Surface Structure Research Articles

A versatile surface micro structure design strategy for porous-based pressure sensors to enhance electromechanical performance

Pressure sensors based on porous structures offer comfortable user experiences and can adapt to the flexible movement of human limbs, which makes them attractive options for human–computer interaction and health monitoring. However, ascribed to the limitation of porous surfaces, foam-based pressure sensors are difficult to achieve accurate electric responses and stable signal output, limiting their great potential in wide application fields. Herein, a surface structure design strategy is proposed for improving the performance of porous foam-based pressure sensors. The coupling of microstructures and the collaboration of dual sensing mechanisms endow the sensor with high performance, achieving a ∼ 12 times signal fluctuation stability when compared to the sensor without any surface design. Even when working under complex vibration conditions, the developed sensor can also maintain a ∼ 7 times more stable output. An intelligent insole based on the algorithm model of a sensor array and multi-layer perceptron was developed for the diagnosis of human foot arch health. The sensors with surface structure could capture and differentiate signals more accurately, which results in a diagnostic accuracy of 99.75 % for the smart insole. The strategy for enhancement of sensor performance proposed in this work can be applied to foam sensors with multiple material systems, which is expected to broaden the potential application of porous flexible devices in fields like the Internet of Things, medical monitoring and brain-computer interface.

Techno-Economic Analysis of Solar PV Electricity Generation at the University of Environment and Sustainable Development in Ghana

The electricity indebtedness of Ghanaian schools is increasing due to the high cost of electricity in the country. As a result, the utility companies frequently disconnect the schools from the grid to force them to settle their debts. Meanwhile, the school can reduce its bills from rooftop solar PV systems, yet little attention is given. The study uses the University of Environment and Sustainable Development (UESD) as a case to assess the technical feasibility, economic viability, and potential benefits of implementing rooftop solar PV electricity in Ghanaian schools. Google Earth software was used to estimate the structure's rooftop surface areas to determine the potential energy harvest from a PV plant.In contrast, the economic analysis uses the net present value (NPV), internal rate of returns (IRR), discounted payback period (DPP) and profitability index (IP) to appraise the intended project. The results show that using rooftops of school structures can provide the needed electricity for local consumption and export excess to the grid for sales. The NPV, IRR, IP, and DPP recorded from the study are million GHS 15.15, 21%, 1.6 and 8 years, respectively. The findings highlight the potential of rooftop solar PV systems to meet educational institutions' electricity demand, exploring the possibility of exporting excess to the national grid for revenue (income generator), reducing operational costs, and contributing to a sustainable energy transition.

Lignin-enhanced wet strength and UV-Blocking properties of nanocellulose-based composite films obtained by casting/hot-pressing methods

We composited nanocellulose, lignin and polyvinyl alcohol (PVA) by using borax as a cross-linking agent, and prepared nanocellulose-based composite films by two simple and convenient methods of the casting and hot-pressing. Results showed that the molding method affected the film properties. The hot-pressing composite film exhibited smoother surface and tighter structures, while the casting one exhibited better stretchability. The composite films showed a good tensile strength (casting: 149.56 MPa; hot-pressing: 179.68 MPa). Due to the addition of lignin, the composite films were endowed with good UV-blocking capabilities, wet strength, oxidation resistance and bacteriostatic properties. The composite film has good application prospects in the field of food packaging and UV-shielding.

Quality assessment standards and production technology of artificial sand based on hydraulic concrete construction specifications

Natural sand and gravel resources are a local resource. Natural sand and gravel are non-renewable in a short time and are not suitable for long-distance transportation. After decades of mining, sand and gravel resources in some areas have been exhausted. The transportation distance of natural sand and gravel is getting farther and farther, and accordingly, the price of natural sand and gravel continues to rise. At the same time, continuous and disorderly mining has caused serious damage to the environment and resources. During the construction of large and medium-sized water conservancy and hydropower projects in China, due to the lack of surrounding natural aggregates, most projects use artificial aggregates. In the current national standards for water conservancy projects, the content of artificial sand and gravel powder is clearly defined. Based on the “Hydraulic Concrete Construction Specifications” (SL677-2014), this article summarizes the particle shape, gradation and surface structure of artificial sand, and also calculates the theoretical gradation of artificial sand. To find out the impact of stone powder content on the performance of artificial sand, different levels of stone powder content need to be selected for research and analysis to clarify the impact of artificial sand powder content on concrete properties. Research shows that for concrete made from artificial sand, increasing the aggregate content with a particle size less than 0.075 mm can significantly increase the compressive strength of the concrete. In artificial sand, the content of stone powder will affect the workability, polishability, durability, permeability and water release of concrete. In the artificial sand and gravel production process system, crushing and sand making equipment are the most important sand and gravel production equipment. The research results provide theoretical reference for the application of artificial sand in concrete and the update of artificial sand production technology and equipment.

