Flexible Multimodal Magnetoresistive Sensors Based on Alginate/Poly(vinyl alcohol) Foam with Stimulus Discriminability for Soft Electronics Using Machine Learning.

Flexible foam-based sensors have attracted substantial interest due to their high specific surface area, light weight, superior deformability, and ease of manufacture. However, it is still a challenge to integrate multimodal stimuli-responsiveness, high sensitivity, reliable stability, and good biocompatibility into a single foam sensor. To achieve this, a magnetoresistive foam sensor was fabricated by an in situ freezing-polymerization strategy based on the interpenetrating networks of sodium alginate, poly(vinyl alcohol) in conjunction with glycerol, and physical reinforcement of core-shell bidisperse magnetic particles. The assembled sensor exhibited preferable magnetic/strain-sensing capability (GF ≈ 0.41 T-1 for magnetic field, 4.305 for tension, -0.735 for bending, and -1.345 for pressing), quick response time, and reliable durability up to 6000 cycles under external stimuli. Importantly, a machine learning algorithm was developed to identify the encryption information, enabling high recognition accuracies of 99.22% and 99.34%. Moreover, they could be employed as health systems to detect human physiological motion and integrated as smart sensor arrays to perceive external pressure/magnetic field distributions. This work provides a simple and ecofriendly strategy to fabricate biocompatible foam-based multimodal sensors with potential applications in next-generation soft electronics.

Study on the variable length simple pendulum oscillation based on the relative mode transfer method.

In this study, we employed the principle of Relative Mode Transfer Method (RMTM) to establish a model for a single pendulum subjected to sudden changes in its length. An experimental platform for image processing was constructed to accurately track the position of a moving ball, enabling experimental verification of the pendulum's motion under specific operating conditions. The experimental data demonstrated excellent agreement with simulated numerical results, validating the effectiveness of the proposed methodology. Furthermore, we performed simulations of a double obstacle pendulum system, investigating the effects of different parameters, including obstacle pin positions, quantities, and initial release angles, on the pendulum's motion through numerical simulations. This research provides novel insights into addressing the challenges associated with abrupt and continuous changes in pendulum length.

Flexible Grid Graphene Electrothermal Films for Real-Time Monitoring Applications.

Flexible electrothermal films are crucial for protecting equipment and systems in cold weather, such as ice blockages in natural gas pipelines and icing on aircraft wings. Therefore, a flexible electric heater is one of the essential devices in industrial operations. One of the main challenges is to develop flexible electrothermal films with low operating voltage, high steady-state temperature, and good mechanical stability. In this study, a flexible electrothermal film based on graphene-patterned structures was manufactured by combining the laser induction method and the transfer printing process. The grid structure design provides accurate real-time monitoring for the application of electrothermal films and shows potential in solving problems related to deicing and clearing ice blockages in pipelines. The flexible electrothermal film can reach a high heating temperature of 165 °C at 15 V and exhibits sufficient heating stability. By employing a simple and efficient method to create a flexible, high-performance electrothermal film, we provide a reliable solution for deicing and monitoring applications.

Mesoscopic Model for Reversible Adsorption Stage of Albumin and Fibrinogen on TiO2 Surface.

The competitive behavior of proteins in the reversible adsorption stage plays a crucial role in determining the composition of the protein layer and the subsequent biological responses to the biomaterial. However, such competitive adsorption is a mesoscopic process at physiological protein concentration, and neither a macroscopic experiment nor microscopic MD (molecular dynamics) simulation is suitable to clarify it. Here, we proposed a mesoscopic DPD (dissipative particle dynamics) model to illustrate the competitive process of albumin and fibrinogen on TiO2 surface with its parameters deduced from our previous MD simulation, and proved the model well retained the diffusion and adsorption properties of proteins in the competitive adsorption on the plane surface. We then applied the model to the competitive adsorption on the surfaces with different nanostructures and observed that when the nanostructure size is much larger than that of protein, the increase in surface area is the main influencing factor; when the nanostructure size is close to that of protein, the coordination between the nanostructure and the size and shape of protein significantly affects the competitive adsorption process. The model has revealed many mechanical phenomena observed in previous experimental studies and has the potential to contribute to the development of high-performance biomaterials.

3D Printing of Individualized Microfluidic Chips with DLP-Based Printer.

Microfluidic chips have shown their potential for applications in fields such as chemistry and biology, and 3D printing is increasingly utilized as the fabrication method for microfluidic chips. To address key issues such as the long printing time for conventional 3D printing of a single chip and the demand for rapid response in individualized microfluidic chip customization, we have optimized the use of DLP (digital light processing) technology, which offers faster printing speeds due to its surface exposure method. In this study, we specifically focused on developing a fast-manufacturing process for directly printing microfluidic chips, addressing the high cost of traditional microfabrication processes and the lengthy production times associated with other 3D printing methods for microfluidic chips. Based on the designed three-dimensional chip model, we utilized a DLP-based printer to directly print two-dimensional and three-dimensional microfluidic chips with photosensitive resin. To overcome the challenge of clogging in printing microchannels, we proposed a printing method that combined an open-channel design with transparent adhesive tape sealing. This method enables the rapid printing of microfluidic chips with complex and intricate microstructures. This research provides a crucial foundation for the development of microfluidic chips in biomedical research.

