A microfluidic chip with an integrated planar microcoil was developed for Nuclear Magnetic Resonance (NMR) spectroscopy on samples with volumes of less than a microliter. Real-time monitoring of imine formation from benzaldehyde and aniline in the microreactor chip by NMR was demonstrated. The reaction times in the chip can be set from 30 min down to ca. 2 s, the latter being the mixing time in the microfluidic chip. Design rules will be described to optimize the microreactor and detection coil in order to deal with the inherent sensitivity of NMR and to minimize magnetic field inhomogeneities and obtain sufficient spectral resolution.

The design, fabrication and high-pressure performance of several in-plane fiber-based interface geometries to microreactor chips for highpressure chemistry are discussed, and an application is presented. The main investigated design parameters are the geometry of the inlet/outlet structure, the manner in which top and bottom wafer are bonded and the way the inlets/outlets turn over into the microfluidic channels.Destructive pressure experiments with H 2 O and liquid CO 2 showed that the maximum pressure that the proposed inlet/outlet structures can withstand is in the range of 180-690 bar. The optimal geometry for high-pressure microreactor chips is a tubular structure that is etched with hydrofluoric acid (HF) and suitable for fibers with a diameter of 110 m. These inlets/outlets can withstand pressures up to 690 bar. On the other hand, small powderblasted inlets/outlets that are smoothened with HF and with a sharp transition towards the flow channels are adequate for working pressures up to 300 bar.Microreactor chips with tubular inlet/outlet geometries were used for studying the formation of the carbamic acid of N-benzylmethylamine and CO 2 . These chips could be used for pressures up to 400 bar without problems/failure, thereby showing that these micromachined microreactor chips are attractive tools for performing high-pressure chemistry in a fast and safe way.

Li and Na metals have the highest theoretical anode capacity for Li/Na batteries, but the operational safety hazards stemming from uncontrolled growth of Li/Na dendrites and unstable electrode-electrolyte interfaces hinder their real-world applications. Recently, the emergence of 3D conductive scaffolds aimed at mitigating the dendritic growth to improve the cycling stability has gained traction. However, while achieving 3D scaffolds that are conducive to completely prevent dendritic Li/Na is challenging, the routes proposed to fabricate 3D scaffolds to date are often complex and expensive. This not only leads to suboptimal battery performance but can make the manufacturing nearly unachievable, compromising their commercial viability. We herein introduce a facile and single-step route to honeycomb-like 3D porous Ni@Cu scaffolds via a hydrogen bubble dynamic template (HBDT) electrodeposition method. The current collectors fabricated by this method offer highly stable cycling performance of Li plating/stripping (> 300 cycles at 0.5 mAh cm-2 and over 200 cycles at 1.0 mAh cm-2), attributed to their ability to effectively accommodate Li/Na deposits in their porous networks and to delocalize the charge distribution. The beneficial role of LiNO3 as an electrolyte additive in improving the mechanical integrity of solid electrolyte interface (SEI) and mechanistic insights into how the 3D porous structure facilitates Li/Na plating/stripping are comprehensively presented. Finally, with an outstanding cycling performance of reversible Na deposition (over 240, 110 and 50 cycles for 0.5, 1.0 and 2.0 mAh cm-2 at 1.0 mA cm-2), our findings open new doors to expedite the development of Li/Na metal battery technology.

Measurements are shown indicating that the drying rate of nanochannels can be enhanced by up to 3 orders of magnitude relative to drying by vapor diffusion, and that the drying rate is independent of the relative humidity of the environment up to a relative humidity of more than 90%. Micromachined Pyrex glass nanochannels of 72 nm height and with sharp corners (corner angles 7 degrees) were used. Available theory shows that the sharp corners function as a low-resistance pathway for liquid water, siphoning (wicking) the water to a location close to the channel exit before it evaporates. The described phenomena are of importance for the understanding of drying processes in industry and agriculture. The introduction of sharp corners or grooves can furthermore be beneficial for the functioning of microheat pipes and capillary-pumped loops. DOI: 10.1103/PhysRevLett.95.256107 PACS numbers: 68.03.Fg Understanding the drying mechanism of porous materials is of importance in many industries such as the food, paper, pharmaceutical, and textile industry [1][2][3]. It has previously been observed that microporous media dried approximately 1 order of magnitude faster than can be expected from vapor diffusion alone [4,5]. Flow in liquid water films held on surfaces and flow of water held in corners or grooves were thought to cause this acceleration [6]. The contribution of film flow to drying has been experimentally investigated in cylindrical nanocapillaries, where it caused a tenfold increase of drying rate, [7] but the contribution of corner flow has never been investigated. Here we report on experiments using noncylindrical micromachined nanochannels to quantify corner flow.Drying results from three water transport mechanisms: vapor diffusion, film flow, and corner flow. To specifically investigate corner flow we designed an array of high aspect ratio (widthheight) noncylindrical channels of equal height but different width (Fig. 1). The three water transport mechanisms schematically are shown in Fig. 2. When corner flow dominates the drying process in a channel, the drying rate will depend on the inverse of the channel width, because the number of corners is independent of width but the total water volume inside the channel proportional with width. Drying due to film flow (for widthheight) and vapor diffusion in contrast does not depend on the channel width. Arrays of Pyrex channels, open on two sides, were manufactured in a clean room. Channels were wet etched (hydrofluoric acid) into one Pyrex wafer using a photolithographic mask. This wafer was bonded by thermal fusion to a second wafer which had access holes for filling. The channels were 4 mm long, 72:4 0:8 nm high (determined by AFM) and the width in the array differed from 2 to 30 m. The channel shape was an isosceles trapezoid of very high aspect ratio (width=height > 40) (Fig. 1 bottom). The angle of the sharp corner was determined to be 6:6 0:7 degrees by SEM measurements of bonded chips and by AFM measurements prior to bonding of the Pyrex plates. The shar...

Electroosmotic flow (EOF) in a microchannel can be controlled by electronic control of the surface charge using an electrode embedded in the wall of the channel. By setting a voltage to the electrode, the zeta-potential at the wall can be changed locally. Thus, the electrode acts as a "gate" for liquid flow, in analogy with a gate in a field-effect transistor. In this paper we will show three aspects of a Field Effect Flow Control (FEFC) structure. We demonstrate the induction of directional flow by the synchronized switching of the gate potential with the channel axial potential. The advantage of this procedure is that potential gas formation by electrolysis at the electrodes that provide the axial electric field is suppressed at sufficiently large switching frequencies, while the direction and magnitude of the EOF can be maintained. Furthermore we will give an analysis of the time constants involved in the charging of the insulator, and thus the switching of the zeta potential, in order to predict the maximum operating frequency. For this purpose an equivalent electrical circuit is presented and analyzed. It is shown that in order to accurately describe the charging dynamics and pH dependency the traditionally used three capacitor model should be expanded with an element describing the buffer capacitance of the silica wall surface.