Massively parallel cantilever-free atomic force microscopy

Probe-Based Mechanical Data Storage on Polymers Made by Inverse Vulcanization

Big data and artificial intelligence are driving increasing demand for high-density data storage. Probe-based data storage, such as mechanical storage using an atomic force microscope tip, is a potential solution with storage densities exceeding hard disks. However, the storage medium must be modifiable on the nanoscale. While polymers are promising storage media, they face challenges with synthesis, erasing temperatures, and stability. Here, a low-cost and robust polymer system is reported that allows repeated writing, reading and erasing. The polymer is made by inverse vulcanization, providing a network of S─S bonds that can be broken and re-formed repeatedly. This property is leveraged in mechanical indentation to encode information, and thermal S─S metathesis and polymer re-flow to erase. Exquisite control of indentation depth is possible over 1-30 nm. This control enables data encoding not just as a function of the presence or absence of an indent, but also indentation depth. This ternary coding increases the data density four-fold over binary coding. Furthermore, the coding can be done at room temperature which is rare for mechanical information storage. The low cost, ease of synthesis, and dynamic S─S bonds in these polymers are a promising advance in polymer storage media for probe-based data storage.

Nanoscale Methods for Longitudinal Extraction of Intracellular Contents

Longitudinal analysis of intracellular contents including gene and protein expression is crucial for deciphering the fundamentally dynamic nature of cells. This offers invaluable insights into complex tissue composition and behavior, and drives progress in disease diagnosis, biomarker discovery, and drug development. Traditional longitudinal analysis workflows, involving the destruction of cells at various timepoints, limit insights to singular moments and fail to account for cellular heterogeneity. Current non-destructive approaches, like temporal modeling with single-cell ribonucleic acid sequencing (RNA-seq) and live-cell fluorescence imaging, either rely on biological assumptions or possess the risk of cellular perturbation. Recent advances in nanoscale technologies for non-destructive intracellular content extraction offer a promising solution to these challenges. These novel methods work at the nanoscale to non-destructively access cellular membranes and can be broadly classified into three mechanisms: tip-facilitated aspiration, membrane-based, and probe-based methods. This perspective focuses on these emerging nanotechnologies for repeated intracellular content extraction. Their potential in longitudinal analysis is discussed, the critical requirements for effective repeated sampling are addressed, and the suitability of each technique for various applications is explored. Furthermore, unresolved challenges in repeated sampling are highlighted to encourage further research in this growing field.

Direct laser writing-enabled 3D printing strategies for microfluidic applications

Over the past decade, additive manufacturing-or "three-dimensional (3D) printing"-has attracted increasing attention in the Lab on a Chip community as a pathway to achieve sophisticated system architectures that are difficult or infeasible to fabricate via conventional means. One particularly promising 3D manufacturing technology is "direct laser writing (DLW)", which leverages two-photon (or multi-photon) polymerization (2PP) phenomena to enable high geometric versatility, print speeds, and precision at length scales down to the 100 nm range. Although researchers have demonstrated the potential of using DLW for microfluidic applications ranging from organ on a chip and drug delivery to micro/nanoparticle processing and soft microrobotics, such scenarios present unique challenges for DLW. Specifically, microfluidic systems typically require macro-to-micro fluidic interfaces (e.g., inlet and outlet ports) to facilitate fluidic loading, control, and retrieval operations; however, DLW-based 3D printing relies on a micron-to-submicron-sized 2PP volume element (i.e., "voxel") that is poorly suited for manufacturing these larger-scale fluidic interfaces. In this Tutorial Review, we highlight and discuss the four most prominent strategies that researchers have developed to circumvent this trade-off and realize macro-to-micro interfaces for DLW-enabled microfluidic components and systems. In addition, we consider the possibility that-with the advent of next-generation commercial DLW printers equipped with new dynamic voxel tuning, print field, and laser power capabilities-the overall utility of DLW strategies for Lab on a Chip fields may soon expand dramatically.

Characteristics and Functionality of Cantilevers and Scanners in Atomic Force Microscopy

In this paper, we provide a systematic review of atomic force microscopy (AFM), a fast-developing technique that embraces scanners, controllers, and cantilevers. The main objectives of this review are to analyze the available technical solutions of AFM, including the limitations and problems. The main questions the review addresses are the problems of working in contact, noncontact, and tapping AFM modes. We do not include applications of AFM but rather the design of different parts and operation modes. Since the main part of AFM is the cantilever, we focused on its operation and design. Information from scientific articles published over the last 5 years is provided. Many articles in this period disclose minor amendments in the mechanical system but suggest innovative AFM control and imaging algorithms. Some of them are based on artificial intelligence. During operation, control of cantilever dynamic characteristics can be achieved by magnetic field, electrostatic, or aerodynamic forces.

Rational Structural Design of Polymer Pens for Energy-Efficient Photoactuation

Photoactuated pens have emerged as promising tools for expedient, mask-free, and versatile nanomanufacturing. However, the challenge of effectively controlling individual pens in large arrays for high-throughput patterning has been a significant hurdle. In this study, we introduce novel generations of photoactuated pens and explore the impact of pen architecture on photoactuation efficiency and crosstalk through simulations and experiments. By introducing a thermal insulating layer and incorporating an air ap in the architecture design, we have achieved the separation of pens into independent units. This new design allowed for improved control over the actuation behavior of individual pens, markedly reducing the influence of neighboring pens. The results of our research suggest novel applications of photoactive composite films as advanced actuators across diverse fields, including lithography, adaptive optics, and soft robotics.

