Immersion Systems Research Articles

Micropropagation in liquid culture using partial immersion systems

Plant tissue culture in liquid medium often has better growth than in semi-solid “gels” (e.g., agar) due to the increased availability of water and solutes. Aerating shoots is necessary to prevent hyperhydricity and anoxia. Choosing a mechanical system for aeration involves increased cost, mechanical complexity and ergonomic problems, balanced against the anticipated improvements in growth responses. Larger vessels are used with these machines to increase the growth area serviced by the more complex mechanized devices. A wide variety of horticultural crops and mechanical devices will be shown to illustrate these points. Simple systems, such as stationary thin films and support matrices often yield quality growth without the complexities and costs of mechanized agitated liquids if interfacial transport properties of media and tissue are correctly incorporated. Mechanical rockers and pumped intermittent immersion systems increase the interfacial transfer surface that may further benefit growth. Two simple systems are demonstrated in this paper. A thin film system for Miscanthus × giganteus was shown to confer the advantages of both TIS and Rocker bioreactors. A novel vessel systems based on Oasis®foam and a flexible film vessel was shown to combine stage III and acclimatization of Hydrangea, resulting in faster growing greenhouse plants. As better materials become available, simpler systems will also be more readily available.

Effect of the anatomical point of hanging and dripping time on water retention of chicken carcasses

Pre-cooling in water tanks (pre-chiller and chiller) is an important step in preserving the quality of chicken meat. After pre-cooling, the carcasses are hung by the wing and neck for 5 min to allow excess water to drain. The weight of the carcasses is monitored before and after pre-cooling to ensure that weight gain due to water absorption does not exceed 8%. However, no information is available as to how hanging the carcass from other anatomical points might affect water retention of carcasses and water loss during dripping. The present study evaluated the effects of the anatomical point of hanging and hanging time on water retention of carcasses and water loss during dripping. One hundred and sixteen carcasses (mean weight 1,662 ± 13 g) were chilled by cold-water immersion systems in 2 steps (pre-chilling and chilling). The results showed that after chilling, the carcasses needed at least 3 min of dripping time (p < 0.05) to maintain water absorption below 8% of the final weight, and that the point of hanging did not affect water absorption (p > 0.05). Data in this study clearly indicate that leg hanging is a practical alternative, and 5 min of dripping time is needed to maintain water absorption within the desired limit.

Evaluation of different temporary immersion systems (BIT®, BIG, and RITA®) in the micropropagation of Vanilla planifolia Jacks

The cultivation of Vanilla planifolia is of great economic importance because vanillin, a chemical valued in the food and cosmetics industry, is extracted from its pods. The conventional propagation of this plant is limited by the low viability of its seeds and the very low germination rate. For this reason, in vitro micropropagation techniques using temporary immersion systems (TIS) represent an alternative propagation mechanism. This work assessed three different bioreactor systems in two different micropropagation phases (multiplication and rooting) of V. planifolia: Temporary Immersion Bioreactors (BIT®), Gravity Immersion Bioreactors (BIG), and Recipient for Automated Temporary Immersion (RITA®). A higher number of shoots/explant were observed in the multiplication phase in BIT® systems (18.06 shoots/explant), followed by RITA® (12.77) and BIG (6.83). In the rooting phase, a higher number of longer roots were obtained in BIT® compared with BIG and RITA®. However, higher chlorophyll content was observed in BIG, followed by RITA® and BIT®. A 100% survival was obtained in vitro micropropagated plantlets in BIT®, exceeding the survival rate observed in RITA® and BIG. In general, our findings confirm the utility of BIT® systems in the optimization of the commercial micropropagation of this species. Furthermore, this system reduces the costs associated with the use of RITA® systems.

