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Perspectives on Light-Driven Micromachines
Published in George K. Knopf, Kenji Uchino, Light Driven Micromachines, 2018
The second objective was to present a holistic view of optically-driven micro-actuators to demonstrate how the physics of light can be used to manipulate material behavior and, thereby, tiny mechanical structures and mechanisms (e.g., cantilevers, rotors, valves). Through clever design it is possible to shape and control a laser beam to trap and manipulate semitransparent micro objects (Chapter 4), or cause a photo-responsive material to change shape (Chapters 5 and 6). Light can also be used to produce a photothermal effect that changes the state of the immediate environment (e.g., liquid to gas) or causes a temperature-based phase transformation in the crystal structure of a functional material (Chapter 7). The third goal was to demonstrate the viability and practicality of light-driven micromachines. Although the focus of the discussion was microfluidics (Chapter 8), the design principles can be applied to solving a wide variety of problems. By addressing these goals, the authors hope to advance the underlying science of light-driven micromachines and provide inspiration for the next generation of researchers, material scientists, and engineers as they move forward to develop innovative solutions far beyond anything that we can imagine today.
Energy
Published in Julie Kerr, Introduction to Energy and Climate, 2017
The second method of energy conversion—atoms absorbing or emitting photons of light—occurs when light falls on an object. An incident photon may either pass through the object, be reflected by the object, or be absorbed by the atoms making up the object. If most of the photons pass through, the object is considered transparent. Depending on the smoothness of the surface on the scale of the photon’s wavelength, the reflection may be either diffuse (rough surface) or coherent (smooth surface). If the photon is absorbed, the photon’s energy may also be split up and converted in the following ways: Photothermal effect: The absorbed energy may simply produce thermal energy, or heat in the object. In this case the photon’s energy is converted into vibrations of the molecules called phonons. This is heat energy.Photoelectric effect: the absorbed energy may be converted into the kinetic energy of conduction electrons, which becomes electrical energy.Photochemical effect: The energy may bring about chemical changes which effectively store the energy.
Study on Apoptosis of Squamous Cell Carcinoma Using Photothermal Therapy with Partial Injection of Gold Nanoparticles
Published in Nanoscale and Microscale Thermophysical Engineering, 2023
In this study, a heat transfer-based numerical study was performed on photothermal therapy for squamous cell carcinoma that occurs inside the skin layer. The light absorption of the medium was improved using GNPs to effectively achieve the photothermal effect. The GNPs in the medium were injected to various positions in the tumor in the form of spheres with a radius of 2.5 mm. The number of injections was set to one-six. The light absorption distribution in the medium was calculated by analyzing the behavior of the laser irradiated to the medium, using the Monte Carlo method. Based on this, the temperature distribution in the tissue was verified through the thermal diffusion equation. In addition, the apoptotic variable (apoptosis retention ratio, thermal hazard retention value, and effective apoptosis retention ratio) that can quantitatively capture the effect of photothermal therapy was calculated over the treatment time based on the determined temperature distribution.