Increasing the Stability of Isolated and Dense High-Aspect-Ratio Nanopillars Fabricated Using UV-Nanoimprint Lithography.

Structural anti-reflective coating and bactericidal surfaces, as well as many other effects, rely on high-aspect-ratio (HAR) micro- and nanostructures, and thus, are of great interest for a wide range of applications. To date, there is no widespread fabrication of dense or isolated HAR nanopillars based on UV nanoimprint lithography (UV-NIL). In addition, little research on fabricating isolated HAR nanopillars via UV-NIL exists. In this work, we investigated the mastering and replication of HAR nanopillars with the smallest possible diameters for dense and isolated arrangements. For this purpose, a UV-based nanoimprint lithography process was developed. Stability investigations with capillary forces were performed and compared with simulations. Finally, strategies were developed in order to increase the stability of imprinted nanopillars or to convert them into nanoelectrodes. We present UV-NIL replication of pillars with aspect ratios reaching up to 15 with tip diameters down to 35 nm for the first time. We show that the stability could be increased by a factor of 58 when coating them with a 20 nm gold layer and by a factor of 164 when adding an additional 20 nm thick layer of SiN. The coating of the imprints significantly improved the stability of the nanopillars, thus making them interesting for a wide range of applications.

Editorial for Special Issue: Nanoimprint Lithography Technology and Applications.

Nanoimprint Lithography (NIL) has been an interesting and growing field over the last years since its beginnings in the mid 1990ies [...].

Mastering of NIL Stamps with Undercut T-Shaped Features from Single Layer to Multilayer Stamps.

Biomimetic structures such as structural colors demand a fabrication technology of complex three-dimensional nanostructures on large areas. Nanoimprint lithography (NIL) is capable of large area replication of three-dimensional structures, but the master stamp fabrication is often a bottleneck. We have demonstrated different approaches allowing for the generation of sophisticated undercut T-shaped masters for NIL replication. With a layer-stack of phase transition material (PTM) on poly-Si, we have demonstrated the successful fabrication of a single layer undercut T-shaped structure. With a multilayer-stack of silicon oxide on silicon, we have shown the successful fabrication of a multilayer undercut T-shaped structures. For patterning optical lithography, electron beam lithography and nanoimprint lithography have been compared and have yielded structures from 10 µm down to 300 nm. The multilayer undercut T-shaped structures closely resemble the geometry of the surface of a Morpho butterfly, and may be used in future to replicate structural colors on artificial surfaces.

Nanoimprint Replication of Biomimetic, Multilevel Undercut Nanostructures.

The nanoimprint replication of biomimetic nanostructures can be interesting for a wide range of applications. We demonstrate the process chain for Morpho-blue-inspired nanostructures, which are especially challenging for the nanoimprint process, since they consist of multilayer undercut structures, which typically cannot be replicated using nanoimprint lithography. To achieve this, we used a specially made, proprietary imprint material to firstly allow successful stamp fabrication from an undercut master structure, and secondly to enable UV-based nanoimprinting using the same material. Nanoimprinting was performed on polymer substrates with stamps on polymer backplanes to be compatible with roller-based imprinting processes. We started with single layer undercut structures to finally show that it is possible to successfully replicate a multilayer undercut stamp from a multilayer undercut master and use this stamp to obtain multilayer undercut nanoimprinted samples.

Nanoimprinted multifunctional nanoprobes for a homogeneous immunoassay in a top-down fabrication approach.

Multifunctional nanoparticles are discussed as versatile probes for homogeneous immunoassays for in-vitro diagnostics. Top-down fabrication allows to combine and tailor magnetic and plasmonic anisotropic properties. The combination of nanoimprint lithography, thin film deposition, and lift-off processing provides a top-down fabrication platform, which is both flexible and reliable. Here, we discuss the material compositions and geometrical designs of monodisperse multicomponent nanoparticles and their consequences on optical and magnetic properties. The rotational hydrodynamics of nanoparticles is measured and considered under the influence of magnetic shape anisotropy in the framework of the Stoner-Wohlfarth theory. The plasmon-optical properties are explained by discrete-dipole finite-element simulations. Rotational dynamical measurements of imprinted nanoprobes for two test proteins demonstrate the applicability as highly sensitive biomolecular nanoprobes.

Successful Bypass Surgery in a Healthy 24-Year-Old Male with Peripheral Artery Disease.

Approximately 40% of peripheral artery disease cases occur in individuals less than 50 years old. Diagnosis is often delayed due to fewer risk factors, atypical presentation, and symptoms attributed to a benign cause. We present an unusual case of an otherwise healthy 24-year-old male presenting with unilateral, intermittent claudication (IC) due to diffuse atherosclerotic disease in his left femoral arteries. Lifestyle-limiting symptoms caused by a four-year delay in diagnosis were improved with successful left femoropopliteal bypass. We use this case to review the differential diagnosis for IC and recommend early revascularization in young patients with severe disease and few comorbidities.

A Case of Spontaneous Isolated Celiac Artery Dissection with Pseudoaneurysm Formation.

