Optical MEMS are micro-electromechanical systems merged with micro-optics. They allow sensing or manipulating optical signals on a very small size scale using integrated mechanical, optical, and electrical systems and hold great promise specifically in biomedical applications, among others. This book describes the current state of optical MEMS in chemical and biomedical analysis with topics covered including fabrication and manufacturing technology for optical MEMS; electrothermally-actuated MEMS scanning micromirrors and their applications in endoscopic optical coherence tomography imaging; electrowetting-based microoptics; microcameras; biologically inspired optical surfaces for miniaturized optical systems; tuning nanophotonic cavities with nanoelectromechanical systems; quantum dot nanophotonics - micropatterned excitation, microarray imaging and hyperspectral microscopy; photothermal microfluidics; optical manipulation for biomedical applications; polymer-based optofluidic lenses; and nanostructured aluminum oxide-based optical biosensing and imaging. Bringing together topics representing the most exciting progress made and current trends in the field in recent years, this book is an essential addition to the bookshelves of researchers and advanced students working on developing, manufacturing or applying optical MEMS and other sensors.
Inspec keywords: optical fabrication; micromechanical devices; optical microscopy; endoscopes; bioMEMS; chemical analysis; biomedical optical imaging; nanophotonics; micromirrors
Other keywords: electrothermally actuated MEMS scanning micromirrors; photothermal microfluidics; miniaturized optical systems; manufacturing technology; nanophotonic cavities; chemical analysis; quantum dot nanophotonics; microarray imaging; micropatterned excitation; nanostructured aluminum oxide-based optical biosensing; biologically inspired optical surfaces; electrowetting-based microoptics; endoscopic optical coherence tomography imaging; nanoelectromechanical systems; biomedicine; optical MEMS
Subjects: Optical and laser radiation (biomedical imaging/measurement); Chemical variables measurement; Nanophotonic devices and technology; Electromagnetic radiation spectrometry (chemical analysis); MEMS and NEMS device technology; Micro-optical devices and technology; Nanophotonic devices and technology; Patient diagnostic methods and instrumentation; General electrical engineering topics; Textbooks; Micromechanical and nanomechanical devices and systems; Optical microscopy; Optical fabrication, surface grinding; Optical lenses and mirrors; Micro-optical devices and technology; Optical and laser radiation (medical uses)
Integration of microfluidics along with micro/nanoscale optics on a single chip can now be performed by exploiting micromachining and nanofabrication processes. The advent of optofluidics has also been an important step in progressing towards lab-on-a-chip devices, which have extensive applications in healthcare, environmental studies, and life science.
To the uninitiated, the phrase “optical microelectromechanical systems”or optical MEMS must appear to refer to a field of incredible specialization. Ironically, the number of disciplines involved, optics, mechanics, and electronics, make the field most accessible to scientists of great technical breadth. This is especially true when optical MEMS is used in chemical and biological applications - the theme of this text. Underlying all of them is the technology of microfabrication. One chapter could not possibly cover all of the techniques developed over the decades for very-large-scale integration (VLSI) and general MEMS systems. Indeed there are entire textbooks devoted specifically to both types. In this chapter then, we present the characteristics of fabrication and design that are specific to bring optics into the system. In particular, there are a number of materials and fabrication techniques that are specific to optical MEMS systems. When dealing with light, one may have to handle visible, ultraviolet, or infrared portions of the spectrum, each of which has its own special set of optimal substances. Since one often has to emit light or detect it in special wavelength regions, semiconductors other than silicon often must be incorporated, each with their own set of wet and dry chemical etching techniques and their own set of mechanical properties. Standard mechanical characteristics that play no role in “normal”MEMS systems may prove problematic in optical MEMS. For example small size may lead to diffraction, typical surface roughness may limit optical cavity resolution, and mechanical or motion may deform mirrors to limit the number of resolvable spots. Even thermal noise may place limits on optical design. Each of these topics is covered in the pages that follow. For the reader who is interested in further exploring many of these areas, we recommend the text by Solgaard.
This chapter is focused on introducing a unique class of electrothermal bimorph MEMS mirrors and their applications in endoscopic OCT imaging. The novel bimorph actuator designs provide the electrothermal MEMS mirrors with unrivaled combination of large linear scan range, small drive voltage, and high fill factor, making them especially suitable for endoscopic in vivo imaging of internal organs. Using the electrothermal MEMS mirror-based OCT probes, clinical imaging experiments have been performed to detect and stage early bladder cancer and oral cancer. Those MEMS OCT probes have also been successfully applied to brain tissue imaging, tooth imaging, and meniscus imaging. All these imaging experiments have demonstrated the potential and feasibility of the electrothermal MEMS-based OCT endoscopic imaging. With further improvement of the robustness of the MEMS mirrors, the clinical use of this technology is coming in the foreseeable future.
This Chapter discussed the following: brief history of electrowetting; surface tension; contact angle; liquid lens focal length; tunable liquid microlens; electrowetting-based microlens on a flexible curvilinear surface; arrayed electrowetting prism and switchable microlens; electrowetting-controlled liquid mirror; electrowetting-driven optical switch and aperture; electrowetting display.