Brillouin scattering from biomedical samples: the challenge of heterogeneity.

Abstract Brillouin light scattering (BLS), a non-destructive and non-contact technique, offers a powerful tool for probing the micromechanical properties of biological tissues. However, the inherent heterogeneity of biological tissues can pose significant challenges in interpreting BLS spectra. In this study, we introduce a novel method that harnesses the intensity information within a single BLS spectrum to directly estimate the Voigt average of the longitudinal modulus. Additionally, we use a method to determine the ratio of the squared Pockels coefficients for photoelastically heterogeneous samples, based on global analysis of a 2D BLS map. This method is shown to effectively determine the photoelastic ratio of soft and hard components of human bone tissues, enabling the calculation of the average elastic moduli. Furthermore, it has the remarkable ability to generate maps of the filling factor of the scattering volume, shedding valuable light on the intricate structure and topography of rough surfaces under BLS mapping.

Interfacial carbonyl groups of propylene carbonate facilitate the reversible binding of nitrogen dioxide.

The interaction of NO2 with organic interfaces is critical in the development of NO2 sensing and trapping technologies, and equally so to the atmospheric processing of marine and continental aerosol. Recent studies point to the importance of surface oxygen groups in these systems, however the role of specific functional groups on the microscopic level has yet to be fully established. In the present study, we aim to provide fundamental information on the interaction and potential binding of NO2 at atmospherically relevant organic interfaces that may also help inform innovation in NO2 sensing and trapping development. We then present an investigation into the structural changes induced by NO2 at the surface of propylene carbonate (PC), an environmentally relevant carbonate ester. Surface-sensitive vibrational spectra of the PC liquid surface are acquired before, during, and after exposure to NO2 using infrared reflection-absorption spectroscopy (IRRAS). Analysis of vibrational changes at the liquid surface reveal that NO2 preferentially interacts with the carbonyl of PC at the interface, forming a distribution of binding symmetries. At low ppm levels, NO2 saturates the PC surface within 10 minutes and the perturbations to the surface are constant over time during the flow of NO2. Upon removal of NO2 flow, and under atmospheric pressures, these interactions are reversible, and the liquid surface structure of PC recovers completely within 30 min.

Development of Sustainable Vegan Pea Protein-Zinc Complex: Characterization, In Vitro Cellular Mineral Uptake, and Application in Functional Biscuit Production

This study aimed to investigate the potential of pea protein concentrate (PPC) to form protein-mineral composites, with a specific focus on its zinc- (Zn-) binding capabilities. In addition, the physical and functional properties of PPC were evaluated. PPC, a potential protein source, was found to possess lipophilic properties, suggesting its suitability for various applications in food production. The investigation involved a comprehensive characterization of pea protein concentrate-zinc complex (PPC-Zn) composites, utilizing various analytical techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, particle size analysis, zeta potential measurement, and thermogravimetric analysis. The findings of this study indicated that the protein content of PPC-Zn (79.02 ± 1.33%) insignificantly increased as compared to PPC (78.86 ± 1.16%). Furthermore, PPC demonstrated improved functional properties, including increased protein solubility (2.55%), enhanced water-holding (13.09%) and oil-holding capacity (11.17%), and improved foaming capacity and stability (2.08% and 6.07%, respectively). These improvements in functional properties were likely attributed to the unique surface structure observed in SEM micrographs. The research also highlighted the maximum binding capacity of PPC for zinc, which was observed at concentrations of 5 mM (95.35 ± 1.86%). This binding of zinc ions to PPC induced changes in the characteristics and internal structures of the protein concentrate. Notably, the presence of functional groups such as -COOH, -OH, and –NH2 in PPC suggested their involvement in coordinating with zinc ions to form PPC-Zn composites. This investigation demonstrated a significant increase (2.26%) in the mineral bioavailability of PPC-Zn. Additionally, the cellular uptake, retention, and transport of PPC-Zn were improved by 9.79%, 7.84%, and 9.51%, respectively. Fortified biscuits (B2) demonstrated enhanced cellular uptake (2.79%), retention (4.84%), and transport (3.51%) compared with control biscuits. Fortified biscuits (B2) had higher microbial counts (total plate count is 3.57 ± 0.03 and the yeast-mold count is 3.96 ± 0.07 cfu/g) than control biscuits (B1) (total plate count is 2.49 ± 0.13 and the yeast-mold count is 3.44 ± 0.11 cfu/g) at the end of storage, and there is no difference in sensory evaluation between the control and fortified biscuits. Furthermore, the key findings indicated that PPC could serve as a promising carrier for mineral supplements, binding with zinc effectively.

