Deep UV Formation of Long-Term Stable Optical Bragg Gratings in Epoxy Waveguides and Their Biomedical Sensing Potentials.

Steffen Hessler,Ralf Hellmann,Marieke Rüth,Bernhard Schmauss,Horst-Dieter Lemke

doi:10.3390/s21113868

Abstract

In this article, we summarize our investigations on optimized 248 nm deep ultraviolet (UV) fabrication of highly stable epoxy polymer Bragg grating sensors and their application for biomedical purposes. Employing m-line spectroscopy, deep UV photosensitivity of cross-linked EpoCore thin films in terms of responding refractive index change is determined to a maximum of Δn = + (1.8 ± 0.2) × 10−3. All-polymer waveguide Bragg gratings are fabricated by direct laser irradiation of lithographic EpoCore strip waveguides on compatible Topas 6017 substrates through standard +1/-1-order phase masks. According near-field simulations of realistic non-ideal phase masks provide insight into UV dose-dependent characteristics of the Bragg grating formation. By means of online monitoring, arising Bragg reflections during grating inscription via beforehand fiber-coupled waveguide samples, an optimum laser parameter set for well-detectable sensor reflection peaks in respect of peak strength, full width at half maximum and grating attenuation are derived. Promising blood analysis applications of optimized epoxy-based Bragg grating sensors are demonstrated in terms of bulk refractive index sensing of whole blood and selective surface refractive index sensing of human serum albumin.

Highlights

Over the past two decades, Bragg grating technology has emerged as an attractive optical sensor tool enabling versatile multi-physical parameter monitoring [1,2,3,4]
A substantially enhanced refractive index sensitivity of EpoCore Bragg gratings was recently attained by high-refractive TiO2 coatings empowering biomedical sensing applications [30]
EpoCore-based devices is demonstrated for rapid biomedical refractive index characterizations of whole blood samples along with the detection of human serum albumin solutions by antigen-antibody-reactions on the sensor surface

Summary

Introduction

Over the past two decades, Bragg grating technology has emerged as an attractive optical sensor tool enabling versatile multi-physical parameter monitoring [1,2,3,4]. Bragg grating (PBG) based sensing concepts, typically in the form of silica and silicon integrated optical waveguide chips, have been investigated for most diverse application scenarios. Maintain attractive potential for integrated optical sensing in low-cost biochemical lab-on-a-chip applications [28], not least because of their proven biocompatibility to human blood [29]. In this context, a substantially enhanced refractive index sensitivity of EpoCore Bragg gratings was recently attained by high-refractive TiO2 coatings empowering biomedical sensing applications [30]. EpoCore-based devices is demonstrated for rapid biomedical refractive index characterizations of whole blood samples along with the detection of human serum albumin solutions by antigen-antibody-reactions on the sensor surface

Deep UV Photosensitivity of EpoCore Thin Films

Schematic for monitoring the reflection signal behavior of stepwise

Biomedical Application Potentials of Epoxy-Based Bragg Grating Sensors

10. Refractive

Conclusions