Surface Modification Techniques Research Articles

Enhancement of Abnormal Grain Growth by Surface Quenching Treatment to Eliminate Cu-Cu Bonding Interfaces Using (111)-Oriented Nanotwinned Copper.

Cu-Cu joints have been adopted for ultra-high density of packaging for high-end devices. However, the processing temperature must be kept relatively low, preferably below 300 °C. In this study, a novel surface modification technique, quenching treatment, was applied to achieve Cu-to-Cu direct bonding using (111)-oriented nanotwinned Cu. The quenching treatment enabled grain growth across the Cu-Cu bonding interface at 275 °C. During quenching treatment, strain energy was induced in the Cu film, resulting in a wrinkled surface morphology. To analyze the strain energy, we utilized an electron backscattered diffraction system to obtain crystallographic information and confirmed it using kernel average misorientation analysis.

Enhancing 3D-printed denture base resins: A review of material innovations.

The limited physical and mechanical properties of polymethyl methacrylate (PMMA), the current gold standard, necessitates exploring improved denture base materials. While three-dimensional (3D) printing offers accuracy, efficiency, and patient comfort advantages, achieving superior mechanics in 3D-printed denture resins remains challenging despite good biocompatibility and esthetics. This review investigates the potential of innovative materials to address the limitations of 3D-printed denture base materials. Thus, this article is organized to provide a comprehensive overview of recent efforts to enhance 3D-printed denture base materials, highlighting advancements. It critically examines the impact of incorporating various nanoparticles (zirconia, titania, etc.) on these materials' physical and mechanical properties. Additionally, it delves into recent strategies for nanofiller surface treatment and biocompatibility evaluation and explores potential future directions for polymeric composites in denture applications. The review finds that adding nanoparticles significantly improves performance compared to unmodified resins, and properties can be extensively enhanced through specific modifications, particularly silanized nanoparticles. Optimizing 3D-printed denture acrylics requires a multifaceted approach, with future research prioritizing novel nanomaterials and surface modification techniques for a novel generation of superior performance, esthetically pleasing, and long-lasting dentures.

Metallic biomaterials in biopharmaceuticals and biomedical applications

Metallic biomaterials have captured a lot of interest because of their distinct mechanical characteristics, biocompatibility, and usefulness in biopharmaceutical and biomedical applications. These materials are essential for the creation of several medical equipment and treatment strategies. They include titanium, cobalt-chromium alloys, stainless steel, and biodegradable metals. Metallic implants in orthopaedics offer strong support for bone mending and joint replacement; they have outstanding load-bearing capacity and are resistant to corrosion and wear. Metallic heart valves and stents provide structural integrity and functionality in cardiovascular applications, enhancing patient outcomes in heart valve and coronary artery illness. Metallic biomaterials are manufactured systems created to give biological tissues intrinsic support, and they are commonly employed in stents, dental implants, orthopaedic fixations, and joint replacements. Increased implant-related issues are linked to higher biomaterial utilization because of weak implant integration, infections, mechanical instability, necrosis, and inflammation, as well as ensuring extended patient care, discomfort, and functional loss. The performance and integration of metallic biomaterials inside biological systems have been improved by developments in surface modification techniques, such as coating with biocompatible polymers and drug-eluting technology. Researchers are exploring the possibility of using biodegradable metals that eventually dissolve within the body reducing the risk of long-term issues and repeat procedures. Metallic nanoparticles have also demonstrated potential in increasing therapeutic efficacy, minimizing systemic adverse effects, and selectively targeting disease locations when included in drug delivery systems. The main metallic biomaterials will be briefly discussed in this review, along with the most important established and new methods for modification, which are used to enhance the durability, flexibility, biointegration, and of the biometals, and boost their suitability for 3D printing.

