The predominant cause of late-state failure of total hip replacements is wear-mediated osteolysis caused by wear particles that originate from the ultrahigh molecular weight polyethylene (UHMWPE) acetabular cup surface. One strategy for reducing wear particle formation from UHMWPE is to modify the surface with a hydrophilic coating to increase lubrication from synovial fluid. This study focuses on the wear behavior of hydrophilic coatings similar to poly(ethylene glycol) (PEG). The coatings were produced by plasma-polymerizing tetraglyme on UHMWPE in a chamber heated to 40°C or 50°C. Both temperatures yielded coatings with PEG-like chemistry and increased hydrophilicity relative to uncoated UHMWPE; however, the 40°C coatings were significantly more resistant to damage induced by atomic force microscopy nanoscratching. The 40°C coatings exhibited only one damage mode (delamination) and often showed no signs of damage after repeated scratching. In contrast, the 50°C coatings exhibited three damage modes (roughening, thinning, and delamination), and always showed visible signs of damage after no more than two scratches. The greater wear resistance of the 40°C coatings could not be explained by coating chemistry or hydrophilicity, but it corresponded to an approximately 26–32% greater degree of crosslinking relative to the 50°C surfaces, suggesting that crosslinking should be a significant design consideration for hydrophilic coatings used for total hip replacements and other wear-dependent applications.

Systems comprised of immiscible liquids held in non-equilibrium shapes by the interfacial assembly and jamming of nanoparticle-polymer surfactants have significant potential to advance catalysis, chemical separations, energy storage and conversion. Spatially directing functionality within them and coupling processes in both phases remains a challenge. Here, we exploit nanoclay-polymer surfactant assemblies at an oil-water interface to produce a semi-permeable membrane between the liquids, and from them all-liquid fluidic devices with bespoke properties. Flow channels are fabricated using micropatterned 2D substrates and liquid-in-liquid 3D printing. The anionic walls of the device can be functionalized with cationic small molecules, enzymes, and colloidal nanocrystal catalysts. Multi-step chemical transformations can be conducted within the channels under flow, as can selective mass transport across the liquid-liquid interface for in-line separations. These all-liquid systems become automated using pumps, detectors, and control systems, revealing a latent ability for chemical logic and learning.

We propose a new scan waveform ideally suited for high-speed atomic force microscopy. It is an optimization of the Archimedean spiral scan path with respect to the X,Y scanner bandwidth and scan speed. The resulting waveform uses a constant angular velocity spiral in the center and transitions to constant linear velocity toward the periphery of the scan. We compare it with other scan paths and demonstrate that our novel spiral best satisfies the requirements of high-speed atomic force microscopy by utilizing the scan time most efficiently with excellent data density and data distribution. For accurate X,Y, and Z positioning our proposed scan pattern has low angular frequency and low linear velocities that respect the instrument's mechanical limits. Using Sensor Inpainting we show artifact-free high-resolution images taken at two frames per second with a 2.2 μ m scan size on a moderately large scanner capable of 40 μm scans.

The self-assembly of carboxylated fullerene with poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) with different molecular weights, poly-2-vinylpyridine, and amine-terminated polystyrene, at the interface between toluene and water was investigated. For all values of the pH, the functionalized fullerene interacted with the polymers at the water/toluene interface, forming a nanoparticle network, reducing the interfacial tension. At pH values of 4.84 and 7.8, robust, elastic films were formed at the interface, such that hollow tubules could be formed in situ when an aqueous solution of the functionalized fullerene was jetted into a toluene solution of PS-b-P2VP at a pH of 4.84. With variation of the pH, the mechanical properties of the fullerene/polymer assemblies can be varied by tuning the strength of the interactions between the functionalized fullerenes and the PS-b-P2VP.

Nanoparticle-surfactants (NPSs) assembled at water-oil interfaces can significantly lower the interfacial tension and can be used to stabilize liquids. Knowing the formation and assembly and actively tuning the packing of these NPSs is of significant fundamental interest for the interfacial behavior of nanoparticles and of interest for water purification, drug encapsulation, enhanced oil recovery, and innovative energy transduction applications. Here, we demonstrate by means of interfacial tension measurements the high ionic strength helps the adsorption of NPSs to the water-oil interface leading to a denser packing of NPSs at the interface. With the reduction of interfacial area, the phase transitions from a "gas"-like to "liquid" to "solid" states of NPSs in two dimensions are observed. Finally, we provide the first in situ real-space imaging of NPSs at the water-oil interface by atomic force microcopy.