Temporary immersion systems in plant biotechnology

Plant tissue and organ cultures in vitro usually face technological challenges. When submerged cultivation of plant cells in a controlled environment is desired, the characteristic growth morphology and physiology of differentiated organ cultures present a problem in process scale‐up. Temporary immersion systems (TIS) were developed several decades ago. These systems are providing the most natural environment for in vitro culture of plant shoots and seedlings. Over the past few years, TIS have been recognized as a perspective technology for plant micropropagation, production of plant‐derived secondary metabolites, expression of foreign proteins, and potential solutions in phytoremediation. Nowadays, several TIS, operating on similar or divergent technological principles, have been developed and successfully applied in the cultivation of various plant in vitro systems, including somatic embryos and transformed root cultures. In this article, the operational principle and technological design of the most popular TIS are reviewed. In addition, recent examples of the application of temporary immersion technology for in vitro cultivation of plant tissue and organ cultures at laboratory and pilot scales are discussed. Finally, future prospects and challenges to the industrial realization of that fast‐developing technique are outlined.

The role of social motivation and sociability of gamers in online game addiction

Massively multiplayer online (MMO) games represent a long-standing, intensive and wide spread type of online applications whose popularity continues to grow. Although just a mere entertainment and leisure activity for most gamers, its potentially negative and addictive outcomes were intensively studied and recently also acknowledged by the American Psychiatric Association (2013). MMOs are essentially a social activity, but empirical studies are equivocal in identifying whether and to what extent the social factors help develop the addictive gaming habits associated with these applications. The present study seeks to directly identify the role of social factors in online addictive gaming. Survey data from 667 MMO gamers were analysed. Together with an online game addiction scale, the investigated psychological factors included social motivation for gaming, online peer attachment and social self-efficacy. The results revealed that although social motivation was a predictor of addictive gaming, high social motivation was typical for intensive gamers regardless of their level of addiction. However, gamers at-risk of addiction scored lower in their social self-efficacy and interpersonal trust measured by peer attachment. This supports the poor-get-poorer hypothesis, that generally less socially skilled gamers face further problems online. However, social factors were only modestly associated to online addictive gaming which indicates higher relevance of other factors identified by literature, e.g. immersion and in-game rewards systems.

Effect of immersion systems, lighting, and TIS designs on biomass increase in micropropagating banana (Musa spp. cv. 'Grande naine' AAA)

Development of in vitro techniques has enabled rapid clonal propagation, regeneration, and multiplication of genetically manipulated superior clones, production of secondary metabolites, and ex situ conservation of valuable germplasm. This has been possible not only due to the refinements of culture methodologies and applications of cutting-edge areas of molecular biology but also due to the judicious inclusion of engineering principles and methods to improve and refine the system. In the present study, we used engineering principles and methods to transform basic in vitro techniques into commercially viable technologies. We investigated two types of temporary immersion systems (TIS), two types of lighting, and two different gas exchange systems during in vitro banana (Musa spp. cv. 'Grande naine') shoot cultures. After 7 wks, all banana shoots cultured in standard TIS (5-L glass vessels, type 1) showed superior vegetative growth for the evaluated parameters. We also found that illumination provided by light emission diodes (LEDs) was superior to the use of white fluorescent lamps at the same light intensity (40 μmol m−2 s−1). Shoots treated with compressed air for immersion and additional gas exchange during the culture period in the glass vessel of TIS systems resulted in higher propagation rates and a larger number of shoots harvested as well as a larger number of roots formed per shoot after the 7-wk culture period.

