This study demonstrates the fabrication of tunable masking layer consisting of gold islands on fused silica substrates. The goal is to produce anti-reflective structured surfaces (ARSS) that correlate to the repeatable and scalable masking step. The transmission enhancement waveband of fused silica is controlled by variations in gold masking islands created through repetitive dewetting process. Gold layer is formed by physical vapor deposition and thermal annealing. Varying deposition thickness and annealing temperature, size and periodicity of gold islands is controlled. With each iterative step of deposition and annealing, relative periodicity established by the initial island formation, or “seed”, is maintained while increasing fill factor in subsequent iterations. Optical transmission spectra were analyzed of the masking layer and formation of metasurface by plasma etching. Results showed that larger deposition thicknesses required higher annealing temperatures to generate circular islands. The seed layer sets the mask periodicity, then the mask fill factor can be increased to allow for deeper etching of ARSS features, for broadband performance. For example, initial deposition thickness of 10nm and repeated iterative steps of deposition and annealing, the fill factor increased (28%, 39%, 47%, 49%), while the island periodicity was maintained at average 91 ± 6nm for all iterative steps. Etching these masked samples resulted in broadband transmission enhancement, over 94% of theoretical maximum. A comprehensive database of masking layer fabrication, resultant surface feature dimensions, and ARSS transmission enhancement capabilities was generated. This scalable masking approach can broaden high laser damage threshold applications utilizing tunable performance ARSS.
Previous benchtop studies demonstrated infrared (IR) laser sealing and cutting of blood vessels, in a sequential, two-step approach. This study describes a smaller, laparoscopic device design, and simultaneous approach to sealing and bisection of vessels. A 1470-nm IR laser sealed and bisected 40 porcine renal arteries, ex vivo. A reciprocating, side-firing, optical fiber, housed in a transparent square quartz optical chamber (2.7 x 2.7 x 25mm OD), delivered laser energy over an 11mm scan length, with a wide range of powers (41 to 59W) and treatment times (5 to 21s). Vessel diameters ranged from 2.5 to 4.8mm. All vessel cut ends were successfully sealed (80/80), as indicated by burst pressures greater than 360mmHg. The highest power, 59W, resulted in short times of 5 to 6s. Peak temperatures on the external chamber surface reached 103 °C. Time to cool down to body temperature was 37s. Infrared lasers simultaneously sealed and bisected blood vessels, with treatment times comparable to, and temperatures and cooling times lower than conventional devices.
Infrared (IR) lasers are being tested as an alternative to radiofrequency (RF) and ultrasonic (US) devices for hemostatic sealing of vascular tissues. In recent studies, a side-firing optical fiber was reciprocated, producing a linear laser beam pattern for sealing blood vessels. Challenges include limited field-of-view of vessel position within the device jaws, and matching fiber scan length to vessel size. A transparent jaw may improve visibility and enable custom treatment. Quartz and sapphire square optical chambers (2.7 x 2.7 x 25mm OD) were tested with a 1470nm laser and 550-μm-core fiber. Peak temperatures and cooling times were recorded on chamber surfaces. Angle polished fiber tips delivered 94% of light at a 90° angle. Porcine renal arteries with diameters of 3.4±0.7mm (n=13) for quartz and 3.2±0.7mm (n=14) for sapphire (P>0.05), were sealed using 30W for 5s. Reflection losses were 3.3% and 7.4% for quartz and sapphire. Peak temperatures on external chamber surface averaged 74±8 °C and 73±10 °C (P>0.05). Times to cool down to 37 °C measured 13±4s and 27±7s (P<0.05). Vessel burst pressures (BP) averaged 883±393mmHg and 412±330mmHg (P<0.05). For quartz, 13/13 (100%) vessels were sealed (BP>360mmHg), versus 9/14 (64%) for sapphire. Quartz provided more consistent seals and shorter cooling times than sapphire.
Protein-based therapeutics are used to treat or prevent a range of diseases, but a challenge for the expanded use of these products is the need for cold storage that makes distribution difficult in low-resource settings. Lyophilization is a common method used to stabilize protein-based products. However, this process remains expensive, and many freeze-dried proteins require cold-chain storage. Anhydrous preservation in an amorphous trehalose matrix has been successfully used as an alternative to lyophilization. A new processing technique called light assisted drying (LAD) has been used to successfully dry proteins in preparation for anhydrous storage. Water is selectively heated via near-infrared (1064 nm) illumination, rapidly removing water from a sample, and forming an amorphous matrix that can be stored at supra-zero temperatures. In previous work, large volume samples (0.25 ml) were successfully LAD processed on glass coverslips, but this substrate is not typically used in industry. In this study, large volume samples are LAD processed in vials that are commonly used to lyophilize vaccines. After LAD processing, the samples are stored at room temperature (20◦C) or refrigerated (4◦C) for one month. The end moisture content of samples was determined immediately after processing/storage to evaluate the effectiveness of water removal via LAD. The trehalose matrix was characterized using polarized light imaging to determine if crystallization occurred during storage, potentially damaging embedded proteins. These preliminary studies indicate that LAD can effectively stabilize large volume samples in glass lyophilization vials and demonstrates the potential use of LAD to stabilize products such as vaccines.
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