Revolutionizing Arthritis Care: Cutting-Edge Nanogel Formulations for Targeted, Long-Lasting Relief and Enhanced Mobility

Arthritis, which impacts individuals all over the globe, is characterized by severe pain and a high prevalence rate. Current treatments for the illness come with a number of obstacles and difficulties. It is necessary to explore alternative paradigms, as systemic medications aren’t necessarily the greatest choice. The new discipline of nanotechnology has the potential to significantly alter several aspects of arthritis treatment. Therefore, the work provides strong support for developing novel therapies employing compositions of topical nanogels. Traditional systemic narcotics have their limitations, and the evolution of arthritis treatments has to take that into consideration. Thus, novel nanogel formulations offered as a nanotechnology solution may out to be quite advantageous. Applying nanogels to product design has been a significant administrative step. Nanogels offer unparalleled precision and efficiency, whether you’re dealing with simple concepts, cutting-edge techniques for surface modification, or intricate strategies for drug encapsulation. New data from pain evaluations, clinical studies, and comparisons to traditional therapies have supported their revolutionary potential and effectiveness. However, the patient’s health must always come first. While we strive to mitigate adverse effects and evaluate long-term ramifications, the positive outcomes of our biocompatibility testing offer reassurance regarding the safety profile of nanogels. For regulatory and ethical considerations, there must be transparency, informed permission, and equitable access for nanotechnology-powered arthritic treatments. This study calls for additional research into the use of nanotechnology in the treatment of arthritis because recent advances in nanogel technology have the ability to completely transform the current approach to treating this debilitating disease, bringing about a new era of precision medicine.

Hydrophobic or hydrophilic microhelices: Crafting surfaces with electrospun magnetic polystyrene fiber and an innovative top‐down technique

AbstractMicrohelices are important structures capable of overcoming low Reynolds number limitations and can be used in various applications. The fabrication of such microhelices is a challenge as existing fabrication techniques are restrictive in material choices and require sophisticated equipment. In this work, we demonstrate a simple top‐down approach to fabricate microhelical structures using surface modification of helical electrospun fibers to produce both hydrophilic, silica‐coated (Si‐HMPF), and hydrophobic, caramel sol‐based (Ca‐HMPF) magnetic microhelices post‐modification. The glassy coating obtained on the surface in both cases facilitated obtaining magnetic microhelices via mechanical fracture of the fibers by grinding at room temperature. SEM images of the samples confirm the successful fabrication of microhelical structures which resemble the popular microswimmer morphology. The FTIR and VSM characterization were performed to study the functional groups present and the magnetic nature of the fabricated microhelices. The thermal stability of the samples was investigated using DSC and TGA studies. Both hydrophilic and hydrophobic magnetic microhelices were successfully fabricated through a simple sol‐based coating technique and confirmed by a wettability study.Highlights Helical microstructures are an important classification of micro/nanomaterial synthesis. A simple method for the fabrication of magnetic polymeric microhelices is proposed and discussed in detail. The current challenges in fabricating such structures are discussed. The advantages of using a simple surface modification technique is summarized.

Advancements in dental implant technology: the impact of smart polymers utilized through 3D printing

The field of dental implantology has witnessed significant advancements in recent years, driven by innovations in materials science and manufacturing technologies. One such innovation that holds promise for revolutionizing dental implant generation is the mixing of smart polymers thru three-D printing. This evaluation article affords a comprehensive overview of the effect of clever polymers in enhancing the performance and functionality of dental implants. We begin by using elucidating the fundamental residences of smart polymers, which include their stimuli-responsive conduct, biocompatibility, and mechanical strength. sooner or later, we discover the evolution and programs of 3ِD printing, e.g. like direct metallic laser sintering (DMLS) and selective laser melting (SLM), in dentistry, highlighting its position in fabricating custom designed dental implants. the combination of smart polymers into dental implants is discussed in element, overlaying surface modification techniques, incorporation of bioactive dealers, and customization for affected person-particular desires. furthermore, we look at how smart polymers make contributions to enhancing aspects such as osseointegration, peri-implantitis management, and average implant toughness. clinical insights and case studies are presented to illustrate the real-global applications and results of clever polymer-based dental implants. ultimately, this evaluation objectives to offer valuable insights for clinicians, researchers, and industry specialists worried within the improvement and utilization of advanced dental implant technologies.

Effect of Electrochemical Aryl Diazonium Salt Modification on Interfacial Properties of CF/PEEK Composites.

