Mechanical Mismatch Research Articles

Composite Hydrogel Sealants for Annulus Fibrosus Repair.

Intervertebral disc (IVD) herniation is a leading cause of disability and lower back pain, causing enormous socioeconomic burdens. The standard of care for disc herniation is nucleotomy, which alleviates pain but does not repair the annulus fibrosus (AF) defect nor recover the biomechanical function of the disc. Existing bioadhesives for AF repair are limited by insufficient adhesion and significant mechanical and geometrical mismatch with the AF tissue, resulting in the recurrence of protrusion or detachment of bioadhesives. Here, we report a composite hydrogel sealant constructed from a composite of a three-dimensional (3D)-printed thermoplastic polyurethane (TPU) mesh and tough hydrogel. We tailored the fiber angle and volume fraction of the TPU mesh design to match the angle-ply structure and mechanical properties of native AF. Also, we proposed and tested three types of geometrical design of the composite hydrogel sealant to match the defect shape and size. Our results show that the sealant could mimic native AF in terms of the elastic modulus, flexural modulus, and fracture toughness and form strong adhesion with the human AF tissue. The bovine IVD tests show the effectiveness of the composite hydrogel sealant for AF repair and biomechanics recovery and for preventing herniation with its heightened stiffness and superior adhesion. By harnessing the combined capabilities of 3D printing and bioadhesives, these composite hydrogel sealants demonstrate promising potential for diverse applications in tissue repair and regeneration.

Assessing the Effect of Twisting and Twisting Fatigue on ZnO:Al Thin Film Performance on PEN and PET Substrates.

This study examines the electromechanical characteristics of aluminium-doped zinc oxide (AZO) films. The films were produced using the RF magnetron sputtering process with a consistent thickness of 150 nm on various polymer substrates. The study focuses on assessing the electro-mechanical failure processes of coated segments using flexible substrates, namely polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), with a specific emphasis on typical cracking and delamination occurrences. This examination involves conducting twisting deformation together with using standardised electrical resistance measurements and optical microscope monitoring instruments. It was found that the crack initiation angle is mostly dependent on the mechanical mismatch between the coating and substrate. Higher critical twisting angle values are observed for the AZO/PEN film during twisting testing. Relative to the perpendicular plane of the untwisted sample, it was found that cracks initiated at a twist angle equal to 42° ± 2.1° and 38° ± 1.7° for AZO/PEN and AZO/PET, respectively, and propagated along the sample length. SEM images indicate that the twisting motion results in deformation in the thin film material, leading to the presence of both types of stress in the film structure. These discoveries emphasise the significance of studying the mechanical properties of thin films under different stress conditions, as it can impact their performance and reliability in real-world applications. The electromechanical stability of AZO was found to be similar on both substrates during fatigue testing. Studying the electromechanical properties of various material combinations is important for selecting polymer substrates and predicting the durability of flexible electronic devices made from polyester.

High‐Resolution Printing‐Based Vertical Interconnects for Flexible Hybrid Electronics

AbstractFlexible hybrid electronics (FHE) is an emerging area that combines printed electronics and ultra‐thin chip (UTC) technology to deliver high performance needed in applications such as wearables, robotics, and internet‐of‐things etc. The integration of UTCs on flexible substrates and the access to devices on them requires high resolution interconnects, which is a challenging task as thermal and mechanical mismatches do not allow conventional bonding methods to work. To address this challenge, the resource‐efficient, area‐efficient, and low‐cost printing routes for obtaining vertical interconnection accesses (VIAs) are demonstrated here. It is demonstrated how high‐resolution printers (electrohydrodynamic and extrusion‐based direct‐ink writing printers) can be used for patterning of high‐resolution, freeform, vertical conductive structures. To access the transistors on UTCs, the VIAs, obtained using conventional photolithography and plasma etching steps, are filled with conductive silver nanoparticle‐based ink/paste using high‐resolution printers. Comprehensive studies are performed to compare and benchmark in terms of: i) the printing speed and throughput of the printers, ii) the electrical performance of vertically connected transistors in UTCs, and iii) the electrical performance stability of FHE system (interconnects and UTCs) under mechanical bending conditions. This in‐depth study shows the potential use of printing technologies for development of high‐density 3D integrated FHE systems.