Temporary immersion systems for Amaryllidaceae alkaloids biosynthesis by Pancratium maritimum L. shoot culture

The alkaloid patterns of sea daffodil (Pancratium maritimum L.) shoot culture, cultivated in a temporary immersion cultivation system were investigated. The shoots accumulated maximal amounts of biomass (0.8 g dry biomass/L and Growth Index = 1.6) at immersion frequency with 15 min flooding and 12 h stand-by periods. At this regime P. maritimum shoots achieved the highest degree of utilization of carbon source. Twenty-two alkaloids, belonging to narciclasine, galanthamine, haemanthamine, lycorine, montanine, tazettine, homolycorine and tyramine types were identified in intracellular and extracellular alkaloid extracts. The immersion frequency affected strongly the capacity of alkaloid biosynthesis in P. maritimum shoots and at the optimum conditions of cultivation, the total intracellular alkaloid content reached up to 3,469 μg/g dry biomass. The main biosynthesized alkaloids were haemanthamine (900.1 μg/g) and lycorine (799.9 μg/g). The obtained results proved that temporary immersion technology, as a cultivation approach, and P. maritimum shoots, as a biological system, are prospective for producing wide range bioactive alkaloids.

Temporary immersion systems (RITA®) for the improvement of cork oak somatic embryogenic culture proliferation and somatic embryo production

Somatic embryogenesis in cork oak (Quercus suber L.) is an efficient tool that allows the production of large number of embryos from selected quality and productive trees. Temporary immersion systems (TIS) are an alternative to semi-solid or liquid culture that combine the advantages of liquid culture and avoid the associated problems. Parameters that affect the TIS multiplication efficiency of Q. suber L. embryogenic cultures were evaluated. Immersion frequencies of 1 min every 6 or 4 h increased the fresh weight 3.7 or 7.5-fold compared with an immersion frequency of 1 min every 12 h or cultures on semi-solid medium, respectively. The cellular fate of embryogenic cultures was also affected by the immersion frequency, 1 min every 6 h was the best for mass propagation of proliferative developmental stages (embryogenic calli and embryo clusters) while 1 min every 4 h promoted the formation of single, fully developed cotyledonary embryos. An initial amount of 1.5 g fresh weight of proliferative tissues produced the best results in RITA® containers while 0.5 g of embryogenic callus was the best for semi-solid cultures.

The status of temporary immersion system (TIS) technology for plant micropropagation

The development of temporary immersion systems (TIS) for in vitro culture, in the late 1990s heralded new and semi-automated means of micropropagation of plants for agricultural and conservation purposes. By 2005, various systems had been developed and tested and their benefits were proven with a variety of commercially-important crops such as sugar-cane, coffee, banana, and yam. Progress in the field and the adoption of these systems in subsequent years has been reviewed. Improvements on previously-developed TIS protocols for economically-important species have been reported, and this continues to attest to their benefits when compared with protocols that employ semi-solid or liquid media. Though TIS protocols have recently been developed for other species, this list is limited. On the other hand, there appears to be an increasingly great interest in TIS technology for the production of secondary metabolites and for physiological studies.

Performance evaluation of cryogenic treated tools in turning

Tool wear is a worn portion over the flank and face of the tool. Tool wear is significant for determining tool life and hence it influences the machining economics. The wear measurements are carried by using a tool makers microscope in the present investigations. All the investigations are carried out using cutting fluid. Life enhancement by using cryogenic treatment on HSS is the objective of study. Investigations are carried on different work materials such as AISI 1040, EN8 and EN24. Improvement in tool life up to 90% is observed for soft material AISI 1040 and enhancement up to 39% is observed on EN24. These investigations are aimed at benefiting small industries that use aforementioned tool work combinations. Regression models are constructed for tool wear for both untreated machining and cryogenic treated machining. To understand the effects of cryogenic processing, it is essential to get acquainted with the heat treating of metals. The primary reason for heat treating steel is to improve its wear resistance through hardening. Gears, bearings and tooling for example are hardened because they need excellent wear resistance, improved fatigue life, stress relieving dimensional stability and corrosion resistance for extended reliability and performance. The steps in heat-treating are frequently explained in a simplistic manner but it takes significant skill and experience to execute heat treatments successfully. The steel tooling in practice would be immersed in liquid nitrogen for a period of time, allowed to warm up and then placed into service. It was also observed that the cryogenic treatment would convert the retained austenite into un-tempered martensite. The tools would experience a greatly enhanced service life. It was theorized that the increase in wear resistance was a direct result of the reduction in the amount of residual austenite. Liquid nitrogen systems have been the customary method for achieving cryogenic temperatures. Three types of systems have been developed viz heat exchanger systems, direct spray systems, and immersion systems. The last method i.e immersion system is used in present investigation. The tool wear can be measured directly by using a microscope. However several indirect methods depending on the measurement of a parameter that influence the tool wear do exist. Some of the methods for indirect prediction are cutting force, vibrations, acoustics, radioactive isotopes, image processing etc. It should be noted that no method is accurate for indirect prediction. Studies by Penn State University researchers in 1996 showed that retained austenite was reduced from near 18% to roughly 8% in T15 tool steel upon cryogenic treatment. Hardness increased by 2 points (HRC) with cryogenic treatment and