Spontaneous isolated celiac artery dissection is a rare disease and patients without evidence of significant complications often resolve with medical therapy alone; however, the extension of the dissection can lead to more serious complications including aneurysmal dilatation, complete occlusion, and rupture of a visceral artery. In these patients, optimal management has not yet been clearly defined and treatment primarily depends on clinical presentation and lesions identified on imaging studies. This case report demonstrates the conservative management of spontaneous celiac artery dissection. A 49-year-old male presented to our emergency department with acute and persistent abdominal pain. A contrast-enhanced computed tomogram (CT) of abdomen showed a pseudoaneurysm involving the ostium of the celiac artery with focal dissection, with no evidence of thrombosis or infarction to the visceral organs. Ultrasound studies demonstrated a prominent but patent celiac artery with adequate distal perfusion. Therefore, conservative medical management with antiplatelet therapy was initiated in our patient. Follow-up repeat ultrasound three weeks following discharge showed no evidence of dissection flap, stenosis, thrombosis or increase in the size of the aneurysm. This case report demonstrates that conservative medical management with antiplatelet therapy can be sufficient in treating spontaneous isolated celiac artery dissection with pseudoaneurysm formation. We suggest endovascular or surgical intervention should be reserved for patients who present with hemodynamic instability, or other serious complications, such as aneurysm rupture or visceral infarction.

Generation of 3D nanopatterns with smooth surfaces.

Ga implantation into Si and reactive ion etching has been previously identified as candidate techniques for the generation of 3D nanopatterns. However, the structures manufactured using these techniques exhibited impedingly high surface roughness. In this work, we investigate the source of roughness and introduce a new patterning process to solve this issue. The novel patterning process introduces an additional layer absorbing the implanted Ga, thus preventing the clustering of the implanted Ga observed with uncoated Si substrates. This process enables 3D nanopatterning with sub-100 nm lateral resolution in conjunction with smooth height transitions and surface roughness down to 4 nm root mean square. Such patterns are ideally suited for optical applications and enable the manufacturing of nanoimprint lithography templates for low-profile Fresnel lenses.

Nano- and microstructuring of graphene using UV-NIL.

In this work we demonstrate for the first time the micro- and nanostructuring of graphene by means of UV-nanoimprint lithography. Exfoliated graphene on SiO(2) substrates, as well as graphene deposited by chemical vapor deposition (CVD) on polycrystalline nickel and copper, and transferred CVD graphene on dielectric substrates, were used to demonstrate that our technique is suitable for large-area patterning (2 × 2 cm(2)) of graphene on various types of substrates. The demonstrated fabrication procedure of micrometer as well as nanometer-sized graphene structures with feature sizes down to 20 nm by a wafer-scale process opens up an avenue for the low-cost and high-throughput manufacturing of graphene-based optical and electronic applications. The processed graphene films show electron mobilities of up to 4.6 × 10(3) cm(2) V (-1) s(-1), which confirms them to exhibit state-of-the-art electronic quality with respect to the current literature.

The use of 23.4% hypertonic saline for the management of elevated intracranial pressure in patients with severe traumatic brain injury: a pilot study.

BACKGROUND: Oncotic agents are a therapeutic mainstay for the management of intracranial hypertension. Both mannitol and varied concentrations of hypertonic saline (HTS) have been shown to be effective at reducing elevated intracranial pressure (ICP). We compared the safety and efficacy of 23.4% HTS to mannitol for acute management of elevated ICP after traumatic brain injury (TBI). METHODS: After approval from our institutional review board, the records of patients admitted with severe TBI who received mannitol or HTS were reviewed. Demographic and physiologic data were recorded. ICP, cerebral perfusion pressure, reduction of ICP after dose administration, serum sodium, osmolality, and magnitude of dose response during the subsequent 60 minutes were analyzed. Efficacy was determined by comparison of proportion of patients with any response and mean change in ICP after dosing with either agent. Safety was determined by recording any new postinfusion electrolyte or neurologic anomalies. Data were compared using chi2 test, accepting p < 0.05 as significant. RESULTS: Twenty-two patients with severe TBI received 210 doses of either mannitol or HTS. All patients suffered severe blunt injury (mean Injury Severity Score 28 +/- 11). HTS patients had a significantly higher ICP at the initiation of therapy than that of mannitol group (30.7 +/- 7.94 mm Hg vs. 28.3 +/- 8.07 mm Hg, respectively). There was no difference in initial cerebral perfusion pressure. Mean ICP reduction in the hour after administration of 102 doses of mannitol and 108 doses of HTS was greater for patients receiving HTS (9.3 +/- 7.37 mm Hg vs. 6.4 +/- 6.57 mm Hg, respectively; p = 0.0028, chi2). More patients responded to HTS (92.6% HTS vs. 74% mannitol; p = 0.0002, chi2). There was no significant difference between groups in the duration of ICP reduction after dose administration (4.1 hours vs. 3.8 hours, respectively). No adverse events after administration of either agent were identified. CONCLUSION: Based on this retrospective analysis, 23.4% HTS is more efficacious than mannitol in reducing ICP. If these results are confirmed in a prospective, randomized study, 23.4% HTS may become the agent of choice for the management of elevated ICP after TBI.