The present invention generally relates, in some aspects, to systems and methods for making and using sensors or other devices, such as optical components. One aspect is generally directed to a sensor or other device comprising a nanometer-sized portion. In some embodiments, the sensor can be used to determine various characteristics such as temperature, humidity, an electric field, a magnetic field, an analyte, or the like. For instance, in one embodiment, a portion of a sensor device may be inserted into a cell and used to study the cell, e.g., using optical techniques such as surface plasma resonance. In some embodiments, such sensors or other devices may comprise metal, glass, or other materials, which can be prepared using etching or other techniques.
