3D Membrane Research Articles

Mass Transfer in Boronate Ester 2D COF Single Crystals.

Unlike graphene and similar structures, 2D covalent organic frameworks (2D COFs) exhibit intrinsic porosity with a high areal density of well-defined and uniform openings. Given the pore size adjustability, 2D COFs are likely to outperform artificially perforated inorganic layers with respect to their prospects in membrane separation. Yet, exploring the mass transport in 2D COFs is hidden by the lack of laterally extended free-standing membranes. This work reports on direct molecular permeation measurements with single crystals of an interfacially synthesized boronate ester 2D COF. In accordance with the material topography, the atmospheric and noble gases readily pass the suspended nanosheets while their areal porosity is quantified to be almost 40% exceeding that in any 2D membranes known. However, bulkier aromatic hydrocarbons are found to deviate substantially from Graham's law of diffusion. Counterintuitively, the permeation rate is demonstrated to rise from benzene to toluene and further to xylene despite the increase in the molecular mass and dimensions. The results are interpreted in terms of adsorption-mediated flow that appears to be an important transport mechanism for microporous planar nanomaterials.

Smart Two‐Dimensional Membranes for Molecular Separations

AbstractMembrane‐based separation technologies are gaining prominence in energy‐efficient separation processes. Smart membranes, which change their physical or chemical characteristics in response to environmental stimuli, are attractive membrane candidates. This review summarizes the recent development and applications of smart membranes based on two‐dimensional (2D) materials, mainly focusing on their design, fabrication, and applications in molecular separations. Furthermore, stimuli for triggering smart 2D membranes are classified and explained. Finally, we propose areas for improvement and further development for future studies, such as the issues of complicated fabrication, long term stability in real operating conditions, and responding to different environmental stimuli at the same time.

Robust and Flexible Optically Active 2D Membranes Based on Encapsulation of Liquid Crystals in Graphene Oxide Pockets

AbstractDesign and engineering of novel low dimensional metamaterials allow for new applications in membrane technology, aerospace and automotive industries, architecture, robotics, medicine, and textiles. Such materials can be strong, flexible, transparent, and can be assigned with different functionalities. Here, the authors explore the possibility of 2D graphene oxide (GO) surface to guide self‐assembly of 4‐cyano‐4′‐pentylbiphenyl (5CB) molecules via multiple hydrogen bonding and their clustering in optically active phases. The encapsulation of 5CB in a 2D geometry and birefringent properties of 5CB are tuned by the regulation of interaction energy between GO surface and 5CB. Chemical reduction of GO‐5CB composites results in electrically conductive reduced graphene oxide‐5CB membranes which change optical properties in response to Joule heating. The sustainable approach to the design of robust and flexible optically active materials will allow the formation of other metamaterials with different functionalities for advanced applications.

Potential Biomedical Applications of Collagen Filaments derived from the Marine Demosponges Ircinia oros (Schmidt, 1864) and Sarcotragus foetidus (Schmidt, 1862)

Collagen filaments derived from the two marine demosponges Ircinia oros and Sarcotragus foetidus were for the first time isolated, biochemically characterised and tested for their potential use in regenerative medicine. SDS-PAGE of isolated filaments revealed a main collagen subunit band of 130 kDa in both of the samples under study. DSC analysis on 2D membranes produced with collagenous sponge filaments showed higher thermal stability than commercial mammalian-derived collagen membranes. Dynamic mechanical and thermal analysis attested that the membranes obtained from filaments of S. foetidus were more resistant and stable at the rising temperature, compared to the ones derived from filaments of I. oros. Moreover, the former has higher stability in saline and in collagenase solutions and evident antioxidant activity. Conversely, their water binding capacity results were lower than that of membranes obtained from I. oros. Adhesion and proliferation tests using L929 fibroblasts and HaCaT keratinocytes resulted in a remarkable biocompatibility of both developed membrane models, and gene expression analysis showed an evident up-regulation of ECM-related genes. Finally, membranes from I. oros significantly increased type I collagen gene expression and its release in the culture medium. The findings here reported strongly suggest the biotechnological potential of these collagenous structures of poriferan origin as scaffolds for wound healing.

