is the part where a multichannel or microfluidic component is placed for the analyte fluid

transport and mixing into the LOC device. Various sample analytes including pathogen,

pesticide, wastewater, blood, food, and urine are developed for the LOC devices. The

recognition element or sensor part in LOC devices consists of components that provide

selectivity to the target analyte and place where detection takes place. The selection of

recognition elements is depending on the type of target analyte. An antibody or aptamer

recognition element is commonly applied for diagnostic, bacteria, and pathogen detection,

whereas the enzymes are commonly applied for the catalytic reaction. A transducer consists

of a component that translates the interaction of analyte and recognition elements into a

measurable and quantifiable signal. The measurable signal can be in the form of an optical,

electrochemical, and electrical signal. Commonly the type of transducer is designated based

on the physicochemical reaction that takes place at the sensing platform [3]. Both trans­

ducers and recognition elements are important for enhancing the sensitivity and detection

limit of the LOC devices. A signal processing unit in LOC devices consists of electronic

components that are responsible to translate and analyze data from the transducer into a

visualized sensing result.

Most importantly, the LOC devices must be able to provide high sensitivity, accuracy,

rapid, reliable, and real-time quantification for the analyte sample. Nanomaterials that have

a large surface area and excellent electrical and chemical properties may improve the op­

tical, electrochemical, and electrical performance of the sensor part in LOC devices [4]. A

range of nanomaterials including metal, metal oxide, and carbon-based nanomaterials are

widely investigated for improvement in the sensor part of the LOC devices [2,5]. Metallic

nanomaterials such as gold (Au), silver (Ag), platinum (Pt), and nickel (Ni) have been used

as a modifier of sensor surface due to their advantages in amplifying the signal of the

sensor. Metallic nanomaterials such as Au and Ag have unique optical and electronic

properties due to the close position of their conduction and valence band. Electrons can

FIGURE 5.1

General components of LOC devices. Adapted with permission [ 4]. Copyright (2015). The Authors, some rights

reserved; exclusive licensee [MDPI]. Distributed under a Creative Commons Attribution License 4.0 (CC BY)

https://creativecommons.org/licenses/by/4.0/.

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Bioelectronics