This chapter provided the latest research grade microcameras that can be used for medical imaging. The optics of the camera was discussed along with the latest innovative solutions for simple fabrication processes, focus tunability, zoom capability, and wide FOV. In addition to the optics, a novel design and implementation for the curvilinear image detector was also realized to minimize aberrations. Insect compound eye inspired microcameras with large FOV were also described in terms of functionality and different fabrication techniques on both curved and planar substrates. In terms of added functionality, a microcamera with multiple viewpoint imaging capability by capturing a single image was discussed. Details of large FOV multi-camera systems with either fixed focal length or tunable lenses were also included in this chapter. Finally, research level endoscopes and laparoscopes were discussed. The different scopes had integrated some of the mentioned innovative techniques and some have shown better performance than current commercial scopes.
Mining smartness from vision organs found in nature becomes of much interest in optical applications such as imaging, display, or lighting. Unlike conventional bulk optics, miscellaneous hierarchical structures at micro- or nanoscale deliver highly efficient light management with a small form factor. For example, natural species have evolved their eyes to obtain all necessary visual information from surrounding environment. Natural imaging schemes can be chiefly classified by three different types of pinholes, camera, and compound eyes. Pinhole eyes found in clam are sensitive enough to allow the animals to protect themselves from dangerous environment but not so sensitive to collect all visual inputs. Unlike other types, the pinhole eye as one of natural eyes with the simplest and thinnest optical configurations is well known for infinite depth-of-field, i.e., no blurred imaging depending on object distance and thus these unique features have been implemented on early-stage simple camera imaging systems. Besides, advanced pinhole eyes are also found in viper snakes of Crotalinae and some python of Boidae, which combine both pinhole eye and ordinary camera eye in order to confer infrared (IR) as well as visible imaging for warm-blooded preys. Compound eyes found in arthropods exhibit many intriguing features for wide field-of-view (FOV), fast motion detection, polarization sensing, color imaging, or high-resolution imaging with compact optical configuration unlike other types. They comprise arrays of integrated optical units called ommatidia. The individual component consists of a facet lens, a crystalline cone, a light-guiding rhabdom, and photoreceptor cells. Furthermore, nature exhibits ten different optical schemes of compound eyes, which have some attractive figures-of-merits for sustainable life style in visual acuity, photon collection efficiency, and polarization or spectral sensitivity. Such biological inspiration recently and actively provides new opportunities for improving optical capability of conventional imaging systems by incorporating nano- and microfabrication methods and furthermore it delivers technical solutions for miniaturized optical systems in medical, industrial, and military fields. In this chapter, we will review engineering approach inspired from diverse biological organs, which can be utilized for miniaturized optical systems in diverse optical applications.
This Chapter discussed the following: nanophotonic cavities tuning; nanoelectromechanical systems; MEMS; NEMS.
The use of QDs allows for hyperspectral imaging of biosamples with a simple microscope configuration. In addition, proper choice of different gold nanoparticles, such as nanorods and nanospheres, enables absorption-based analysis of multiple biomarkers. Combination of QDs and gold nanoparticles provides a potential on-chip hyperspectral imaging tool for multi-biomarkers recognition at cellular level. In addition to microscopy, QD light sources can be used for several types of absorption spectroscopy techniques, such as pulse oximetry [90] or tissue spectroscopy [91], where the absorption spectra are correlated with physical characteristics. A possible application area beyond biomedical applications is the use as an illumination source alternative to conventional RGB-LEDs. Conventional RGB color spaces, such as sRGB or Adobe RGB, cover only a portion of visible colors [92], while our light source can simulate any spectrum expressed as linear combinations of multiple QD emission peaks. The QD light source can be a strong illumination tool for medical and industrial imaging.
This chapter includes three parts. The first part covers the basic physics and principles of photothermal microfluidics. The second part focuses on cell manipulation using photothermal microfluidics and nanofluidics, and the third part covers the applications of photothermal microfluidics and nanofluidics for flow and droplet control.
This chapter will first cover the use of optical gradient forces for the trapping of cells and other biological objects. This method is also widely known as optical tweezers (OT). Other types of direct optical manipulation will be discussed, such as optical cell sorters and optically driven fluids, droplets, and bubbles. Indirect optical manipulation via optically induced electrokinetic forces will be reviewed, in particular, optically induced dielectrophoresis (ODEP). The chapter will also discuss the use of optical manipulation for cell poration, lysis, and surgery. The chapter will finish with a brief discussion of future directions in this field.
Optofluidic lenses that can image or manipulate light at the microscale have attracted increased attention in recent years due to their tunability and reconfigurability. The discovery on transparent and elastic polymer materials has contributed to the development of the optofluidic lenses. These polymer-based optofluidic lenses feature better mechanical stability while remaining high tunability. The chapter begins with a brief introduction of optofluidic technologies. This is then followed by a summary of past and recent work on out-of-plane and in-plane optofluidic lenses, which is categorized according to their operation modes. The chapter is concluded with a commentary by the authors, which discusses possible future directions relating to optofluidic lenses.
In this chapter, the fabrication, characterization, and applications of the NAO, one of the most widely used nanostructures, the NAO thin film and the NAO micropatterns on glass substrates have been covered. Specifically, the fabrication processes of the NAO thin film at a wafer scale and the NAO micropatterns on the glass substrate have been described in detail. The optical properties such as the optical interference and optical emission of the NAO thin film and micropatterns have also been evaluated, which offers essentially the same quality of those from the NAO fabricated directly from an Al plate or foil. In addition, the fluorescence enhancement capability of the NAO and the possible physical mechanisms behind the enhancement capability have been discussed in detail. The optical blue emission of the NAO micropatterns can facilitate the determination of the level of the anodization of the Al micropatterns, while the optical interference signal from and fluorescence enhancement of the NAO micropatterns can be exploited for a variety of biosensing applications.