Naturally derived highly resilient and adhesive hydrogels with application as surgical adhesive.

The inadequacy of conventional surgical techniques for wound closure and repair in soft and resilient tissues may lead to poor healing outcomes such as local tissue fibrosis and contracture. Therefore, the development of adhesive and resilient hydrogels that can adhere firmly to irregular and dynamic wound interfaces and provide a "tension-free proximity" environment for tissue regeneration has become extremely important. Herein, we describe an integrated modeling-experiment-application strategy for engineering a promising hydrogel-based bioadhesive based on recombinant human collagen (RHC) and catechol-modified hyaluronic acid (HA-Cat). Molecular modeling and simulations were used to verify and explore the hypothesis that RHC and HA-Cat can form an assembly complex through physical interactions. The complex was synergistically crosslinked via a catechol/o-quinone coupling reaction and a carbodiimide coupling reactions, resulting in superior hydrogels with strong adhesion and resilience properties. The application of this bioadhesive to tissue adhesion and wound sealing in vivo was successfully demonstrated, with an optimum collagen index, epidermal thickness, and lowest scar width. Furthermore, subcutaneous implantation demonstrated that the bioadhesive exhibited good biocompatibility and degradability. This newly developed hydrogel may be a highly promising surgical adhesive for medical applications, including wound closure and repair.

Effects of six pyrimidine analogs on the growth of Tetrahymena thermophila and their implications in pyrimidine metabolism.

Tetrahymena are ciliated protists that have been used to study the effects of toxic chemicals, including anticancer drugs. In this study, we tested the inhibitory effects of six pyrimidine analogs (5-fluorouracil, floxuridine, 5'-deoxy-5-fluorouridine, 5-fluorouridine, gemcitabine, and cytarabine) on wild-type CU428 and conditional mutant NP1 Tetrahymena thermophila at room temperature and the restrictive temperature (37°C) where NP1 does not form the oral apparatus. We found that phagocytosis was not required for pyrimidine analog entry and that all tested pyrimidine analogs inhibited growth except for cytarabine. IC50 values did not significantly differ between CU428 and NP1 for the same analog at either room temperature or 37°C. To investigate the mechanism of inhibition, we used two pyrimidine bases (uracil and thymine) and three nucleosides (uridine, thymidine, and 5-methyluridine) to determine whether the inhibitory effects from the pyrimidine analogs were reversible. We found that the inhibitory effects from 5-fluorouracil could be reversed by uracil and thymine, from floxuridine could be reversed by thymidine, and from 5'-deoxy-5-fluorouridine could be reversed by uracil. None of the tested nucleobases or nucleosides could reverse the inhibitory effects of gemcitabine or 5-fluorouridine. Our results suggest that the five pyrimidine analogs act on different sites to inhibit T. thermophila growth and that nucleobases and nucleosides are metabolized differently in Tetrahymena.

Three dimensional high-performance micro-supercapacitors with switchable high power density and high energy density.

In the field of microscale energy storage, the fabrication of micro-supercapacitors (MSCs) with high power density and high energy density has always been a focus of research. In this work, laser-induced porous graphene and chemically deposited manganese dioxide nanoparticles are used as electrode materials, and a switchable MSC with two energy storage principles is obtained by designing symmetric interdigitated and square electrode structures. The aim is to overcome the preparation challenge of supercapacitors with high energy density and high power density by switching between two modes. In this MSC, the energy density of the high energy density mode (5.89 µW h cm-2) is 3.36 times that of the high power density mode (1.75 µW h cm-2), while the power density of the high power density mode (43.06 µW cm-2) is 1.44 times that of the high energy density mode (29.96 µW cm-2). In addition, under the drive of five serially connected MSCs, 27 LED lights can be continuously lit for 5 minutes. Therefore, this work provides a facile and novel method for the development of MSCs with high power density and high energy density, suggesting a great practical application value in the development of MSCs.

Preparation and Magnetic Manipulation of Fe3O4/Acrylic Resin Core-Shell Microspheres.

Core-shell microspheres refer to duo-layer or multilayer microspheres, which are widely used in drug delivery, microreactors, etc. Accurate manipulation of microspheres is a research hot spot, while traditional manipulation methods including ultrasonic manipulation and laser manipulation still face some limitations. In this study, magnetic core-shell microspheres were adopted to realize the accurate manipulation of microspheres. Combined with microfluidic technology, polystyrene sulfonic acid (PSSA)/Fe3O4 magnetic fluid was utilized as the core material and photosensitive acrylic resin became the shell material. After UV curing, a magnetic core-shell microsphere with an average size of 55 µm could be achieved, and the diameter was uniform and controllable. By adjusting the flow rate of the dispersed phase, the dual-core microspheres with different core particle sizes that ranged from 9.3 to 28.4 µm could be prepared. Experimental results showed that the prepared Fe3O4/acrylic resin core-shell microspheres can be used as functionalized microspheres that have good magnetic response properties and self-assembly ability. In addition, the magnetic manipulation and self-assembly of the prepared core-shell microspheres were presented with different external magnetic fields. The magnetic core-shell microspheres have shown great potential in the fields of biomedical engineering and targeted delivery of drugs.