Ion Selective Membranes

Ion Selective Membranes

Biomineralization of ZrO2 nanoparticles on graphene oxide-supported peptide/cellulose binary nanofibrous membranes for high-performance removal of fluoride ions

Two-dimensional (2D) nanomaterial-based functional nanoporous membranes exhibit potential applications for economic, rapid, and highly efficient water purification. In order to improve the removal efficiency of various pollutants from water, it is necessary to introduce functional metal oxides into the 2D membranes to form hybrid membranes. In this work, we demonstrate the design and synthesis of graphene oxide (GO)-supported conjugation with cellulose nanofibers (CNFs) and self-assembled peptide nanofibers (PNFs). Ascribing to the biomimetic properties of both CNFs and PNFs, ZrO2 nanoparticles were synthesized along the as-formed binary nanofibers to form GO/PNF/CNF-ZrO2 nanohybrids via a biomineralization process. Through the vacuum filtration, nanofibrous membranes were fabricated easily, which exhibited high performance for the removal of fluoride ions (F-) from water. The removal efficiency of the designed hybrid membranes towards F- samples with the concentration range from 20 to 200 mg/L can exceed 96%. In addition, the nanofibrous filtration membranes showed good recyclability for continuous adsorption and removal of F-. The sustainability of the fabricated functional filtration membranes was further evaluated using the Sustainability Footprint method. This study will be valuable to promote the design and synthesis of nanoporous membranes via biomimetic synthesis with high sustainability for water purification applications.

Graphene oxide nanofiltration membrane with trimethylamine-N-oxide zwitterions for robust biofouling resistance

Biofouling is one of the most critical issues that jeopardizes membrane separation performance, accounting for nearly half of all types of membrane fouling. Herein, inspired by the actions of cuttlefish, we propose an effective strategy to mitigate fouling by fabricating a zwitterionic polymer-brush-modified graphene oxide tethered with trimethylamine-N-oxide (TMAO) head groups. Following a facile vacuum filtration approach with in situ crosslinking, the corresponding 2D membranes (T-GO) were constructed with tunable surface thicknesses and reasonable mechanical robustness. Owing to its unique transport pathways, an optimal membrane exhibits a typical characteristic of nanofiltration with excellent water permeability and a considerably high “solute–solute” selectivity of 18.6 ± 0.3 (toward Congo red/Na2SO4), demonstrating a great potential for desalinating textile wastewaters. As the positively and negatively charged head groups are directly connected via a single covalent N–O bond, the O atom can accept three hydrogen bonds in a single polymeric chain, as revealed by the first-principles molecular dynamics simulations. The robust surface hydration layer, induced by surface hydrophilicity, and the disinfection effect, brought by the quaternary ammonium groups, both contribute to the remarkable antiadhesion and contact inactivation ability of the T-GO membrane. Therefore, the antibacterial properties of the T-GO membrane were significantly enhanced, which was experimentally verified for the first time in both the static contact mode and dynamic microfluidic operations. In general, our results provide a robust methodology for designing a new class of nonfouling zwitterionic membranes for sustainable membrane applications.

Two-dimensional metal−porphyrin framework membranes for efficient molecular sieving

Two-dimensional (2D) membranes were constructed using porphyrin-based metal organic frameworks (MOFs), i.e., copper-tetrakis(4-carboxyphenyl) porphyrin (Cu-TCPP), for efficient molecular sieving of dye/salt mixture solutions. These novel membranes contained a regular Cu-TCPP nanosheet filter layer fabricated by the vacuum filtration method to retain the oriented interlayer structure of the MOF material, resulting in a robust 2D membrane. The hydrated Cu-TCPP membrane with a thickness of 300 nm displayed high retention rates for dyes (90.1% for crystal violet (CV), 93.3% for Chrome black T (CB-T), 99.7% for Methyl blue (MB) and 99.8% for Congo red (CR); CV, Mw= 407.9 g/mol; CB-T, Mw=416.4 g/mol) with diameters approximately greater than 1.3 nm. A water permeance of 840.1 L·m−2·h−1·bar−1 and a CR (Mw= 696.7 g/mol) rejection rate of 99.9% were obtained with the optimal metal−porphyrin framework membrane (small lamellar dimension nanosheets) undergoing the cross-flow mode filtration of dye/salt mixture solutions for 24 h. More importantly, due to the abundant interlayers and regular surface nanochannels, the Cu-TCPP membrane exhibited a low salt rejection rate (0.4% for NaCl) and an outstanding CR/NaCl selectivity (as high as 249.5), which was more superior compared with that of other reported two-dimensional membranes. Additionally, the nanochannels of the membrane presented strong rigidity under pressure load as high as 0.4 MPa, endowing the membrane with high tolerance to shear stress and good antifouling performance after several fouling-cleaning cycles.

