In this work, for the first time, a dynamic electrical control of the wetting behavior of liquids on nanostructured surfaces, which spans the entire possible range from the superhydrophobic behavior to nearly complete wetting, has been demonstrated. Moreover, this kind of dynamic control was obtained at voltages as low as 22 V. We have demonstrated that the liquid droplet on a nanostructured surface exhibits sharp transitions between three possible wetting states as a function of applied voltage and liquid surface tension. We have examined experimentally and theoretically the nature of these transitions. The reported results provide novel methods of manipulating liquids at the microscale.

From rolling ball to complete wetting: the dynamic tuning of liquids on nanostructured surfaces

We propose a statistical process control scheme that can be implemented in industrial practice, in which the quality of a process can be characterized by a general linear profile. We start by reviewing the general linear profile model and the existing monitoring methods. Based on this, we propose a novel multivariate exponentially weighted moving average monitoring scheme for such a profile. We introduce two other enhancement features, the variable sampling interval and the parametric diagnostic approach, to further improve the performance of the proposed scheme. Throughout the article, we use a deep reactive ion etching example from semiconductor manufacturing, which has a profile that fits a quadratic polynomial regression model well, to illustrate the implementation of the proposed approach.

Monitoring General Linear Profiles Using Multivariate Exponentially Weighted Moving Average Schemes

Biology is replete with examples of functional structures, whose properties are unmatched in today’s man-made materials. Key features of biological structures are their dynamic nature, responsive behavior, and often multifunctionality, which all comprise the goals for the next-generation smart artificial materials. There is a growing body of information describing natural structures with sophisticated design strategies, which lend the organisms and plants superior mechanical, optical, adhesive, self-cleaning, actuation, and sensing capabilities. [1‐9] Interestingly, the common feature of these largely unrelated designs is the use of fibers and high-aspect-ratio nano- and microstructures. Nanostructures on the surface of the lotus leaf render the leaves superhydrophobic, and the droplets of water containing the collected insects and dust will roll off, and so maintain a clean leaf surface. [1] A gecko’s feet are comprised of half a million setae fibers. Each seta is tipped with ! 1000 nanometer-sized spatulae. This multiscale fibrous assembly offers a unique reversible adhesion mechanism, which holds geckos to surfaces in a self-cleaning fashion. [2,3] Complex, hierarchically structured high-aspect-ratio silica fibers in the sponge Venus’s Flower Basket provide amazing fiber‐optical capabilities, combined with superior mechanical properties. [4,5] Fish and amphibians have fibrous structures (cilia) on the surfaces of their bodies connected to a hair cell at their base that detect water flow. [6,7] Due to this sensing ability, fish can swim in narrow caves" " even without the possibility of eye sight" " and sense other organisms moving in their vicinity. [6] Echinoderms cover their skin with high-aspect-ratio spines and mobile pedicellaria, which provide an effective antifouling mechanism, preventing the settlement and growth of other organisms by active movement. [8] Pedicellaria" " small claw-like extensions on the aboral surface of starfish and sea urchins" " essentially exist as dense arrays of environmentally responsive biological m-actuators. [8]

Fabrication of Bioinspired Actuated Nanostructures with Arbitrary Geometry and Stiffness

Silicon platelet corrugated feedhorn arrays for cosmic microwave background (CMB) measurements at millimeter wavelengths (130 GHz to 170 GHz) have been developed for deployment for the polarization-sensitive upgrade to both the Atacama Cosmology Telescope (ACTpol) and the South Pole Telescope (SPTpol). We present fabrication developments and the first results of a prototype monolithic feedhorn array consisting of 84 horns. Measurements at room temperature show good beam quality across the needed bandwidth, return loss of <−20 dB, an insertion loss of <−0.4 dB, and cross polarization of <−23 dB. The 32 platelets were aligned to a 1σ variation of 8 μm.

An 84 Pixel All-Silicon Corrugated Feedhorn for CMB Measurements

The application of gas discharge plasmas has assumed an important place in many manufacturing processes. Plasma methods contribute significantly to the economic prosperity of industrialized societies. However, plasma is mainly an enabling method and therefore its role remains often hidden. Hence the success of plasma technologies is described for different examples and commercial areas. From these examples and emerging applications, the potential of plasma technologies is discussed. Economic trends are anticipated together with research needs. The community of plasma scientists strongly believes that more exciting advances will continue to foster innovations and discoveries in the first decades of the 21st century, if research and education will be properly funded and sustained by public bodies and industrial investors.

The future for plasma science and technology

Dry etching of Si is critical in satisfying the demands of the micromachining industry. The micro-electro-mechanical systems (MEMS) community requires etches capable of high aspect ratios, vertical profiles, good feature size control and etch uniformity along with high throughput to satisfy production requirements. Surface technology systems' (STS's) high-density inductively coupled plasma (ICP) etch tool enables a wide range of applications to be realized whilst optimizing the above parameters. Components manufactured from Si using an STS ICP include accelerometers and gyroscopes for military, automotive and domestic applications. STS's advanced silicon etch (ASETM) has also allowed the first generation of MEMS-based optical switches and attenuators to reach the marketplace. In addition, a specialized application for fabricating the next generation photolithography exposure masks has been optimized for 200 mm diameter wafers, to depths of ~750 µm. Where the profile is not critical, etch rates of greater than 8 µm min-1 have been realized to replace previous methods such as wet etching. This is also the case for printer applications. Specialized applications that require etching down to pyrex or oxide often result in the loss of feature size control at the interface; this is an industry wide problem. STS have developed a technique to address this. The rapid progression of the industry has led to development of the STS ICP etch tool, as well as the process.

https://iopscience.iop.org/article/10.1088/0022-3727/34/18/309/pdf

Silicon micromachining using a high-density plasma source

Advances in Deep Anisotropic Silicon Etch Processing for Mems

In high-density fluorinated plasma processes, the mechanisms that fundamentally limit the etching of silicon are poorly understood. In an effort to improve our understanding of limits to the performance of such systems, the etching of silicon wafers in an inductive coupled plasma reactor, using SF6, has been studied. A systematic empirical investigation has allowed us to define many of the experimental parameters that control the etching rate. There is little temperature dependence of etching which suggests a diffusion limited process. Systematic variation of parameters controlling the rate of etching: total pressure in the reactor, flow rate, partial pressure of reactive species and the rf power supplied to the discharge enable us to accurately define the performance of the system. Experiments, which segregate the physical and chemical components of the etching process, support the conclusion that etching is dominated by electrically neutral species. These various results are interpreted in terms of accepted models for the reactive chemistry in plasmas containing SF6. The MEMS industry is placing ever greater demands on etching processes, and there is a need to achieve the high degrees of anisotropy, and critical dimension control, at high etch-rates. The approach outlined allows us to develop effective strategies for evolving improved systems for the high rate plasma etching of silicon.

Defining Conditions for the Etching of Silicon in an Inductive Coupled Plasma Reactor

Adsorption in complex nanoporous materials is important for many applications. We report a novel approach for measuring adsorption in situ that uses a nanoporous silica waveguide and near-infrared spectroscopy for selective measurement of adsorbed compounds.

S. Mcauley

Papers

Silicon micromachining using a high-density plasma source

Advances in Deep Anisotropic Silicon Etch Processing for Mems

Defining Conditions for the Etching of Silicon in an Inductive Coupled Plasma Reactor

Adsorption of volatile organic compounds inside a nanoporous silica waveguide

Spectral comparison of nanoporous silica-adsorbed organic molecules with gaseous and liquid states using a new waveguide technology