Fabricating Superhydrophobic Surfaces with Solid Freeform Fabrication Tools

Superhydrophobic surfaces exhibit a range of properties such as large contact angle, low contact angle hysteresis and decreased hydrodynamic drag. These properties make superhydrophobic surfaces of fundamental and commercial interest as they can enable a wide variety of applications including microfluidic components, biomedical devices, and micro-batteries. Superhydrophobic behavior is achieved through a combination of the hydrophobicity of the polymer and the roughness of the surface. We have used a commercially available multi-jet modeling rapid prototyping machine to fabricate 3D objects where the superhydrophobic surface is monolithic with the part. This approach was used to fabricate non-planar components with novel structures including helical conduits and porous meshes. In addition, we have developed a robotic dispensing tool that enables greater freedom of material selection. Both approaches have been used to fabricate arrays of surface features with diameters below 175 microns and with aspect ratios greater than 8:1. The fabrication and wetting properties of surfaces made using these two techniques will be discussed.Mechanical Engineerin

Singlet Oxygen Generation on Porous Superhydrophobic Surfaces: Effect of Gas Flow and Sensitizer Wetting on Trapping Efficiency

We describe physical-organic studies of singlet oxygen generation and transport into an aqueous solution supported on superhydrophobic surfaces on which silicon–phthalocyanine (Pc) particles are immobilized. Singlet oxygen (1O2) was trapped by a water-soluble anthracene compound and monitored in situ using a UV–vis spectrometer. When oxygen flows through the porous superhydrophobic surface, singlet oxygen generated in the plastron (i.e., the gas layer beneath the liquid) is transported into the solution within gas bubbles, thereby increasing the liquid–gas surface area over which singlet oxygen can be trapped. Higher photooxidation rates were achieved in flowing oxygen, as compared to when the gas in the plastron was static. Superhydrophobic surfaces were also synthesized so that the Pc particles were located in contact with, or isolated from, the aqueous solution to evaluate the relative effectiveness of singlet oxygen generated in solution and the gas phase, respectively; singlet oxygen generated on particles wetted by the solution was trapped more efficiently than singlet oxygen generated in the plastron, even in the presence of flowing oxygen gas. A mechanism is proposed that explains how Pc particle wetting, plastron gas composition and flow rate as well as gas saturation of the aqueous solution affect singlet oxygen trapping efficiency. These stable superhydrophobic surfaces, which can physically isolate the photosensitizer particles from the solution may be of practical importance for delivering singlet oxygen for water purification and medical devices

Hepatic artery stenosis angioplasty and implantation of Wingspan neurovascular stent: A case report and discussion of stenting in tortuous vessels.

BACKGROUND:Hepatic artery stenosis is a complication of orthotopic liver transplant occurring in 3.1%-7.4% of patients that can result in graft failure and need for re-transplantation. Endovascular therapy with angioplasty and stenting has been used with a high degree of technical success and good clinical outcomes, but tortuous hepatic arteries present a unique challenge for intervention. Suitable stents for this application should be maneuverable and conformable while also exerting adequate radial force to maintain a patent lumen. CASE SUMMARY:Herein we report our experience with a neurovascular Wingspan stent system in a challenging case of recurrent hepatic artery stenosis and discuss the literature of stenting in tortuous transplant hepatic arteries. CONCLUSION:Wingspan neurovascular stent is self-expanding, has good conformability, and adequate radial resistance and as such it could be added to the armamentarium of interventionalists in the setting of a tortuous and stenotic transplant hepatic artery

Point‐of‐care magnetic resonance technology to measure liver fat: Phantom and first‐in‐human pilot study