Field performance and (epi)genetic profile of plantain (Musa AAB) clone ‘CEMSA ¾’ plants micropropagated by temporary immersion systems

Use of meta-topolin (mT) [6-(3-hydroxybenzylamino) purine] to scale up the plantain clone ‘CEMSA ¾’ in temporary immersion systems (TIS), when compared with conventional micropropagation protocols, has been shown to improve production and quality of microplants. To evaluate the impact of those innovations on plant field performance, in vitro plants of ‘CEMSA ¾’ were subjected to either an additional multiplication cycle using TIS or semi-solid medium (SS) in the presence of 4.44μM mT or N6-benzyladenine (BA). Growth and yield components in the microplants grown in field – plant crop – and in the developed plants of the following field generation – first ratoon – were evaluated. Also (epi)genomic traits were studied by flow cytometry, fluorimetry-based AFLP and HPLC analyses of global genomic DNA methylation. Neither in vitro microprogation systems – TIS and SS – nor cytokinins – mT and BA – had any factorial effect on yield productivity of the plant crop. In the first ratoon, significant differences in yield appeared, with TIS-BA plants being more productive than those generated from TIS-mT. For most of the measured variables, the plant crop had higher values than the first ratoon, but true-to-type and each off-type phenotype of the plant crop was always inherited by their corresponding offspring of the first ratoon. The proportion of true-to-type plants was higher for SS-BA and TIS-mT culture conditions. Irrespective of micropropagation protocol and phenotype, in the plant crop, average genomic DNA content was maintained and global genomic methylation levels were similar. Nevertheless, dwarf individuals showed more AFLP polymorphisms with respect to mother plants than the rest of the micropropagated plants, and a dwarfism-related AFLP marker is proposed. On the basis of the results obtained and previous reports, the innovative TIS-mT protocol was deemed to be the most suitable plantain multiplication technique among those tested.

Increased cardenolides production by elicitation of Digitalis lanata shoots cultured in temporary immersion systems

Digitalis lanata is an important source of cardenolides such as digoxin and lanatoside C, which have been widely applied in the treatment of cardiac insufficiencies. Elicitation is one of the most effective methods to enhance the biosynthesis of several secondary metabolites in medicinal plants. We studied the effect of elicitation with Chitoplant®, Silioplant® and methyl jasmonate on biomass and cardenolides accumulation in shoots of D. lanata cultivated in temporary immersion systems. Morphological response of the shoots was influenced by elicitors. A reduction in length and number of shoots was evident with all MJ concentrations. Regarding biomass production, Chitoplant® (0.1 g l−1) was found to impact significantly on fresh and dry weight of the shoots. HPLC analysis revealed a higher content of lanatoside C compared to digoxin in all treatments. The highest accumulation of lanatoside C was achieved with Chitoplant® (0.1 g l−1), which resulted in 316 μg g-DW−1 and with Silioplant® (0.01 g l−1; 310 μg g-DW−1), which accounted for a 2.2-fold increase in lanatoside C content compared to non-elicited shoot cultures. Additionally, elicitation of D. lanata shoots in temporary immersion systems resulted in an oxidative stress characterized by hydrogen peroxide and malondialdehyde accumulation. These observations point to a connection between hydrogen peroxide generation, lipid peroxidation and cardenolide accumulation. The optimization of elicitor treatment and culture conditions for cardenolide production as well as the advantages of TIS for this purpose are discussed.

