Metal-Oxide Nanomaterials Synthesis and Applications in Flexible and Wearable Sensors

Abstract

Metal-oxide nanomaterials (MONs) have gained considerable interest in the construction of flexible/wearable sensors due to their tunable band gap, low cost, large specific area, and ease of manufacturing. Furthermore, MONs are in high demand for applications, such as gas leakage alarms, environmental protection, health tracking, and smart devices integrated with another system. In this Review, we introduce a comprehensive investigation of factors to boost the sensitivity of MON-based sensors in environmental indicators and health monitoring. Finally, the challenges and perspectives of MON-based flexible/wearable sensors are considered.

Morphological Engineering of Sensing Materials for Flexible Pressure Sensors and Artificial Intelligence Applications

“…The resistance of the material can be expressed by the following equation: where R is the resistance of the material, ρ is the resistivity, L is the length, and A is the cross-sectional area. Commonly used sensing materials for piezoresistive sensors are conductive carbon material (e.g., carbon nanotubes (CNTs) [ 50 , 131 ], graphene [ 132 ], MXene [ 62 ], carbon black (CB) [ 133 ], carbonized silk [ 134 ] carbonized wood [ 61 ], and carbonized crepe paper [ 110 ]), conductive polymer (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) [ 37 ], polypyrrole (PPy) [ 82 ], polyaniline (PANI) [ 111 ]), metal nanowire (NW) [ 135 – 138 ], nanoparticle (NP) [ 139 ] and film [ 140 ] (e.g., AuNW [ 136 , 138 ], Ag NW [ 141 ], Cu NW [ 142 ], Pd NPs [ 139 ], Pt film [ 140 ]), metal-oxide (Fe 2 O 3 [ 78 ], ZnO [ 74 ], SnO 2 [ 143 ], In 2 O 3 [ 143 ], NiO [ 143 ]), liquid metal [ 144 , 145 ], and metal–organic frameworks (MOFs) [ 146 ]. The internal microstructure of the sensing material [ 102 ] and the electrode [ 89 , 147 ] includes cracks [ 98 , 99 ], micro-rough structures [ 93 , 102 , 103 , 148 ], porous hierarchical structures [ 104 , 106 , 149 ], and multiscale hierarchical structures [ 74 , 82 , 107 – 110 ].…”

A Kinetic Model for the Generation and Annihilation of Thermally Induced Carrier Donors in a Semiconducting Metal‐Oxide Thin Film

“…Offering relative benefits of optical transparency, adequate field-effect mobility and low-temperature processing, electronic devices based on metal-oxide (MO) semiconducting thin films [1][2][3] are being deployed not only in advanced active-matrix displays, [4,5] but also finding their ways to other applications including flexible electronic circuits, [6][7][8] wearable health care systems, [9,10] artificial skin [11,12] and human-computer interaction systems; [13][14][15] low-power consumption memory [16,17] and implementation of in-memory computation. [18][19][20] Despite such recent deployments, much remains to be investigated regarding material and device characteristics.…”

Nanomaterial Ecotoxicology in the Terrestrial and Aquatic Environment: A Systematic Review

“…Besides CNT, Ag, and TiO 2 dioxide NPs, many other of the NMs (e.g., metal NMs, metal oxide NMs, fullerene, nanoplastics) have been extensively used in several applications, but they have not yet been investigated in the aquatic and terrestrial environment. Among these, the metal oxide NMs are in high demand for several reliable advanced technological applications (e.g., sensors, fuel cells, batteries, actuators, optical devices) due to their flexible mechanical, electronic, optical, electrical, catalytic, magnetic, and photochemical properties [ 63 ]. As an example, among the sensing NMs, CuO, SnO, ZnO, and NiO present high sensitivity, reproducibility, and stability, fast response/recovery time, and cheap and rapid fabrication processes.…”