Biophotonics_Concepts_to_Applications

Example 11.3Consider an optical trap that has a trapping efficiency of

Q = 0.25. What is the total force Ftotalexerted on a particle if a power level of

10 mW is used in the trap and the refractive index in the medium is

nmed= 1.36?

Solution: From Eq. (11.4) the total force is found to be

Ftotal¼Q

nmedP

c

¼ 0 : 25

ð 1 : 36 Þð10 mWÞ

3  108 m=s

¼ 11 :3pN

11.2 Miniaturized Analyses Tools

In the biophotonics world, greatly miniaturized photonics-based functions and
devices are appearing in the form oflab-on-a-chip technologyandlab-on-fiber
technology. These compact integrated biosensors, which are based on biochip and
opticalfiber technology, are used to manipulate and analyzefluid samples in vol-
umes on the order of microliters. A key use of lab-on-a-chip technology is in
microfluidic devices, which nominally are built on a substrate that is the size of a
microscope slide. Lab-on-fiber technology is aimed at the creation of multiple
sensing and analysis functions through the integration of miniaturized photonic
devices onto a singlefiber segment.

11.2.1 Lab-on-a-Chip Technology

Lab-on-a-chip (LOC) technology involves the use of different configurations of
micrometer-sized or smallerfluid channels that are built on glass, thermoplastic
polymer, or paper-based substrates, with polymers being the preferred material [ 12 –
19 ]. The substrates typically have a standard laboratory format, such as a micro-
scope slide. Such devices are compact integrated biosensors that manipulate and
analyzefluid samples in volumes on the order of microliters as the liquids pass
through the device channels. This technology has enabled the creation of portable
and easy-to-use test and measurement tools for rapidly characterizingfluids in
applications such as low-cost point-of-care diagnostics, analysis of the character-
istics of biomolecules, evaluations of food conditions, and drug development.
Depending on the device structure, LOCs can perform functions such as mixing of
liquids, amplification of biomolecules (duplicating certain gene sets multiple times),
synthesis of new materials, optical or electrical detection of specific substances, and
hybridization of DNA molecules.

11.1 Optical Manipulation 329