Comparison of static immersion and intravenous injection systems for exposure of zebrafish embryos to the natural pathogen Edwardsiella tarda

BackgroundThe zebrafish embryo is an important in vivo model to study the host innate immune response towards microbial infection. In most zebrafish infectious disease models, infection is achieved by micro-injection of bacteria into the embryo. Alternatively, Edwardsiella tarda, a natural fish pathogen, has been used to treat embryos by static immersion. In this study we used transcriptome profiling and quantitative RT-PCR to analyze the immune response induced by E. tarda immersion and injection.ResultsMortality rates after static immersion of embryos in E. tarda suspension varied between 25-75%, while intravenous injection of bacteria resulted in 100% mortality. Quantitative RT-PCR analysis on the level of single embryos showed that expression of the proinflammatory marker genes il1b and mmp9 was induced only in some embryos that were exposed to E. tarda in the immersion system, whereas intravenous injection of E. tarda led to il1b and mmp9 induction in all embryos. In addition, microarray expression profiles of embryos subjected to immersion or injection showed little overlap. E. tarda-injected embryos displayed strong induction of inflammatory and defense genes and of regulatory genes of the immune response. E. tarda-immersed embryos showed transient induction of the cytochrome P450 gene cyp1a. This gene was also induced after immersion in Escherichia coli and Pseudomonas aeruginosa suspensions, but, in contrast, was not induced upon intravenous E. tarda injection. One of the rare common responses in the immersion and injection systems was induction of irg1l, a homolog of a murine immunoresponsive gene of unknown function.ConclusionsBased on the differences in mortality rates between experiments and gene expression profiles of individual embryos we conclude that zebrafish embryos cannot be reproducibly infected by exposure to E. tarda in the immersion system. Induction of il1b and mmp9 was consistently observed in embryos that had been systemically infected by intravenous injection, while the early transcriptional induction of cyp1a and irg1l in the immersion system may reflect an epithelial or other tissue response towards cell membrane or other molecules that are shed or released by bacteria. Our microarray expression data provide a useful reference for future analysis of signal transduction pathways underlying the systemic innate immune response versus those underlying responses to external bacteria and secreted virulence factors and toxins.

Diluição celular, características do meio de cultura e biorreatores de imersão temporária na diferenciação e regeneração de células em suspensão de bananeira

Altos custos de produção geralmente limitam o uso comercial da micropropagação. O uso de meios de cultura líquidos é considerado uma solução para a automação e redução de custos. Entretanto, dependendo da cultivar de bananeira, esse processo pode mostrar diferentes níveis de dificuldade, e adaptações nos protocolos são necessárias. Neste estudo, experimentos de diferenciação celular e regeneração de plantas foram desenvolvidos em células em suspensão de banana pela avaliação da densidade inicial de células, meios de cultura e sistemas de imersão temporária. Para tanto, uma sequência de três experimentos foi realizada: o primeiro avaliou os efeitos da densidade celular (0,5; 1 e 2 mL), meios de cultura (M1: 1/2MS, 0,1 g.L-1 de ácido ascórbico, 0,1 g.L-1 de L-prolina, 30 g.L-1 de sacarose e 10 µM de 2iP; M2: MS, 30 g.L-1 de sacarose, 2,2 µM de BAP e 11,4 µM de AIA) e períodos de diferenciação celular (40 e 130 dias); o segundo experimento analisou o efeito do tamanho dos propágulos diferenciados em meio líquido (aprox. 2,5; 5 e 10 mm em diâmetro) na formação de embriões somáticos ou na regeneração de plantas; finalmente, um terceiro experimento avaliou o efeito de sistemas de cultivo com papel-filtro cobrindo o meio de cultura semissólido e sistemas de imersão temporários na diferenciação dos propágulos e na regeneração de plantas. Não foram observadas diferenças significativas entre os meios de diferenciação, porém as melhores diluições de células para a diferenciação foram de 1 e 2 mL/30mL de meio de cultura, enquanto diluições de 0,5 mL/30 mL de meio aumentaram a oxidação celular. A extensão do período de diferenciação de 40 para 130 dias foi importante para produzir maior número de calos/propágulos uniformes e com pelo menos de 10 mm de diâmetro, que puderam ser usados em sistemas de imersão temporária (biorreatores) para a diferenciação de embriões somáticos e regeneração de plantas. Considerando todos os sistemas de regeneração, verificou-se que o uso de meios de regeneração de consistência semissólida com papel-filtro na superfície do meio é o mais responsivo para a diferenciação de embriões somáticos e regeneração de plantas.

