A lower critical solution temperature (LCST) in an aqueous environment has been observed with poly(N-isopropylacrylamide) (pNIPAM) deposited onto solid surfaces from a plasma glow discharge of NIPAM vapor. The synthesis and spectroscopic data (ESCA, FTIR) for the plasma polymerized NIPAM (ppNIPAM) shows a remarkable retention of the monomer structure. The phase transition at 29 degrees C was measured by a novel AFM method. The phase transition was surprising because of the expectation that the plasma environment would destroy the specific NIPAM structure associated with the thermal responsiveness. The phase change of ppNIPAM is also responsible for the changes in the level of the meniscus when coated capillaries are placed in warm and cold water. Plasma polymerization of NIPAM represents a one-step method to fabricate thermally responsive coatings on real-world biomaterials without the need for specially prepared substrates and functionalized polymers.
While 3D printing of rechargeable batteries has received immense interest in advancing the next generation of 3D energy storage devices, challenges with the 3D printing of electrolytes still remain. Additional processing steps such as solvent evaporation were required for earlier studies of electrolyte fabrication, which hindered the simultaneous production of electrode and electrolyte in an all-3D-printed battery. Here, a novel method is demonstrated to fabricate hybrid solid-state electrolytes using an elevated-temperature direct ink writing technique without any additional processing steps. The hybrid solid-state electrolyte consists of solid poly(vinylidene fluoride-hexafluoropropylene) matrices and a Li -conducting ionic-liquid electrolyte. The ink is modified by adding nanosized ceramic fillers to achieve the desired rheological properties. The ionic conductivity of the inks is 0.78 × 10 S cm . Interestingly, a continuous, thin, and dense layer is discovered to form between the porous electrolyte layer and the electrode, which effectively reduces the interfacial resistance of the solid-state battery. Compared to the traditional methods of solid-state battery assembly, the directly printed electrolyte helps to achieve higher capacities and a better rate performance. The direct fabrication of electrolyte from printable inks at an elevated temperature will shed new light on the design of all-3D-printed batteries for next-generation electronic devices.
In the field of robotics, researchers are aiming to develop soft or partially soft bodied robots that utilize the motion and control system of various living organisms in nature. These robots have the potential to be robust and versatile, even safer for human interaction compared to traditional rigid robots. Soft robots based on biomimetic principles are being designed for real life applications by paying attention to different shape, geometry, and actuation systems in these organisms that respond to surrounding environments and stimuli. Especially, caterpillars or inchworms have garnered attention due to their soft compliant structure and crawling locomotion system making them ideal for maneuvering in congested spaces as a transport function. Currently, there are two major challenges with design and fabrication of such soft robots: using an efficient actuation system and developing a simple manufacturing process. Different actuation systems have been explored, which include shape memory alloy based coils and hydraulic and pneumatic actuators. However, the intrinsic limitations due to overall size and control system of these actuators prevent their integration in flexibility, lightweight, and compact manner, limiting practical and untethered applications. In comparison, magnetic actuation demonstrates simple wireless noncontact control. In terms of manufacturing process, additive manufacturing has emerged as an effective tool for obtaining structural complexity with high resolution, accuracy, and desired geometry. This study proposes a fully three-dimensional (3D) printed, monolithic, and tetherless inchworminspired soft robot that uses magnetic actuation for linear locomotion and crawling. Its structure is multimaterial heterogeneous particle-polymer composite with locally programmed material compositions. This soft robot is directly printed in one piece from a 3D computer model, without any manual assembly or complex processing steps, and it can be controlled by an external wireless force. This article presents its design and manufacturing with the novel magnetic field assisted projection stereolithography technique. Analytical models and numerical simulations of the crawling locomotion of the soft robot are also presented and compared with the experimental results of the 3D printed prototype. The overall locomotion mechanism of the magnetically actuated soft robot is evaluated with friction tests and stride efficiency analysis.
The ability to print fully packaged integrated energy storage components (e.g., supercapacitors) is of critical importance for practical applications of printed electronics. Due to the limited variety of printable materials, most studies on printed supercapacitors focus on printing the electrode materials but rarely the full-packaged cell. This work presents for the first time the printing of a fully packaged single-wall carbon nanotube-based supercapacitor with direct ink writing (DIW) technology. Enabled by the developed ink formula, DIW setup, and cell architecture, the whole printing process is mask free, transfer free, and alignment free with precise and repeatable control on the spatial distribution of all constituent materials. Studies on cell design show that a wider electrode pattern and narrower gap distance between electrodes lead to higher specific capacitance. The as-printed fully packaged supercapacitors have energy and power performances that are among the best in recently reported planar carbon-based supercapacitors that are only partially printed or nonprinted.
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