The interfacial properties between carbon fiber (CF) and thermoplastic resin are relatively weak, which can be problematic for composites in structural applications. Improving the surface roughness of CF is regarded as an effective way to enhance the interface of composites. However, most CF modifying methods are complex and time-consuming, which cannot meet the demand for industrial production. Therefore, it is of great significance to research a fast technique of CF surface modification to strengthen the interface of composites. Herein, a one-pot reaction based on the aryl diazonium salt modification was applied to enhance the interface between CF and poly ether ether ketone (PEEK) resin. Carbon nanotubes (CNTs) were linked to CF by p-phenylenediamine (PPD) via cyclic voltammetry (CV). The surface morphology, chemical characteristics and surface energy of modified CF illustrated the effectiveness of this method, and the interfacial properties of as-prepared modified CF/PEEK demonstrated the increased tendency. All the CF was treated within 5 min and the interfacial shear strength (IFSS) of CF/PEEK was increased to the maximum of 99.62 MPa by aryl diazonium salt modification. This work may shed some light on the industrialized application of CF reinforced high-performance engineering thermoplastic composites.

Electrospun Polymeric Nanofibers: Current Trends in Synthesis, Surface Modification, and Biomedical Applications.

Electrospun polymeric nanofibers are essential in various fields for various applications because of their unique properties. Their features are similar to extracellular matrices, which suggests them for applications in healthcare fields, such as antimicrobials, tissue engineering, drug delivery, wound healing, bone regeneration, and biosensors. This review focuses on the synthesis of electrospun polymeric nanofibers, their surface modification, and their biomedical applications. Nanofibers can be fabricated from both natural and synthetic polymers and their composites. Even though they mimic extracellular matrices, their surface features (physicochemical characteristics) are not always capable of fulfilling the purpose of the target application. Therefore, they need to be improved via surface modification techniques. Both needle-based and needleless electrospinning are thoroughly discussed. Various techniques and setups employed in each method are also reviewed. Furthermore, pre- and postspinning modification approaches for electrospun nanofibers, including instrument design and the modification features for targeted biomedical applications, are also extensively discussed. In this way, the remarkable potential of electrospun polymeric nanofibers can be highlighted to reveal future research directions in this dynamic field.

In Situ Electronic Structure Analysis of Water-Corroded UNx in High Vacuum

Nitriding technologies are promising surface modification techniques of uranium based on pulsed laser irradiating and glow plasma treatment. Nitrided layers with different nitrogen contents (UN0.35, UN0.75, UN1.08 and UN1.5) were prepared on the surface of uranium. The present study aims to investigate the microstructure and corrosion properties of the reaction of the UNx layers with ultra-low water vapor at room temperature. The electronic structures were analyzed in situ by X-ray photoelectron spectroscopy in high vacuum. The results showed that the UN0.35, UN0.75, and UN1.08 samples were mainly composed of uranium nitride (UN) and metallic uranium, while the surface microstructure of the UN1.5 sample was U2N3. The dense and uniform nitride layer with a grain size of 20 to 50 nm was obtained on the uranium surface, which acted as a barrier and prevented the further diffusion of anions into the matrix. The corrosion products of the UN0.35, UN0.75, and UN1.08 samples were mainly UO2-xNy and UO2 after reaction with the water vapor. The contents of UO2-xNy increased with increasing nitrogen contents, and the corrosion rate decreased significantly. The intermediate compounds UO2-xNy reacted slowly with the water vapor, and eventually converted to UO2. Meanwhile, the corrosion products of the UN1.5 sample were mainly U2N3+xOy and UO2-xNy after reaction with the water vapor. The percentage of U2N3+xOy and UO2-xNy remained almost stable over a long period of time, which indicated that the high contents of U2N3+xOy and UO2-xNy prolonged the time for complete conversion to UO2. It can be concluded that the U-N-O ternary compounds retarded the corrosion process and the UNx layers with high nitrogen contents showed excellent corrosion resistance.

Hydrophobization of Cold Plasma Activated Glass Surfaces by Hexamethyldisilazane Treatment.

