Laboratory for Scientific Instrumentation and Engineering
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What is LaSIE? - Japanese -
LaSIE: An acronym for Laboratory for Scientific Instrumentation and Engineering

LaSIE has been established for over a decade and has targeted a diverse range of research topics at the forefront of applied physics and biology. Originally focused on signal processing with a strong background in optics, the laboratory is now doing some of the world's frontier research in photonics, nanotechnology, and bio-related areas. Laboratory members enjoy a diverse working environment with regular visiting researchers from around the world, and weekly seminars and meetings held in English to facilitate the rapid adaptation of overseas researchers and graduate students into the group. Topics of research in the laboratory include ultrahigh resolution microscopy, photonic nanofabrication, photonic crystals, nanoparticles, laser-induced anisotropy, photochemistry, live-cell spectroscopy and imaging, and laser-cell interactions. Bio-related research is carried out jointly with the Laboratory for Biophysical Dynamics in the graduate school of Frontier Biosciences.
When a light beam encounters an object, the resulting interaction can be surprisingly complex. The rules that govern photon interactions have been known for some time, and result in some fundamental limitations on technology (e.g. the resolution of a microscope is limited by the wavelength of the light). Recently, methods of circumventing these limitations have been invented. Pioneering work done in LaSIE showed that the use of a metallic nano-needle can locally enhance the electric field at the surface of a sample. Electromagnetically, this is equivalent to increasing the resolving power of the microscope by a large factor, around ten times higher, and allows imaging of samples at previously unheard of scales. Combining the "tip-enhanced nearfield microscope" with multiple wavelength illuminating beams allows sensitive vibrational spectroscopy to be achieved at high resolution. Recent results have demonstrated optical imaging and spectroscopy of carbon nanotubes (a newly discovered cylindrical form of molecular carbon, similar to buckminsterfullerene) with a resolution of 10nm. This is an improvement in resolution of around 50 times compared to traditional microscopy, and represents a breakthrough in the ability to observe and measure the nanoworld.

Field-enhancing nanotip (left two images) and ultrahigh resolution imaging (right images).
Nanofabrication and advanced materials
As we move into the 21st century, we see more and more applications being developed that involve light, either directly or indirectly. One major target of photonics research is the development of photonics crystals, which have many uses, including being applied as an optical replacement of the semiconductor transistor. LaSIE has created some of the first photonic crystal structures in the world, using a soft resin that can be polymerized and hardened by a scanning laser beam. This type of scanning polymerization allows the creation of arbitrary structures with nanoscale resolution, and has been applied, among other uses, to create the world's smallest bull (Guinness Book of World Records). Research is continuing in the pursuit of new types of materials, particularly those that respond to, or can be modified, by laser light. Since a scanning laser beam can be made to penetrate an object with little or no effect at the surface, reactive and interactive materials in combination with controlled laser fields will allow the creation of nanoscale, three dimensional dynamic objects. Creation of microgears by photopolymerization, and rotation of the gears by optically trapping the cogs has already been demonstrated. In the future, we can expect to see optically reacting materials by using hybrid compounds including nanotechnology. Hybrid materials can have anomalous properties that allow the creation of truly new types of objects. One exciting example of this is the use of nanofabrication to create materials with a negative index of light refraction. Such a material could be used to create a lens that can focus light without being subject to the traditional rules that constrain ordinary optics. Such a lens is called a "perfect lens" since it can in theory focus light to infintisimal point. If the technical challenges in creating the required new materials can be overcome, negative refractive index materials can be used to focus light and create microscopes with previously unheard-of resolution.

Photopolymerizable resin allows the creation of photonic crystals (top two images) and the world's smallest bull (lower image).
The invention of the laser has revolutionized the field of microscopy, allowing high-resolution imaging with scanning laser excitation and nonlinear interactions between the imaging light and the sample. However, before the laser was combined with microscopy to improve signal acquisition and increase imaging modes, researchers realized that it could be used as a tool to manipulate and investigate cells and biological samples. Research was carried out in the 1970s to investigate the effects of this newfound radiation source on cellular health, and even to use the locomotive force resulting from the laser radiation pressure to manipulate cells in a technique known as optical trapping. Researchers in LaSIE have used optical trapping to measure the binding forces in cells by optically trapping objects that are fixed to ligand-receptor pairs. Using interferometry to measure motion and optical trapping to control the binding molecules, the physics of attraction between nanoscale can be demonstrated. Other work in the laboratory has been focused on the physical effects of laser irradiation inside living cells. Focused laser light can interact with targets inside a cell, allowing the focused laser beam to be used as a tool for cutting (cellular surgery) moving (subcellular optical trapping) or otherwise modifying the cell organelles. An example of this is where the use of multiphoton nonlinear deposition of laser energy has been shown to elevate the resting calcium concentration in living cells, providing a means to control the ion concentration in the cell cytosol, which is in turn responsible for a variety of fundamental cell responses such as mitosis, muscle contraction, and nerve firing. Although the use of laser irradiation cannot be described as fully "hands-off" control, it is a method with which to control cellular activities from the inside of a single cell without needing to physically broach the outer cell membrane. Other active topics in the laboratory include research into new types of imaging, both optical and spectroscopic, for biological samples. By utilizing extremely high peak power pulsed lasers, nonlinear interactions between the laser light and sample can be evoked, leading to emission of fundamentally new signals from the sample. For example, the peculiar nonlinearities that govern a particular laser-sample interaction known as second-harmonic generation constrain the emission of signal light to areas that are not symmetric. In practice, this means that the emission of second-harmonic light can be made to occur only from the membrane region in a group of cells. This allows high contrast observation of an ultrathin boundary at the edge of the cell, whereas traditional types of microscopy can not easily discern the nanoscale membrane.

Second harmonic generation image of cultured cells (top), and laser-induced cytosolic calcium wave (bottom).

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