Editing Nanosensor (section)

==Production methods==
The production method plays a central role in determining the characteristics of the manufactured nanosensor in that the function of nanosensor can be made through controlling the surface of nanoparticles. There are two main approaches in the manufacturing of nanosensors: top-down methods, which begin with a pattern generated at a larger scale, and then reduced to microscale. Bottom-up methods start with atoms or molecules that build up to nanostructures.

=== Top-down methods ===

==== Lithography ====
It involves starting out with a larger block of some material and carving out the desired form. These carved out devices, notably put to use in specific [[MEMS sensor generations|microelectromechanical systems]] used as microsensors, generally only reach the [[microscopic scale|micro]] size, but the most recent of these have begun to incorporate nanosized components.<ref name="F1" /> One of the most common method is called electron beam lithography. Although very costly, this technique effectively forms a distribution of circular or ellipsoidal plots on the two dimensional surface. Another method is electrodeposition, which requires conductive elements to produce miniaturized devices.<ref name=":6">Pison, U., Giersig, M., & Schaefer, Alex. (2014). US 8846580 B2. Berlin, Germany.</ref>

==== Fiber pulling ====
This method consists in using a tension device to stretch the major axis of a fiber while it is heated, to achieve nano-sized scales. This method is specially used in optical fiber to develop optical-fiber-based nanosensors.<ref name=":2" />

==== Chemical etching ====
Two different types of chemical etching have been reported. In the [https://patents.google.com/patent/US4469554A/en#patentCitations Turner method], a fiber is etched to a point while placed in the meniscus between [[hydrofluoric acid]] and an organic [[overlayer]]. This technique has been shown to produce fibers with large taper angles (thus increasing the light reaching the tip of the fiber) and tip diameters comparable to the pulling method. The second method is tube etching, which involves etching an optical fiber with a single-component solution of [[hydrogen fluoride]]. A silica fiber, surrounded with an organic [[Cladding (fiber optics)|cladding]], is polished and one end is placed in a container of hydrofluoric acid. The acid then begins to etch away the tip of the fiber without destroying the cladding. As the silica fiber is etched away, the polymer cladding acts as a wall, creating microcurrents in the hydrofluoric acid that, coupled with [[capillary action]], cause the fiber to be etched into the shape of a cone with large, smooth tapers. This method shows much less susceptibility to environmental parameters than the Turner method.<ref name=":2" />

=== Bottom-up methods ===
This type of methods involve assembling the sensors out of smaller components, usually individual [[atoms]] or molecules. This is done by arranging atoms in specific patterns, which has been achieved in laboratory tests through use of [[atomic force microscopy]], but is still difficult to achieve [[en masse]] and is not economically viable.

==== Self-assembly ====
Also known as “growing”, this method most often entails an already complete set of components that would automatically assemble themselves into a finished product. Accurately being able to reproduce this effect for a desired sensor in a laboratory would imply that scientists could manufacture nanosensors much more quickly and potentially far more cheaply by letting numerous molecules assemble themselves with little or no outside influence, rather than having to manually assemble each sensor.

Although the conventional fabrication techniques have proven to be efficient, further improvements in the production method can lead to minimization of cost and enhancement in performance. Challenges with current production methods include uneven distribution, size, and shape of nanoparticles, which all lead to limitation in performance. In 2006, researchers in Berlin patented their invention of a novel diagnostic nanosensor fabricated with nanosphere lithography (NSL), which allows precise control oversize and shape of nanoparticles and creates nanoislands. The metallic nanoislands produced an increase in signal transduction and thus increased sensitivity of the sensor. The results also showed that the sensitivity and specification of the diagnostic nanosensor depend on the size of the nanoparticles, that decreasing the nanoparticle size increases the sensitivity.<ref name=":6" />

[[Current density]] is influenced by distribution, size, or shape of nanoparticles. These properties can be improved by exploitation of [[capillary force]]s. In recent research, capillary forces were induced by applying five microliters of [[ethanol]] and, as result, individual nanoparticles have been merged in a larger islands (i.e. 20 micrometer-sized) particles separated by 10 micrometers on average, while the smaller ones were dissolved and absorbed. On the other hand, applying twice as much (i.e. 10 microliters) of ethanol has damaged the nanolayers, while applying too small (i.e. two microliters) of ethanol has failed to spread across them.<ref>{{cite journal | doi=10.1002/adfm.202302808 | title=Capillary-Driven Self-Assembled Microclusters for Highly Performing UV Photodetectors | date=2023 | last1=Chen | first1=Xiaohu | last2=Bagnall | first2=Darren | last3=Nasiri | first3=Noushin | journal=Advanced Functional Materials | volume=33 | issue=49 | s2cid=260666252 | doi-access=free }}</ref>