ABSTRACT
Optical forces for pa rticle manipulation have been w idely applied i n v arious elds si nce t he te chnique w as rst i ntroduced by A shkin (1970). rough s culpturing t he spatial d istribution of l ight elds, versatile f unctional manipulations i ncluding opt ical t rapping (Ashkin e t a l., 1986), rotation (Curtis and Grier, 2003), sorting of micro-and nanoscale particles (MacDonald et al., 2003; Wang et al., 2005), and large-scale trapping (Garces-Chavez et al., 2006) have been demonstrated. Accurate control of optical forces also makes optical tweezers a powerful tool for studying fundamental biological sciences, including molecular forces in molecular motors (Svoboda et al., 1993; Svoboda and Block, 1994; Mehta et al., 1999), DNAs (Purohit et al., 2003; Chemla et al., 2005) and cell mechanics (Samuel and Berg, 1996; Jass et al., 2004). Recent progress in near- eld trapping (Yang et a l., 2009) and p lasmonic t rapping ( Yannopapas, 2 008) a lso promise opt ical m anipulation o f na noscale pa rticles with near- eld intensity en hanced by na nostructures. Integrating opt ical manipulation w ith micro uidic s ystems i s a lso a nother v ibrant eld si nce opt ical f orces a re b iocompatible a nd p rovide unique features of trapping, transport, and sorting functions (MacDonald et al., 2003; Wang et al., 2005). Several semi-optical trapping and manipulation mechanisms have also been proposed in recent years. Optoelectronic tweezers (OET) utilize a light-patterned electric eld to achieve particle manipulation functions (Chiou et a l., 2005). Since the l ight eld in OETs is used to trigger an electric eld, the optical power required to s culpt a p otential pro le i s orders of magnitude lower than conventional optical tweezers. is promises optical manipulation on a large area without facing the trade-o b etween t rap forces a nd opt ical p ower. O ptical m anipulation w ith ot her i ndirect opt ical forces such as light-actuated ac electroosmosis (LACE) (Chiou et al., 2008), optomagnetic tweezers
(Mehta et al., 2008), and anti-Brownian electrokinetic (ABEL) trap (Cohen and Moerner, 2005, 2006) will also be discussed.
