Page 228 - Optofluidics Fundamentals, Devices, and Applications

Bio-Inspir ed Fluidic Lenses for Imaging and Integrated Optics 203

Among these systems are miniaturized universal imagers integrating
the functions of cameras and microscopes, the world’s smallest optical
zoom lens, and the design of next-generation surgical cameras for
minimally invasive surgery. To show the potential of the fluidic lens as
a paradigm-shifting technology for future optical systems, examples
are discussed in Sec. 9-2.
The potential application of the fluidic lens as an IOL after cataract
removal is described in Sec. 9-3. This section demonstrates how the flu-
idic lens inspired by the optics in nature can restore human vision.
Because of the length limit, we have skipped many medical-related
discussions involving biocompatibility and surgical procedures for
lens implantation. Instead, we focus on the potentially achievable per-
formance of the fluidic IOL. Readers interested in the medical discus-
sions may find additional information in the references.
Another interesting subject is to extend the fluidic lens technol-
ogy into a tunable molding process to fabricate aspherical lenses of
designed properties. Aspherical lenses are indispensable for compact,
high-performance imaging systems, and can be found in almost all
human-made devices as well as in animal eyes. Creating the mold
master for aspherical lenses, however, is a tedious, difficult, and
expensive task. In Sec. 9-4, we demonstrate that our fluidic tunable
molding method enables us to achieve aspherical lenses of designed
shapes for fast prototyping and design verification, a major contribu-
tion in the general field of optics.
Finally, in Sec. 9-5, we extend the fluidic lens technology to two-
dimensional, in-plane optics as a new platform for polymer-based
integrated optics that may find broad applications in biosensing.
Here we discuss not only in-plane fluidic lenses but also a large fam-
ily of optical elements including beam stops, prisms, waveguides,
and the like that can be readily integrated with microfluidics to form
lab-on-a-chip devices. We use one of the most important biomedical
instruments, flow cytometer or fluorescence-activated cell sorter
(FACS), as an example to demonstrate the potential benefits of fluidic
photonic integrated circuits (PICs).

9-1 Bio-Inspired Fluidic Lens: Structures and Operations
There are two general light bending mechanisms for lenses: index of
refraction gradient and lens curvature. These mechanisms are also
utilized in fluidic lenses. Over the past decade, there have been
numerous studies on fluidic lenses using these two mechanisms. A
brief discussion of various fluidic lenses is given next.

9-1-1 Graded-Index-Tunable Fluidic Lens
One way to form an index gradient is to use liquid crystal (LC).
The molecular structure of liquid crystal is either elongated (rod-
like) or flat (disklike) [1]. Because of its structure, liquid crystal