Effect of Welding Gap of Thin Plate Butt Welds on Inherent Strain and Welding Deformation of a Large Complex Box Structure.

In this study, an effective numerical model was developed for the calculation of the deformation of laser-welded 3 mm 304L stainless steel plates with different gaps (0.2 mm, 0.5 mm, and 1.0 mm). The welding deformation would become larger when the welding gaps increased, and the largest deformation values along the Z direction, of 4 mm, were produced when the gap value was 1.0 mm. A larger plastic strain region was generated in the location near the weld seam, since higher plastic deformation had occurred. In addition, the tensile stress model was also applied at the plastic strain zone and demonstrated that a larger welding gap led to a wider residual stress area. Based on the above results, inherent deformations for butt and corner joints were calculated according to inherent strain theory, and the welding formation for the complex structure was calculated with different gaps. The numerical results demonstrated that a larger deformation was also produced with a larger welding gap and that it could reach the highest value of 10.1 mm. This proves that a smaller welding gap should be adopted during the laser welding of complex structures to avoid excessive welding deformation.

The Gut Microbiota-Constipation Connection: Insights from a Two Sample Bidirectional Mendelian Randomization Study.

OBJECTIVE: The dysbiosis of the gut microbiota has been implicated in various maladies. Research has identified an association between the dysbiosis of the gut microbiota and the risk of constipation, prompting this study to elucidate the potential causal relationship between gut microbiota imbalance with constipation through a two sample bidirectional Mendelian randomization (MR) study, shedding light on the genetic mechanisms underlying the connection between gut microbiota and constipation. METHODS: The forward MR analysis aimed to scrutinize whether alterations in the composition and abundance of gut microbiota impact the risk of constipation, while the reverse MR analysis explored whether the genetic predisposition to constipation influences the abundance of gut microbiota. Genomic correlation data for the gut microbiota were sourced from the comprehensive statistics of the MiBioGen consortium. Genomic correlation data for constipation were obtained from the IEU database, encoded as the dataset ebi-a-GCST90018829. The correlation was assessed using various analytical techniques, including inverse variance weighting (IVW), Mendelian randomization-Egger regression (MR-Egger), and weighted median and mode methodologies. To ensure the robustness of the results, a meticulous sensitivity analysis was conducted, incorporating Cochran's Q test, MR-Egger intercept test, Mendelian Randomization Pleiotropy RESidual Sum and Outlier (MR-PRESSO), and a Leave-one-out analysis. RESULTS: In the forward Mendelian randomization analyses, a negative correlation was discerned between the abundance of Coprococcus in the gut microbiota and the occurrence of constipation (IVW: OR = 0.74, 95% CI = 0.64-0.86, p = 0.0001), whereas a positive correlation was observed between the abundance of Bacteroidetes in the gut microbiota and constipation (IVW: OR = 1.22, 95% CI = 1.00-1.50, p = 0.04).In the forward Mendelian randomization analyses, we were unsuccessful in obtaining valid instrumental variables for scrutiny, and we deemed that constipation exerts no influence on the composition of the gut microbiota. CONCLUSION: Genetic predisposition towards increased abundance of Coprococcus and decreased abundance of Bacteroidetes is correlated with a diminished susceptibility to constipation. This investigation showed that alterations in the gut microbiota precipitated the onset of constipation, rather than constipation inducing modifications in the microbial flora.

High-efficiency flexible organic solar cells with a polymer-incorporated pseudo-planar heterojunction.

Organic solar cells (OSCs) are considered as a crucial energy source for flexible and wearable electronics. Pseudo-planar heterojunction (PPHJ) OSCs simplify the solution preparation and morphology control. However, non-halogenated solvent-printed PPHJ often have an undesirable vertical component distribution and insufficient donor/acceptor interfaces. Additionally, the inherent brittleness of non-fullerene small molecule acceptors (NFSMAs) in PPHJ leads to poor flexibility, and the NFSMAs solution shows inadequate viscosity during the printing of acceptor layer. Herein, we propose a novel approach termed polymer-incorporated pseudo-planar heterojunction (PiPPHJ), wherein a small amount of polymer donor is introduced into the NFSMAs layer. Our findings demonstrate that the incorporation of polymer increases the viscosity of acceptor solution, thereby improving the blade-coating processability and overall film quality. Simultaneously, this strategy effectively modulates the vertical component distribution, resulting in more donor/acceptor interfaces and an improved power conversion efficiency of 17.26%. Furthermore, PiPPHJ-based films exhibit superior tensile properties, with a crack onset strain of 12.0%, surpassing PPHJ-based films (9.6%). Consequently, large-area (1 cm2) flexible devices achieve a considerable efficiency of 13.30% and maintain excellent mechanical flexibility with 82% of the initial efficiency after 1000 bending cycles. These findings underscore the significant potential of PiPPHJ-based OSCs in flexible and wearable electronics.