The objective of this study was to investigate the modification of glass surfaces by the synergistic combination of cold plasma and chemical surface modification techniques. Glass surface hydrophobicity was obtained as a result of various plasma and deposition operational conditions. The mechanisms governing the hydrophobization process were also studied. Glass plates were activated with plasma using different gases (oxygen and argon) at different treatment times, ranging from 30 to 1800 s. Then, the plasma-treated surfaces were exposed to hexamethyldisilazane vapors at different temperatures, i.e., 25, 60, and 100 °C. Complete characterization, including contact angle measurements, surface free energy calculations, 3D profilometry, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy, was accomplished. It was found that the extent of the hydrophobicity effect depends on both the plasma pre-treatment and the specific conditions of the hexamethyldisilazane deposition process. Plasma activation led to the formation of active sites on the glass surface, which promoted the adsorption and reaction of hexamethyldisilazane species, thereby inducing surface chemical modification. Longer plasma pre-treatment resulted in stronger modification on the glass surface, resulting in changes in the surface roughness. The largest water contact angle of ≈100° was obtained for the surface activated by argon plasma for 1800 s and exposed to hexamethyldisilazane vapors at 25 °C. The changes in the surface properties were caused by the introduction of the hydrophobic trimethylsilyl groups onto the glass surface as well as roughness development.

A Review on Surface Modification of Plant Fibers for Enhancing Properties of Biocomposites

AbstractOver the past decade, significant progress has been made in creating environmentally friendly products using natural resources. Plant fibers, also known as lignocellulosic fibers, are hydrophilic due to the interaction and attraction between water molecules and the hydroxyl groups present in their components. The inherent hydrophilicity of plant fibers often prevents them from interacting effectively with hydrophobic polymer matrices. In order to improve the adhesion between plant fibers and the matrix, it is necessary to modify the surface of the fibers. Commonly used chemical processes include mercerization, silane treatment, acetylation, permanganate treatment, acrylation, benzoylation, peroxide treatment, stearic acid treatment, isocyanate treatment and sodium chlorite intervention. The desirability of chemically modifying the surface of plant fibers has declined due to several limitations. Plant fibers can be modified in an environmentally friendly way by various methods, such as plasma therapy and treatments using fungi, enzymes and bacteria. This part provides an analysis of the impact of different environmentally friendly surface modification techniques on the properties of plant fibers and reinforced polymers.

Facile Synthesis of Surface-Modified Hollow-Silica (SiO2) Aerogel Particles via Oil-Water-Oil Double Emulsion Method.

Due to their high surface area and low weight, silica aerogels are ideally suited for several uses, including drug delivery, catalysis, and insulation. Oil-water-oil (OWO) double emulsion is a simple and regulated technique for encasing a volatile oil phase in a silica shell to produce hollow silica (SiO2) aerogel particles by using hydrophilic and hydrophobic emulsifiers. In this study, the oil-water-oil (OWO) double emulsion method was implemented to synthesize surface-modified hollow silica (SiO2) aerogel particles in a facile and effective way. This investigation mainly focused on the influence of the N-hexane-to-water glass (OW) ratio (r) in the first emulsion, silica (water glass) content concentration (x), and surfactant concentration (s) variations. Furthermore, surface modification techniques were utilized to customize the aerogel's characteristics. The X-ray diffraction (XRD) patterns showed no imprints of impurities except SiO2. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images highlight the hollow microstructure of silica particles. Zeta potential was used to determine particle size analysis of hollow silica aerogel particles. The oil-water-oil (OWO) double emulsion approach was successfully employed to synthesize surface-modified hollow silica (SiO2) aerogel particles, providing precise control over the particle characteristics. By the influence of the optimization condition, this approach improves the aerogel's potential applications in drug delivery, catalysis, and insulation by enabling surface modifications.

Enhancing Resistance to Corrosion, Erosion and Oxidation of Boiler Steels by Surface Modification Techniques

In coal based thermal power plant, the boiler components (superheater, combustion chamber, superheater tubes, boiler walls, reheater etc.) are subjected to harsh environment characterized by high temperatures, aggressive combustion products, and abrasive particles. Corrosion, erosion, and oxidation relentlessly reduce their lifespan and efficiency, posing significant economic and safety concerns. This review explores the potential of surface modification techniques to act as a valiant shield against these destructive forces, extending the life, enhancing the performance, and ensuring the safe operation of boiler components. In this articles various surface modifications techniques including their merits and demerits are discussed with emphasis on thermal spray techniques. From established methods like thermal spraying and laser cladding to innovative approaches like nanocoatings and electrochemical treatments, each technique is meticulously examined for its effectiveness in boosting corrosion resistance, mitigating erosion wear, and minimizing oxidation at crucial boiler locations. This review culminates in a compelling vision of the future, where sophisticated surface modification techniques become an integral part of boiler design and maintenance strategies. By harnessing the power of these technologies, we can usher in an era of more efficient, reliable, and sustainable boiler operation, safeguarding investments and protecting the environment.