Annular Conductive Hydrogel-Mediated Wireless Electrical Stimulation for Augmenting Neurogenesis.

Electrical stimulation (ES) has a remarkable capacity to regulate neuronal differentiation and neurogenesis in the treatment of various neurological diseases. However, wired devices connected to the stimulating electrode and the mechanical mismatch between conventional rigid electrodes and soft tissues restrict their motion and cause possible infections, thereby limiting their clinical utility. An approach integrating the advantages of wireless techniques and soft hydrogels provides new insights into ES-induced nerve regeneration. Herein, a flexible and implantable wireless ES-responsive electrode based on an annular gelatin methacrylate-polyaniline (Gel/Pani) hydrogel is fabricated and used as a secondary coil to achieve wireless ES via electromagnetic induction in the presence of a primary coil. The Gel/Pani hydrogels exhibit favorable biocompatibility, biodegradability, conductivity, and compression resistance. The annular electrode of the Gel/Pani conductive hydrogel (AECH) supports neural stem cell growth, while the applied wireless ES facilitates neuronal differentiation and the formation of functional neural networks in vitro. Furthermore, AECH is implanted in vivo in rats with ischemic stroke and the results reveal that AECH-mediated wireless ES significantly ameliorates brain impairment and neurological function by activating endogenous neurogenesis. This novel flexible hydrogel system addresses wireless stimulation and implantable technical challenges, holding great potential for the treatment of neurodegenerative diseases.

Lattice optimization of fiber-reinforced polymer parts fabricated by additive manufacturing: the impact of Bezier curve order on mechanical properties

PurposeLattice structures are widely used for achieving optimal topology in additive manufacturing. However, the use of different lattices in a single design can result in stress concentrations at the transition points. This study aims to investigate the influence of Bezier curves on mechanical properties during the transformation from one lattice structure to another. It specifically focuses on the transition from a hexagonal to diamond lattice, using Bezier curves of various orders.Design/methodology/approachThe curves were designed by passing them through the same control points for different orders, such as third, fifth and seventh. The samples were sliced for 3D printing, and a tensile test was conducted. Young’s modulus and energy absorption abilities were measured to compare the mechanical properties of the models created with Bezier curves for the transformation between hexagonal and diamond models.FindingsThe analysis revealed a gradual change in mechanical properties from the hexagonal to the diamond lattice. Moreover, different orders of Bezier curves exhibited varying mechanical properties during the transformation between the two lattices. As the order of the Bezier curve increased, the mechanical properties smoothly changed from the hexagonal to diamond lattice. This prevented stress concentrations or mechanical behavior mismatch caused by sudden deformations at the transitions between the curves used in the design.Originality/valueThe study’s innovative use of Bezier curves of different orders to smoothly transformation between hexagonal and diamond lattices in additive manufacturing offers a practical solution to prevent stress concentrations and mechanical inconsistencies during such design transitions.

Soft Bioelectronics Using Nanomaterials and Nanostructures for Neuroengineering.