Establishment of a risk prediction model for bowel necrosis in patients with incarcerated inguinal hernia.

INTRODUCTION: Incarceration occurred in approximately 5% to 15% of inguinal hernia patients, with around 15% of incarcerated cases progressing to intestinal necrosis, necessitating bowel resection surgery. Patients with intestinal necrosis had significantly higher mortality and complication rates compared to those without necrosis.The primary objective of this study was to design and validate a diagnostic model capable of predicting intestinal necrosis in patients with incarcerated groin hernias. METHODS: We screened the clinical records of patients who underwent emergency surgery for incarcerated inguinal hernia between January 1, 2015, and December 31, 2022. To ensure balanced representation, the enrolled patients were randomly divided into a training set (n = 180) and a validation set (n = 76) using a 2:1 ratio. Logistic regression analysis was conducted using the rms package in R software, incorporating selected features from the LASSO regression model, to construct a predictive model. RESULTS: Based on the results of the LASSO regression analysis, a multivariate logistic regression model was developed to establish the predictive model. The predictors included in the model were Abdominal effusion, Hernia Sac Effusion, and Procalcitonin. The area under the receiver operating characteristic (ROC) curve for the nomogram graph in the training set was 0.977 (95% CI = 0.957-0.992). In the validation set, the AUC for the nomogram graph was 0.970. Calibration curve and decision curve analysis (DCA) verified the accuracy and practicability of the nomogram graph in our study. CONCLUSION: Bowel necrosis in patients with incarcerated inguinal hernia was influenced by multiple factors. The nomogram predictive model constructed in this study could be utilized to predict and differentiate whether incarcerated inguinal hernia patients were at risk of developing bowel necrosis.

Interfacial Charge Transfer for Enhancing Nonlinear Saturable Absorption in WS2/graphene Heterostructure.

Interlayer charge-transfer (CT) in 2D atomically thin vertical stacks heterostructures offers an unparalleled new approach to regulation of device performance in optoelectronic and photonics applications. Despite the fact that the saturable absorption (SA) in 2D heterostructures involves highly efficient optical modulation in the space and time domain, the lack of explicit SA regulation mechanism at the nanoscale prevents this feature from realizing nanophotonic modulation. Here, the enhancement of SA response via CT in WS2/graphene vertical heterostructure is proposed and the related mechanism is demonstrated through simulations and experiments. Leveraging this mechanism, CT-induced SA enhancement can be expanded to a wide range of nonlinear optical modulation applications for 2D materials. The results suggest that CT between 2D heterostructures enables efficient nonlinear optical response regulation.

Inducing preferential growth of the Zn (002) plane by using a multifunctional chelator for achieving highly reversible Zn anodes.

Aqueous zinc-ion batteries (AZIBs) have demonstrated great potential for large-scale energy storage. However, their practical applications have been restricted by fast Zn dendrite growth and severe side reactions at the Zn/electrolyte interface. Herein, sodium gluconate is incorporated into a mild acidic electrolyte as a multifunctional additive to stabilize the Zn anode. Experiments and theoretical calculations reveal that the SG additive can induce planar growth of Zn along its (002) direction, thereby inhibiting Zn dendrite growth. This dendrite inhibition effect is attributed to the preferential adsorption of Zn2+ on the Zn (002) plane, while the Zn (100) and (101) planes are shielded by gluconate ions. Consequently, Zn||Zn symmetric cells with the electrolyte additive exhibit significantly prolonged cycle lives of 2000 h at 1 mA cm-2, 1 mA h cm-2 and 900 h at 5 mA cm-2, 2.5 mA h cm-2. Futhermore, the Zn||NH4V4O10 full cell retains 95% of its initial capacity after 2000 cycles at a current density of 5 A g-1 with an average CE of nearly 100%. This work offers a cost-effective strategy to enhance the electrochemical performance of AZIBs.

Bibliometric and visualized analysis of cancer nanomedicine from 2013 to 2023.