3D Dirac semimetal supported thermal tunable terahertz hybrid plasmonic waveguides

By depositing the trapezoidal dielectric stripe on top of the 3D Dirac semimetal (DSM) hybrid plasmonic waveguide, the thermal tunable propagation properties have been systematically investigated in the terahertz regime, taking into account the influences of the structure of the dielectric stripe, temperature and frequency. The results manifest that as the upper side width of the trapezoidal stripe increases, the propagation length and figure of merit (FOM) both decrease. The propagation properties of hybrid modes are closely associated with temperature, in that when the temperature changes in the scope of 3-600 K, the modulation depth of propagation length is more than 96%. Additionally, at the balance point of plasmonic and dielectric modes, the propagation length and FOM manifest strong peaks and indicate an obvious blue shift with the increase of temperature. Furthermore, the propagation properties can be improved significantly with a Si-SiO₂ hybrid dielectric stripe structure, e.g., on the condition that the Si layer width is 5 µm, the maximum value of the propagation length reaches more than 6.46 × 10⁵µm, which is tens of times larger than those pure SiO₂ (4.67 × 10⁴µm) and Si (1.15 × 10⁴µm) stripe. The results are very helpful for the design of novel plasmonic devices, such as cutting-edge modulator, lasers and filters.

Morphology Engineering in Multicomponent Hollow Metal Chalcogenide Nanoparticles

Hollow metal chalcogenide nanoparticles are widely applicable in environmental and energy-related processes. Herein, we synthesized such particles with large compositional and morphological diversity by combining scanning probe block copolymer lithography with a Kirkendall effect-based sulfidation process. We explored the influence of temperature-dependent diffusion kinetics, elemental composition and miscibility, and phase boundaries on the resulting particle morphologies. Specifically, CoNi alloys form single-shell sulfides for the synthetic conditions explored because Co and Ni exhibit similar diffusion rates, while CuNi alloys form sulfides with various types of morphologies (yolk-shell, double-shell, and single-shell) because Cu and Ni have different diffusion rates. In contrast, Co-Cu heterodimers form hollow heterostructured sulfides with varying void numbers and locations depending on synthesis temperature and phase boundary. At higher temperatures, the increased miscibility of CoS₂ and CuS makes it energetically favorable for the heterostructure to adopt a single alloy shell morphology, which is rationalized using density functional theory-based calculations.

Targeting cell-matrix interface mechanobiology by integrating AFM with fluorescence microscopy

Mechanosensing at the interface of a cell and its surrounding microenvironment is an essential driving force of physiological processes. Understanding molecular activities at the cell-matrix interface has the potential to provide novel targets for improving tissue regeneration and early disease intervention. In the past few decades, the advancement of atomic force microscopy (AFM) has offered a unique platform for probing mechanobiology at this crucial microdomain. In this review, we describe key advances under this topic through the use of an integrated system of AFM (as a biomechanical testing tool) with complementary immunofluorescence (IF) imaging (as an in situ navigation system). We first describe the body of work investigating the micromechanics of the pericellular matrix (PCM), the immediate cell micro-niche, in healthy, diseased, and genetically modified tissues, with a focus on articular cartilage. We then summarize the key findings in understanding cellular biomechanics and mechanotransduction, in which, molecular mechanisms governing transmembrane ion channel-mediated mechanosensing, cytoskeleton remodeling, and nucleus remodeling have been studied in various cell and tissue types. Lastly, we provide an overview of major technical advances that have enabled more in-depth studies of mechanobiology, including the integration of AFM with a side-view microscope, multiple optomicroscopy, a fluorescence recovery after photobleaching (FRAP) module, and a tensile stretching device. The innovations described here have contributed greatly to advancing the fundamental knowledge of extracellular matrix biomechanics and cell mechanobiology for improved understanding, detection, and intervention of various diseases.

Binary-state scanning probe microscopy for parallel imaging

Scanning probe microscopy techniques, such as atomic force microscopy and scanning tunnelling microscopy, are harnessed to image nanoscale structures with an exquisite resolution, which has been of significant value in a variety of areas of nanotechnology. These scanning probe techniques, however, are not generally suitable for high-throughput imaging, which has, from the outset, been a primary challenge. Traditional approaches to increasing the scalability have involved developing multiple probes for imaging, but complex probe design and electronics are required to carry out the detection method. Here, we report a probe-based imaging method that utilizes scalable cantilever-free elastomeric probe design and hierarchical measurement architecture, which readily reconstructs high-resolution and high-throughput topography images. In a single scan, we demonstrate imaging with a 100-tip array to obtain 100 images over a 1-mm² area with 10⁶ pixels in less than 10 min. The potential for large-scale tip integration and the advantage of a simple probe array suggest substantial promise for our approach to high-throughput imaging far beyond what is currently possible.

High-throughput imaging has generally been challenging for scanning probe microscopy techniques. Here, the authors introduce binary-state scanning probe microscopy, which uses a cantilever-free elastomeric probes and a hierarchical measurement architecture for parallel topography imaging.