This PDF file contains the front matter associated with SPIE Proceedings Volume 11098, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Compared to the conventional uniform illumination microscopes, a laser scanning microscope takes much longer time of image acquisition, because a focus-beam scans a sample pixel by pixel in 2D or even in 3D. In this presentation, I will discuss a new scanning method that extremely reduces the time of imaging in scanning microscopy. The method is beneficial to the samples that weakly scattering with sparsely distributed molecules or nano-materials. Raman scattering microscopy, dark-field microscopy, and phase-contrast microscopy are good examples. The proposed method of scanning is based on statistics and stochastic process theory. The method mimics the human's behavior of finding unknown places in a large map and animal’s hunting their prey from a large area. In the method, starting points of searching are given by a random distribution (the first layer), and the scanning starts at individual starting points to diffuse the search area based on a given stochastic process (the second layer). The diffusion area of scanning is limited by the entropy of local information of the sample. We will show experimental results of Raman scattering microscopic images obtained with the proposed scanning method and will compare the results with those obtained by conventional deterministic scanning paths. The effectiveness and the limit of the method will be also discussed. The idea proposed here is an extension of our previous work for intracellular nano-Raman microscope with a plasmonic nanoparticle [1]. [1] J. Ando.et. al., Nano Lett. 11, 5344, 2011

We have developed several fluorescence photoswitchable molecules based on a photochromic energy transfer or electron transfer process and successfully demonstrated reversible fluorescence photoswitching with non-destructive readout capability even at the single-molecule level. In this study, as a novel method to achieve reversible fluorescence photoswitching and non-destructive fluorescence readout, we focused on the stimuli-responsive orientation behavior of a liquid crystalline polymer (LCP) containing a photochromic azobenzene unit. We attempted to cooperatively control the molecular orientation of a fluorescent dye by incorporating into an azobenzene LCP (PMAz6Ac) film and reversibly switch the fluorescence intensity along with the orientation change of PMAz6Ac induced by the polarized-light irradiation or thermal annealing process. We successfully observed cooperative orientation behavior of a doped fluorescent dye along with the orientation change of PMAz6Ac by choosing an appropriate fluorescent dye. This cooperative orientation allows us to demonstrate the reversible modulation of fluorescence intensity with non-destructive readout under irradiation with the polarized excitation light.

I will show that, in concept, particles should move when they are photochemically activated in a gradient of light intensity, and the motion occurs in the direction of the vector of the intensity gradient, and its efficiency depends on the respective orientations of the vectors of light polarization and intensity gradient. The theory describes well experimental observations, and it opens important perspectives for the manipulation of matter by light.

Optical vortex possesses an on-axial phase singularity and an orbital angular momentum (OAM) due to its spiral wavefront characterized by a topological charge ℓ. OAM of the optical vortex can twist or spin the target materials, such as silicon, metal, and polymer, to form chiral structures. In this paper, we report on the creation of helical microfibers by irradiating picosecond optical vortex pulses with a wavelength of 532 nm to ultraviolet curing resin via a two-photon-absorption photopolymerization process. Self-focusing effect of incident vortex pulses, arising from the photo-polymerization, confines efficiently optical vortex field to form a self-written helical fiber waveguide with the help of OAM transfer effect. The resulting helical microfibers exhibited a length of ~300 μm Also, we could control the twisted direction of fibers merely by changing the sign of the topological charge of optical vortex. These experiments will open up a new way to the practical application of helical microfiber to optical communications.