Cancer nanomedicine has been an emerging field for drug development against malignant tumors during the past three decades. A bibliometric analysis was performed to characterize the current international trends and present visual representations of the evolution and emerging trends in the research and development of nanocarriers for cancer treatment. This study employed bibliometric analysis and visualization techniques to analyze the literature on antitumor nanocarriers published between 2013 and 2023. A total of 98,980 articles on antitumor nanocarriers were retrieved from the Web of Science Core Collection (WoSCC) database and analyzed using the Citespace software for specific characteristics such as publication year, countries/regions, organizations, keywords, and references. Network visualization was constructed by VOSviewer and Citespace. From 2013 to 2023, the annual global publications increased 7.39 times, from 1851 to 13,683. People's Republic of China (2588 publications) was the most productive country. Chinese Academy of Sciences (298 publications) was the most productive organization. The top 5 high-frequency keywords were "nanoparticles," "drug delivery," "nanomedicine," "cancer," and "nanocarriers." The keywords with the strongest citation bursts recently were "cancer immunotherapy," "microenvironment," "antitumor immunity," etc., which indicated the emerging frontiers of antitumor nanomedicine. The co-occurrence cluster analysis of the keywords formed 6 clusters, and most of the top 10 publications by citation counts focused on cluster #1 (nanocarriers) and cluster #2 (cancer immunotherapy). We further provided insightful discussions into the identified subtopics to help researchers gain more details of current trends and hotspots in this field. The present study processes a macro-level literature analysis of antitumor nanocarriers and provides new perspectives and research directions for future development in cancer nanomedicine.

Electronic Structure Modulation of Fe-N4-C for Oxygen Evolution Reaction via Transition Metal Dopants and Axial Ligands.

The popular single-atom catalyst (SAC) Fe-N4 is generally believed to be an excellent oxygen reduction reaction (ORR) electrocatalyst, which is less active in the oxygen evolution reaction (OER). Herein, FeM-N6 configuration catalysts (M = Fe, Co, Ni, Cu, Ag, and Au) were constructed for the oxygen evolution reaction by embedding M dopants on Fe-N4 systems based on the density functional theory. The electronic structure analysis reveals that the Fe-M metal interactions play dominant roles in regulating the d orbital distributions of Fe sites, which in turn alter the catalytic OER performance. Subsequent thermodynamic results indicate that the potential-determining step (PDS) for all catalysts is the formation of OOH*, which exhibits a tendency of decreased overpotentials with enhanced metal interactions. Apart from these, the effects of axial ligands on the OER activity of the catalysts in practical conditions were considered. Generally, most of the axial ligands are found to be thermodynamically favorable for the OER process. Interestingly, a competitive relationship of the electrons from the d orbital of Fe sites was found between the axial ligand and the adsorbed intermediate species during the reaction, which raises the energy barrier for OH* to O* conversion and can even alter the PDS in certain cases. The present work sheds new light on the design of future high-performance OER catalysts.

Highly Sensitive Detection of Formaldehyde by Laser-Induced Graphene-Coated Silver Nanoparticles Electrochemical Sensing Electrodes.

Formaldehyde (HCHO) poses a grave threat to human health because of its toxicity, but its accurate, sensitive, and rapid detection in aqueous solutions remains a major challenge. This study proposes a novel electrochemical sensor composed of a graphene-based electrode that is prepared via laser induction technology. The precursor material, polyimide, is modified via the metal ion exchange method, and the detective electrode is coated with graphene and silver nanoparticles. And the special structure of graphene-coated Ag was demonstrated using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS) results show that graphene provides more sites for Ag NRs to be exposed and increases the surface area of contact between the solution and the detection object. In addition, differential pulse voltammetry (DPV) analysis exhibits high linearity over the HCHO concentration range from 0.05 to 5 µg/mL, with a detection limit of 0.011 µg/mL (S/N = 3). The Ag NPs in the electrochemical reaction will adsorb the intermediate •CO and •OH, catalyze their combination, and finally convert to CO2 and H2O, respectively. A microdetection device, specially designed for use with commercial micro-workstations, is employed to fully demonstrate the practical application of the electrode, which paves a way for developing formaldehyde electrochemical sensors.

Engineered lytic phage of Bacillus cereus and its application in milk.

