Elastic tunable grating powered by MEMS actuators for fluorescence spectroscopy applications

In fields such as cell biology, fluorescent markers have become increasingly valuable tools for studying cellular interactions. Many of these tags have signature spectral emissions, and measuring light intensity as a function of wavelength allows the simultaneous use of multiple fluorescent tags to study multiple parameters. Unfortunately, fluorescent signals are often very weak. Researchers must employ complex and costly optical systems and photodetectors in order to measure different wavelengths separately. A need exists for a less complicated optical system capable of making the same types of measurements.;This research designs and implements a microelectromechanical system (MEMS) optical component to meet this challenge. A tunable optical grating is created by implementing elastomer-silicon hybrid MEMS technology. This method allows for polymer microstructures to be seamlessly integrated into silicon MEMS devices. The tunable grating is a suspended polymer microbridge that is elastically stretched by MEMS electrostatic actuators. The generated high strain dramatically changes the period of the grating pattern on the polymer bridge's top surface. The MEMS devices can displace over 50 microm to alter the grating period from 700 nm up to 820 nm. The devices can cycle this large range at speeds up to 2 kHz, a feat very difficult for other tunable grating technologies. This tuning of a submicron grating period at high strain and fast speeds creates the necessary tunable optical component needed for the fluorescence spectroscopy applications.;This work describes the design, fabrication, characterization, and implementation of this device. After characterization proving the device's utility, the MEMS optical component is paired with a single photomultiplier tube detector to take spectral measurements at fast speeds and high sensitivity. These components are then implemented as the detection system for a fluorescence microscope. Spectral flow cytometry measurements are taken as a demonstration of applications. Fluorescent beads are run through a microfluidic channel, and the detection system takes spectral readings at kHz speed in order to distinguish beads by their spectral profile. The development of this MEMS device and its optical system can help several fields of research reduce the dependency on complex optics needed for high speed, highly sensitive fluorescent measurements.