Performance of yam microtubers from temporary immersion system in field conditions

The yam clones ´Pacala Duclos´ and ´Belep´ of Dioscorea alata were used to evaluate the performance of microtubers formed in temporary immersion systems (TIS) in field conditions. Previously sprouted microtubers with a fresh weight higher than 3.0 gFW were used while in vitro plants and tuber crowns from conventional propagation methods served as control. In both clones there were no significant differences in qualitative morphological characters between plants from microtubers and in vitro plants for all traits but both differed significantly from plants obtained from tuber crowns. The same trend was observed for number, length, diameter and fresh weight of tubers produced 36 weeks after field planting. The number of tubers formed per plant raised from microtubers doubled that raised from tuber crowns in both clones. Microtubers from temporary immersion systems can be grown on the field and used in original seed production programs. Key words: Microtuber, yam, field, temporary immersion system.

DETERMINING CONVECTIVE HEAT TRANSFER COEFFICIENT (h) FOR HEATING AND COOLING OF BOTTLES IN WATER IMMERSION

ABSTRACTThermal process, specially the in‐package process, is one of the safest and most frequently used methods for food preservation. Mathematical models for heat transfer have been widely used as a powerful tool in safety and high‐quality food process design. The convective heat transfer coefficient (h) is essential for heat flux calculation in model boundary conditions, and its determination must be done by the actual heat transfer system. The present study has determined the h‐values for two commercial bottles (G1 and G2) in two water immersion systems, one for heating and one for cooling. It was calculated by an inverse heat transfer problem, using computational fluid dynamics. Two methodologies for h determination were compared, using either a conductive material or a convective material inside the packages. The methodology that uses a conductive material showed simpler and faster computational simulation, but presented a limitation related with the Biot number of the process. Results indicated a limitation in the most used methodology for h determination, and suggest that the convective material methodology can be an alternative for this analysis. For the same systems, the hheating value for G1 was almost 50% higher than for G2, and hcooling values for G1 were almost 70% higher than for G2. Differences obtained between bottles highlight the need to determine h for the exact heat transfer system. Moreover, these results indicate that there is a potential for process optimization only by varying its package format, as it can influence the heat flux for the packaging.PRACTICAL APPLICATIONSThe results obtained from this study highlight the influence of geometry on the convective heat transfer coefficient among bottles and immersion water systems. It also confirms the possibility of optimizing the thermal process through package format changes, allowing the obtainment of safer products with better sensorial and nutritional characteristics at a lower cost and energy expenditure. However, further studies are needed to better understand the package geometry in thermal processes. On the other hand, it contributes for thermal processes studies as it stands out the importance of determining this property for the actual system studied, besides showing its limitations for determination based on a conductive product widely utilized in the literature.

