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This study systematically explores the wetting characteristics of re‐entrant microstructures, focusing on the interplay between the unique geometries and material compositions. While silicon dioxide (SiO₂) re‐entrant microstructures are previously studied, this research pioneers the fabrication of silicon carbide (SiC) re‐entrant microstructures. Through experimental approaches and theoretical analysis, the research assesses how variations in geometry and material impact wettability. Key findings reveal that SiC re‐entrant structures achieve an average contact angle of 145°, closely matching the 148° observed for SiO₂, indicating similar hydrophobic behavior. Although flat SiC surfaces exhibit higher inherent hydrophobicity than flat SiO₂ (59° vs 26° contact angle), re‐entrant geometry predominantly influences wetting behavior, overshadowing material differences. Structures with lower solid area fractions show increased hydrophobicity, with a distinct hierarchy: microlines are the least hydrophobic, followed by shark‐skin textures, rectangles, circles, and triangles. Additionally, increasing the gap size between structures enhanced hydrophobicity up to a critical point. This study paves the way for optimizing re‐entrant microstructures for specific applications, significantly enhancing the understanding of surface science and advancing material design. [ABSTRACT FROM AUTHOR]

Microneedles hold remarkable potential for providing convenient and unique solutions for disease diagnosis and therapy. However, their integration into clinical practices has been slow, primarily due to the challenge of developing models that meet the criteria of a particular application. A comprehensive and systematic analysis of all aspects of microneedle platforms is imperative to overcome this bottleneck. The analysis involves gathering performance‐related information and understanding the factors affecting the functionality of microneedles. The performance of microneedles is heavily influenced by parameters such as dimensions, needle shape, array arrangement, and materials (flexible, stretchable, stimuli‐responsive, biodegradable). This article presents a fresh perspective on microneedles, introducing concepts toward optimal designs across various microneedle platforms. This includes application, design, fabrication techniques, and understanding how a specific microneedle design can effectively meet the requirements of a particular application. By addressing these crucial issues, further advancement of microneedle technology occurs. [ABSTRACT FROM AUTHOR]

The evaporation dynamics of sessile droplets on re-entrant microstructures are critical for applications in microfluidics, thermal management, and self-cleaning surfaces. Re-entrant structures, such as mushroom-like shapes with overhanging features, trap air beneath droplets to enhance non-wettability. The present study examines the evaporation of a water droplet on silicon carbide (SiC) and silicon dioxide (SiO2) re-entrant structures, focusing on the effects of material composition and solid area fraction on volume reduction, contact angle, and evaporation modes. Using surface free energy (SFE) as an indicator of wettability, we find that the low SFE of SiC promotes quick depinning and contact line retraction, resulting in shorter CCL phases across different structures. For instance, the CCL phase accounts for 55–59% of the evaporation time on SiC surfaces, while on SiO2 it extends to 51–68%, reflecting a 7–23% increase in duration due to stronger pinning effects. Additionally, narrower pillar gaps, which increase the solid area fraction, further stabilize droplets by extending both CCL and constant contact angle (CCA) phases, while wider gaps enable faster depinning and evaporation. These findings illustrate how hydrophobicity (via SFE) and structural geometry (via solid area fraction) influence microscale interactions, offering insights for designing surfaces with optimized liquid management properties. [ABSTRACT FROM AUTHOR]

Surface wettability, the interaction between a liquid droplet and the surface it contacts, plays a key role in influencing droplet behavior and flow dynamics. There is a growing interest in designing surfaces with tailored wetting properties across diverse applications. Advanced fabrication techniques that create surfaces with unique wettability offer significant innovation potential. This study investigates the wettability transition of laser-textured anisotropic surfaces featuring shark skin-inspired microstructures using four post-processing methods: spray coating, isopropyl alcohol (IPA) treatment, silicone oil treatment, and silanization. The impact of each method on surface wettability was assessed through water contact angle measurements, scanning electron microscopy (SEM), and laser scanning microscopy. The results show a transition from superhydrophilic behavior on untreated laser-textured surfaces to various (super)hydrophobic states following surface treatment. Chemical treatments produced different levels of hydrophobicity and anisotropy, with silanization achieving the highest hydrophobicity and long-term stability, persisting for one year post-treatment. This enhancement is attributed to the low surface energy and chemical properties of silane compounds, which reduce surface tension and increase water repellence. In conclusion, this study demonstrates that post-processing techniques can effectively tailor surface wettability, enabling a wide range of wetting properties with significant implications for practical applications. [ABSTRACT FROM AUTHOR]

Microstructured surfaces are renowned for their unique properties, such as waterproofing and low adhesion, making them highly applicable in the biomedical field. These surfaces play a crucial role in influencing cell response by mimicking the native microenvironment of biological tissues. In this study, we engineered a series of biomimetic micropatterned surfaces using polydimethylsiloxane (PDMS) to explore their effects on primary breast cancer cell lines, contrasting these effects with those observed on conventional flat surfaces. The surface topography was varied to direct cells' attachment, growth, and morphology. Our findings elucidate that surface-free energy is not merely a background factor but plays a decisive role in cell dynamics, strongly correlating with the spreading behaviour of breast cancer cells. Notably, on micropillar surfaces with high surface-free energy, an increase in the population of cancer cells was observed. Conversely, surfaces characterised by lower surface-free energies noted a reduction in cell viability. Moreover, the structural parameters, such as the gaps and diameters of the pillars, were found to critically influence cellular dispersion and adherence, underscoring the importance of the microstructures' topography in biomedical applications. These insights pave the way for designing advanced microstructured surfaces tailored to specific cellular responses, opening new avenues for targeted cancer therapies and tissue engineering. [ABSTRACT FROM AUTHOR]

Electrical neuron stimulation holds promise for treating chronic neurological disorders, including spinal cord injury, epilepsy, and Parkinson's disease. The implementation of ultrathin, flexible electrodes that can offer noninvasive attachment to soft neural tissues is a breakthrough for timely, continuous, programable, and spatial stimulations. With strict flexibility requirements in neural implanted stimulations, the use of conventional thick and bulky packages is no longer applicable, posing major technical issues such as short device lifetime and long-term stability. We introduce herein a concept of longlived flexible neural electrodes using silicon carbide (SiC) nanomembranes as a faradic interface and thermal oxide thin films as an electrical barrier layer. The SiC nanomembranes were developed using a chemical vapor deposition (CVD) process at the wafer level, and thermal oxide was grown using a high-quality wet oxidation technique. The proposed material developments are highly scalable and compatible with MEMS technologies, facilitating the mass production of long-lived implanted bioelectrodes. Our experimental results showed excellent stability of the SiC/silicon dioxide (SiO2) bioelectronic system that can potentially last for several decades with well-maintained electronic properties in biofluid environments. We demonstrated the capability of the proposed material system for peripheral nerve stimulation in an animal model, showing muscle contraction responses comparable to those of a standard non-implanted nerve stimulation device. The design concept, scalable fabrication approach, and multimodal functionalities of SiC/SiO2 flexible electronics offer an exciting possibility for fundamental neuroscience studies, as well as for neural stimulation-based therapies. [ABSTRACT FROM AUTHOR]