Optical micro manipulation of live cells has been extensively used to study a wide range of cellular phenomena with relevance in basic research or in diagnostics. The approaches span from manipulation of many cells for high throughput measurement or sorting, to more elaborated studies of intracellular events on trapped single cells when coupled with modern imaging techniques. In case of direct cell trapping the damaging effects of light-cell interaction must be minimized, for instance with the choice of proper laser wavelength. Microbeads have already been used for trapping cells indirectly thereby reducing the irradiation damage and increasing trapping efficiency with their high refractive index contrast. We show here that such intermediate objects can be tailor-made for indirect cell trapping to further increase cell-to-focal spot distance while maintaining their free and fast maneuverability. Carefully designed structures were produced with two-photon polymerization with shapes optimized for effective manipulation and cell attachment. Functionalization of the microstructures is also presented that enables cell attachment to them within a few seconds with strength much higher that the optical forces. Fast cell actuation in 6 degrees of freedom is demonstrated with the outlook to possible applications in cell imaging.
We demonstrate the use of microfabricated supporting structures for maneuvering and supporting polystyrene microspheres for use as magnifying lenses in imaging applications. The supporting structure isolates the trapping light from the magnifier, hence avoiding direct radiation to the sample being observed which could be damaging, especially for biological specimens. Using an optical trapping setup, we demonstrate the actuation of a microsphere not held by optical traps, and show the possibility of imaging through such microspheres.
Robotics can use optics feedback in vision-based control of intelligent robotic guidance systems. With light’s miniscule momentum, shrinking robots down to the microscale regime creates opportunities for exploiting optical forces and torques in microrobotic actuation and control. Indeed, the literature on optical trapping and micromanipulation attests to the possibilities for optical microrobotics. This work presents an optical microrobotics perspective on the optical microfabrication and micromanipulation work that we performed. We designed different three-dimensional microstructures and fabricated them by two-photon polymerization. These microstructures were then handled using our biophotonics workstation (BWS) for proof-of-principle demonstrations of optical actuation, akin to 6DOF actuation of robotic micromanipulators. Furthermore, we also show an example of dynamic behavior of the trapped microstructure that can be achieved when using static traps in the BWS. This can be generalized, in the future, towards a structural shaping optimization strategy for optimally controlling microstructures to complement approaches based on lightshaping. We also show that light channeled to microfabricated, free-standing waveguides can be used not only to redirect light for targeted delivery of optical energy but can also for targeted delivery of optical force, which can serve to further extend the manipulation arms in optical robotics. Moreover, light deflection with waveguide also creates a recoil force on the waveguide, which can be exploited for controlling the optical force.
We demonstrate a system for constructing reconfigurable microstructures using multiple, real-time configurable
counterpropagating-beam traps. We optically assemble geometrically complementary microstructures with complex
three-dimensional (3D) topologies produced by two-photon polymerization. This demonstrates utilization of
controllable 3D optical traps for building hierarchical structures from microfabricated building blocks. Optical
microassembly with translational and tip-tilt control in 3D achieved by dynamic multiple CB traps can potentially
facilitate the construction of functional microdevices and may also lead to the future realization of optically actuated
micromachines. Fabricating morphologically complex microstructures and then optically manipulating these archetypal
building blocks can also be used to construct reconfigurable microenvironments that can aid in understanding cellular
development processes.
The emerging field of micro fluidics is challenged with a desire to pump, move and mix minute amounts of fluid. Such micro devices are operated by means of light matter interaction, namely they can be driven through utilizing birefringence and the polarization of the light as well as the reflection and refraction of light. The latter one enables micro motors to be operated in a tangential setup where the rotors are on axis with an optical waveguide. This has the advantage that the complexity of driving such a device in a lab on a chip configuration is reduced by delivering the driving light by means of a waveguide or fiber optics. In this publication we study a micro motor being driven by a fiber optically delivered light beam. We present experimentally and theoretically how light is getting diffracted when in interaction with the rotors of a turning micro motor. By utilizing the two photon signal from a fluorescein dye being excited by a pulsed femtosecond Laser which was used to drive the motor. Additionally the rotation rate is investigated in dependence of the light field parameters.
Photopolymerisation by computer controlled scanning of a focused laser beam is a powerful method to build structures of arbitrary complexity with submicrometer resolution. The procedure has already proven effective to produce complex structures that can be manipulated in optical tweezers. These micromechanical systems consist of static and moving parts and are expected to be building blocks of highly capable microfluidic systems. To enhance the efficiency of structure building, we developed single shot photopolymerisation. Instead of complicated multidimensional scanning the whole structure is generated simultaneously with special diffractive patterns. We experimented with fixed diffractive optical elements, kinoforms, and Spatial Light Modulators (SLMs). By using kinoforms, cross shaped structures were produced in single shots as an illustration. These propellers were produced about an order of magnitude faster than by simple scanning, and can be rotated by optical tweezer. The complexity of the structure depends on the quality of the kinoform and the available laser power. With the concerted movement of the appropriately chosen basic pattern and the sample, the building of more complicated structures can also be greatly accelerated due to the parallel nature of the polymerisation. The possibilities of photopolymerisation using SLM were also explored: the added flexibility using the programmable device is demonstrated.
We have shown earlier that photopolymerization offers a relatively simple method to produce microscopic particles of arbitrary shape that are practical to expand the possibilities of optical manipulation. Propeller shaped micrometer sized rotors are rotated in optical tweezers, while flat objects are oriented in traps formed by linearly polarized light. Such elements and the possibilities opened up by their use would find numerous applications in lab-on-a-chip devices. We have extended these methods by developing new elements for applications. We have built microscopic wheels ad gears that have a central flat component so that its rotational position can be controlled by linearly polarized light. These rotors are rotated by rotating the polarisation of the light. Such gears can be used as actuators of more complex micromechanical devices (pumps, valves,) also built by photopolymerization in a single process. Important component of such devices are gears rotating on fixed axes, readily built by the method. An alternative way of optically actuating rotating devices by light is the illumination of cogwheel shaped rotors from a tangential direction. The advantage of this latter approach is that the whole system (i.e. the rotors on axes and optical waveguides that carry the actuating as well as possibly the sensing light) can be built as an integrated system in a single process. Such devices would not need optical tweezers and thus bulky microscopes for actuation, significantly reducing the complexity of eventual lab-on-a-chip devices. Operational examples will be demonstrated and the properties of the different approaches will be compared.
Tin oxide pattern generation by laser deposition from SnCl4(DOT)5H2O in isopropanol is reported. Smooth, even stripes of thicknesses ranging from 20 to 120 nm with sharp, well defined edges and cross-section are deposited by scanning an Ar+ laser beam ((lambda) equals 514.5 nm) focused onto the substrate--solution interface with a constant speed of 1 mm/s. The linewidth linearly increases from 26 to 42 micrometers with increasing the power from 40 to 120 mW. The reproducibility of pattern generation is extremely good as revealed by scanning electron microscopy, energy dispersive X-ray and micro-area Rutherford backscattering analyses. The minimum DC resistivity of 1.7(DOT)10-2 (Omega) cm, measured without any process optimization, favorably compares with those reported for films prepared by other techniques. The chemical composition of the film material in SnOx with 1.1 < x < 1.5 as determined by X-ray photoelectron spectroscopy.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.