Flexible tactile sensors with high sensitivity, good flexibility and the capability of measuring multidirectional forces are urgently required in modern robot technology and flexible electronic applications. Here, we present a flexible three-axial tactile sensor using piezoelectricity enhanced P(VDF-TrFE) micropillars. For achieving three-axis force measurement, the vertical aligned P(VDF-TrFE) micropillars are sandwiched between four square bottom electrodes and a common top electrode to form four symmetrically arranged piezoelectric sensing units. An elastomeric PDMS bump is fixed on the common top electrode surface to effectively transfer the contact force to the four sensing units. Taking advantage of the high sensitivity and good flexibility of the imprinted P(VDF-TrFE) micropillars, the resultant four distributed piezoelectric units are highly sensitive to the strain and can generate related signals corresponding to the compressive and tensile stress, from which the direction and the amplitude of the applied force can be deduced. The structural design, manufacturing technique,the three-axial force measuring principle, and sensing performance characterization of the proposed tactile sensor are presented in this paper. The sensitivities for X-, Y-, and Z-axis force components are calibrated as 0.3738 V N −1 , 0.4146 V N −1 , and 0.3443 V N −1 in experimental study. Furthermore, the proposed tactile sensor array is successfully integrated with a magnetic bar consist of NdFeB/ PDMS composites to construct a magnetic actuator with sensing ability. These results give the flexible three-axial tactile sensor high potential for use in advanced robots, wearable electronics and a variety of human-machine interface implementations.
The recyclable, shape-memory, and self-healing soy oil-based polyurethane (S-PU) networks were constructed by the thermoreversible Diels-Alder (DA) reaction between S-PU (sealed with furfuryl alcohol) and 1,5-bis(maleimido)-2-methylpentane. The DA and retro-DA reactions between furan and maleimide were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, solubility, and recycle testing. Moreover, the shape-memory properties of the S-PU networks were studied by qualitative recovery testing and quantitative cyclic tensile testing. Furthermore, the self-healing properties of S-PU networks were confirmed by cut, scratch, and tensile testing. The results showed that, compared to the traditional S-PU, the novel S-PU prepared in this work was recyclable and self-healing. And although both of them have shape-memory effect, the novel S-PU has a higher shape fixed rate and shape recovered rate than the traditional S-PU.
The thiol−ene click reaction to prepare biobased polyols is a strategy to promote the green and environmental protection of polyurethane. The excessive usage of thiol and low conversion of carbon− carbon double bonds (CC) would severely limit the properties of polyurethane (PU). In this work, a set of eugenol-based polyols were prepared via the thiol−ene click reaction. Interestingly, the conversion of the CC was nearly 100% at the eugenol and various thiol compounds (SH) in a stoichiometric ratio without excess of SH. Then, the prepared polyols were reacted with diphenylmethane-diisocyanate (MDI), followed by a series of structure-adjustable thermosetting polyurethane networks with colorless transparency, high glass transition temperature (T g ), and good mechanical properties being obtained. In particular, the tensile strength was up to 54.88 MPa, and T g can be adjusted from 36.45 to 77.21 °C. Moreover, it is revealed that the compounds with an allyl structure are conducive to the efficient click reaction, and its application in PU can be greatly extended.
Geckos, which can walk upside down on smooth or rough surfaces, owe this ability to the hierarchical structures under their toes. These structures are responsible for substantial adhesion and, at the same time, for quick attachment/detachment by mechanical stimulus of toe muscles. Inspired by such stimuli‐responsive systems in nature, an active adhesive soft gripper for rough surfaces is proposed in this study, consisting of the mushroom‐like morphology acting as adhesive structures and the pressure controllable deformation working as toe muscles. Through tunable pressure, the adhesive force can be increased and reduced by roughly 20‐fold for a ground glass, in which it can quickly reach high adhesion with positive pressure and reduce to small adhesion under negative pressure. This gecko inspired soft gripper is tested and found successful as a pick‐up and drop‐down system for transporting a surface with different features, composed of rough acrylic plate, steel ball, flexible photo paper, heavy glass block/plate, etc., which will have great potential for applications in industrial line and daily life as well as providing a novel perspective for the design of soft grippers.
As a p-type multifunctional semiconductor,
CuSe nanostructures
show great promise in optoelectronic, sensing, and photocatalytic
fields. Although great progress has been achieved, controllable synthesis
of CuSe nanosheets (NSs) with a desirable spacial orientation and
open frameworks remains a challenge, and their use in supercapacitors
(SCs) has not been explored. Herein, a highly vertically oriented
and interpenetrating CuSe NS film with open channels is deposited
on an Au-coated polyethylene terephthalate substrate. Such CuSe NS
films exhibit high specific capacitance (209 F g
–1
) and can be used as a carbon black- and binder-free electrode to
construct flexible, symmetric all-solid-state SCs, using polyvinyl
alcohol–LiCl gel as the solid electrolyte. A device fabricated
with such CuSe NS films exhibits high volumetric specific capacitance
(30.17 mF cm
–3
), good cycling stability, excellent
flexibility, and desirable mechanical stability. The excellent performance
of such devices results from the vertically oriented and interpenetrating
configuration of CuSe NS building blocks, which can increase the available
surface and facilitate the diffusion of electrolyte ions. Moreover,
as a prototype for application, three such solid devices in series
can be used to light up a red light-emitting diode.
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