Observation of parabolic electron bands on superconductor LaRu2As2

Abstract Ru-based superconductor LaRu2As2 has been discovered exhibiting the highest critical temperature of ~7.8 K among iron-free transition metal pnictides with the ThCr2Si2-type crystal structure. However, microscopic research on this novel superconducting material is still lacking. Here, we utilize scanning tunneling microscopy/spectroscopy to uncover the superconductivity and surface structure of LaRu2As2. Two distinct terminating surfaces are identified on the cleaved crystals, namely the As surface and the La surface. Atomic missing line defects are observed on the La surface. Both surfaces exhibit a superconducting gap of ~1.0 meV. By employing quasiparticle interference techniques, we observe standing wave patterns near the line defects on the La atomic plane. These patterns were attributed to quasiparticle scattering from two electron type parabolic bands.

Nanopatterning and nanostructure formation with femtosecond laser: Revolutionizing surface engineering on soda-lime glass

Glass, due to its high transparency and chemical stability, has found extensive use in electrical, electronic, and optoelectronic devices. This study presents a novel approach to modify the morphological features of laser-generated tracks and produced nanoparticles in soda-lime glass using the accuracy of micro processing by femtosecond laser pulses. The investigation has meticulously examined how variations in the incident laser pulse energy and scanning velocity dictate the formation of distinct morphological characteristics on the glass surface. FESEM has revealed three distinct morphological formations, including particulate, self-ordered periodic surface structures, and a combination of the two. Additionally, TEM analysis has shown the generation of both spherical and irregular-shaped nanoparticles with diameters ranging from 10 nm to less than 2 μm, and an amorphous structure confirmed by SAED patterns. The periodicity of the LIPSS was found to be 550±25 nm, and they were oriented perpendicular to the laser polarization vector.

Surface-Based Multimeric Aptamer Generation and Bio-Functionalization for Electrochemical Biosensing Applications.

Multimeric aptamers have gained more attention than their monomeric counterparts due to providing more binding sites for target analytes, leading to increased affinity. This work attempted to engineer the surface-based generation of multimeric aptamers by employing the room temperature rolling circle amplification (RCA) technique and chemically modified primers for developing a highly sensitive and selective electrochemical aptasensor. The multimeric aptamers, generated through surface RCA, are hybridized to modified spacer primers, facilitating the positioning of the aptamers in the proximity of sensing surfaces. These multimeric aptamers can be used as bio-receptors for capturing specific targets. The surface amplification process was fully characterized, and the optimal amplification time for biosensing purposes was determined, using SARS-CoV-2 spike protein (SP). Interestingly, multimeric aptasensors produced considerably higher response signals and affinity (more than 10-fold), as well as higher sensitivity (almost 4-fold) compared to monomeric aptasensors. Furthermore, the impact of surface structures on the response signals was studied by utilizing both flat working electrodes (WEs) and nano-/microislands (NMIs) WEs. The NMIs multimeric aptasensors showed significantly higher sensitivity in buffer and saliva media with the limit of detection less than 2 fg/ml. Finally, the developed NMIs multimeric aptasensors were clinically challenged with several saliva patient samples.