The identification of neural networks for large areas and the regulation of neuronal activity at the single-neuron scale have garnered considerable attention in neuroscience. In addition, detecting biochemical molecules and electrically, optically, and chemically controlling neural functions are key research issues. However, conventional rigid and bulky bioelectronics face challenges for neural applications, including mechanical mismatch, unsatisfactory signal-to-noise ratio, and poor integration of multifunctional components, thereby degrading the sensing and modulation performance, long-term stability and biocompatibility, and diagnosis and therapy efficacy. Implantable bioelectronics have been developed to be mechanically compatible with the brain environment by adopting advanced geometric designs and utilizing intrinsically stretchable materials, but such advances have not been able to address all of the aforementioned challenges.Recently, the exploration of nanomaterial synthesis and nanoscale fabrication strategies has facilitated the design of unconventional soft bioelectronics with mechanical properties similar to those of neural tissues and submicrometer-scale resolution comparable to typical neuron sizes. The introduction of nanotechnology has provided bioelectronics with improved spatial resolution, selectivity, single neuron targeting, and even multifunctionality. As a result, this state-of-the-art nanotechnology has been integrated with bioelectronics in two main types, i.e., bioelectronics integrated with synthesized nanomaterials and bioelectronics with nanoscale structures. The functional nanomaterials can be synthesized and assembled to compose bioelectronics, allowing easy customization of their functionality to meet specific requirements. The unique nanoscale structures implemented with the bioelectronics could maximize the performance in terms of sensing and stimulation. Such soft nanobioelectronics have demonstrated their applicability for neuronal recording and modulation over a long period at the intracellular level and incorporation of multiple functions, such as electrical, optical, and chemical sensing and stimulation functions.In this Account, we will discuss the technical pathways in soft bioelectronics integrated with nanomaterials and implementing nanostructures for application to neuroengineering. We traced the historical development of bioelectronics from rigid and bulky structures to soft and deformable devices to conform to neuroengineering requirements. Recent approaches that introduced nanotechnology into neural devices enhanced the spatiotemporal resolution and endowed various device functions. These soft nanobioelectronic technologies are discussed in two categories: bioelectronics with synthesized nanomaterials and bioelectronics with nanoscale structures. We describe nanomaterial-integrated soft bioelectronics exhibiting various functionalities and modalities depending on the integrated nanomaterials. Meanwhile, soft bioelectronics with nanoscale structures are explained with their superior resolution and unique administration methods. We also exemplified the neural sensing and stimulation applications of soft nanobioelectronics across various modalities, showcasing their clinical applications in the treatment of neurological diseases, such as brain tumors, epilepsy, and Parkinson's disease. Finally, we discussed the challenges and direction of next-generation technologies.

Modelling of microscopic crack initiation behaviour of fretting fatigue based on X-ray micro-computed tomography scan

Fretting fatigue is a particularly destructive form of fatigue failure that has drawn significant attention from researchers. This paper proposes a numerical modelling method based on tomography scan to investigate the impact of inclusions on fretting fatigue crack initiation behaviour. The results reveal that inclusions can affect the crack initiation direction and reduce the initiation lifetime. The difference between the properties of inclusions and matrix leads to local mechanical response mismatch, resulting in local stress, strain, and damage concentration. The mismatch in strain and damage follows a gradient distribution along the thickness as the distribution in these mechanical responses. These could explain why particles closer to the surface are more likely to cause damage. Additionally, the aggregation distribution of inclusions results in merging and connecting local regions with high stress, strain, and damage concentration, ultimately promoting fracture behaviour. Finally, the numerical models are validated with experimental data from fretting fatigue tests. Compared to the homogeneous model, the numerical model that considers inclusions from topography data can more accurately analyse the material damage and provide a more comprehensive understanding of fretting fatigue behaviour.

A stretchable, electroconductive tissue adhesive for the treatment of neural injury

AbstractSuccessful nerve repair using bioadhesive hydrogels demands minimizing tissue–material interfacial mechanical mismatch to reduce immune responses and scar tissue formation. Furthermore, it is crucial to maintain the bioelectrical stimulation‐mediated cell‐signaling mechanism to overcome communication barriers within injured nerve tissues. Therefore, engineering bioadhesives for neural tissue regeneration necessitates the integration of electroconductive properties with tissue‐like biomechanics. In this study, we propose a stretchable bioadhesive based on a custom‐designed chemically modified elastin‐like polypeptides (ELPs) and a choline‐based bioionic liquid (Bio‐IL), providing an electroconductive microenvironment to reconnect damaged nerve tissue. The stretchability akin to native neural tissue was achieved by incorporating hydrophobic ELP pockets, and a robust tissue adhesion was obtained due to multi‐mode tissue–material interactions through covalent and noncovalent bonding at the tissue interface. Adhesion tests revealed adhesive strength ~10 times higher than commercially available tissue adhesive, Evicel®. Furthermore, the engineered hydrogel supported in vitro viability and proliferation of human glial cells. We also evaluated the biodegradability and biocompatibility of the engineered bioadhesive in vivo using a rat subcutaneous implantation model, which demonstrated facile tissue infiltration and minimal immune response. The outlined functionalities empower the engineered elastic and electroconductive adhesive hydrogel to effectively enable sutureless surgical sealing of neural injuries and promote tissue regeneration.