Bio-inspired ferromagnetic graphene oxide/magnetic ionic liquid membrane for highly efficient CO2 separation

The design of high-performance CO2 separation membrane with both ultrathin thickness and robust stability remains a challenge. Herein, inspired by the function of AQP1 within the biological membrane for gas selectivity, an untrathin (∼45 nm) graphene oxide/magnetic ionic liquid membrane (GO/MILM) is prepared by infusing [P6,6,6,14][FeCl4] into the 2D nano-space of stacked GO nanosheets. Due to the affinity difference of various gases in MIL, the synergy of electrostatic and magnetic interaction between GO and MIL, ordered arrangement of magnetic anions [FeCl4]− in the nanospace between GO nanosheets is achieved, resulting efficient CO2 separation. The molecular dynamics simulation manifests the separation mechanism. In consequence, the optimized GO/MILM exhibits fast CO2 permeance of 82.9 GPU with high CO2/N2 and CO2/CH4 selectivity of 180 and 76, respectively, surpassing most of reported membranes. Moreover, a stable performance more than 7 days renders the GO/MILM great potential for industrial CO2 separation. This bioinspired strategy may provide a potential to fabricate 2D membranes integrating high-performance, low cost and ultrathin thickness for CO2 capture.

Supported MXene/GO Composite Membranes with Suppressed Swelling for Metal Ion Sieving.

Novel two-dimensional (2D) membranes have been utilized in water purification or seawater desalination due to their highly designable structure. However, they usually suffer from swelling problems when immersed in solution, which limits their further applications. In this study, 2D cross-linked MXene/GO composite membranes supported on porous polyamide substrates are proposed to improve the antiswelling property and enhance the ion-sieving performance. Transition-metal carbide (MXene) nanosheets were intercalated into GO nanosheets, where the carboxyl groups of GO combined the neighboring hydroxyl terminal groups of MXene with the formation of -COO- bonds between GO and MXene nanosheets via the cross-linking reaction (−OH + −COOH = −COO− + H2O) after heat treatment. The permeation rates of the metal ions (Li+, Na+, K+, Al3+) through the cross-linked MXene/GO composite membrane were 7–40 times lower than those through the pristine MXene/GO membrane. In addition, the cross-linked MXene/GO composite membrane showed excellent Na+ rejection performance (99.3%), which was significantly higher than that through pristine MXene/GO composite membranes (80.8%), showing improved ion exclusion performance. Such a strategy represents a new avenue to develop 2D material-derived high-performance membranes for water purification.

Heterogeneous MXene/PS‐b‐P2VP Nanofluidic Membranes with Controllable Ion Transport for Osmotic Energy Conversion

AbstractMembrane‐based osmotic power harvesting is a strategy for sustainable power generation. 2D nanofluids with high ion conductivity and selectivity are emerging candidates for osmotic energy conversion. However, the ion diffusion under nanoconfinement is hindered by homogeneous 2D membranes with monotonic charge regulation and severe concentration polarization, which results in an undesirable power conversion performance. Here, an asymmetric nanochannel membrane with a two‐layered structure is reported, in which the angstrom‐scale channels of 2D transition metal carbides/nitrides (MXenes) act as a screening layer for controlling ion transport, and the nanoscale pores of the block copolymer (BCP) are the pH‐responsive arrays with an ordered nanovoid structure. The heterogeneous nanofluidic device exhibits an asymmetric charge distribution and enlarged 1D BCP porosity under acidic and alkaline conditions, respectively; this improves the gradient‐driven ion diffusion, allowing a high‐performance osmotic energy conversion with a power density of up to 6.74 W m−2 by mixing artificial river water and seawater. Experiments and theoretical simulations indicate that the tunable asymmetric heterostructure contributes to impairing the concentration polarization and enhancing the ion flux. This efficient osmotic energy generator can advance the fundamental understanding of the MXene‐based heterogeneous nanofluidic devices as a paradigm for membrane‐based energy conversion technologies.

