Highly Sensitive Pressure Sensor Based on Elastic Conductive Microspheres.

Elastic pressure sensors play a crucial role in the digital economy, such as in health care systems and human-machine interfacing. However, the low sensitivity of these sensors restricts their further development and wider application prospects. This issue can be resolved by introducing microstructures in flexible pressure-sensitive materials as a common method to improve their sensitivity. However, complex processes limit such strategies. Herein, a cost-effective and simple process was developed for manufacturing surface microstructures of flexible pressure-sensitive films. The strategy involved the combination of MXene-single-walled carbon nanotubes (SWCNT) with mass-produced Polydimethylsiloxane (PDMS) microspheres to form advanced microstructures. Next, the conductive silica gel films with pitted microstructures were obtained through a 3D-printed mold as flexible electrodes, and assembled into flexible resistive pressure sensors. The sensor exhibited a sensitivity reaching 2.6 kPa-1 with a short response time of 56 ms and a detection limit of 5.1 Pa. The sensor also displayed good cyclic stability and time stability, offering promising features for human health monitoring applications.

A Sensitivity-Optimized Flexible Capacitive Pressure Sensor with Cylindrical Ladder Microstructural Dielectric Layers.

Flexible capacitive pressure sensors have attracted extensive attention due to their dynamic response and good sensing capability for static and small pressures. Using microstructural dielectric layers is an effective method for improving performance. However, the current state of microstructure design is primarily focused on basic shapes and is largely limited by simulation results; there is still a great deal of potential for further innovation and improvement. This paper innovatively proposes to increase the ladder structure based on the basic microstructures, for example, the long micro-ridge ladder, the cuboid ladder, and cylindrical ladder microstructures. By comparing 9 kinds of microstructures including ladder structure through finite element simulation, it is found that the sensor with a cylindrical ladder microstructure dielectric layer has the highest sensitivity. The dielectric layers with various microstructures are obtained by 3D printed molds, and the sensor with cylindrical ladder microstructure dielectric layer has the sensitivity of 0.12 kPa-1, which is about 3.9 times higher than that without microstructure. The flexible pressure sensor developed by us boasts sensitivity-optimized and operational stability, making it an ideal solution for monitoring rainfall frequency in real time.

Quasi-1D Conductive Network Composites for Ultra-Sensitive Strain Sensing.

Highly performance flexible strain sensor is a crucial component for wearable devices, human-machine interfaces, and e-skins. However, the sensitivity of the strain sensor is highly limited by the strain range for large destruction of the conductive network. Here the quasi-1D conductive network (QCN) is proposed for the design of an ultra-sensitive strain sensor. The orientation of the conductive particles can effectively reduce the number of redundant percolative pathways in the conductive composites. The maximum sensitivity will reach the upper limit when the whole composite remains only "one" percolation pathway. Besides, the QCN structure can also confine the tunnel electron spread through the rigid inclusions which significantly enlarges the strain-resistance effect along the tensile direction. The strain sensor exhibits state-of-art performance including large gauge factor (862227), fast response time (24 ms), good durability (cycled 1000 times), and multi-mechanical sensing ability (compression, bending, shearing, air flow vibration, etc.). Finally, the QCN sensor can be exploited to realize the human-machine interface (HMI) application of acoustic signal recognition (instrument calibration) and spectrum restoration (voice parsing).

Advances in Flexible Magnetosensitive Materials and Devices for Wearable Electronics.

Emerging fields, such as wearable electronics, digital healthcare, the Internet of Things, and humanoid robots, highlight the need for flexible devices capable of recording signals on curved surfaces and soft objects. In particular, flexible magnetosensitive devices garner significant attention owing to their ability to combine the advantages of flexible electronics and magnetoelectronic devices, such as reshaping capability, conformability, contactless sensing, and navigation capability. Several key challenges must be addressed to develop well-functional flexible magnetic devices. These include determining how to make magnetic materials flexible and even elastic, understanding how the physical properties of magnetic films change under external strain and stress, and designing and constructing flexible magnetosensitive devices. In recent years, significant progress is made in addressing these challenges. This study aims to provide a timely and comprehensive overview of the most recent developments in flexible magnetosensitive devices. This includes discussions on the fabrications and mechanical regulations of flexible magnetic materials, the principles and performances of flexible magnetic sensors, and their applications for wearable electronics. In addition, future development trends and challenges in this field are discussed.

Structural Design and DLP 3D Printing Preparation of High Strain Stable Flexible Pressure Sensors.