Integrated Parameter Identification Based on a Topological Structure for Servo Resonance Suppression

In the dual-inertia servo system, the servo resonance in which the characteristics are closely related to the mechanical parameters is usually suppressed by adding a notch filter. As a result, accurate mechanical parameter identification facilitates adjusting the notch parameters and avoiding the failed servo resonance suppression caused by the mechanical parameter mismatch. In this paper, a topological structure expanded by five improved Sliding-Mode Observers (ISMOs) is proposed to simultaneously identify the load speed, the motor inertia, the load inertia, the stiffness coefficient, and the load disturbance, where the load speed and the load disturbance are considered as intermediate variables to provide sufficient load-side information to ensure the identification accuracy of the mechanical parameters. Furthermore, according to the natural knowledge of the dual-inertia servo system, a time-varying interconnected gain with an equal derivative to the identification parameter in each ISMO is designed to promote the global convergence of the topological structure. Finally, the identified mechanical parameters are utilized to adjust the notch parameters for the servo resonance suppression. Simulation and experimental results are presented to indicate the superiority of the topological structure and the effectiveness of the servo resonance suppression.

Softening implantable bioelectronics: Material designs, applications, and future directions

Implantable bioelectronics, integrated directly within the body, represent a potent biomedical solution for monitoring and treating a range of medical conditions, including chronic diseases, neural disorders, and cardiac conditions, through personalized medical interventions. Nevertheless, contemporary implantable bioelectronics rely heavily on rigid materials (e.g., inorganic materials and metals), leading to inflammatory responses and tissue damage due to a mechanical mismatch with biological tissues. Recently, soft electronics with mechanical properties comparable to those of biological tissues have been introduced to alleviate fatal immune responses and improve tissue conformity. Despite their myriad advantages, substantial challenges persist in surgical handling and precise positioning due to their high compliance. To surmount these obstacles, softening implantable bioelectronics has garnered significant attention as it embraces the benefits of both rigid and soft bioelectronics. These devices are rigid for easy standalone implantation, transitioning to a soft state in vivo in response to environmental stimuli, which effectively overcomes functional/biological problems inherent in the static mechanical properties of conventional implants. This article reviews recent research and development in softening materials and designs for implantable bioelectronics. Examples featuring tissue-penetrating and conformal softening devices highlight the promising potential of these approaches in biomedical applications. A concluding section delves into current challenges and outlines future directions for softening implantable device technologies, underscoring their pivotal role in propelling the evolution of next-generation bioelectronics.

Calculation and Discussion for Crack Driving Force of Dissimilar Metal Welded Joint of Nuclear Power Equipment Nozzle and Safe End

This study investigates the effects of the material mechanical properties heterogeneity and strength mismatch variation on crack driving forces for cracks in a dissimilar metal welded joint (DMW) of a reactor pressure vessel inlet nozzle to the safe end. Linear elastic and elastic-plastic analyses are carried out to calculate the stress intensity factor (SIF) and J-integral for cracks in the DMW. The effects of crack locations, crack depths, and strength mismatch factors on the SIF and J-integral are studied. The SIF results obtained by finite element analysis are compared with those obtained by the influence function method adopted in the nuclear power code. Results show that the effect of crack location on the SIF can be ignored. The SIFs calculated by the influence function method for cracks in the DMW are basically reasonable, although its conservatism is slightly insufficient. Moreover, with moving the crack location from the nozzle through buttering and weld metal to the safe end, the J-integral increases. The effect of the crack location and strength mismatch factors on the J-integral is essentially caused by variation of the plastic zone and the material properties of the crack front. The crack sizes affect the level of influence of the crack location and the strength mismatch factors on the J-integral. The J-integral increases with decrease of the strength mismatch factor.