04. Recent techniques of surface modification for textile fabrics

04. Recent techniques of surface modification for textile fabrics

Effect of Y2O3 Content on Microstructure and Wear Resistance of Laser Cladding Layer of Stellite-6 Alloy

Laser cladding technology is an effective surface modification technique. In order to prepare coating with excellent properties on the surface of the cold heading die punch, stellite-6 cladding coating with different proportions of Y2O3 was prepared on the surface of W6Mo5Cr4V2 high-speed steel using laser cladding technology in this paper. The effects of different Y2O3 contents on the macroscopic morphology, microstructure, phase analysis, microhardness, and tribological properties of the stellite-6 coatings were investigated. It was determined that the optimal Y2O3 content for the stellite-6 powder was 2%. The results showed that the coating with 2%Y2O3 had the least number of pores and cracks and exhibited good surface flatness when joined. The microstructure became finer and denser, composed mainly of branch, cellular, equiaxed, and columnar grains. The coating consisted mainly of γ-Co, Fe-Cr, and Co3Fe7 strengthening phases, indicating good metallurgical bonding between the coating and the substrate. The average microhardness reached 539 HV when 2%Y2O3 was added, a 15.2% increase compared with the unmodified multilayer coating. The friction coefficient of the clad layer was 0.356, a 21.8% improvement over the unmodified stellite-6 coating. The average worn area of the cross-section was 3398.35 μm2, a reduction of approximately 27.8% compared with the unmodified stellite-6 clad layer. The wear surface primarily exhibited abrasive wear, with fewer cavities and a smoother surface.

Patterning of COC Polymers by Middle‐Energy Ion Beams for Selective Cell Adhesion in Microfluidic Devices

AbstractMicrofluidic devices play a crucial role in advanced cell biology applications, including cell separations, cultivations, migration and interaction studies, diagnostic devices, and organ‐on‐chips. One of the frequent purposes of such devices is the ability to selectively address the attachment of cells at defined locations on the surface. This study explores the application of middle‐energy carbon, oxygen, and nitrogen ions to locally modify the surface of cyclic olefin copolymer (COC) thermoplastic material, allowing selective cell growth on patterned polymer surfaces. The investigation considers ion element type, ion beam energy, and ion irradiation fluence, analyzing their influence on the modification effect. Characterization of the modified surfaces involves various surface‐analytical methods such as contact angle, energy dispersive spectroscopy (SEM‐EDX), atomic force microscopy (AFM), x‐ray photoelectron spectroscopy (XPS), rutherford backscattering spectrometry (RBS), and elastic recoil detection analysis (ERDA). The study extends to practical aspects, with a representative cancer cell line, MCF‐7, grown on the patterned surface to evaluate the degree of selective attachment. Additionally, the stability of the irradiated patterns is tested under elevated temperatures beyond the glass transition temperature (Tg), demonstrating the compatibility of the approach with hot embossing technology. The findings underscore the potential of ion beam treatment for COC in cell‐biology‐related applications, offering insights into surface modification techniques for enhanced functionality in microfluidic devices.

Lysine-mediated surface modification of cellulose nanocrystal films for multi-channel anti-counterfeiting

Utilizing advanced multiple channels for information encryption offers a powerful strategy to achieve high-capacity and highly secure data protection. Cellulose nanocrystals (CNCs) offer a sustainable resource for developing information protection materials. In this study, we present an approach that is easy to implement and adapt for the covalent attachment of various fluorescence molecules onto the surface of CNCs using the Mannich reaction in aqueous-based medium. Through the use of the Mannich reaction-based surface modification technique, we successfully achieved multi-color fluorescence in the resulting CNCs. The resulting CNC derivatives were thoroughly characterized by two dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron (XPS) spectroscopy. Notably, the optical properties of CNCs were well maintained after modification, resulting in films exhibiting blue and red structural colors. This enables the engineering of highly programmable and securely encoded anti-counterfeit labels. Moreover, subsequent coating of the modified CNCs with MXene yielded a highly secure encrypted matrix, offering advanced security and encryption capabilities under ultraviolet, visible, and near-infrared wavelengths. This CNC surface-modification enables the development of multimodal security labels with potential applications across various practical scenarios.

