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A biophotonic platform incorporating various optical techniques into a single system was designed, built, and characterized. The primary goal of building this kind of system was to study living cells. The techniques incorporated as modules into an inverted optical microscope were optical trapping with a single trap or dynamically reconfigurable multiple traps, back focal plane interferometry, and fluorescence microscopy. An integrated instrument control program with a graphical user interface was developed to maximize the system’s capabilities and simplify data acquisition. It allowed the simultaneous or independent use of the optical techniques. The system was used to study green biflagellated microalgae Dunaliella tertiolecta placed in a 50 μm thick glass chamber. Optical trapping without apparent photodamage of this highly motile microorganism was possible with a 1064 nm wavelength laser. Excitation of the chlorophyll fluorescence in the microalgae’s body was done with a 405 nm wavelength laser. Back focal plane interferometry was applied to record the cell’s motility, obtaining the rotation frequency of the body and flagella as the microalgae were held in the optical trap. One of the main results of using the developed biophotonic platform was the in vivo observation of laser-induced detachment of Dunaliella tertiolecta from a glass surface, providing some insight into the photostimulus produced by near-infrared light on this species. The biophotonic platform techniques were tested individually and imultaneously, demonstrating that the developed system can be a reliable tool to study live cells. En este trabajo se diseñó, construyó y caracterizó una plataforma biofotónica que incorpora diversas técnicas ópticas en un solo sistema. El objetivo principal de la construcción de este tipo de sistema fue estudiar células vivas. Las técnicas incorporadas como módulos a un microscopio óptico invertido fueron el atrapamiento óptico con una sola trampa o con trampas múltiples reconfigurables dinámicamente, interferometría de plano focal posterior, y microscopía de fluorescencia. Un programa para control de la instrumentación con una interfase gráfica de usuario fue desarrollado para maximizar las capacidades del sistema y simplificar la adquisición de datos. Esto permitió el uso simultáneo o independiente de las técnicas ópticas. El sistema se utilizó para estudiar microalgas verdes biflageladas Dunaliella tertiolecta colocadas en una cámara de vidrio de 50 μm de espesor. El atrapamiento óptico sin fotodaño aparente de este microorganismo de alta motilidad fue posible con un laser de longitud de onda de 1064 nm. La excitación de la clorofila del cuerpo se realizó con un láser de longitud de onda de 405 nm. La interferometría de plano focal posterior se aplicó para capturar la motilidad de la célula, obteniendo las frecuencias de rotación del cuerpo y los flagellos mientras la célula se encontraba detenida en una trámpa óptica. Uno de los principales resultados obtenidos al utilizar la plataforma biofotónica desarrollada fue la observación in vivo del desprendimiento inducido por láser de Dunaliella tertiolecta de una superficie de vidrio, proporcionando información sobre el fotoestímulo producido por luz en el infrarojo cercano en esta especie. Las técnicas de la plataforma biofotónica se probaron de forma individual y simultánea, demostrando que el sistema desarrollado puede ser una herramienta confiable para el estudio de células vivas.

Green biflagellated microalgae have proven to be of interest in biotechnology and biomedicine due to the production of lipids, carotenoids, and other components that have an environment dependent yield. In this work, we use back focal plane interferometry to obtain information about the behavior of microalgae held by an optical trap under different conditions. It has been observed that the elongated body of a microalga entering an optical trap will align along the beam axis and rotate counter-clockwise. The rotation is produced by the beating flagella, as we conclude from our observation of non-rotation of deflagellated or photodamaged cells. The dependence of rotation frequency on growth phase of the microalgae and on optical trapping power is investigated. To study these effects, each cell is held in the optical trap, and the laser light transmitted by the sample is collected with a microscope objective. Then, the back focal plane of the collection objective is imaged onto a quadrant photodiode. The voltage outputs of the photodiode are then recorded with a computer through the use of a custom Arduino circuit, and written to a text file for post-processing.

Cell adhesion forces have been of interest since the 1920’s. These forces are estimated to be in the nano-Newton range, which is inaccessible to the majority of optical tweezers systems, so most studies use direct contact methods such as atomic force microscopy or micropipettes. In the case of weakly adhered cells such as biflagellated plant cells attached to a coverglass surface, separation does seem possible with the use of an optical trap system. We report the detachment of microalgae Dunaliella tertiolecta from the top and bottom of a coverglass sample chamber using a single nearinfrared CW trapping laser focused with an underfilled high numerical aperture microscope objective. We show that the time required for detachment of a cell is dependent on the incident laser power, taking 3 seconds for a power of 319 mW, and about 90 seconds for a power of 41 mW. We are able to hold the cell in the optical trap after being detached using the same laser beam. The cells detached from the bottom were levitated at an equilibrium position determined by the incident power, while the ones on the top were held in the trap against the top surface. After the cells were released, they were seen to be unaffected in their motion. One advantage of our described method is that, from the large range of sizes of the microalgae within the prepared sample chamber, we are able to select a specific size for further studies.

An optical and morphological study has been carried out to understand the role of intrinsic defects in opal-based photonic crystals. The inherent polydispersity in sphere size distribution yields imperfect crystallizations and worsens the photonic properties of these systems. By doping poly-(mehtymethacrylate) thin films opals with polystyrene spheres of larger size it is possible to study the disorder caused by the dopants and the negative influence in the optical response. In addition, it is feasible to grow mixed structures (alloys) with intermediate photonic properties by mixing spheres of different nature and the same size.