MRI: Acquisition of a Holographic Laser Tweezer Array for Submicron Control of Soft Materials and Novel Network Dynamics

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This grant supports the acquisition of a holographic laser tweezer array. The instrument supports a broad range of cross-disciplinary research projects in nonlinear dynamics, soft condensed matter physics, physical chemistry, and biophysics. The holographic laser tweezer array permits the fabrication of complex materials and the study of dynamical processes using up to 200 independently moveable laser light beams focused through a microscope objective. The instrument permits the generation of complex shaped force fields, and the simultaneous manipulation of multiple trapped objects. The system can generate optical vortices, which can trap reflective particles and apply torque to trapped objects. Based on these unique properties, the investigators plan the following research activities: (1) ??Complex shaped objects such as giant vesicles and cells will be trapped with rings of low power laser spots, which provide the same trapping power through intensity gradient, but have less peak intensity than a single laser spot, and are thus less damaging to the sample. It will permit stretching cells and vesicles into arbitrary shapes by deforming the ring of laser spots for studies of membrane elasticity to aid in understanding spontaneous cell deformations, such as those observed during nerve growth and during the spread of cancerous cells. ?(2) ??Complex force or torque fields generated by the laser tweezer array will be utilized to study the distribution of forces exerted by growing biopolymer networks and their response to external forces or strains. In conjunction with the ring traps described above this will permit studies of sticking or repulsive forces between cells or bacteria. One particular application will be the study of biofilms, which often infect medical implants. (3) ?Arrays of laser tweezers will allow creation of experimental versions of small-world networks, composed of coupled optical oscillators, in order to help understand conditions for synchronization and coherence in sparsely connected networks. Such novel distributed laser sources have potential applications in medical diagnostics and microwave detection. The establishment of an experimental research facility at the interface between physics, chemistry and biology will foster cross-disciplinary interactions among faculty, post- docs and graduate students. Additionally, the instrument will have impact on K-12 education through the PIs ongoing participation in outreach efforts, such as laboratory tours and summer internships for underrepresented groups from DC area high schools. For the University, the instrument will enhance the research infrastructure, which will add to a new effort to expand and connect biophysics research into a visible, top quality research and education program. With its unique capabilities, the system will also be useful for the regional research community. The PIs have developed joint projects with researchers at NIH and NIST, which take advantage of the great regional strengths in the biosciences at NIH, and in materials research at NIST.