Since the growing interest in Lab-On-a-Chip (LOC) applications, the demand for a high multifunctional and portable devices in order to increase the achievement of complex laboratories analysis on a small size chips. This need pushed the research to integrate in the substrates several tools with different tasks, and consequently, the requirements of the material exploited become rapidly more restricted. In particular, the performances of multiple toolkit device are related to its capabilities of combining and matching stages, thus avoiding any detrimental interferences between the material properties needed for their realization. During the last 20 years, several materials have been proposed for the combination of different tools on the same device. Only recently our group proposed Lithium Niobate (LiNbO3) as a valid alternative for a monolithic substrate in LOC application. This material is well-known in the field of integrated optics, due to its interesting optical properties, that brought it to be the main component in optical modulators in the telecom devices. The excellent performances in this field can be combined to the microfluidic for the realization of reliable optofluidic stages for LOC application. Moreover, LiNbO3 was demonstrated as a substrate for several micro-manipulation tools, exploiting its further properties, such as photovoltaic tweezers of micro-sized objects, nano-droplets pipetting with pyroelectric induced field, acoustic driven particle transports via piezoelectric generated surface acoustic wave respectively. For these reasons, the merge of all these tools on the same monolithic substrate could represent the optimal improvement to push even further the LOC technology. This thesis aimed to demonstrate that a multifunctional opto-microfluidic platform can be realized in one monolithic substrate of lithium niobate, achieving properties that can be properly exploited for LOC application. In particular, the attention was focused on combining integrated optics and microfluidics in a unique platform, where light is confined in an optical waveguide and crossed a microfluidic channel allowing for a transmission detection. The realization of microchannel for the coupling with microphotonic structures is presented: so in particular channel configurations, such as droplet generator, are characterized and compared to those achieved with other standard material, in order to show the better performances provided by LiNbO3. In this platform the crucial aspect was played by the optical quality of the lateral walls of the microfluidic channel in order to guarantee an optimized optical coupling of the integrated optical waveguide and the microchannel. Such an optical grade quality allows for the integration of microchannels with Ti-indiffused waveguide, in an unexplored way alternative to the standards in optofluidics. This optofluidic coupling is performed by crossing the waveguide with an engraved microfluidic channel. This configuration enables the analysis of the transmitted light guided by the first half of the waveguide to the second half of it. The self-aligned geometry allows for the traveling of the light beam from one waveguide (input waveguide) across the channel until it recouples in the other part of the waveguide (output waveguide). This optical transmission signal of the medium inside the channel is exploited for LOC applications, such as optical measurements of the droplet geometrical properties (such as frequency, length, volume), and controlled microfluidic pH titration, which allows for the pH determination and the neutralization of strong acidic or basic solution, and finally as an optical multiplexer actuated microfluidically. In all these applications, the devices showed not only high level of integration and accurate response, but also superior performances than the standard procedures and materials. Moreover, a further tool was integrated to this optofluidic platform: a photovoltaic tweezers, exploiting the lithium niobate capability of photoinducing electric field on its surfaces. These multifunctional stages are proposed for the effectively manipulation of the orientation liquid crystal inside a microchannel, and the consequent polarization control waveguide transmission beam.

Study of light driven phenomena for optofluidic applications in Lab-on-a-chip platforms in lithium niobate / Zamboni, Riccardo. - (2019 Dec 01).

Study of light driven phenomena for optofluidic applications in Lab-on-a-chip platforms in lithium niobate

Zamboni, Riccardo
2019

Abstract

Since the growing interest in Lab-On-a-Chip (LOC) applications, the demand for a high multifunctional and portable devices in order to increase the achievement of complex laboratories analysis on a small size chips. This need pushed the research to integrate in the substrates several tools with different tasks, and consequently, the requirements of the material exploited become rapidly more restricted. In particular, the performances of multiple toolkit device are related to its capabilities of combining and matching stages, thus avoiding any detrimental interferences between the material properties needed for their realization. During the last 20 years, several materials have been proposed for the combination of different tools on the same device. Only recently our group proposed Lithium Niobate (LiNbO3) as a valid alternative for a monolithic substrate in LOC application. This material is well-known in the field of integrated optics, due to its interesting optical properties, that brought it to be the main component in optical modulators in the telecom devices. The excellent performances in this field can be combined to the microfluidic for the realization of reliable optofluidic stages for LOC application. Moreover, LiNbO3 was demonstrated as a substrate for several micro-manipulation tools, exploiting its further properties, such as photovoltaic tweezers of micro-sized objects, nano-droplets pipetting with pyroelectric induced field, acoustic driven particle transports via piezoelectric generated surface acoustic wave respectively. For these reasons, the merge of all these tools on the same monolithic substrate could represent the optimal improvement to push even further the LOC technology. This thesis aimed to demonstrate that a multifunctional opto-microfluidic platform can be realized in one monolithic substrate of lithium niobate, achieving properties that can be properly exploited for LOC application. In particular, the attention was focused on combining integrated optics and microfluidics in a unique platform, where light is confined in an optical waveguide and crossed a microfluidic channel allowing for a transmission detection. The realization of microchannel for the coupling with microphotonic structures is presented: so in particular channel configurations, such as droplet generator, are characterized and compared to those achieved with other standard material, in order to show the better performances provided by LiNbO3. In this platform the crucial aspect was played by the optical quality of the lateral walls of the microfluidic channel in order to guarantee an optimized optical coupling of the integrated optical waveguide and the microchannel. Such an optical grade quality allows for the integration of microchannels with Ti-indiffused waveguide, in an unexplored way alternative to the standards in optofluidics. This optofluidic coupling is performed by crossing the waveguide with an engraved microfluidic channel. This configuration enables the analysis of the transmitted light guided by the first half of the waveguide to the second half of it. The self-aligned geometry allows for the traveling of the light beam from one waveguide (input waveguide) across the channel until it recouples in the other part of the waveguide (output waveguide). This optical transmission signal of the medium inside the channel is exploited for LOC applications, such as optical measurements of the droplet geometrical properties (such as frequency, length, volume), and controlled microfluidic pH titration, which allows for the pH determination and the neutralization of strong acidic or basic solution, and finally as an optical multiplexer actuated microfluidically. In all these applications, the devices showed not only high level of integration and accurate response, but also superior performances than the standard procedures and materials. Moreover, a further tool was integrated to this optofluidic platform: a photovoltaic tweezers, exploiting the lithium niobate capability of photoinducing electric field on its surfaces. These multifunctional stages are proposed for the effectively manipulation of the orientation liquid crystal inside a microchannel, and the consequent polarization control waveguide transmission beam.
1-dic-2019
Lab-on-a-chip, lithium niobate, optofluidics, microfluidics, photonics
Study of light driven phenomena for optofluidic applications in Lab-on-a-chip platforms in lithium niobate / Zamboni, Riccardo. - (2019 Dec 01).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3423177
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