Phages have been approved for use in the food industry to control bacterial contamination in some countries. However, their broader adoption is hindered by some limitations. For instance, the persistence of infectious phages in the food industry can lead to the emergence of resistant bacteria, which negatively impacts the long-term effectiveness of phages. Additionally, the narrow host range of phages limits their effectiveness against various strains. To address these deficiencies, phage engineering has been proposed as a rational approach for modifying phages. In this study, we developed a simple and efficient engineering method for Bacillus cereus phage, using DK1 as an example, to reduce the number of residual phages and expand its range of hosts. Specifically, we knocked out the appendage gene, which codes for the receptor-binding protein, to produce phage progeny with structural defects in their appendages, resulting in the loss of infectivity after host elimination. Furthermore, we used plasmid-mediated means to express different appendage proteins during phage preparation, which allowed altering the host spectrum of the engineered phages without gene insertion. In practical applications, our engineered phages effectively reduced the number of B. cereus in milk and prevented the amplification of active progeny. Our strategy transformed phages from active viruses into more controllable antibacterial agents, making them safer and more efficient for the prevention and control of B. cereus. Moreover, we believe this strategy will help drive the use of engineered phages in the food industry.

Effect of Process Parameters on the Formability, Microstructure, and Mechanical Properties of Laser-Arc Hybrid Welding of Q355B Steel.

Thick plate steel structure is widely used in the construction machinery, pressure vessels, ships, and other manufacturing fields. To obtain an acceptable welding quality and efficiency, thick plate steel is always joined by laser-arc hybrid welding technology. In this paper, Q355B steel with a thickness of 20 mm was taken as the research object, and the process of narrow-groove laser-arc hybrid welding was studied. The results showed that the laser-arc hybrid welding method could realize one-backing and two-filling welding with the single-groove angles of 8-12°. At different plate gaps of 0.5 mm, 1.0 mm, and 1.5 mm, the shapes of weld seams were satisfied with no undercut, blowhole, or other defects. The average tensile strength of welded joints was 486~493 MPa, and the fracture position was in the base metal area. Due to the high cooling rate, a large amount of lath martensite formed in heat-affected zone (HAZ) and this zone exhibited higher hardness values. The impact roughness of the welded joint was almost 66-74 J, with different groove angles.

Self-Healing and Self-Adhesive Substrate-Free Tattoo Electrode.

Electronic tattoos have great potential application in the biomedical field; moreover, the substrate-free electronic tattoo offers better comfortability and conformal contact. However, the substrate-free electronic tattoo is more prone to malfunction, including fall off and fracture. In this paper, a self-healing and self-adhesive substate-free tattoo based on PEDOT: PSS is studied and reported. The dry composite electrode will turn into self-healing material while it transforms into hydrogel, and a cut with a width up to 24 µm could be healed in 1 s. In terms of adhesion performance, the substrate-free electrode can hang a 28.2 g weight by a contact area of 8 mm × 8 mm. Additionally, the substate-free electrode could maintain fully conformal contact with porcine skin in 15 days by its self-adhesiveness. When applied as a substrate-free tattoo, the contact impedance and ECG signal measurement performance before and after self-healing are almost the same. At a frequency of 10 Hz, the contact impedance of the undamaged electrode, healed electrode, and Ag/AgCl gel electrode are 32.2 kΩ, 39.2 kΩ, and 62.9 kΩ, respectively. In addition, the ECG signals measured by the undamaged electrode and healed electrode are comparable to that of Ag/AgCl electrode. The self-healing and self-adhesive substrate-free tattoo electrode reported here has broad application in health monitoring.

Recent advances in phage defense systems and potential overcoming strategies.

Bacteriophages are effective in the prevention and control of bacteria, and many phage products have been permitted and applied in the field. Because bacteriophages are expected to replace other antimicrobial agents like antibiotics, the antibacterial effect of bacteriophage has attracted widespread attention. Recently, the diversified defense systems discovered in the target host have become potential threats to the continued effective application of phages. Therefore, a systematic summary and in-depth illustration of the interaction between phages and bacteria is conducive to the development of this biological control approach. In this review, we introduce different defense systems in bacteria against phages and emphasize newly discovered defense mechanisms in recent years. Additionally, we draw attention to the striking resemblance between defense system genes and antibiotic resistance genes, which raises concerns about the potential transfer of phage defense systems within bacterial populations and its future impact on phage efficacy. Thus, attention should be given to the effects of phage defense genes in practical applications. This article is not exhaustive, but strategies to overcome phage defense systems are also discussed to further promote more efficient use of phages.

A Quick DNA Extraction Method for High Throughput Screening in Gram-positive Bacteria.

