Tobias N. Ackermann

Photonic Lab-on-a-Chip: Integration of Optical Spectroscopy in Microfluidic Systems

The integration of micro-optical elements with microfluidics leads to the highly promising photonic lab-on-a-chip analytical systems (PhLoCs). In this work, we re-examine the main principles which are underneath the on-chip spectrophotometric detection, approaching the PhLoC concept to a nonexpert audience.

Polymeric variable optical attenuators based on magnetic sensitive stimuli materials

Magnetically-actuable, polymer-based variable optical attenuators (VOA) are presented in this paper. The design comprises a cantilever which also plays the role of a waveguide and the input/output alignment elements for simple alignment, yet still rendering an efficient coupling. Magnetic properties have been conferred to these micro-opto-electromechanical systems (MOEMS) by implementing two different strategies: in the first case, a magnetic sensitive stimuli material (M-SSM) is obtained by a combination of polydimethylsiloxane (PDMS) and ferrofluid (FF) in ratios between 14.9 wt % and 29.9 wt %. An M-SSM strip under the waveguide-cantilever, defined with soft lithography (SLT), provides the required actuation capability. In the second case, specific volumes of FF are dispensed at the end of the cantilever tip (outside the waveguide) by means of inkjet printing (IJP), obtaining the required magnetic response while holding the optical transparency of the waveguide-cantilever. In the absence of a magnetic field, the waveguide-cantilever is aligned with the output fiber optics and thus the intrinsic optical losses can be obtained. Numerical simulations, validated experimentally, have shown that, for any cantilever length, the VOAs defined by IJP present lower intrinsic optical losses than their SLT counterparts. Under an applied magnetic field (B-app), both VOA configurations experience a misalignment between the waveguide-cantilever and the output fiber optics. Thus, the proposed VOAs modulate the output power as a function of the cantilever displacement, which is proportional to B-app. The experimental results for the three different waveguide-cantilever lengths and six different FF concentrations (three per technology) show maximum deflections of 220 mu m at 29.9 wt % of FF for VOA(SLT) and 250 mu m at 22.3 wt % FF for VOA(IJP), at 0.57 kG for both. These deflections provide maximum actuation losses of 16.1 dB and 18.9 dB for the VOA(SLT) and VOA(IJP), respectively.

Living photonics: monitoring light propagation through cells (LiPhos)

The LiPhos project (EU FP7 Grant Agreement No.: 317916, www.liphos.eu) aims to develop three different biophotonic diagnosis tools (BDTs), based on living photonics, namely: single layer living photonics (SLLP), single cell analysis (SCA); and multi-layer living photonics (MLLP). By Measuring of what we term the Photonic Fingerprint (or PIN), of the cells in such BDTs, should make it is possible to differentiate between healthy and non-healthy cell or tissue states. Moreover, the effect of specific drugs and pro-inflammatory agents could be assessed. This concept is currently being applied to the diagnosis of cardiovascular diseases (CVD).

Modular optofluidic systems: A toolbox for fast and simple assembly of a photonic lab on a chip

A powerful modular optofuidic systems (MOPS) toolbox, which allows in-situ implementation of reconfigurable Photonic lab on a chip (PhLoC) has been developed. Each module has specific optic, fluidic or optofluidic elements that enable defining arbitrarily complex PhLoC systems. After having measured the optical total losses of the MOPS concept, it has been used for defining either absorbance or fluorescence measurements. In the first case, LoD below the μM level of Crystal Violet was obtained, whereas in fluorescence, the use of a specifically designed MOPS building block allows blocking excitation wavelength, resulting in a 2-fold increase of the sensitivity.

Modular Optofluidic Systems (MOPS)

Elementary PDMS-based building blocks of fluidic, optical and optofluidic components for Lab on a chip (LOC) platforms has here been developed. All individual modules are compatible and can be anchored and released with the help of puzzle-type connectors This approach is a powerful toolbox to create modular optofluidic systems (MOPS), which can be modified/upgraded to user needs and in-situ reconfigurable. In addition, the PDMS can locally be functionalized, defining a modular biosensor. Measurements in absorbance and fluorescence have been pursued as demonstrator.

All-photonic SU-8 Variable Optical Attenuator

A polymer-based Micro-optoelectromechanical system (MOEMS) design as a Variable Optical Attenuator (VOA) is presented. It consists on a SU-8 quad-beam structure containing a suspended waveguide aligned to input/output fiber optics. Actuation is achieved by defining photonic-heat transition regions at the anchoring of the mechanical beams. Such actuation points are manufactured by means of a dye-doped SU-8 with a strong absorption at specific wavelengths. When irradiated, the actuation points increase in size, entailing a displacement of the seismic mass, This causes a misalignment (i.e. an increase of the coupling losses) between the waveguides and the input/output fiber optics. Experimental results have validated this approach, by showing the effect of the pumping power on the optical losses, with an excellent repeatability and a response time of 1 ms.