Flexible pressure sensors are crucial force-sensitive devices in wearable electronics, robotics, and other fields due to their stretchability, high sensitivity, and easy integration. However, a limitation of existing pressure sensors is their reduced sensing accuracy when subjected to stretching. This study addresses this issue by adopting finite element simulation optimization, using digital light processing (DLP) 3D printing technology to design and fabricate the force-sensitive structure of flexible pressure sensors. This is the first systematic study of how force-sensitive structures enhance tensile strain stability of flexible resistive pressure sensors. 18 types of force-sensitive structures have been investigated by finite element design, simultaneously, the modulus of the force-sensitive structure is also a critical consideration as it exerts a significant influence on the overall tensile stability of the sensor. Based on simulation results, a well-designed and highly stretch-stable flexible resistive pressure sensor has been fabricated which exhibits a resistance change rate of 0.76% and pressure sensitivity change rate of 0.22% when subjected to strains ranging from no tensile strain to 20% tensile strain, demonstrating extremely low stretching response characteristics. This study presents innovative solutions for designing and fabricating flexible resistive pressure sensors that maintain stable sensing performance even under stretch conditions.

Spontaneously Restoring Specific Bioaffinity of RGD in Linear RGD-containing Peptides by Conjugation with Zwitterionic Dendrimers.

Peptides are more versatile than small molecule drugs, but their specific bioaffinities are usually lower than their original native proteins because of the loss of preferred conformations. To overcome this key obstacle, we demonstrated a hydrogen bond-induced conformational constraint method to enhance the specific bioaffinities of peptides to achieve a high success rate by using linear RGD-containing peptides as a model of bioactive peptides. By performing molecular simulation, we found that the chemically immobilized linear CRGDS via cysteine (C) at the N-terminus on zwitterionic PAMAM G-5 can not only spontaneously restore the natural conformation of the RGD segment through the assistance of the dynamic hydrogen bond from serine (S) at the C-terminus of the peptide, but it can also narrow the distribution of all possible conformations. Consequently, the conjugates showed comparable or even better high affinity than native proteins without the use of conventional, labor-intensive, synthesis-based structure search methods to construct a binding conformation. In addition, the conjugates showed globular protein-like characteristics chemically, physically, and physiologically. They exhibited not only high efficacy and biosafety both in vitro and in vivo, but they also showed extremely high thermostability even upon boiling in a solution. This approach offers great design flexibility for reviving functional peptides without impairing their high specific affinity for their targets. STATEMENT OF SIGNIFICANCE: In this work, we developed a swift approach to spontaneously restore the natural conformation of a linear peptide from a nature protein and thus enhance its specific bioaffinity instead of constructing a binding conformation by the labor-intensive, synthesis-based structure search method. In details, our new approach involves dynamically constraining the linear peptide on a zwitterionic PAMAM G-5 surface by a combination of chemical bonding at one terminus and dynamic hydrogen bonding at the other terminus of the linear peptide. The zwitterionic background offers abundant interaction sites for hydrogen bonding as well as resistance to nonspecific interactions. This approach fully restores the specific bioaffinity of RGD segments on a zwitterionic PAMAM G-5 through only one conjugation point at the C-terminus of the peptide. Moreover, the bioaffinity of all three types of RGD-containing peptides is successfully restored, which indicates the high rate of success of this approach in affinity restoring.

Peritoneal adhesions: Occurrence, prevention and experimental models.

Peritoneal adhesions (PA) are a postoperative syndrome with high incidence rate, which can cause chronic abdominal pain, intestinal obstruction, and female infertility. Previous studies have identified that PA are caused by a disordered feedback of blood coagulation, inflammation, and fibrinolysis. Monocytes, macrophages, fibroblasts, and mesothelial cells are involved in this process, and secreted signaling molecules, such as tumor necrosis factor alpha (TNF-α), interleukin-10 (IL-10), tissue plasminogen activator (tPA), and type 1 plasminogen activator inhibitor (PAI-1), play a key role in PA development. There have been many attempts to prevent PA formation by anti-PA drugs, barriers, and other therapeutic methods, but their effectiveness has not been widely accepted. Treatment by biomaterial-based barriers is believed to be the most promising method to prevent PA formation in recent years. In this review, the pathogenesis, treatment approaches, and animal models of PA are summarized and discussed to understand the challenges faced in the biomaterial-based anti-PA treatments.

Enhancing the Low-Frequency Induction Heating Effect of Magnetic Composites for Medical Applications.

This study aims to enhance the low-frequency induction heating (LFIH) effect in a thermoplastic polymer doped with iron oxide magnetic particles, which are promising candidates for several medical applications thanks to their confirmed biocompatibility. Two main approaches were proposed to successfully boost the heating ability; i.e., improving the magnetic concentration of the composite with higher filler content of 30 wt %, and doubling the frequency excitation after optimization of the inductor design. To test the magnetic properties of the ferromagnetic composite, a measurement of permeability as a function of temperature, frequency, and particle content was carried out. Thermal transfer based COMSOL simulations together with experimental tests have been performed, demonstrating feasibility of the proposed approach to significantly enhance the target temperature in a magnetic composite. These results are encouraging and confirmed that IH can be exploited in medical applications, especially for the treatment of varicose veins where local heating remains a true challenge.