Efficacy of Different Disinfectant Systems on Alginate and Addition Silicone Impression Materials of Indian and International Origin: A Comparative Evaluation

Study was planned to evaluate the efficacy of commonly used disinfectants and to study qualitatively and quantitatively the persistence of microflora on the untreated (control group) and the disinfected impression surface after 24h. Disinfectant systems used were immersion systems like glutaraldehyde, sodium hypochlorite and the ultraviolet chamber. The effect of disinfectant on most commonly used Indian impression materials was carried out in this study and results compared with the most commonly used foreign brands for irreversible hydrocolloid and addition silicone. Impressions were made of 25 healthy volunteers. These were disinfected and incubated in an incubator for 24h at 37°C for aerobic organisms. The inoculation in nutrient media was done to test the viability of microorganisms that can persist after rinsing and disinfection of the impression surface. The colony forming units were counted and compared with that of control group. Control group of all the impression material samples showed growth of Streptococcus viridans, Diphtheroids, Streptococcus pneumoniae to a greater extent. The growth of Candida albicans, Pseudomonas aerugenosa and Staphyloccus albus was present in all the groups but to a lesser extent. The persistence of the microflora on the impression surface of both the studied brands was similar but the concentration of organisms in the alginate control group was two folds as compared to addition silicone group. Use of ultraviolet chamber gave better results compared to the studied immersion systems. All the disinfection systems were effective in reducing the microbial load with ultraviolet chamber as the most effective.

Practical Considerations Relating to Immersion Cooling of Power Electronics in Traction Systems

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MULTIPLICACIÓN IN VITRO DE BROTES DE TRES VARIEDADES DE CALLAS (Zantedeschia sp.) EMPLEANDO SISTEMA DE INMERSIÓN TEMPORAL

Las Callas (Zantedeschia spp.) son plantas de la familia Araceae de gran interés como plantas ornamentales en maceteros y como flores de corte. Resulta de gran interés la propagación in vitro de las nuevas variedades obtenidas, por la diversidad de colores de sus flores. Cuando se desean introducir nuevos híbridos en el mercado, las técnicas de propagación tradicional son insuficientes, por lo que resultan de gran interés las técnicas de propagación in vitro. Con el objetivo de establecer un protocolo para la propagación in vitro más eficiente se evaluaron diferentes formas de cultivo (semi-sólido; líquido en movimiento e inmersión temporal), en la proliferación y calidad de los brotes. Se logró el establecimiento de un protocolo para la multiplicación in vitro de la Zantedeschia en Sistemas de Inmersión Temporal de mayor eficiencia biológica que los métodos convencionales de propagación (semi-sólido y liquido en movimiento).

Investigation on the critical velocity for liquid loss in immersion lithography

Immersion lithography seeks to extend the resolution of optical lithography by filling the gap between the final optical element and the wafer with a liquid characterized by a high index of refraction. The semiconductor industry demands high throughput, leading to relatively large wafer scanning velocities and accelerations. For higher scanning velocities, an issue that has been identified is the deposition of the immersion liquid while confining a relatively small amount of liquid to the under-lens region. Liquid loss occurs at the receding contact line that forms when a substrate is withdrawn from a liquid, which potentially leads to defects on printed patterns. There has been substantial prior work relative to understanding and building semi-empirical correlations and numerical models to investigate this behavior of the receding three-phase contact line. In the current work, a new liquid injection and collection model with analytic solutions is presented and compared with experimental results, in which the critical velocity for liquid loss is mainly a function of the vacuum degree, the injection flow rate, the properties of the immersion liquid. This correlation allows the critical velocity to be predicted with a given gap height between wafer and lens using only a measurement of the injection speed and knowledge of the fluid properties. Experimentally, glycerin–water mixtures of varying viscosities and different injection flow rates were tested, with variable outlet vacuum degree and inlet speed, showing a mean average error within 12%. This correlation represents a useful tool that can serve to approximately guide the development of fluid control for immersion systems as well as to evaluate alternative immersion fluid candidates to minimize liquid deposition while maximizing throughput.