In this study, a sonication-based DNA extraction method was developed, in which the whole process can be finished within 10 min. This method is almost zero cost and time-saving, which is useful for high throughput screening, especially in the screening of mutants generated in random mutagenesis. This method is effective in genomic DNA extraction for PCR amplification in several Gram-positive bacteria, including Bacillus cereus, Bacillus thuringiensis, Bacillus subtilis, and Listeria monocytogenes.

A deep capsule neural network with data augmentation generative adversarial networks for single and simultaneous fault diagnosis of wind turbine gearbox.

The fault diagnosis (FD) of wind turbine gearbox (WTG) is of special importance for keeping the wind turbine drivetrain working normally and safely. However, owing to the limited training data and the mutual interference of various mechanical parts, it is of great difficulty to realize the simultaneous-fault monitoring task of WTG using existing intelligent FD methods or manual inspection-based approaches. To tackle the issue, a deep capsule neural network with data augmentation generative adversarial networks, named ST-DAGANs-CapNet, is developed for the single and simultaneous FD of WTG by integrating capsule neural network (CapsNet) with Stockwell transform (ST) and data augmentation generative adversarial networks (DAGANs). The proposed ST-DAGANs-CapNet method mainly consists of three steps. First of all, ST is adopted to extract two-dimension (2-d) image features of time-frequency domain from raw time-domain vibration signals of WTG. Then, DAGANs are employed for generating more fake image samples to address the problem of lacking training data. At last, the built CapsNet model is utilized to diagnose the single and compound faults of WTG by the primary 2-d feature images and the made fake 2-d feature images in training set. Two experimental studies are implemented to prove the effectiveness of the proposed method, and the result is compared with some existing intelligent FD of WTG. It indicates that DAGANs are effective in helping to tackle the issue of limited and unbalanced training samples in real FD of WTG, and the diagnosis result of the proposed approach in test sample set is better than that of several commonly used FD methods in literatures.

A General Descent Aggregation Framework for Gradient-Based Bi-Level Optimization.

In recent years, a variety of gradient-based methods have been developed to solve Bi-Level Optimization (BLO) problems in machine learning and computer vision areas. However, the theoretical correctness and practical effectiveness of these existing approaches always rely on some restrictive conditions (e.g., Lower-Level Singleton, LLS), which could hardly be satisfied in real-world applications. Moreover, previous literature only proves theoretical results based on their specific iteration strategies, thus lack a general recipe to uniformly analyze the convergence behaviors of different gradient-based BLOs. In this work, we formulate BLOs from an optimistic bi-level viewpoint and establish a new gradient-based algorithmic framework, named Bi-level Descent Aggregation (BDA), to partially address the above issues. Specifically, BDA provides a modularized structure to hierarchically aggregate both the upper- and lower-level subproblems to generate our bi-level iterative dynamics. Theoretically, we establish a general convergence analysis template and derive a new proof recipe to investigate the essential theoretical properties of gradient-based BLO methods. Furthermore, this work systematically explores the convergence behavior of BDA in different optimization scenarios, i.e., considering various solution qualities (i.e., global/local/stationary solution) returned from solving approximation subproblems. Extensive experiments justify our theoretical results and demonstrate the superiority of the proposed algorithm for hyper-parameter optimization and meta-learning tasks. Source code is available at https://github.com/vis-opt-group/BDA.

A Flagella Hook Coding Gene flgE Positively Affects Biofilm Formation and Cereulide Production in Emetic Bacillus cereus.

Bacillus cereus, an important foodborne pathogen, poses a risk to food safety and quality. Robust biofilm formation ability is one of the key properties that is responsible for the food contamination and food poisoning caused by B. cereus, especially the emetic strains. To investigate the mechanism of biofilm formation in emetic B. cereus strains, we screened for the mutants that fail to form biofilms by using random mutagenesis toward B. cereus 892-1, an emetic strain with strong biofilm formation ability. When knocking out flgE, a flagellar hook encoding gene, the mutant showed disappearance of flagellar structure and swimming ability. Further analysis revealed that both pellicle and ring presented defects in the null mutant compared with the wild-type and complementary strains. Compared with the flagellar paralytic strains Δ motA and Δ motB, the inhibition of biofilm formation by Δ flgE is not only caused by the inhibition of motility. Interestingly, Δ flgE also decreased the synthesis of cereulide. To our knowledge, this is the first report showing that a flagellar component can both affect the biofilm formation and cereulide production in emetic B. cereus, which can be used as the target to control the biohazard of emetic B. cereus.