Wafer‐Scale Van der Waals Assembly of Free‐Standing Near Atom Thickness Hetero‐Membranes for Flexible Photo‐Detectors (Adv. Electron. Mater. 8/2021)

Spontaneous Delamination In article 2100395, Yeonwoong Jung and coworkers report the deterministic van der Waals assembly of wafer-scale 2D and 3D free-standing membranes by exploring their capillary forcedriven spontaneous delamination inside water. The assembled near atom thickness 2D/3D hetero-membranes exhibit an excellent combination of large mechanical flexibility and high photoresponsiveness at a wide range of illumination wavelength, implying high promise for futuristic opto-electronic devices.

Interfaces is Growing!

We are reaching out with some exciting news! From 1st of May, I, Jolke Perelaer have been appointed to the position of Editor-in-Chief of Advanced Materials Interfaces. Three Deputy Editors have been appointed as well: Lu Shi strengthens the journal from China, and we welcome Ingeborg Stass from our team in Berlin and John Uhlrich from the Weinheim office. Under the leadership of Peter Gregory, Advanced Materials Interfaces started in 2014 as a journal that provided a dedicated home for research with a focus on the interface of the materials. Over the last 4 years, Anna Troeger and I worked together as Deputy Editors to carry the journal forward; she has now been appointed Editor-in-Chief of Solar RRL, and will remain involved in Advanced Materials Interfaces as a peer-review editor. With its newly installed leaders, Advanced Materials Interfaces will continue to provide a forum for interface-related research across different disciplines with a demonstrable potential for application. Amongst the many topics we have published, well-cited topics include 2D materials, opto-electronic devices, biomaterials, nature-inspired surfaces, membranes, surface reactions, and energy storage materials. And there is more exciting news to share! The new Impact Factor for Advanced Materials Interfaces has increased to 6.147 (Clarivate Journal Citation Reports 2021), which is an increase of 24% compared to the previous one. With this Advanced Materials Interfaces further strengthened its position as an important journal in the area of interface-based research. Don't forget to take a look into our Hall of Fame virtual issue, which is frequently updated series with invited-only review articles from the top scientists in their fields, and the Biomaterials issue, where articles are collected on all topics of biomaterials, including hydrogels, tissue engineering, and drug delivery. Finally, we would like to thank our Advisory Board members, authors, reviewers, and readers for their continuous interest as well as their support for Advanced Materials Interfaces. We hope to serve up more great publications! On behalf of the editorial team,

Evaluating gas permeance through graphene nanopores and porous 2D-membranes: A generalized approach

Porous graphene and 2D-membranes are known for favorable nanofluidic properties, such as high gas permeability and selectivity, depending on energy barrier for the molecule translocated through the nanopore. Despite the immense demand for proper theoretical description of gas flow through nanopores, a formalism including the energy barrier and steric effects to translocation remains conspicuously absent. Here, using both analytical and first-principles calculations, we study the permeance properties of porous 2D membranes. In particular, we develop the general equation for the permeance (and selectivity) of gases through circular nanopores, including both energy barrier and additional steric effects. Our theory captures sensitivity to the pore size, yields easy estimates for permeance through nanopores of less regular shape, and corroborates experimental findings. For completeness of the analysis, we disclose the importance of the energy barrier against surface diffusion of the permeance and report that e.g. the energy barrier against surface diffusion of He (CH4) through a pore with effective size 0.55 nm is 32 meV (114 meV), which is four times larger than the barrier predicted by the classical force fields. Presented upgrades of the long-standing gas flow theory are critical for further development of nano-patterned 2D membranes, as needed for emergent gas separation and purification technology.

Durable and super-hydrophilic/underwater super-oleophobic two-dimensional MXene composite lamellar membrane with photocatalytic self-cleaning property for efficient oil/water separation in harsh environments

Super-wetting membranes with outstanding permeation and anti-fouling performance are promising candidates for highly-efficient oily wastewater treatment. Herein, we designed a facile strategy to fabricate the super-hydrophilic/underwater super-oleophobic two-dimensional MXene-based composite membrane via vacuum-assisted self-assembly of two-dimensional MXene nanosheets on porous polyvinylidene fluoride (PVDF) substrate and in situ mineralization of photocatalyst β-FeOOH on the membrane surface. Benefiting from the inherent super-wettability and regulated lamellar structure (Short transport pathway and abundant nanochannels), the resultant MXene-based composite membrane displayed fast permeation flux (500.38–1022.7 L m−2 h−1) and favorable separation efficiency (99.32–99.72%) for a series of micro-scaled oil-in-water emulsions. Importantly, the excellent photo-induced self-cleaning capability and low oil-adhesion contributed to the high anti-fouling resistance, outstanding reusability, and durability of 2D MXene composite membrane. Moreover, the 2D MXene composite membrane exhibited superior chemical stability, which enabled it to maintain highly efficient oil/water separation performance in high-temperature, high salty, and strongly corrosive conditions. This work provides a feasible route to fabricate durable super-wetting 2D membranes with photo-Fenton self-cleaning capability for the oily wastewater treatment in harsh environments.

