The resolution of optical patterning is constrained by the far-field diffraction limit. In this letter, we describe an approach that exploits the unique photo- and electro-chemistry of diarylethene photochromic molecules to overcome this diffraction limit and achieve sub-wavelength nanopatterning.
The ability to pattern nanometric features on various substrates with high throughput, accuracy, and uniformity is the key driving force enabling novel applications in nanophotonics, nanoelectronics, nano-electro-mechanical systems, and nanofluidics. Patterning via Optical Saturable Transitions (POST) is an optical nanopatterning technique that circumvents the far-field diffraction limit by exploiting the linear switching properties of thermally stable photochromic molecules. Previously, POST was enabled by an electrochemical oxidation “locking step.” In this letter, we report an electrode-free “locking step” that exploits the difference in solubility between the two isomeric states of a photochromic molecule in a polar solvent. The reported method obviates the need for a conducting underlayer and also reduces the number of required steps. Using this method, we demonstrated isolated lines of width ∼λ/4 and spacing between features as small as ∼λ/2.5 for an exposure wavelength of λ.
We present a novel, compliant mechanism that provides the capability to navigate extremely confined spaces for the purpose of infrastructure inspection. Extremely confined spaces are commonly encountered during infrastructure inspection. Examples of such spaces can include pipes, conduits, and ventilation ducts. Often these infrastructure features go uninspected simply because there is no viable way to access their interior. In addition, it is not uncommon for extremely confined spaces to possess a maze-like architecture that must be selectively navigated in order to properly perform an inspection. Efforts by the imaging sensor community have resulted in the development of imaging sensors on the millimeter length scale. Due to their compact size, they are able to inspect many extremely confined spaces of interest, however, the means to deliver these sensors to the proper location to obtain the desired images are lacking. To address this problem, we draw inspiration from the field of endoscopic surgery. Specifically we consider the work that has already been done to create long flexible needles that are capable of being steered through the human body. These devices are typically referred to as ‘steerable needles.’ Steerable needle technology is not directly applicable to the problem of navigating maze-like arrangements of extremely confined spaces, but it does provide guidance on how this problem should be approached. Specifically, the super-elastic nitinol tubing material that allows steerable needles to operate is also appropriate for the problem of navigating maze-like arrangements of extremely confined spaces. Furthermore, the portion of the mechanism that enters the extremely confined space is completely mechanical in nature. The mechanical nature of the device is an advantage when the extremely confined space features environmental hazards such as radiation that could degrade an electromechanically operated mechanism. Here, we present a compliant mechanism developed to navigate maze-like arrangements of extremely confined spaces. The mechanism is shown to be able to selectively navigate past three 90° bends. The ability to selectively navigate extremely confined spaces opens up new possibilities to use emerging miniature imaging technology for infrastructure inspection.
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