A flexible electrochemical glucose sensing platform based on an electrospun PVA mat covered with in situ grown silver nanoparticles and a mixed self-assembled monolayer of glucose oxidase and ferrocene.

An electrochemical glucose sensor based on flexible materials is significant for wearable devices used for real-time health monitoring and diagnosis. However, applying flexible electrodes involves complex fabrication processes and might reduce detection sensitivity. To overcome these obstacles, we herein report a novel strategy for preparing a highly flexible enzyme electrode based on an electrospun poly(vinyl alcohol) (PVA) mat decorated with in situ grown silver nanoparticles (nano-Ag) for electrochemical glucose sensing. Ferrocene (Fc) was selected as an electron acceptor for glucose oxidase (GOD) in order to minimize the influence of oxygen. Electron transfer between GOD and Fc was facilitated by confining them within a mixed self-assembled monolayer (SAM) formed on a thin layer of gold deposited on top of the PVA/nano-Ag film. Nano-Ag was found to significantly increase the surface area of the electrode and improve the stability of electrode conductivity during tensile deformation. Electrochemical glucose detection was performed by chronoamperometry in the electroactivity domain of ferrocene, and good linearity (R2 = 0.993) was obtained in the range of 0.2-7 mM with a detection limit of 0.038 mM and a relative standard deviation (RSD) of 1.45% (n = 6). After being stuck to a bendable PDMS slice and bent, respectively, at 30° and 60° 50 times, the electrode showed slight changes in detection results (<4.78%), which remained within 8% when the bending angle increased to 90°. With its high flexibility, good detection performance, and convenient fabrication process, the proposed enzyme electrode showed good potential as a flexible platform for wearable glucose sensing systems.

Microparticle Manipulation Based on the Bulk Acoustic Wave Combined with the Liquid Crystal Backflow Effect Driving in 2D/3D Platforms.

Microparticle manipulation has been widely used in clinical diagnosis, cell separation, and biochemical analysis via optics, electronics, magnetics, or acoustic wave driving. Among them, the bulk acoustic wave (BAW) driving method has been increasingly adopted because of non-contact, easy control, and precise manipulation. However, its low manipulation efficiency limits the usage of the BAW driving in high viscosity solutions. Therefore, in order to obtain larger driving force and more flexible manipulation of microparticles, both two-dimensional (2D) and three-dimensional (3D) platforms based on the BAW and liquid crystal backflow effect (LCBE) driving in liquid crystal (LC) solutions are proposed. The driving forces applied on the microparticles allow for the change of microparticle moving direction, which is also ascertained through theory analysis combined with various driving methods. Specifically, the maximum moving speed (68.78 µm/s) of the polystyrene particles is obtained by the BAW (13 Vpp) combined with LCBE (30 V) at a low frequency of 7.2 kHz in the 2D platform. Precise position manipulation in 3D is also fulfilled through a programmable logic control model using polystyrene particles as a demonstration. In addition, red blood cells mixed with LC solutions are arranged in a line or gathered in the pressure nodes of the BAW forces along with sinusoid signals generated by various transducer combinations. Therefore, it is approved that the LC solution that induces the LCBE force could increase the microparticle manipulation efficiency in both 2D and 3D platforms. The proposed method will open up new avenues in particle manipulation and benefit a variety of applications in cell separation, drug synthesis, analytical chemistry, and others.

A plantar wearable pressure sensor based on hybrid lead zirconate-titanate/microfibrillated cellulose piezoelectric composite films for human health monitoring.

Flexible and wearable electronic sensors hold great promise for improving the quality of life, especially in the field of healthcare monitoring, owing to their low cost, flexibility, high electromechanical coupling performance, high sensitivity, and biocompatibility. To achieve high piezoelectric performance similar to that of rigid materials while satisfying the flexible requirements for wearable sensors, we propose novel hybrid films based on lead zirconate titanate powder and microfibrillated cellulose (PZT/MFC) for plantar pressure measurements. The flexible films made using the polarization process are tested. It was found that the maximum piezoelectric coefficient was 31 pC N-1 and the maximum tensile force of the flexible films was 26 N. A wide range of bending angles between 15° and 180° proves the flexibility capability of the films. In addition, the charge density shows a proportional relation with the applied mechanical force, and it could sense stress of 1 kPa. Finally, plantar pressure sensors are arranged and packaged with a film array followed by connection with the detection module. Then, the pressure curves of each point on the plantar are obtained. Through analysis of the curve, several parameters of human body motions that are important in the rehabilitation of diabetic patients and the detection of sports injury can be performed, including stride frequency, length and speed. Overall, the proposed PZT/MFC wearable plantar pressure sensor has broad application prospects in the field of sports injury detection and medical rehabilitation training.