Mechanical low-frequency filter via modes separation in 3D periodic structures

This work presents a strategy to design three-dimensional elastic periodic structures endowed with complete bandgaps, the first of which is ultra-wide, where the top limits of the first two bandgaps are overstepped in terms of wave transmission in the finite structure. Thus, subsequent bandgaps are merged, approaching the behaviour of a three-dimensional low-pass mechanical filter. This result relies on a proper organization of the modal characteristics, and it is validated by performing numerical and analytical calculations over the unit cell. A prototype of the analysed layout, made of Nylon by means of additive manufacturing, is experimentally tested to assess the transmission spectrum of the finite structure, obtaining good agreement with numerical predictions. The presented strategy paves the way for the development of a class of periodic structures to be used in robust and reliable wave attenuation over a wide frequency band

3D-Printed Stationary Phases with Ordered Morphology: State of the Art and Future Development in Liquid Chromatography Chromatographia

Stationary phases with precisely ordered morphology have the potential to drastically 9 improve the performance of chromatographic operations, both in the analytical and in the 10 preparative/industrial fields. The recent wave of additive manufacturing, aka 3D printing, 11 gives the unprecedented ability to fabricate such stationary phases and to experimentally 12 prove theoretical principles of ordered chromatographic beds. The manufacture of highly 13 efficient chromatographic columns is becoming a reality as 3D printers become more 14 affordable and accessible, and their resolution, speed and material flexibility continue to 15 grow. This brings fresh ideas to the design of chromatographic beds, moving away from 16 stereotypical “packed” beds with spherical particles to bespoke monolithic structures to suit 17 a range of specific applications. This review aims to cover the state of the art of ordered 18 beds for liquid chromatography applications, drawing analogies between the well-19 established pillar-array columns in two-dimensions to their three-dimensional counterparts. 20 The potential use of 3D printing to create entirely new column formats and cartridge 21 designs such as microchip columns will also be discussed. Finally, key opportunities and 22 challenges which remain in the field of 3D-printed chromatography are summarised, with 23 the hope that 3D printed chromatographic columns will soon become the standard

Magnetohydrodynamic pumping in nuclear magnetic resonance environments

We present a DC magnetohydrodynamic (MHD) pump as component of a nuclear magnetic resonance (NMR) microfluidic chip. This is the first time that MHD pumping in an NMR environment was observed and demonstrated. This chip generates a maximum flow rate of 1.5 μL min−1 (2.8 mm s−1 in the microchannel) for an applied voltage of 19 V with only 38 mW of power consumption in a 7 T superconductive magnet. We developed a simple method of flow rate measurement inside the bulky NMR magnet by monitoring the displacement of a liquid–liquid interface of two immiscible liquids in an off-chip capillary. We compared and validated this flow measurement technique with another established technique for microfluidics based on the displacement of microbeads. This allowed us to characterize and compare the flow rate generated by the micropump on top of a permanent magnet (B1 = 0.33 T) with the superconductive magnet (B0 = 7.05 T). We observed a 21-fold increase in flow rate corresponding to the ratio of the magnetic field intensities (B0/B1 = 21) in accordance with the theoretical flow dependence on the magnetic field intensity. The final aim is to integrate MHD pumps together with planar coils in a microfluidic system for NMR analysis. The high performance of MHD pumps at relatively low flow rates is seen as an asset for NMR and MRI applications

Rapid Prototyping of 3D Phononic Crystals using High-resolution Stereolithography Fabrication

AbstractWe present proof-of-concept devices to validate the suitability of high-resolution stereolithography fabrication, polymer material properties, and increased design freedom for realizing 3D phononic crystals. The maskless, single-step technology enables the fabrication of freeform 3D microstructures with high accuracy, which allows rapid prototyping of novel designs and leads to fast optimization cycles. Experimental results for devices with feature sizes down to 100 μm successfully indicate phononic band gap behavior, which is required for applications as sensor and microsystem structures