Numerical Investigation of the Influence of Ultimate-Strength Heterogeneity on Crack Propagation and Fracture Toughness in Welded Joints.

The mechanical properties of dissimilar metal-welded joint materials are heterogeneous, which is an obstacle to the safety evaluation of key welded structures. The variation of stress-strain conditions at the crack tip caused by mismatch of material mechanical properties in dissimilar metal-welded joints is an important factor affecting crack propagation behavior. To understand the influence of uneven distribution of ultimate strength of the base metal and the welded metal on the crack propagation path, fracture toughness, as well as the mechanical field at the crack tip in the small-scale yield range, the user-defined field variable subroutine method is used to express continuous variation characteristics of welded joint ultimate strength in finite element software. In addition, the J-integral during crack propagation is calculated, and the effect of the ultimate strength on the J-integral and the stress field at the crack tip are analyzed. The results show that as the crack propagation direction is perpendicular to the direction of ultimate strength, the gradient of ultimate strength increases from |Gy|= 50 to |Gy|= 100 MPa/mm, the crack deflection angle increases by 0.018%, and the crack length increases by 1.46%. The fracture toughness of the material decreased slightly during crack propagation. Under the condition that the crack propagation direction is the same as the direction of ultimate strength, the crack propagation path is a straight line. As the gradient of ultimate strength increases from Gx = 50 to Gx = 100 MPa/mm, the crack propagation length decreases by 5.17%, and the slope of fracture toughness curve increases by 51.63%. On the contrary, as the crack propagates to the low ultimate strength side, the crack propagation resistance decreases, the ultimate strength gradient increases from Gx = -100 to Gx = -50 MPa/mm, and the slope of the fracture toughness curve decreases by 51.01%. It is suggested to consider the relationship between crack growth behavior and ultimate strength when designing and evaluating the structural integrity of cracks at the material interface of dissimilar metal-welded joints.

A novel Bacillus cereus bacteriophage DLn1 and its endolysin as biocontrol agents against Bacillus cereus in milk.

Bacillus cereus is a common foodborne pathogen that causes vomiting and diarrheal symptoms. Due to its spore-forming ability, B. cereus can resist physical sterilization and possess a relatively high contamination level in dairy products; therefore, it is necessary to develop an efficient strategy to control the growth of B. cereus. In this study, a novel bacteriophage, named DLn1, was isolated and characterized, and its endolysin was expressed. Morphological and genomic analyses revealed that the phage is a new species belonging to the Northropvirinae subfamily of the Salasmaviridae family. The life cycle and stability assays showed that the phage DLn1 exhibited a short latent period (15 min) and high burst size (618 plaque-forming units (PFU)/cell) and was tolerant to a wide range of pH (4-10) and temperature (4-55 °C) conditions. This lytic phage had narrow but specific host range to B. cereus strains, and could effectively reduce the number of B. cereus in milk within 6 h. More interestingly, the purified endolysin of phage DLn1 had a much wider lytic range and the inhibitory effect against B. cereus in milk was more efficient. Taken together, the new phage DLn1 and its endolysin could be promising biocontrol agents against B. cereus in dairy products.

Substrate-free, ultra-conformable PEDOT: PSS E-tattoo achieved by energy regulation on skin.

Electronic tattoo has great potential application in mobile health. Fully conformal contact between E-tattoo and skin is critical for reliable monitoring. In this paper, we reported a substrate-free, ultra-conformable PEDOT: PSS (3,4-ethylenedioxythiophene):poly(styrene-sulfonate) E-tattoo achieved by interface energy regulation on skin. The controllable gel/dry electrode mutual transformation property of PEDOT: PSS was carefully studied and reported. Then a novel transfer approach was studied to transfer thin, substrate-free PEDOT: PSS E-tattoo onto skin. Meanwhile, PEDOT: PSS E-tattoo was gelled, then dried directly on skin, regulating its bending energy, contact area, and interface adhesion energy with skin. Through this method, the critical thickness of the after-transformation dry E-tattoo that could form fully conformal contact with skin was increased by 4 times. The electrode-skin interface impedance and ECG measurement performance of the reported E-tattoo were on par with commercial Ag/AgCl gel electrodes, while offering superior comfort and reliability. The substrate-free, ultra-conformable PEDOT: PSS E-tattoo could be applied as sensing electrode for reliable monitoring in mobile health.