Surface‐Based Multimeric Aptamer Generation and Bio‐Functionalization for Electrochemical Biosensing Applications

Multimeric aptamers have gained more attention than their monomeric counterparts due to providing more binding sites for target analytes, leading to increased affinity. This work attempted to engineer the surface‐based generation of multimeric aptamers by employing the room temperature rolling circle amplification (RCA) technique and chemically modified primers for developing a highly sensitive and selective electrochemical aptasensor. The multimeric aptamers, generated through surface RCA, are hybridized to modified spacer primers, facilitating the positioning of the aptamers in the proximity of sensing surfaces. These multimeric aptamers can be used as bio‐receptors for capturing specific targets. The surface amplification process was fully characterized, and the optimal amplification time for biosensing purposes was determined, using SARS‐CoV‐2 spike protein (SP). Interestingly, multimeric aptasensors produced considerably higher response signals and affinity (more than 10‐fold), as well as higher sensitivity (almost 4‐fold) compared to monomeric aptasensors. Furthermore, the impact of surface structures on the response signals was studied by utilizing both flat working electrodes (WEs) and nano‐/microislands (NMIs) WEs. The NMIs multimeric aptasensors showed significantly higher sensitivity in buffer and saliva media with the limit of detection less than 2 fg/ml. Finally, the developed NMIs multimeric aptasensors were clinically challenged with several saliva patient samples.

Investigation of the Compound Strength of Hybrid Casting Components with Different Variations of Coated and Undercut Sheet Metal

AbstractLightweight design can reduce CO2 emissions and improve energy efficiency, especially in the fuel-intensive transportation sector. Multi-material design approaches can combine specific properties of materials for effective lightweight design. A multi-material component made from two metals used widely in industry could combine the exceptionally lightweight properties of aluminum with the strength and structural integrity of steel. However, joining aluminum and steel is a challenge due to their different thermo-physical properties and the possible formation of brittle intermetallic phases. In hybrid casting, aluminum is cast around a steel sheet insert in a high-pressure die casting process to produce complex parts. In a first approach, a cold gas sprayed aluminum coating on the insert was tested as a bonding agent between the steel substrate and the molten aluminum. The joint was achieved by a combination of metallurgical bonding and micro-clamping. As a second option, surface structures with undercuts were applied to the steel sheet by modified cold rolling, which allowed the molten aluminum to flow into the channels and interlock with the solid steel. Different orientations of the structure on the insert were tested. In addition, the combination of both approaches was used to potentially enhance the positive effect of the pretreatment techniques. Given the critical importance of joint strength, the quality of these approaches was tested by static tensile tests and dynamic fatigue tests. The results show that the joint by coatings is strongly influenced by the process temperature. The improvement of the joint by the surface structure depends on its orientation to the melt flow.

Structure and Chemical Reactivity of Y-Stabilized ZrO2 Surfaces: Importance for the Water-Gas Shift Reaction.

The surface structure and chemical properties of Y-stabilized zirconia (YSZ) have been subjects of intense debate over the past three decades. However, a thorough understanding of chemical processes occurring at YSZ powders faces significant challenges due to the absence of reliable reference data acquired for well-controlled model systems. Here, we present results from polarization-resolved infrared reflection absorption spectroscopy (IRRAS) obtained for differently oriented, Y-doped ZrO2 single-crystal surfaces after exposure to CO and D2O. The IRRAS data reveal that the polar YSZ(100) surface undergoes reconstruction, characterized by an unusual, red-shifted CO band at 2132 cm-1. Density functional theory calculations allowed to relate this unexpected observation to under-coordinated Zr4+ cations in the vicinity of doping-induced O vacancies. This reconstruction leads to a strongly increased chemical reactivity and water spontaneously dissociates on YSZ(100). The latter, which is an important requirement for catalysing the water-gas-shift (WGS) reaction, is absent for YSZ(111), where only associative adsorption was observed. Together with a novel analysis scheme these reference data allowed for an operando characterisation of YSZ powders using DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy). These findings facilitate rational design and tuning of YSZ-based powder materials for catalytic applications, in particular CO oxidation and the WGS reaction.