(Invited) Graphene and 2D-Materials for Gas, Pressure and Mass Sensing

Introduction Graphene and related materials are by their very definition as “two-dimensional” (2D) suitable for sensing applications that exploit their high surface to volume ratio and / or their low mass [1]. In this talk, I will summarize ongoing research on graphene and platinum diselenide-based (PtSe2) sensors, both integrated on conventional semiconductor substrates and suspended to form micro- and nanoelectromechanical systems (MEMS/NEMS).Gas Sensors We demonstrated humidity sensing using resistance changes in single- layer chemical vapor deposited (CVD) graphene on top of oxidized silicon wafers [2]. The selectivity of the sensors towards the most common constituents in air was investigated individually for water vapor (H2O), nitrogen (N2), oxygen (O2), and argon (Ar). Humidity sensing works efficiently from 1% relative humidity (RH) to 96% RH. We further analyzed the cross sensitivity with carbon dioxide [3], and humidity sensing when bilayer graphene is used as the active sensor material [4]. Finally, the noble metal dichalcogenide PtSe2 has been investigated with respect to its gas sensing properties, in particular its selectivity regarding nitrogen dioxide (NO2) [5].Suspended Membrane-based SensorsMembrane-based sensors benefit mainly form the ultimate thinness of 2D materials. We have investigated a number of potential sensor applications for such 2D membranes. First, we have proposed pressure sensors from single and bilayer graphene membranes with very high sensitivity, despite a low, single-digit gauge factor of graphene [6]–[8]. This work has been expanded to PtS2 membranes, which show even higher sensitivity and miniaturability due to a much larger piezoresistive gauge factor [9]. Recently, we have been successful in attaching silicon proof masses to graphene membranes that result in highly sensitive accelerometers [10], [11]. Without proof masses, nanoscale graphene membranes may even have the potential to resonantly detect single molecule weights [12]. Finally, graphene membranes can be utilized as highly sensitive Hall sensors and microphones that are resonance-free in the acoustic wave region for frequencies up to 700 kHz, which is an advantage over conventional MEMS microphones [13]. Results and Conclusions Graphene and 2D materials have tremendous potential for sensing applications due to their intrinsic material properties. Whether these can be utilized in future products for applications such as the Internet of Things, autonomous mobility or smart cities now depends largely on the availability of process technologies for large scale manufacturing, reliability and, ultimately, on the cost / functionality ratio [14]. Acknowledgements The authors acknowledge funding through the European Union’s Horizon 2020 research and innovation programme under grant agreements 881603 (Graphene Flagship) and 825272 (ULISSES), the German BMBF grants NobleNEMS and GIMMIK (16ES1121, 03XP0210) and the German Research Foundation, DFG (2DNEMS, LE 2440/11-1).

Self-assembly enabled nano-intercalation for stable high-performance MXene membranes

Two-dimensional (2D) lamellar membranes, such as graphene and MXene based surfaces have attracted growing interest for water purification. However, 2D membranes still face critical challenges, such as low stability, high internal resistance, and the tradeoff between permeability and selectivity, leading to unsatisfactory separation performance. Herein, high-performance MXene membranes with stable and tunable lamellar nanochannels are fabricated by facile self-assembly of negatively charged 2D MXene (Ti3C2Tx) nanosheets and positively charged 0D alumina (Al2O3) nanoparticles. The internal nanochannels (e.g., d-spacing) and surface properties (e.g., hydrophilicity and roughness) of the prepared MXene membranes can be precisely tailored by self-assembly of MXene/Al2O3 with different mass ratios. The optimized membrane with an MXene/Al2O3 mass ratio of 1:1 exhibits an outstanding water permeability of 88.8 LMH/bar (four times higher than that of the unmodified MXene membrane) and high molecule separation performance (>99.5% rejections to Rhodamine B and Methyl Blue). Such high separation performance outperforms many 2D membranes reported in literature, mainly because of the tunable interlayer spacing and favorable surface properties. The optimized MXene membrane also shows significantly enhanced channel stability after nano-Al2O3 intercalation during self-assembly. The self-assembly enabled nano-intercalation demonstrated in this work provides a facile method for engineering high-performance 2D membranes with stable and tunable nanochannels for precise molecular separation.

