Measurement of 3D-forces on a Micro Particle in Acoustofluidic Devices Using an Optical Trap

Andreas Lamprecht, Stefan Lakämper, Iwan A.T. Schaap, Jurg Dual

Here, we use a calibrated high gradient laser trap to directly measure the total time-averaged 3D force on a dielectric silica parti- cle in the regime of an ultrasonic standing wave. Acoustic radiation and acoustic streaming apply forces on an optically trapped particle within an acoustofluidic device. From measuring the induced displacements from the laser trap center in three dimen- sions the acoustic forces (0.2-50pN) can be calculated in dependence of the particle position and excitation frequency. Thus, the real pressure distributions within acoustofluidic devices can be mapped out. The three dimensional direct measurement, as pre- sented here, opens up the possibility to quantify so far inaccessible small scale phenomena such as the effects of: a.) local and global acoustic streaming, and b.) boundaries or close-by objects.

DOI

Generating Nanostructures with Multiphoton Absorption Polymerization using Optical Trap Assisted Nanopatterning

Yu-Cheng Tsai, Karl-Heinz Leitz, Romain Fardel, Michael Schmidt, Craig B. Arnold

The need to generate sub 100 nm features is of interest for a variety of applications including optics, optoelectronics, and plasmonics. To address this requirement, several advanced optical lithography techniques have been developed based on either multiphoton absorption polymerization or near-field effects. In this paper, we combine strengths from multiphoton absorption and near field using optical trap assisted nanopatterning (OTAN). A Gaussian beam is used to position a microsphere in a polymer precursor fluid near a substrate. An ultrafast laser is focused by that microsphere to induce multiphoton polymerization in the near field, leading additive direct-write nanoscale processing.

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Optical Tweezers Array System Based on 2D Photonic Crystals

Xuechang Ren, Canhui Wang, Yanshuang Li, Shaoxin Shen, Shou Liu

A simple optical interference method for creating multiple optical tweezers from a single laser beam, using two dimentional photonic crystals (PhCs) as a diffractive beam splitter, was described. To obtained clear periodic traps, all diffracted beams sould be used and the intensity of each splitted beam should be same. So the period and the surface features of PhCs was adjusted in the present study As a demonstration of this technique, using 2D PhCs with 700 nanometer period, hexagonal lattice patterns with one micrometer period have been implemented. The image of periodic intensity gradient of light fabricated by this method is presented.

DOI

Optically based manufacturing with polymer particles

Reza Ghadiri, Mario Surbek, Cemal Esen and Andreas Ostendorf

We present a new single-laser optical trapping technique for the exact manipulation and durable assembly of transparent polymer microparticles. This technique comprises the trapping of microparticles and the assembly by using a laser-driven thermal process for the joining of the particles. The thermal energy necessary for the systematic joining is applied partly by global heating of the processing chamber and by absorption of the electromagnetic radiation of the laser tweezer. The main advantage of this contact free joining technology is to use the same laser for the optical trapping, positioning and the durable assembly. The generated joints are stable and cannot be broken up with optical forces. In summary, a new micromanufacturing process based on an optical machining process is reported with promising applications in the MEMS and photonics area.

DOI