Ultrathin Al2O3 film modification on waterborne epoxy coatings by atomic layer deposition for augmenting the corrosion resistance

The polar channels formed by the curing of waterborne anticorrosive coatings compromise their water resistance, leading to coating degradation and metal corrosion. To enhance the anticorrosive performance of waterborne coatings, this study proposed a novel method of depositing ultrathin Al2O3 films on the surface of waterborne epoxy coatings by atomic layer deposition, a technique that can modify the surface properties of polymer materials by depositing functional films. The Al2O3-modified coatings exhibited improved sealing and barrier properties by closing the polar channels and surface defects and cracks. The surface structure and morphology of the modified coatings were characterized by x-ray photoelectron spectroscopy and scanning electron microscopy. The hydrophilicity and corrosion resistance of the modified coatings were evaluated by water contact angle measurement, Tafel polarization curve, and electrochemical impedance spectroscopy. The results indicated that the water contact angle of the Al2O3-modified coating increased by 48° compared to the unmodified coating, and the protection efficiency of the modified coating reached 99.81%. The Al2O3-modified coating demonstrated high anticorrosive efficiency and potential applications for metal anticorrosion in harsh marine environments.

Assessment of the potential structure and nucleation efficacy of multi-component heterogeneous substrate

In recent years, nucleation of multi-component heterogeneous interface structures has attracted increasing attention due to their excellent grain refinement and anti-poisoning capabilities in Al-Si alloy. In this research, a general methodology was proposed to predict the surface structure and meanwhile evaluate the grain refinement efficacy of the multi-component boride nucleants based on a comprehensive experimental and theoretical study of a novel Al-Si alloy refiner, i.e., Al-3.5Nb-1V-1B. By using high-resolution electron microscopy, the (Nb, V)B2 particle with a characteristic “core-shell” surface structure was observed, attributed to V adsorption driven by interfacial energy minimization, validated by ab initio calculations. A general interfacial energy-based model was then proposed which predicts the multi-component boride substrate structure, well consistent with the experimental findings. The nucleation potency of different substrates was analyzed in atomic scale and only if the interfacial atomic vibration was considered together with the nucleation-influencing factors (i.e., the lattice mismatch and the anti Si-poisoning effect), the predicted nucleation potency order can agree well with the experimental results. A thermodynamics-kinetics combined analytic model was summarized by coupling the lattice mismatch parameter, the interfacial Si adsorption energy and the interfacial atomic vibration amplitude, which accurately evaluates the multi-component boride grain refiners for the Al-Si alloys.

Time-resolved surface reaction kinetics in the pressure gap.

We extend the use of our recently developed Near-Ambient Pressure Velocity Map Imaging (NAP-VMI) technique to study the kinetics and dynamics of catalytic reactions in the pressure gap. As an example, we show that NAP-VMI combined with molecular beam surface scattering allows the direct measurement of time- and velocity-resolved kinetics of the scattering and oxidation of CO on the Pd(110) surface with oxygen pressures at the surface up to 1 × 10-5 mbar, where different metastable surface structures form. Our results show that the c(2 × 4) oxide structure formed at low O2 pressure is highly active for CO oxidation. The velocity distribution of the CO2 products shows the presence of two reaction channels, which we attribute to reactions starting from two distinct but rapidly interconverting CO binding sites. The effective CO oxidation reaction activation energy is Er = (1.0 ± 0.13) eV. The CO2 production is suppressed at higher O2 pressure due to the number of antiphase domain boundaries increasing, and the missing row sites are filled by O-atoms at O2 pressures approaching 1 × 10-6 mbar. Filling of these sites by O-atoms reduces the CO surface lifetime, meaning the surface oxide is inactive for CO oxidation. We briefly outline further developments planned for the NAP-VMI and its application to other types of experiments.

A high-precision 3D reconstruction method for the internal structure of small Solar System bodies

Small Solar System bodies (SSSBs) hold crucial information for understanding the formation and evolution of the Solar System. However, due to their considerable distance, small size, fast rotation, and a lack of prior information, the detection of these celestial bodies, especially their internal structures, faces numerous challenges. We explore whether the 3D structure of SSSBs can be reconstructed using monostatic radar. We investigated a more convenient observation mode and addressed the issue of the poor imaging quality of internal structures within existing imaging algorithms. Our study focused on a high-precision 3D imaging method for the internal structure of SSSBs based on radar signals. First, we considered a flyby observation mode that uses the spinning characteristics of the target for global observations, and we set up a scaled-down experimental system in the laboratory to simulate this observation mode. Next, we constructed a 3D printed physical surface model based on the shape of the asteroid 162173 Ryugu. We filled it with sand and inserted a small bottle containing different materials separately to construct two distinct layered analogs. The analogs were employed in laboratory measurements to acquire radar echoes, which were then inverted using both a classic back-projection (BP) algorithm and a modified multilayer back-projection (MLBP) method. The results shown that the 3D surface structure of the target can be reconstructed well through the BP and MLBP algorithms. The MLBP algorithm exhibits a higher reconstruction accuracy for internal structures. Moreover, compared to the BP method, the MLBP method is less sensitive to the quality of echo signals, resulting in a relatively stable imaging performance. Our findings reveal that observing and reconstructing the high-precision structure of SSSBs is feasible through our proposed method. The observation mode, experimental setup, and analog modeling approach are widely applicable and can be applied in future research on the detection of SSSBs with more diverse and complex structures.

