Hierarchically porous piezoresistive sensor for application to the cambered palm of climbing robot with a high payload capacity

Abstract

Effective sensitivity within a large responding range is a crucial parameter of flexible tactile sensors for a robot, especially for engineering climbing robots under high shear force conditions. While introducing microstructures can improve the sensitivity, in turn, it leads to a limited pressure-response range due to the poor structural compressibility. To achieve effective sensing under large loading forces, the flexible sensor needs to have a hierarchical sensing system and an optimal mechanic design. Herein, we report a strategy of embedded hierarchically porous piezoresistive foam that can significantly boost the sensitivity (S min > 0.084 kPa−1 at 20 Pa–500 kPa) while simultaneously broadening the pressure responding range, together with remarkable mechanical stability and robustness. Depending on the pressure distribution of the appreciable palm, the climbing robot with a high payload (40 kg) was demonstrated a series of recognitions of obstacles and feedback controls at slipping state. The soft piezoresistive material with the assembly architecture would be a general design expected to be applied to other types of robots to achieve a broader pressure-response range and a higher sensitivity.

A Flexible Multimodal Sole Sensor for Legged Robot Sensing Complex Ground Information during Locomotion

“…The observable piezoelectricity signal appears only at on and off moments of the dynamic stimulus, and it is difficult to be induced by a mild static stimulus. Response times of piezoelectricity and piezoresistance are 16 ms and 150 ms, respectively, and the durability of piezoresistance has been demonstrated by our earlier studies [25].…”

“…Layers in piezoresistance need flat full-face contact and a hard substrate to map the force distribution, so they are put under the hard ankle connector and above the the piezoelectric sensor. The cross-arranged piezoresistive array was assembled by four laser-cut hierarchical porous piezoresistive cells (sizes of about 10 × 10 mm) and an FPCB with interdigital electrodes (Figures 2a and 3c) [24,25]. The cross-sectional image of a field-emission scanning electron microscope (FESEM, Supra 55 Sapphire, ZEISS) shows abundant micro-and nano-pores distributed into the conductive elastomer (TPU) uniformly (Figure 3d).…”

A soft tactile sensing array with high sensitivity based on MWCNTs-PDMS composite of hierarchically porous structure

“…Deformity optimization usually came along with expanse of reproducibility and repeatability, and the degree of sensitivity improvement was relatively limited, so adding packing to the dielectric to improve the electroconductivity or dielectric constant and thereby improve sensitivity was another extensively applied scheme. Ag nanowires [24], Ag nanoparticles [28], carbon nanotubes (CNTs) [29][30][31], carbon black [32], graphene [29] and other various fillers were all successfully introduced into the solid elastomers. Among those, CNTs were widely applied either for piezoresistive or capacitive pressure sensors, electroconductivity or dielectric permittivity changes were greatly enhanced under increasing external pressures [33][34][35].…”

Ultrathin Superhydrophobic Flexible Tactile Sensors for Normal and Shear Force Discrimination

“…With the development and popularity of the Internet of things, robots are required to have intelligent sensing and recognition capabilities. 22−24 Tactile sensors help robots to detect the physical environment, monitor body activity and position (i.e., proprioception), 17,25,26 and thus perform tasks such as handling and manipulating objects 26,27 and human−robot interactions. 17,18,28 Therefore, flexible tactile sensors are one of the key technologies for robots to achieve intelligence.…”

“…Because of its ability to adapt to arbitrarily shaped substrates, it has great application prospects in the fields of wearable electronic devices, , health monitoring, , motion monitoring, − soft robots, , smart prosthesis, − and so forth. With the development and popularity of the Internet of things, robots are required to have intelligent sensing and recognition capabilities. − Tactile sensors help robots to detect the physical environment, monitor body activity and position (i.e., proprioception), ,, and thus perform tasks such as handling and manipulating objects , and human–robot interactions. ,, Therefore, flexible tactile sensors are one of the key technologies for robots to achieve intelligence.…”