The promising idea of using self-propelled particles in fields such as microfabrication and environmental remediation has led to the appearance of a plethora of different approaches for their motion during the past years. [1] Among them, the combination of living swimmers and nanocontainer cargos is especially attractive [2]. However, the usual necessity of a fuel in the environment hinders their application in biological tissue and consequently, their bio-medical usage. Here, we propose a novel propulsion mechanism based solely on the refraction of light in the volume of micro-scale particles. In order to understand these artificial swimmers, numerical simulations were undertaken to identify optimized geometries and refractive index distributions of particles. In particles with broken symmetry, a resultant directional photon momentum transfer is intiating a propulsion force, which in turn can be enhanced by the inclusion of a GRadient of refractive INdex (GRIN). We demonstrate fabrication of such artificial swimmers by femtosecond laser lithography based on two photon polymerization (TPP). The versatility of TPP along with the well-suited fabrication polymer Ormocomp allow replicating any of the numerically suggested particles, especially those containing GRIN distributions. We demonstrate the directional motion of the fabricated artificial swimmers under collimated illumination, with the GRIN particles outperforming their homogeneous counterparts. With this first proof-of-principle we pave the way for numerous applications this new generation of fuel-free, refraction-driven self propelled swimmers. [1] M. Guix, S. M. Weiz, O. G. Schmidt, M. Medina‐Sánchez, Part. Part. Syst. Charact. 35, 1700382 (2015). [2] Á. Barroso et al., Biomedical Microdevices 17, 26 (2015);A. Barroso et al., SPIE Newsroom (2015); doi:10.1117/2.1201507.006023

Two-Photon stereolithography is considered to be a promising technique for 3D microfabrication. In particular, microstructures containing noble metals or semiconducting quantum dot nanocrystals are of interest for applications in optoelectronics, photonics and biophotonics. Quantum size effects become relevant in noble metal nanoparticles. Because of this there are many issues regarding the use of photo-lithography in fabricating noble metal containing microstructures including undesirable optical and thermal effects. Realizing well defined ordered structures containing noble metals and quantum dots are hence a challenge in the realm of microfabrication. In this lecture, 3D organic-inorganic hybrid structures achieving by the different approaches will be presented. In addition, recent developments of novel 3D cancer cell chips using a three-floor hierarchical 3D pyramid structure for the in vitro 3D cell growth simulation of tumor cells and detection of anticancer drugs is also reported.

Direct laser writing based on two-photon polymerization is one of the most advanced techniques to fabricate multifunctionally advanced micro- devices. The voxel is considered as a feature key to control the resolution of the fabricated microstructures. The fabricated voxel can be much smaller than the cube of the laser wavelength, λ³ . To achieve a high resolution, it is known from a long literature that low laser intensity is needed. Oppositely, we introduce a new approach to control the spatial resolution by combining high laser intensity and fast writing speed. By using this approach, a resolution of ~36 𝑛𝑚, e.g. ~1/21 λ, is achieved. In this paper, we investigate on the improvement of the spatial resolution by using a systematic nanofabrication process which we developed. We discuss the factors influencing the resolution, including the laser intensity, the exposure time and the scanning speed by fabricating polymerized- voxels, nanolines and suspended nanofibers connecting two voxels. Lastly, we have fabricated stable 3D microstructures with a sub-diffraction-limit accuracy.

DNA changes its conformation by combining a transcription factor or transcription factor complex on specific base sequences. We investigated the conformation changes by using local surface plasmon resonance of two gold nanoparticles linked to each other via the DNA, which compose a nano-dimer. Gap distance of the nano-dimer is reduced due to the DNA conformation change or bending, then the plasmon resonance shifts to longer wavelength. By measuring the plasmon resonant wavelength, gap distance is determined with a calibration curve prepared beforehand. Hence, conformation change of DNA bound with transcription factors is evaluated at nanoscale or sub-nanoscale. For example, a bending angle was determined to be 61.3º when SOX2, one of transcription factors, was bound on a double-stranded DNA having DC5 sequence and the DNA changes conformation. Binding SOX2 and PAX6 together on DC5 sequence, bending angles were evaluated to be 61.3º at SOX2 side and 5.7º at PAX6 side, respectively. When we used DNA having a DC5-con sequence which is a little different from DC5 sequence, bending angles were evaluated to be 61.1º at SOX2 side and 2.3º at PAX6 side. Such small difference in DNA conformations can be distinguished by using the local surface plasmon resonance. We also observed DNA conformation change by binding SOX2 on DC5 in real time and duration for conformation change was determined to be less than 100 msec. Such binding of DNA and transcription factors has possibility for a driving component for nano-machines.

