Planar potentiometric sensors based on Au and Ag microelectrodes and conducting polymers for flow-cell analysis

Back-side contact Au and Ag microelectrodes were used as transducers to construct planar all-solid-state electrodes suitable for flow-through analysis. The microsensors were based on plasticized PVC potassium-selective membranes containing ion-electron conducting polymer—polypyrrole doped with di(2-ethylhexyl) sulfosuccinate. The proposed technique allowed simple construction of microsensors in one step, by membrane solution casting directly on the surface of the planar metallic transducers. The performance of the microsensors based on Au and Ag transducers were determined and compared with planar sensors based on internal electrolyte immobilized in polyHEMA. The addition of the polypyrrole to the membrane composition did not influence on the selectivity, reproducibility and long-term stability of the microsensors but improved their standard potential stability in time in comparison with coated-wire type sensors. Moreover, all-solid-state microsensors based on Au transducers exhibited better signal stability than Ag based sensors.     

Metal island coated polymer sensor for direct determination of the volume effect of chaotropic agents

A new optical sensor is presented, based on the analyte reaction resulting in swelling and shrinking of a thin polymer layer. Changing the concentration of ions in a new bisazide photo-cross-linked poly(vinylpyrrolidone) polymer results in a concentration-dependent volume change of the hydrated gel. The volume response of the sensor induced by different ions is fully reversible over more than 250 cycles. The response of the device depends on the type, the charge and the concentration of the ions. The sensor material is part of an optical thin film system which transforms the variations in volume of the polymer into spectral information. The steady state of the sensor response is obtained within 60 s. The response time is mainly limited by the pump rate, the back pressure and the total volume of the system but not by the swelling of the sensor polymer. A comparative study of ion effects has demonstrated a fundamental correlation of the polymer swelling properties with the Hofmeister series of chaotropic agents. Thus it is concluded that the photopolymer, which is solubilized in aqueous solutions by the interaction of its amide structure with the solvent, behaves like the backbone amide structure of proteins.     

基于工业传感器示教平台的课堂教学改革

以学生发展为中心的教学理念逐渐深入人心,目前的传感课程存在一个实际问题——学生在课堂上学到的理论知识很难转变成实践能力。为了解决这个问题,自主开发了具有知识产权的工业传感器示教平台,在课堂上创设工业教学环境,现场演示或远程直播工业级传感器的测量实验,让同学们能把理论知识用得好。通过以上创新,解决了课堂教学的真实问题,提升了学生实践能力,建设为省一流本科课程。     

Floating Catalyst Chemical Vapor Deposition Patterning Nitrogen-Doped Single-Walled Carbon Nanotubes for Shape Tailorable and Flexible Micro-Supercapacitors

Micro-supercapacitors (MSCs) as high-power density energy storage units are designed to meet the booming development of flexible electronics, requiring simple and fast fabrication technology. Herein, a fast and direct solvent-free patterning method is reported to fabricate shape-tailorable and flexible MSCs by floating catalyst chemical vapor deposition (FCCVD). The nitrogen-doped single-walled carbon nanotubes (N-SWCNTs) are directly deposited on a patterned filter by FCCVD with designable patterns and facilely dry-transferred on versatile substrates. The obtained MSCs deliver an excellent areal capacitance of 3.6 mF cm⁻² and volumetric capacitance of 98.6 F cm⁻³ at a scan rate of 5 mV s⁻¹ along with excellent long-term cycle stability over 125 000 circles. Furthermore, the MSCs show good performance uniformity, which can be readily integrated via connection in parallel or series to deliver a stable high voltage (4 V with five serially connected devices) and large capacitance (5.1 mF with five parallel devices) at a scan rate of 100 mV s⁻¹, enabling powering the light emitting displays. Therefore, this method blazes the trail of directly preparing flexible, shape-customizable, and high-performance MSCs.     

High-Resolution and Stable Ruddlesden–Popper Quasi-2D Perovskite Flexible Photodetectors Arrays for Potential Applications as Optical Image Sensor

The development of an efficient fabrication route to achieve high-resolution perovskite pixel array is key for large-scale flexible image sensor devices. Herein, a high-resolution and stable 10 × 10 flexible PDs array based on formamidinium(FA⁺) and phenylmethylammonium (PMA⁺) quasi-2D (PMA)₂FAPb₂I₇ (n = 2) perovskite is demonstrated by developing SiO₂-assisted hydrophobic and hydrophilic treatment process on polyethylene terephthalate substrate. By introducing Au nanoparticles (Au NPs),  the perovskite film quality is improved and grain boundaries are reduced. The mechanism by which Au NPs upgrade the photoelectric quality of perovskite is mainly revealed by glow discharge-optical emission spectroscopy (GD-OES) and grazing-incidence wide-angle X-ray scattering (GIWAXS). To further improve the photoelectric performance of the devices, a post-treatment strategy with formamidinium chloride (FACl) is used . The optimized flexible PDs arrays show excellent optoelectronic properties with a high responsivity of 4.7 A W⁻¹, a detectivity of 6.3 × 10¹² Jones, and a broad spectral sensitivity. The device also exhibits excellent electrical stability even under severe bending and excellent flexural strength, as well as excellent environmental stability. Finally, the integrated flexible PDs arrays are used as sensor pixels in an imaging system to obtain high-resolution imaging patterns, demonstrating the imaging capability of the PDs arrays.     

