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The unique components of PDMS-based microfluidic systems are those combined with liquid crystalline materials. Their functionality, especially when it comes to optical applications, highly depends on the LC molecular arrangement. This work summarizes experimental investigations on the orientation of molecules within LC:PDMS structures according to the manufacturing technologies. The availability of high-quality molds to pattern PDMS is a significant barrier to the creation of advanced microfluidic systems. The possibility of using inexpensive molds in the rapid and reproducible fabrication process has been particularly examined as an alternative to photolithography. Different geometries, including an innovative approach for the electrical control of the molecular arrangement within PDMS microchannels, are presented. These studies are critical for novel optofluidic systems, introducing further research on LC:PDMS waveguiding structures.

Microchannels in LC:PDMS structures must be of good quality and suitable geometry to achieve the desired orientation of the liquid crystalline molecules inside. When applying a casting technique, with the molds obtained even by the most accurate method, i.e., photolithography, it is still crucial to inspect the cross-section of the structure and the surface roughness of the PDMS material. This paper presents a study of PDMS microchannels using a Scanning Electron Microscope (SEM) to make such a characterization as accurate as possible. By comparing images of the samples taken using standard polarized light microscopy and SEM, it is likely to understand the mechanism of the liquid crystal molecular orientation occurring in the samples. The results obtained in this work may be used for numerical simulations and further development of LC:PDMS structures.

This work presents research on unique optofluidic systems in the form of air channels fabricated in PDMS and infiltrated with liquid crystalline material. The proposed LC:PDMS structures represent an innovative solution due to the use of microchannel electrodes filled with a liquid metal alloy. The latter allows for the easy and dynamic reconfiguration of the system and eliminates technological issues experienced by other research groups. The paper discusses the design, fabrication, and testing methods for tunable LC:PDMS structures. Particular emphasis was placed on determining their properties after applying an external electric field, depending on the geometrical parameters of the system. The conclusions of the performed investigations may contribute to the definition of guidelines for both LC:PDMS devices and a new class of potential sensing elements utilizing polymers and liquid crystals in their structures.

Optofluidics is a constantly developing research area that combines known technologies from chemistry and photonics. Various systems have been created, which are used in biology and chemistry as well as in other subjects. The combination of materials such as polydimethylsiloxane (PDMS) and liquid crystal (LC) provides a number of possibilities to create functional structures. The properties of LC allow systems to be developed in PDMS, e.g., lenses with different focal lengths depending on the polarization of light or multiplexers have been proposed. Appropriately controlling LC molecule orientation is a crucial element in creating tunable systems. The motivation of this research is to determine the proper arrangement of an electrode array to control the orientation of liquid crystal molecules and thus the refractive index. The performed tests allowed the initial parameters to be determined to produce LC:PDMS structures with a periodic orientation of LC molecules. As the channel sizes have to be micrometer-scale, a proper electrode arrangement has to be developed. The materials from which electrodes can be created are also limited due to PDMS properties as well as the size of the channels. The plan is to create a tunable LC:PDMS structure with LC molecules in a periodic reorientation, which would allow the system to function as a tunable Bragg grating. It would be the first achievement of this kind, and it would open up new possibilities for the combination of liquid crystal and PDMS in photonic systems.