Optical vortex possesses an annular intensity profile and an optical orbital angular momentum arising from its helical wavefront. In particular, it is noteworthy that optical vortex can twist the irradiated materials, such as silicon, metal, and polymer, to form chiral structures. In this paper, we report on a spatial symmetry breaking of optical vortex propagating through bacteriorhodopsin (bR) suspensions. A 1 µm picosecond optical vortex mode propagated through bR suspensions (concentration: ~10 µM diluted in a 16 % NaCl solution) was broken into a twin mode with two bright spots. Also, the twin mode rotated towards a clockwise or counter-clockwise direction assigned by the handedness of the incident optical vortex mode. The rotation speed of the twin mode was measured to be 0.05 cycle/second. It was worth mentioning that such symmetry breaking of the optical vortex mode manifests an interaction between a helical wavefront and a helical bacteriorhodopsin. In fact, this phenomenon was never observed by using a NaCl solution without bacteriorhodopsin.

In this presentation we discuss our attempts at balancing the desirable, and often mutually exclusive properties of resolution and mechanical stability with radical polymerizable photoresists in two-photon lithography (TPL). The photopolymerization dynamics at and around voxels (volume pixels) were controlled by the combined action of a co-initiator and a radical quencher added into the photoresist. In the second part of the manuscript longitudinal scanning during microfabrication is studied as a method to achieve fast fabrication of hierarchical microstructures with hexahedral unit cells.

Photoswitchable organic molecules can undergo reversible structural changes, with an external light stimulus. These special molecules have found uses in the development of “smart”polymers, optical writing of grating films, and even controllable in-vivo drug release. Traditional photoswitchable small molecules include azobenzenes, spiropyrans, diarylethenes, and a whole host of their derivatives. These classes of molecules can either photoisomerize or undergo reversible ring opening, respectively. Being the simplest class of photoswitches in terms of structure, azobenzenes have become the most ubiquitous, well-characterized, and implemented organic molecular switch. In this work, an azobenzene derivative is utilized and covalently attached to the surface of a silica microtoroidal optical resonator and is used to tune the resonance around fifty percent of the cavity’s free spectral range. An evanescently coupled 1300nm laser is used as the probe wavelength to monitor the trans-cis isomerization initiated by a 450nm laser source which is also coupled into the device. Results and kinetics are compared to UV-Vis spectroscopy and ellipsometry, and the tuning sensitivity is compared to other established methods in the literature.

We use the concept of vectorial photochemical tweezing to rationalize experimental observations of surface relief gratings in azo-polymers, e.g., the photochemically induced motion of the polymer in a one-dimensional intensity gradient produced by two-laser beams interference. Vectorial motion of matter occurs when photochemically active, polarization sensitive, molecules are photo-selected in a gradient of light intensity. Directional motion is imposed parallel to the gradient vector with an efficiency that depends on the respective orientations of the vectors of light polarization and intensity gradient. Different combinations of polarizations of the interfering beams leading to differing efficiencies of matter motion are revisited and discussed. We show that the magnitude of photoisomerization force dictates the efficiency of the observed matter motion. We also show that the spatial distribution of the photo-moved matter is Gaussian. Future prospects in the field are discussed.

Multicolor fluorescent nanomaterials that exhibit multiple distinguishable emission signals are especially attractive due to their potential applications in flexible full-color displays, in next-generation lighting sources, and in probes to decipher multiple biological events simultaneously. Recently, we found that a photoswitchable fluorescent NP composed of a photochromic diarylethene (DAE) and a fluorescent benzothiadiazole (BTD) unit exhibits a remarkable nonlinear fluorescence photoswitching due to the efficient intermolecular FRET process in the densely packed NP state, in which only a small amount of the non-fluorescent closed-ring isomer (quencher) was enough to quench the whole fluorescence signal. This unique property allows us the demonstration of high-contrast multicolor fluorescence photoswitching. In this study, we tried to prepare several photoswitchable NPs, which have a different emission maximum in the fluorescence unit and a different absorption maximum in the closed-ring isomer of the photochromic DAE unit. All compounds showed the giant amplified fluorescence quenching in the NP state. Based on this property, we tried to demonstrate the sequential red-green-blue (RGB) fluorescence color photoswitching in a multicomponent photochromic fluorescent NP containing three different fluorescence-colored molecules and the wavelength-selective multicolor fluorescence photoswitching in a mixture of two emission colored photochromic NPs composed of different pairs of a photoswitching unit and a fluorescence unit upon irradiation with appropriate wavelength of lights. Such multicolor fluorescence photoswitchable systems have great potential for various applications.