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.
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.
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.
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.
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.
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.
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.