Deep-subwavelength single grooves prepared by femtosecond laser direct writing on Si

Abstract It is well known that, femtosecond-laser pulses are easy to spontaneously induce deep-subwavelength periodic surface structures on transparent dielectrics, but not on non-transparent semiconductors. Nevertheless, in the study we demonstrate that by high-NA 800-nm femtosecond-laser direct writing with controlling the pulse energy and scanning speed in the near-damage-threshold regime, polarization-dependent deep-subwavelength single grooves with linewidths of ~180 nm can be controllably prepared on Si. Generally, the single-groove linewidth increases slightly with the increase of pulse energy and the decrease of scanning speed, whereas the single-groove depth significantly increases from ~300 to ~600 nm with the decrease of scanning speed, or even over 1 μm with the multi-processing, indicating the characteristics of transversal clamping and longitudinal growing of such deep-subwavelength single grooves. Then, EDS composition analysis of the near-groove region confirms that the single-groove formation tends to be an ultrafast, non-thermal ablation process, and the oxidized deposits nearby the grooves are easy to clean up. Furthermore, the results showing the strong dependence of groove orientation on laser polarization, and the occurrence of double-groove structures due to the interference of pre-formed orthogonal grooves, both indicate that the extraordinary field enhancement of strong polarization sensitiveness in the deep-subwavelength groove plays an important role for single-groove growth with high stability and collimation.

Oxygen Vacancy-Rich NiCo2O4 on Carbon Framework with Controlled Pore Architectures as Efficient Bifunctional Electrocatalysts for Zn-Air Batteries

Transition metal oxides are considered alternative electrocatalysts for ZAB owing to their multiple oxidation states. However, they have limitations such as low electrical conductivity and the deficiency of reactive sites. In this study, to overcome these shortcomings and improve electrocatalytic activity, oxygen vacancies and porous architectures were introduced through a partial reduction process and a porous carbon framework. Open porous carbon microspheres with uniformly loaded NiCo2O4 nanosheets and oxygen vacancies (V-NCO/OPC) displayed enhanced electrocatalytic performance with a low Tafel slope (68 mV dec-1) in the oxygen reduction reaction (ORR) and a low overpotential (402 mV) at 10 mA cm–2 in the oxygen evolution reaction (OER). The combined effect of the oxygen vacancies and porous architecture can offer sufficient active sites, modify the electronic structure of the metal oxide surface, and facilitate mass transport, enhancing the electrocatalytic properties of V-NCO/OPC. Furthermore, when applied for ZAB, V-NCO/OPC demonstrated better electrochemical performance including discharge power density (154.9 mW cm-2) at the current density of 175.9 mA cm-2, low voltage gap (0.85 V) at the initial cycle, and long-term (250 h) cycle stability at the current density of 10 mA cm−2 than those of noble-metal electrocatalysts.

Tuning Surface Organic Structures by Small Gas Molecules through Catassembly and Coassembly.

The field of molecular assembly has seen remarkable advancements across various domains, such as materials science, nanotechnology, and biomedicine. Small gas molecules serve as pivotal modulators, capable of altering the architecture of assemblies via tuning a spectrum of intermolecular forces including hydrogen bonding, dipole-dipole interactions, and metal coordination. Surface techniques, notably scanning tunneling microscopy and atomic force microscopy, have proven instrumental in dissecting the structural metamorphosis and characteristic features of these assemblies at an unparalleled single-molecule resolution. Recent research has spotlighted two innovative approaches for modulating surface molecular assemblies with the aid of small gas molecules: "catassembly" and "coassembly". This Perspective delves into these methodologies through the lens of varying molecular interaction types. The strategies discussed here for regulating molecular assembly structures using small gas molecules can aid in understanding various complex assembly processes and structures and provide guidance for the further fabrication of complex surface structures.