Roberto S. Aga

DNA biopolymer conductive cladding for polymer electro-optic waveguide modulators

A deoxyribonucleic acid (DNA) biopolymer has been studied for use as a conductive cladding layer in polymer electro-optic (EO) waveguide modulators due to its low optical loss and high electrical conductivity relative to its inorganic polymer counterparts. Electric field contact poling measurements using a DNA biopolymer cladding layer with an amorphous polycarbonate/chromophore (APC/CLD1) guest-host system core layer have been made and compared to a UV15 cladding layer. Using the EO coefficient of APC/CLD1 with no cladding layer as a baseline, the DNA biopolymer cladding layer yielded relative poling efficiencies of 96% while the UV15 poling efficiencies were only 51%.

Modified processing techniques of a DNA biopolymer for enhanced performance in photonics applications

Significant modifications have been made in the processing techniques developed to transform purified, marine-based deoxyribonucleic acid (DNA) into a biopolymer suitable for optical and electronic device fabrication. This technique employs a modified soxhlet-dialysis rinsing process to completely remove excess ionic contaminants from the DNA biopolymer, resulting in a material with greater mechanical stability and enhanced performance reproducibility.

Performance of a Printed Photodetector on a Paper Substrate

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.

Polymeric waveguide electro-optic beam-steering device with DNA biopolymer conductive cladding layers

Abstract. A polymer electro-optic (EO) waveguide beam-steering device with deoxyribonucleic acid (DNA) biopolymer conductive cladding layers and a core layer of the commercially available EO polymer SEO100 is demonstrated with 100% relative poling efficiency. This demonstration device exhibits a deflection efficiency of 99  mrad/kV with a corresponding in-device EO coefficient r33 of 124  pm/V at 1550 nm. When the DNA biopolymer bottom cladding layer is replaced by the commonly used cladding polymer UV15, the deflection efficiency and in-device r33 drop to 34  mrad/kV and 43  pm/V, respectively.

Metal Electrode Work Function Modification Using Aerosol Jet Printing

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.

Origin of dielectric tunability in DNA-CTMA film at microwave frequencies

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.

In situ study of current-induced thermal expansion in printed conductors using stylus profilometry

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.

Advances in DNA photonics

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.

Considerations in printing conductive traces for high pulsed power 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.

Nanoimprint lithography of deoxyribonucleic acid biopolymer films

Abstract. Thermal nanoimprint lithography (NIL) is presented as an alternative fabrication technique for patterning deoxyribonucleic acid (DNA) biopolymer films for photonic device applications. The techniques and procedures developed for directly imprinting optical waveguide structures on a DNA biopolymer using NIL, bypassing the use of a resist layer and any chemical processing, are outlined here. The fabrication technique was developed with a Nanonex NX-2600 NIL flexible membrane system. Additionally, a process for using a Suss MicroTec ELAN CB6L substrate bonder is discussed as an alternative to commercially available NIL systems.