A Superhuman Sensing Triboelectric Nanogenerator with Boosted Power Density and Durability via a Bio‐Inspired Janus Structure

AbstractTriboelectric nanogenerators (TENG) not only enable sustainable self‐powered sensing of devices, but also have superhuman noncontact/contact identification capabilities, which are propelling humanity toward the intelligent era. However, the inherently low dielectric constant of triboelectric materials as well as the mechanical mismatch between electrodes and dielectric materials severely limited their efficient and stable output performance. Taking inspiration from the asymmetric structure and function of human skin, a novel single‐electrode TENG is developed, whose electrode and dielectric layer are integrated in a Janus architecture. By tuning the balance between gravity and the internal noncovalent interactions, gradient dispersion of carbon nanotubes in waterborne polyurethane networks can be feasibly achieved, which can boost the device performance by reinforcement in both the charge trapping capacity of the dielectric layer and the charge transfer of the electrode layer. As a proof‐of‐concept, triboelectric sensing and deep learning are integrated to realize the evolution from perception to identification under both noncontact (motion prediction) and contact (material identification) modes. The bionic design strategy of gradient Janus film can offer valuable insights into improving the output performance and durability of TENG. Additionally, the proximal prediction and tactile identification functions are also desirable attempts for future human‐machine interfaces.

Biodegradable suture development-based albumin composites for tissue engineering applications

Recent advancements in the field of biomedical engineering have underscored the pivotal role of biodegradable materials in addressing the challenges associated with tissue regeneration therapies. The spectrum of biodegradable materials presently encompasses ceramics, polymers, metals, and composites, each offering distinct advantages for the replacement or repair of compromised human tissues. Despite their utility, these biomaterials are not devoid of limitations, with issues such as suboptimal tissue integration, potential cytotoxicity, and mechanical mismatch (stress shielding) emerging as significant concerns. To mitigate these drawbacks, our research collective has embarked on the development of protein-based composite materials, showcasing enhanced biodegradability and biocompatibility. This study is dedicated to the elaboration and characterization of an innovative suture fabricated from human serum albumin through an extrusion methodology. Employing a suite of analytical techniques—namely tensile testing, scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA)—we endeavored to elucidate the physicochemical attributes of the engineered suture. Additionally, the investigation extends to assessing the influence of integrating biodegradable organic modifiers on the suture's mechanical performance. Preliminary tensile testing has delineated the mechanical profile of the Filament Suture (FS), delineating tensile strengths spanning 1.3 to 9.616 MPa and elongation at break percentages ranging from 11.5 to 146.64%. These findings illuminate the mechanical versatility of the suture, hinting at its applicability across a broad spectrum of medical interventions. Subsequent analyses via SEM and TGA are anticipated to further delineate the suture’s morphological features and thermal resilience, thereby enriching our comprehension of its overall performance characteristics. Moreover, the investigation delves into the ramifications of incorporating biodegradable organic constituents on the suture's mechanical integrity. Collectively, the study not only sheds light on the mechanical and thermal dynamics of a novel suture material derived from human serum albumin but also explores the prospective enhancements afforded by the amalgamation of biodegradable organic compounds, thereby broadening the horizon for future biomedical applications.

Modulus-tunable multifunctional hydrogel ink with nanofillers for 3D-Printed soft electronics

Seamless integration and conformal contact of soft electronics with tissue surfaces have emerged as major challenges in realizing accurate monitoring of biological signals. However, the mechanical mismatch between the electronics and biological tissues impedes the conformal interfacing between them. Attempts have been made to utilize soft hydrogels as the bioelectronic materials to realize tissue-comfortable bioelectronics. However, hydrogels have several limitations in terms of their electrical and mechanical properties. In this study, we present the development of a 3D-printable modulus-tunable hydrogel with multiple functionalities. The hydrogel has a cross-linked double network, which greatly improves its mechanical properties. Functional fillers such as XLG or functionalized carbon nanotubes (fCNT) can be incorporated into the hydrogel to provide tunable mechanics (Young's modulus of 10–300 kPa) and electrical conductivity (electrical conductivity of ∼20 S/m). The developed hydrogel exhibits stretchability (∼1000% strain), self-healing ability (within 5 min), toughness (400–731 kJ/m3) viscoelasticity, tissue conformability, and biocompatibility. Upon examining the rheological properties in the modulated region, hydrogels can be 3D printed to customize the shape and design of the bioelectronics. These hydrogels can be fabricated into ring-shaped strain sensors for wearable sensor applications.