Background: Encased cantilevers are novel force sensors that overcome major limitations of liquid scanning probe microscopy. By trapping air inside an encasement around the cantilever, they provide low damping and maintain high resonance frequencies for exquisitely low tip-sample interaction forces even when immersed in a viscous fluid. Quantitative measurements of stiffness, energy dissipation and tip-sample interactions using dynamic force sensors remain challenging due to spurious resonances of the system. Results: We demonstrate for the first time electrostatic actuation with a built-in electrode. Solely actuating the cantilever results in a frequency response free of spurious peaks. We analyze static, harmonic, and sub-harmonic actuation modes. Sub-harmonic mode results in stable amplitudes unaffected by potential offsets or fluctuations of the electrical surface potential. We present a simple plate capacitor model to describe the electrostatic actuation. The predicted deflection and amplitudes match experimental results within a few percent. Consequently, target amplitudes can be set by the drive voltage without requiring calibration of optical lever sensitivity. Furthermore, the excitation bandwidth outperforms most other excitation methods. Conclusion: Compatible with any instrument using optical beam deflection detection electrostatic actuation in encased cantilevers combines ultra-low force noise with clean and stable excitation well-suited for quantitative measurements in liquid, compatible with air, or vacuum environments.

Scanning probe microscopy (SPM) has facilitated many scientific discoveries utilizing its strengths of spatial resolution, non-destructive characterization and realistic in situ environments. However, accurate spatial data are required for quantitative applications but this is challenging for SPM especially when imaging at higher frame rates. We present a new operation mode for scanning probe microscopy that uses advanced image processing techniques to render accurate images based on position sensor data. This technique, which we call sensor inpainting, frees the scanner to no longer be at a specific location at a given time. This drastically reduces the engineering effort of position control and enables the use of scan waveforms that are better suited for the high inertia nanopositioners of SPM. While in raster scanning, typically only trace or retrace images are used for display, in Archimedean spiral scans 100% of the data can be displayed and at least a two-fold increase in temporal or spatial resolution is achieved. In the new mode, the grid size of the final generated image is an independent variable. Inpainting to a few times more pixels than the samples creates images that more accurately represent the ground truth.

Structured liquids stabilized by interfacial assemblies enable spatial control over chemical systems. To prescribe a lifetime for structured liquids requires that the interfacially trapped material eventually reverts to molecularly dissolved species. Here, we show that poly(acrylic acid) fueled with carbodiimide segregates to an oil-water interface and forms assemblies of aggregates, solidifying the interface. When the fuel is consumed, the assembly dissipates into soluble polymer chains, destroying any out-of-equilibrium structure imparted to the liquid. We exploit this phenomenon to control liquid compartment temporal stability. Using interfacial rheology, we identify crossover points in the interfacial storage and loss moduli at times commensurate with the fuel concentration, evidencing transitions from solid-like to liquid-like assemblies that cause compartmentalized liquids to burst. These solid-like assemblies demonstrate reduced permeability to dye, showing the potential of this system for timed partitioning or release of chemical species. This work opens a pathway to time- and shape-programmable chemical systems.

The conformational dynamics of nucleosome arrays generate a diverse spectrum of microscopic states, posing challenges to their structural determination. Leveraging cryogenic electron tomography (cryo-ET), we determine the three-dimensional (3D) structures of individual mononucleosomes and arrays comprising di-, tri-, and tetranucleosomes. By slowing the rate of condensation through a reduction in ionic strength, we probe the intra-array structural transitions that precede inter-array interactions and liquid droplet formation. Under these conditions, the arrays exhibite irregular zig-zag conformations with loose packing. Increasing the ionic strength promoted intra-array compaction, yet we do not observe the previously reported regular 30-nanometer fibers. Interestingly, the presence of H1 do not induce array compaction; instead, one-third of the arrays display nucleosomes invaded by foreign DNA, suggesting an alternative role for H1 in chromatin network construction. We also find that the crucial parameter determining the structure adopted by chromatin arrays is the angle between the entry and exit of the DNA and the corresponding tangents to the nucleosomal disc. Our results provide insights into the initial stages of intra-array compaction, a critical precursor to condensation in the regulation of chromatin organization.

Interactions between supercritical (sc) CO₂ and minerals are important when CO₂ is injected into geologic formations for storage and as working fluids for enhanced oil recovery, hydraulic fracturing, and geothermal energy extraction. It has previously been shown that at the elevated pressures and temperatures of the deep subsurface, scCO₂ alters smectites (typical swelling phyllosilicates). However, less is known about the effects of scCO₂ on nonswelling phyllosilicates (illite and muscovite), despite the fact that the latter are the dominant clay minerals in deep subsurface shales and mudstones. Our studies conducted by using single crystals, combining reaction (incubation with scCO₂), visualization [atomic force microscopy (AFM)], and quantifications (AFM, X-ray photoelectron spectroscopy, X-ray diffraction, and off-gassing measurements) revealed unexpectedly high CO₂ uptake that far exceeded its macroscopic surface area. Results from different methods collectively suggest that CO₂ partially entered the muscovite interlayers, although the pathways remain to be determined. We hypothesize that preferential dissolution at weaker surface defects and frayed edges allows CO₂ to enter the interlayers under elevated pressure and temperature, rather than by diffusing solely from edges deeply into interlayers. This unexpected uptake of CO₂, can increase CO₂ storage capacity by up to ∼30% relative to the capacity associated with residual trapping in a 0.2-porosity sandstone reservoir containing up to 18 mass % of illite/muscovite. This excess CO₂ uptake constitutes a previously unrecognized potential trapping mechanism.