Hypersonic impact properties of pristine and hybrid single and multi-layer C3N and BC3 nanosheets

Carbon, nitrogen, and boron nanostructures are promising ballistic protection materials due to their low density and excellent mechanical properties. In this study, the ballistic properties of C3N and BC3 nanosheets against hypersonic bullets with Mach numbers greater than 6 were studied. The critical perforation conditions, and thus, the intrinsic impact strength of these 2D materials were determined by simulating ballistic curves of C3N and BC3 monolayers. Furthermore, the energy absorption scaling law with different numbers of layers and interlayer spacing was investigated, for homogeneous or hybrid configurations (alternated stacking of C3N and the BC3). Besides, we created a hybrid sheet using van der Waals bonds between two adjacent sheets based on the hypervelocity impacts of fullerene (C60) molecules utilizing molecular dynamics simulation. As a result, since the higher bond energy between N–C compared to B-C, it was shown that C3N nanosheets have higher absorption energy than BC3. In contrast, in lower impact speeds and before penetration, single-layer sheets exhibited almost similar behavior. Our findings also reveal that in hybrid structures, the C3N layers will improve the ballistic properties of BC3. The energy absorption values with a variable number of layers and variable interlayer distance (X = 3.4 Å and 4X = 13.6 Å) are investigated, for homogeneous or hybrid configurations. These results provide a fundamental understanding of ultra-light multilayered armors' design using nanocomposites based on advanced 2D materials. The results can also be used to select and make 2D membranes and allotropes for DNA sequencing and filtration.

Computer vision AC-STEM automated image analysis for 2D nanopore applications

Transmission electron microscopy (TEM) has led to important discoveries in atomic imaging and as an atom-by-atom fabrication tool. Using electron beams, atomic structures can be patterned, annealed and crystallized, and nanopores can be drilled in thin membranes. We review current progress in TEM analysis and implement a computer vision nanopore-detection algorithm that achieves a 96% pixelwise precision in TEM images of nanopores in 2D membranes (WS2), and discuss parameter optimization including a variation on the traditional grid search and gradient ascent. Such nanopores have applications in ion detection, water filtration, and DNA sequencing, where ionic conductance through the pore should be concordant with its TEM-measured size. Standard computer vision methods have their advantages as they are intuitive and do not require extensive training data. For completeness, we briefly comment on related machine learning for 2D materials analysis and discuss relevant progress in these fields. Image analysis alongside TEM allows correlated fabrication and analysis done simultaneously in situ to engineer devices at the atomic scale.

Direct visualization of local deformations in suspended few-layer graphene membranes by coupled in situ atomic force and scanning electron microscopy

Suspended membranes of two-dimensional (2D) materials are of interest for many applications. Much of their characterization relies on scanning probe microscopy (SPM) techniques such as atomic force microscopy (AFM) or scanning tunneling microscopy (STM). Unlike rigid samples, the suspended atomically thin 2D membranes are, however, flexible and do not remain mechanically undisturbed during SPM measurements. Local deformations can occur at the location of the scanning tip and thus result in measurements that misrepresent actual membrane topography and nanomechanical properties. Exact levels of such SPM tip-induced deformations in 2D membranes remain largely unknown, as they are to date only indirectly accessible via dual probe microscope concepts that either are not mechanically independent (e.g., SPM-SPM setups resulting in complicated imaging crosstalk) or suffer from intrinsically limited lateral resolution (e.g., optical far-field techniques as the second probe). Circumventing these shortcomings, we here demonstrate that by coupling an AFM with a scanning electron microscope (SEM) as the second, mechanically independent probe, we can directly and in situ visualize by SEM at high resolution 2D membrane deformations that result from controllable AFM tip manipulations in the nN range. Employing few-layer graphene as model membranes, we discuss the experimental realization of our coupled in situ AFM-SEM approach.