Flexible and Stretchable Electrodes for In Vivo Electrophysiological and Electrochemical Monitoring†

Comprehensive SummaryIn vivo monitoring of bioelectrical and biochemical signals with implanted electrodes has received great interest over the past decades. However, this faces huge challenges because of the severe mechanical mismatch between conventional rigid electrodes and soft biological tissues. In recent years, the emergence of flexible and stretchable electrodes offers seamless and conformable biological‐electronic interfaces and has demonstrated significant advantages for in vivo electrochemical and electrophysiological monitoring. This review first summarizes the strategies for electrode fabrication from the point of substrate and conductive materials. Next, recent progress in electrode functionalization for improved performance is presented. Then, the advances of flexible and stretchable electrodes in exploring bioelectrical and biochemical signals are introduced. Finally, we present some challenges and perspectives ranging from electrode fabrication to application.Key ScientistsIn 2001, a seminal work by Kipke et al. first showed flexible polyimide‐based intracortical electrode arrays.[1] This electrode was further expanded to 252‐channel using microelectromechanical systems technology by Stieglitz et al. in 2009 and achieved large‐scale cortical recordings.[2] Later, Lieber et al. created mesh electronics that allow for seamless and minimally invasive three‐dimensional interpenetration with nerve tissues, opening up unique applications for flexible electronics.[3] Subsequently, Rogers et al. described bioresorbable electronics for transient electrical activity recordings in 2016.[4] And Frank et al. proposed polymer electrode arrays capable of resolving single neurons in 2019.[5] It wasn't until 2020 that a significant breakthrough in biochemical signals monitoring by Peng et al. demonstrated functionalized carbon nanotube fibre bundles for multiple disease biomarkers monitoring.[6] Later on, Mooney et al. established the first fully viscoelastic electrode arrays for neural recordings from the brain and heart in 2021.[7] Recently, Bao et al. presented tissue‐mimicking, stretchable neurotransmitter interfaces for monitoring the brain and gut.[8]

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

For dissimilar metal welds (DMWs) involving nickel-based weld metal (WM) and ferritic heat resistant steel base metal (BM) in power plants, there must be an interface between WM and BM, and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure. In this study, a new form of WM/BM interface form, namely double Y-type interface was designed for the DMWs. Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests, and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization. By applying double Y-type interface instead of conventional I-type interface, failure location of DMW could be shifted from the WM/ferritic heat-affected zone (HAZ) interface into the ferritic HAZ or even the ferritic BM, and the failure mode change improved the creep life of DMW. The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation, stress and strain concentrations, and oxide notch on the WM/HAZ interface. The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ, which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries. The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface, preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking. It is a novel scheme to prolong creep life and enhance reliability of DMW, by means of optimizing the interface form, decoupling the damage factors from WM/HAZ interface, and then changing the failure mechanism and shifting the failure location.

A study protocol for evaluating aortic stiffness modifications in patients treated with endovascular aortic repair.

Arterial stiffness, particularly aortic stiffness (AoS), is associated with an increased risk of cardiovascular disease. Endovascular repair for abdominal (EVAR) and thoracic (TEVAR) aortic disease may increase AoS. This study protocol aims to assess changes in AoS before and after interventions for aortic disease. Patients scheduled for EVAR or TEVAR during a three-year period will be enrolled. An indirect AoS indicator, carotid-to-femoral pulse wave velocity (cf-PWV) will be measured non-invasively using applanation tonometry and reported with others perioperative data before and after the endovascular treatment. Moreover, cardiological data will be collected through echocardiography. Fifty EVAR and 50 TEVAR will be enrolled. We will primarily analyze changes in cf-PWV. To ensure the reliability of our findings, we will also include supplementary data such as clinical information, morphological data, and functional echocardiographic data. By examining AoS modifications before and after endovascular aortic repair, this study aims to enhance our understanding of how arterial stiffness changes following endoprosthesis deployment. The findings from the applied protocol are expected to be informative for innovative graft designs with minimized mechanical mismatch with the aortic wall and with improved vascular hemodynamic, aligning with the current trend in improving patient outcomes. Moreover, understanding these modifications is important for predicting and improving long-term cardiovascular outcomes in patients undergoing such interventions.