PurposeTo assess feasibility and accuracy of point-of-care (POC) NMR-proton density fat fraction (PDFF) in phantoms and in a human pilot study in a POC setting.MethodsPOC NMR (LiverScope, Livivos, San Diego CA) PDFF measurements were obtained of certified phantoms with known PDFF values (0%-40%). In an institutional review board-approved, Health Insurance Portability and Accountability Act-compliant prospective human study, a convenience sample of participants from an obesity clinic was enrolled (November 2020 to June 2021). The inclusion criteria required body mass index (BMI) = 27-40 kg/m2 and willingness to undergo POC NMR and MRI-PDFF measurements. Liver PDFF was measured by POC NMR and, within 35 days after, by a confounder corrected CSE MRI PDFF acquisition and reconstruction method. The adverse events were documented and linear regression analyses were performed.ResultsPOC NMR-PDFF measurements agreed with known phantom PDFF values (R2  = 0.99). Fourteen participants were enrolled in the pilot human study. MRI-PDFF could not be obtained in 4 participants (claustrophobia reaction, n = 3, exceeded size of MR scanner bore, n = 1). POC NMR was unevaluable in 2 participants (insufficient signal penetration depth, n = 1, failure to comply with instructions, n = 1). Technical success was 11 of 13 (85%) for POC NMR PDFF. In 7 participants (4 female; 31-74 years old; median BMI 35 kg/m2 ), MRI-PDFF (range, 2.8%-18.1%), and POC NMR-PDFF (range, 3%-25.2%), agreed with R2  = 0.94. POC NMR had no adverse events.ConclusionPOC NMR measures PDFF accurately in phantoms and, in a first-in-human pilot study, is feasible and accurate in adults with obesity. Further testing to determine precision and accuracy across larger and more diverse cohorts is needed

Superhydrophobic Photosensitizers. Mechanistic Studies of ¹O₂ Generation in the Plastron and Solid/Liquid Droplet Interface

We describe here a physical-organic study of the first triphasic superhydrophobic sensitizer for photooxidations in water droplets. Control of synthetic parameters enables the mechanistic study of “borderline” two- and three-phase superhydrophobic sensitizer surfaces where ¹O₂ is generated in compartments that are wetted, partially wetted, or remain dry in the plastron (i.e., air layer beneath the droplet). The superhydrophobic surface is synthesized by partially embedding silicon phthalocyanine (<i>Pc</i>) sensitizing particles to specific locations on polydimethylsiloxane (PDMS) posts printed in a square array (1 mm tall posts on 0.5 mm pitch). In the presence of red light and oxygen, singlet oxygen is formed on the superhydrophobic surface and reacts with 9,10-anthracene dipropionate dianion (<b>1</b>) within a freestanding water droplet to produce an endoperoxide in 54–72% yields. Control of the ¹O₂ chemistry was achieved by the synthesis of superhydrophobic surfaces enriched with <i>Pc</i> particles either at the PDMS end-tips or at PDMS post bases. Much of the ¹O₂ that reacts with anthracene <b>1</b> in the droplets was generated by the sensitizer “wetted” at the <i>Pc</i> particle/water droplet interface and gave the highest endoperoxide yields. About 20% of the ¹O₂ can be introduced into the droplet from the plastron. The results indicate that the superhydrophobic sensitizer surface offers a unique system to study ¹O₂ transfer routes where a balance of gas and liquid contributions of ¹O₂ is tunable within the same superhydrophobic surface

Singlet Oxygen Generation on Porous Superhydrophobic Surfaces: Effect of Gas Flow and Sensitizer Wetting on Trapping Efficiency

We describe physical-organic studies of singlet oxygen generation and transport into an aqueous solution supported on superhydrophobic surfaces on which silicon–phthalocyanine (Pc) particles are immobilized. Singlet oxygen (¹O₂) was trapped by a water-soluble anthracene compound and monitored <i>in situ</i> using a UV–vis spectrometer. When oxygen flows through the porous superhydrophobic surface, singlet oxygen generated in the plastron (i.e., the gas layer beneath the liquid) is transported into the solution within gas bubbles, thereby increasing the liquid–gas surface area over which singlet oxygen can be trapped. Higher photooxidation rates were achieved in flowing oxygen, as compared to when the gas in the plastron was static. Superhydrophobic surfaces were also synthesized so that the Pc particles were located in contact with, or isolated from, the aqueous solution to evaluate the relative effectiveness of singlet oxygen generated in solution and the gas phase, respectively; singlet oxygen generated on particles wetted by the solution was trapped more efficiently than singlet oxygen generated in the plastron, even in the presence of flowing oxygen gas. A mechanism is proposed that explains how Pc particle wetting, plastron gas composition and flow rate as well as gas saturation of the aqueous solution affect singlet oxygen trapping efficiency. These stable superhydrophobic surfaces, which can physically isolate the photosensitizer particles from the solution may be of practical importance for delivering singlet oxygen for water purification and medical devices