Ultraprecise 3D Printed Graphene Aerogel Microlattices on Tape for Micro Sensors and E-Skin

3D printed graphene aerogels hold promise for flexible sensing fields due to their flexibility, low density, conductivity, and piezo-resistivity. However, low printing accuracy/fidelity and stochastic porous networks have hindered both sensing performance and device miniaturization. Here, printable graphene oxide (GO) inks are formulated through modulating oxygen functional groups, which allows printing of self-standing 3D graphene oxide aerogel microlattice (GOAL) with an ultra-high printing resolution of 70 µm. The reduced GOAL (RGOAL) is then stuck onto the adhesive tape as a facile and large-scale strategy to adapt their functionalities into target applications. Benefiting from the printing resolution of 70 µm, RGOAL tape shows better performance and data readability when used as micro sensors and robot e-skin. By adjusting the molecular structure of GO, the research realizes regulation of rheological properties of GO hydrogel and the 3D printing of lightweight and ultra-precision RGOAL, improves the sensing accuracy of graphene aerogel electronic devices and realizes the device miniaturization, expanding the application of graphene aerogel devices to a broader field such as micro robots, which is beyond the reach of previous reports.     

Toward Flexible Embodied Energy: Scale-Inspired Overlapping Lithium-Ion Batteries with High-Energy-Density and Variable Stiffness

High performance flexible batteries are essential ingredients for flexible devices. However, general isolated flexible batteries face critical challenges in developing multifunctional embodied energy systems, owing to the lack of integrative design. Herein, inspired by scales in creatures, overlapping flexible lithium-ion batteries (FLIBs) consisting of energy storage scales and connections using LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) and graphite electrodes are presented. The scale-dermis structure ensures a high energy density of 374.4 Wh L⁻¹ as well as a high capacity retention of 93.2% after 200 charge/discharge cycles and 40 000 bending times. A variable stiffness property is revealed that can be controlled by battery configurations and deformation modes. Furthermore, the overlapping FLIBs can be housed directly into the architecture of several flexible devices, such as robots and grippers, allowing to create multifunctionalities that go far beyond energy storage and include load-bearing and variable flexibility. This study broadens the versatility of FLIBs toward energy storage structure engineering of flexible devices.     

Bio-Inspired Artificial Fast-Adaptive and Slow-Adaptive Mechanoreceptors With Synapse-Like Functions

Development of artificial mechanoreceptors capable of sensing and pre-processing external mechanical stimuli is a crucial step toward constructing neuromorphic perception systems that can learn and store information. Here, bio-inspired artificial fast-adaptive (FA) and slow-adaptive (SA) mechanoreceptors with synapse-like functions are demonstrated for tactile perception. These mechanoreceptors integrate self-powered piezoelectric pressure sensors with synaptic electrolyte-gated field-effect transistors (EGFETs) featuring a reduced graphene oxide channel. The FA pressure sensor is based on a piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin film, while the SA pressure sensor is enabled by a piezoelectric ionogel with the piezoelectric-ionic coupling effect based on P(VDF-TrFE) and an ionic liquid. Changes in post-synaptic current are achieved through the synaptic effect of the EGFET by regulating the amplitude, number, duration, and frequency of tactile stimuli (pre-synaptic pulses). These devices have great potential to serve as artificial biological mechanoreceptors for future artificial neuromorphic perception systems.     

Soft Robotic-Adapted Multimodal Sensors Derived from Entirely Intrinsic Self-Healing and Stretchable Cross-Linked Networks

Flexible sensing technologies that play a pivotal role in endowing robots with detection capabilities and monitoring their motions are impulsively desired for intelligent robotics systems. However, integrating and constructing reliable and sustainable flexible sensors with multifunctionality for robots remains an everlasting challenge. Herein, an entirely intrinsic self-healing, stretchable, and attachable multimodal sensor is developed that can be conformally integrated with soft robots to identify diverse signals. The dynamic bonds cross-linked networks including the insulating polymer and conductive hydrogel with good comprehensive performances are designed to fabricate the sensor with prolonged lifespan and improved reliability. Benefiting from the self-adhesiveness of the hydrogel, strong interfacial bonding can be formed on various surfaces, which promotes the conformable integration of the sensor with robots. Due to the ionic transportation mechanism, the sensor can detect strain and temperature based on piezoresistive and thermoresistive effect, respectively. Moreover, the sensor can work in triboelectric mode to achieve self-powered sensing. Various information can be identified from the electrical signals generated by the sensor, including hand gestures, soft robot crawling motions, a message of code, the temperature of objects, and the type of materials, holding great promise in the fields of environmental detection, wearable devices, human-machine interfacing, and robotics.