Influence of Electrode Structure on Performance of Laser Direct Writing Cu-PI Flexible Humidity Sensor

Abstract

Electrode structure is an essential factor affecting the performance of flexible humidity sensors. In this study, Cu and Cu2 + 1O electrodes were printed by the one-step method using laser direct writing technology to reduce the nano–CuO ink on flexible substrate PI and to be used for a humidity sensor. The resistance of the humidity sensors with nine various electrode structures was measured under the relative humidity (RH) of 16–78%. It was observed that all sensors showed good humidity sensing characteristics, and the sensitivity of the copper-based humidity sensor was not affected by the electrode structure under low humidity conditions but was significant under high humidity conditions. The sensor with the length of 1960 μm and the width of 120 μm shows the lowest sensitivity of 180.2 KΩ/%RH under 35% RH, and the sensor with the length of 2430 μm and the width of 180 μm shows the highest sensitivity of 1744 kΩ/%RH under 65% RH. It is expected that the results can provide an assessment of the performance improvement of the flexible humidity sensor and a reference for the research and development of intelligent wearable devices.

Rheological Investigation of Highly Filled Copper(II) Oxide Nanosuspensions to Optimize Precursor Particle Content in Reductive Laser-Sintering

“…Mueller et al observed that this effect increases with increasing aspect ratio of the NPs [28]. In a majority of previous studies, spin coating was chosen as the coating method [8,[15][16][17][18][19]. However, due to the shear thinning behavior of the PC, the coating thickness decreases outward from the center of rotation, making it difficult to achieve uniform coating thickness.…”

“…In addition to ionic solutions based on copper salts [9][10][11] or complexes [12] and deep eutectic solvents [13,14], copper oxides in the form of nanoparticles (NPs) suspensions can also be used. This enables a maskless, vacuum-free, flexible and direct writing technology that can be used on a wide range of substrates, such as glass [8,[15][16][17] and polymers [18][19][20]. A wide range of applications have already been demonstrated.…”

Humidity-Sensing Mattress for Long-Term Bedridden Patients with Incontinence-Associated Dermatitis

“…The repeatability test with increasing RH proves the suitability of patients with IAD in clinical settings. Therefore, we validated 100 kHz as the operating frequency in the following testing, related to previous studies [ 1 , 4 , 5 , 31 , 34 ]. With a variation of 20–90% RH, the change in five-volt voltage exhibited a relatively small pore size of 0.1 This means that, if a mattress is subjected to a high humidity change, it can be inconvenient and the sensing material of the humidity sensor is not good for patients with IAD in clinical settings [ 1 , 2 , 4 , 8 , 28 ].…”

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

“…Another common mechanism based on reduction principles is the use of metal oxide NPs as metallic precursors. This method has been adopted for several transition metals, using CuO x , [ 36,38,87,175–178 ] NiO x , [ 86,149,179 ] CoO x , [ 180 ] as well as NP mixtures. [ 181,182 ] This mechanism is based on mixing oxide NP precursors with similar reducing agents (e.g., PVP, [ 38,87 ] ethylene glycol), [ 36,182 ] while laser irradiation and resulting photothermal processes promote the removal of oxygen over the metal oxide NP structure.…”