few minutes. Moreover, the observed decrease was faster in an air ambient than in a nitrogen ambient. This is most likely due to photo-oxidation that degrades the polymer surface resulting in an increase in the non-radiative recombination. In order to investigate the photoconductivity of these two materials, metal-biopolymer-metal (MBM) ultraviolet photodetectors with interdigitated electrodes were fabricated and characterized. The photoresponsivity of these devices was limited by the transport dynamics within the film. The prospects for the use of these materials in optical devices will be discussed.

DNA, a biopolymer processed from purified marine-based waste products, has been explored in recent years for photonic applications. Among these, using a DNA-surfactant biopolymer as a conductive cladding layer in electro-optic polymer waveguide modulators has been proposed due to the biopolymer's low optical loss and relatively high electrical conductivity compared to current polymer materials. Electric-field contact poling measurements using a DNA-surfactant biopolymer as a cladding layer have been made. The DNA cladding layer yielded high poling efficiency and the results are reported here.

In this paper we present our current research in developing non-conductive, optically transparent electromagnetic interference (EMI) or radio frequency (RF) shielding. It uses metallic nanopowders blended with deoxyribonucleic acid (DNA) based host materials. Recent results of this DNA-based EMI shielding demonstrate 18-27dB over a frequency range of 18 - 6 GHz, respectively, with an electrical resistivity measuring > 20MΩ for a 20 μm dielectric spacing. These films were optical transparent in the visible wavelength range.

In this paper we investigate the electrical properties of DNA-PEDOT blends, with particular interest as semiconducting materials in thin film based Field Effect Transistors (FET) applications. We report the template polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) using a biomacromolecule, DNA, as the polyelectrolyte. The obtained biocomposite stability is very dependent on the type of oxidant used in the chemical synthesis route. The resultant polymer system is water processable and undergoes the same redox processes as PEDOT alone. Films with thicknesses of 0.5 to 1 microns were drop cast from water based solution using different ratios EDOT to DNA.

Organic electro-optic materials have potential applications in optical communication and data processing. One major obstacle to the realization of the full potential of OEO materials is the interchromophore electrostatic interactions which have prevented the poling-induced chromophore order parameter from reaching above 0.3. In this presentation, we show designs of new chromophores that have ring structures surrounding the center of chromophores to prevent chromophores from packing in the antiparallel fashion, and modification of such chromophores with complementary DNA nucleobases to strengthen head-tail interactions.

Resistivity studies were carried out on DNA-based polymer films and selected traditional polymer films, including PMMA and APC. The films were spin coated on glass slides configured for guarded electrode measurements of resistance. The measurements used the alternating polarity method to determine the applied-voltage-dependent current independent of charging and background currents. The data for the temperature dependence of all the polymers were fitted to a common Arrhenius-type expression plus a constant. The poling studies described various dependencies of the measured electro-optic coefficient on how the heating and electric field are applied to the films. The severe impact of poling DNA-based films with vacuum-deposited gold electrodes and the persistent problem of electrode burning and failure presumably due to the high electric fields at the electrode edges are described. How these problems were managed is discussed. The presence of an emf following poling of the DNA-based films is described.