Pollen-Shaped Hierarchical Structure for Pressure Sensors with High Sensitivity in an Ultrabroad Linear Response Range

Abstract

High sensitivity and linear response over a wide sensing range are important in flexible pressure sensors for their practical applications in biomimetic electronics and human−machine interactions. Previous studies regarding flexible pressure sensors have primarily focused on their high sensitivity, whereas they generally exhibit a narrow linear sensing range. In this article, a hierarchical structure with conical secondary features is reported, and its role in enhancing the linear sensing range of piezoresistive pressure sensors is demonstrated. We find that the conical secondary features on the hierarchical structure significantly improve the linear relationship between the contact area and applied force over a broad range. This advantage endows the sensor with a wide linear sensing range. To obtain this type of hierarchical structure, pollen grains of wild chrysanthemum are exploited as templates, and the prepared sensor presents a high sensitivity of 3.5 kPa −1 over an ultrawide response range of 0−218 kPa with good linearity via a coefficient of determination (R 2 ) of 0.997. Furthermore, owing to the simple and scalable process, a sensor array with high density is fabricated to map the spatial pressure distribution and simulate an electronic skin to detect Braille characteristics.

Flexible Sensory Systems: Structural Approaches

“…Research applying nano/microstructure arrays has advanced into multiaxial force sensing [ 234 , 235 , 236 ], signal linearity [ 237 , 238 , 239 ], and response time improvement [ 211 ]. Multi–axis force sensing is essential in robotics and many other applications [ 240 ].…”

“…Thus, pressure, shear, torsion, and bending signals can be distinguished. Recently, research has been conducted to improve sensor performance, by simulating various hierarchical [ 247 , 248 ] and natural structures [ 239 ] and basic structures. In addition, research on a sensor capable of simultaneously measuring a mechanical stimulus and a temperature [ 249 , 250 ] or a magnetic field [ 251 ], beyond distinguishing the stimulus, is in progress.…”

“…Nano/microstructure arrays are applied to pressure and tactile sensors and are studied for the purpose of increasing the performance of the sensor, such as sensitivity and hysteresis, without changing the material [ 214 , 234 , 235 , 237 , 238 , 239 , 240 ]. However, when two or more stimuli act simultaneously, studies on the discrimination of stimuli are insufficient, and additionally, there are limitations due to mass production difficulties and low durability.…”

Wearable Pressure Sensors for Pulse Wave Monitoring

“…[76][77][78][79] Consequently, microengineering developments have been aimed at improving the production performance of pressure sensors using a wide range of material nanostructure designs including pyramids, [80][81][82][83][84] lines or ridges, [85][86][87][88][89] hemispheres, [90][91][92] micropores, [93][94][95][96] and bionic structures. [97][98][99][100][101][102][103][104][105][106] These sensors exhibited high signal-to-noise ratios (SNR) and remarkable pressure sensitivity that allow for accurate epidermal pulse waveform measurement.…”

A water‐soluble micropatterned MoS2 quantum dots/polyvinyl alcohol film as a transient contact (pressure) and non‐contact (humidity) as touch and proximity sensor

“…Similarly, it improves the sensitivity of sensor and reduces the rise and fall time 25 . Also, microstructure sensor can enable to detect wide range of pressures with linear response 26 . The fabricated sensor has a sensitivity of 1.44 kPa −1 , demonstrating superior sensing capabilities compared to the plain MoS 2 QDs/PVA film with a sensitivity of 0.51 kPa −1 .…”