Surface modification of biomedical titanium alloy for hard tissue repair and reconstruction

In biomedical applications, various materials are used, including metals and their alloys, polymers and ceramics. Among them, titanium (Ti) and titanium alloys are widely utilised in implant materials due to their excellent corrosion resistance and high mechanical strength. However, despite these advantages, titanium is biologically inert and does not integrate well with human cells. Therefore, surface modification of titanium implants plays a crucial role in determining the rate of osseointegration and the overall success of the implants. The primary objective of this review is to provide a detailed introduction to surface modification technologies for titanium alloy implants. The aim is to enhance the biological activity, wear resistance, corrosion resistance and antibacterial properties and reduce the release of ions from the implants. By modifying the surface of titanium implants, it is possible to create a more favourable environment for cell adhesion, proliferation and differentiation. Various techniques, such as physical methods (e.g. sandblasting, acid etching) and chemical methods (e.g. surface oxidation, plasma treatment) can be employed to modify the surface properties of titanium implants. These surface modification techniques can enhance the interaction between the implant and the surrounding biological environment, promoting osseointegration and improving the long-term stability of the implant. Additionally, surface modifications can help reduce the release of potentially harmful ions from the implant, minimise bacterial adhesion and improve the overall biocompatibility of the implant. In conclusion, surface modification of titanium alloy implants is a critical aspect of biomedical engineering. By improving the biocompatibility of titanium implants, these modifications contribute to the success and longevity of implants used in hard tissue repair and reconstruction.

In-vitro fretting tribocorrosion and biocompatibility aspects of laser shock peened Ti-6Al-4V surfaces

Laser shock peening without coating (LSPwC), a prospective surface modification technique for improving the mechanical aspects of Ti-6Al-4V alloy for automotive/aerospace sector, is also expected to dictate the efficiency of this material class for implant application. Here we unravel the impact of LSPwC on Ti-6Al-4V material surface characteristics, in-vitro tribocorrosion and biocompatibility. Micrography shows the presence of nano and sub-micron sized pores after LSPwC process. The role of nano and sub-micron sized pores along with topography modification induced by LSPwC to serve as cues for controlling gene expressions, cell adhesion and activities offer novel insights in this research direction. A detailed X-ray photoelectron spectroscopy analysis detected local chemical non-stoichiometry with reduced number of oxygen diffusion channels. A crucial outcome of this oxide layer modification is the negative skewness (−0.55 ± 0.11) and reduced kurtosis (3.49 ± 0.14) of the surface, along with localized plastic deformation. These factors are correlated with the shift in potential during fretting tribo-corrosion from −800 to −250 mV after LSPwC, accompanied by a lower coefficient of friction of 0.4. Furthermore, the presence of well-spread cells and the up-regulation of beneficial genetic markers (Ki67) on LSPwC surfaces have the potential to form a better bone-material interface. The findings open new frontiers of the LSPwC-treated Ti-6Al-4V surface to synergistically modulate the tribocorrosion and biocompatibility aspects, with exciting possibilities for biomedical implants.

Surface Engineering on Bacteria for Tumor Immunotherapy: Strategies and Perspectives

AbstractBacteria have garnered significant attention in tumor immunotherapy recently years, owing to their immune‐activating properties, ease of genetic manipulation, and colonization abilities. In order to further enhance the safety, efficacy, and clinical translation potential of bacterial therapy, and to endow bacteria with additional functions, modifications or engineering of bacterial surfaces have emerged as a current research hotspot. This review systematically summarizes the primary methods and strategies for bacterial surface modification and engineering, including chemical alteration, physical modification, and bio‐modification. Subsequently, it is delve into the roles of these techniques in enhancing bacterial tumor immunotherapy, such as improving immunotherapeutic efficacy and reducing toxic side effects, and elucidate the underlying mechanisms. Finally, the current challenges faced in this field are deeply explored, and potential solutions for the future are presented. This work offers a comprehensive overview of the advancements in the new generation of bacterial surface modification techniques and their implications in bacterial‐based tumor immunotherapy.