Disregarded Free Chains Affect Bacterial Adhesion on Cross-Linked Polydimethylsiloxane Surfaces.

The surface properties exhibited by chemically cross-linked polydimethylsiloxanes (CPDMS) such as morphology, stiffness, and wettability have garnered great interest in the study of bacteria-material interactions. Nevertheless, the hidden factor of uncross-linked free PDMS chains that dissociate in CPDMS has often been overlooked when studying the biofilm formation on these polymeric elastomer surfaces. Here, we undertake a comparative characterization of the effects of free chains in CPDMS on bacterial adhesion to both flat and textured Sharklet CPDMS surfaces. Surprisingly, compared to unextracted surfaces, removing free chains from flat and textured CPDMS through solvent extraction results in a tremendous increase in bacterial colony-forming units for both Gram-negative and Gram-positive bacteria up to 2-3 orders in the initial adhesion stage of 2 h. These findings demonstrate that the solvent extraction of free chains from CPDMS is essential in studying the interactions between bacteria and silicone elastomer materials when focusing on a single variable.

A nanonewton-scale biomimetic mechanosensor.

Biomimetic mechanosensors have profound implications for various areas, including health care, prosthetics, human‒machine interfaces, and robotics. As one of the most important parameters, the sensitivity of mechanosensors is intrinsically determined by the detection resolution to mechanical force. In this manuscript, we expand the force detection resolution of current biomimetic mechanosensors from the micronewton to nanonewton scale. We develop a nanocrack-based electronic whisker-type mechanosensor that has a detection resolution of 72.2 nN. We achieve the perception of subtle mechanical stimuli, such as tiny objects and airflow, and the recognition of surface morphology down to a 30 nm height, which is the finest resolution ever reported in biomimetic mechanosensors. More importantly, we explore the use of this mechanosensor in wearable devices for sensing gravity field orientation with respect to the body, which has not been previously achieved by these types of sensors. We develop a wearable smart system for sensing the body's posture and movements, which can be used for remote monitoring of falls in elderly people. In summary, the proposed device offers great advantages for not only improving sensing ability but also expanding functions and thus can be used in many fields not currently served by mechanosensors.

Editorial for the Special Issue on Ultra Precision Technologies for Micromachining, Volume II.

With the increasing demand for ultra-high-precision products and micro-products in fields such as aerospace, national defense, military, transportation, and people's livelihoods, it has become an important development trend in the field of machining to realize ultra-high-precision machining and miniaturization with a higher level and higher quality [...].

Supramolecular Network Structured Gel Polymer Electrolyte with High Ionic Conductivity for Lithium Metal Batteries.

Polymer-based solid electrolytes (PSEs) offer great promise in developing lithium metal batteries due to their attractive features such as safety, light weight, low cost, and high processability. However, a PSE-based lithium battery usually requires a relatively high temperature (60 °C or above) to complete charge and discharge due to the poor ionic conductivity of PSEs. Herein, a gel polymer electrolytes (GPEs) film with a supramolecular network structure through a facile one-step photopolymerization is designed and developed. The crosslinked structure and quadruple hydrogen bonding fulfil the GPEs with high thermal stability and good mechanical property with a maximum tensile strain of 48%. The obtained GPEs possess a high ionic conductivity of 3.8 × 10-3 S cm-1 at 25 °C and a decomposition voltage ≥ 4.6 V (vs Li/Li+ ). The cells assembled with LiFePO4 cathode and Li anode, present an initial discharge specific capacity of 155.6 mAh g-1 and a good cycling efficiency with a capacity retention rate of 81.1% after 100 charges/discharge cycles at 0.1 C at ambient temperature. This work encompasses a route to develop high performance PSEs that can be operated at room temperature for future lithium metal batteries.

Rolling Nanoelectrode Lithography.

Non-uniformity and low throughput issues severely limit the application of nanoelectrode lithography for large area nanopatterning. This paper proposes, for the first time, a new rolling nanoelectrode lithography approach to overcome these challenges. A test-bed was developed to realize uniform pressure distribution over the whole contact area between the roller and the silicon specimen, so that the local oxidation process occurred uniformly over a large area of the specimen. In this work, a brass roller wrapped with a fabricated polycarbonate strip was used as a stamp to generate nanopatterns on a silicon surface. The experimental results show that a uniform pattern transfer for a large area can be achieved with this new rolling nanoelectrode lithography approach. The rolling speed and the applied bias voltage were identified as the primary control parameters for oxide growth. Furthermore, the pattern direction showed no significant influence on the oxide process. We therefore demonstrated that nanoelectrode lithography can be scaled up for large-area nanofabrication by incorporating a roller stamp.

Spatially Engraving Morphological Structure on a Polymeric Surface by Ion Beam Milling.

Polymer surface patterning and modification at the micro/nano scale has been discovered with great impact in applications such as microfluidics and biomedical technologies. We propose a highly efficient fabricating strategy, to achieve a functional polymer surface, which has control over the surface roughness. The key development in this fabrication method is the polymer positive diffusion effect (PDE) for an ion-bombarded polymeric hybrid surface through focused ion beam (FIB) technology. The PDE is theoretically explored by introducing a positive diffusion term into the classic theory. The conductivity-induced PDE constant is discussed as functions of substrates conductivity, ion energy and flux. The theoretical results agree well with the experiential results on the conductivity-induced PDE, and thus yield good control over roughness and patterning milling depth on the fabricated surface. Moreover, we demonstrate a controllable surface wettability in hydrophobic and superhydrophobic surfaces (contact angles (CA) range from 108.3° to 150.8°) with different CA hysteresis values ranging from 31.4° to 8.3°.

A New Grinding Force Model for Micro Grinding RB-SiC Ceramic with Grinding Wheel Topography as an Input.

The ability to predict the grinding force for hard and brittle materials is important to optimize and control the grinding process. However, it is a difficult task to establish a comprehensive grinding force model that takes into account the brittle fracture, grinding conditions, and random distribution of the grinding wheel topography. Therefore, this study developed a new grinding force model for micro-grinding of reaction-bonded silicon carbide (RB-SiC) ceramics. First, the grinding force components and grinding trajectory were analysed based on the critical depth of rubbing, ploughing, and brittle fracture. Afterwards, the corresponding individual grain force were established and the total grinding force was derived through incorporating the single grain force with dynamic cutting grains. Finally, a series of calibration and validation experiments were conducted to obtain the empirical coefficient and verify the accuracy of the model. It was found that ploughing and fracture were the dominate removal modes, which illustrate that the force components decomposed are correct. Furthermore, the values predicted according to the proposed model are consistent with the experimental data, with the average deviation of 6.793% and 8.926% for the normal and tangential force, respectively. This suggests that the proposed model is acceptable and can be used to simulate the grinding force for RB-SiC ceramics in practice.

Editorial for the Special Issue on Micro-Machining: Challenges and Opportunities.

Micro-machining is an enabling technology for the manufacture of micro-products in which functional features, or at least one dimension, are in the order of µm. [...].