A personalized electronic textile for ultrasensitive pressure sensing enabled by biocompatible MXene/PEDOT:PSS composite

AbstractFlexible, breathable, and highly sensitive pressure sensors have increasingly become a focal point of interest due to their pivotal role in healthcare monitoring, advanced electronic skin applications, and disease diagnosis. However, traditional methods, involving elastomer film‐based substrates or encapsulation techniques, often fall short due to mechanical mismatches, discomfort, lack of breathability, and limitations in sensing abilities. Consequently, there is a pressing need, yet it remains a significant challenge to create pressure sensors that are not only highly breathable, flexible, and comfortable but also sensitive, durable, and biocompatible. Herein, we present a biocompatible and breathable fabric‐based pressure sensor, using nonwoven fabrics as both the sensing electrode (coated with MXene/poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate [PEDOT:PSS]) and the interdigitated electrode (printed with MXene pattern) via a scalable spray‐coating and screen‐coating technique. The resultant device exhibits commendable air permeability, biocompatibility, and pressure sensing performance, including a remarkable sensitivity (754.5 kPa−1), rapid response/recovery time (180/110 ms), and robust cycling stability. Furthermore, the integration of PEDOT:PSS plays a crucial role in protecting the MXene nanosheets from oxidation, significantly enhancing the device's long‐term durability. These outstanding features make this sensor highly suitable for applications in full‐range human activities detection and disease diagnosis. Our study underscores the promising future of flexible pressure sensors in the realm of intelligent wearable electronics, setting a new benchmark for the industry.

PAM/CNTs-Au microcrack sensor with high sensitivity and wide detection range for multi-scale human motion detection

As the quintessential material for flexible sensors, conductive hydrogels face an inherent sensitivity-sensing range paradox and electrical-mechanical balance, which significantly curtail its applicability in multiscale motion detection. Inspired by the spider slit sensor, PAM/CNTs-Au hydrogel microcrack sensor is obtained by depositing conductive gold film on the surface of PAM/CNTs hydrogel using magnetron sputtering. By modulating the cross-linking density of conductive hydrogels and the content of carbon nanotubes (CNTs), it is possible to tailor the mechanical properties and adhesion of PAM/CNTs-Au hydrogel crack-based sensors. This self-adhering flexible sensor aids in minimizing detection errors arising from mechanical mismatch between flexible sensors and human tissues. Moreover, the exceptional electrical conductivity of CNTs, coupled with their unique one-dimensional structure, facilitates the formation of an interconnected conductive network "bridge" within the hydrogel. The harmonization of electrical and mechanical attributes in the PAM/CNTs flexible substrate is achieved by finely tuning the crosslinking density of the PAM hydrogel and the content of carbon CNTs. Simultaneously, the high-conductivity "islands" formed by the Au conductive layer during stretching ensures elevated sensitivity (gauge factor (GF) = 54.89) over an extensive detection range (>1200%). The distinctive "island-bridge" configuration of the PAM/CNTs-Au hydrogel microcrack sensor effectively suppresses crack propagation, thereby markedly augmenting the sensor's stability. Successful monitoring of physiological and motion signals across various scales attests to the potential of the PAM/CNTs-Au hydrogel microcrack sensor in wearable biosensor.

Effects of micromachining on anti-oxidant elution from a mechanically-adaptive polymer

Intracortical microelectrodes (IMEs) can be used to restore motor and sensory function as a part of brain–computer interfaces in individuals with neuromusculoskeletal disorders. However, the neuroinflammatory response to IMEs can result in their premature failure, leading to reduced therapeutic efficacy. Mechanically-adaptive, resveratrol-eluting (MARE) neural probes target two mechanisms believed to contribute to the neuroinflammatory response by reducing the mechanical mismatch between the brain tissue and device, as well as locally delivering an antioxidant therapeutic. To create the mechanically-adaptive substrate, a dispersion, casting, and evaporation method is used, followed by a microfabrication process to integrate functional recording electrodes on the material. Resveratrol release experiments were completed to generate a resveratrol release profile and demonstrated that the MARE probes are capable of long-term controlled release. Additionally, our results showed that resveratrol can be degraded by laser-micromachining, an important consideration for future device fabrication. Finally, the electrodes were shown to have a suitable impedance for single-unit neural recording and could record single units in vivo.