Hydrothermal liquefaction (HTL) is a process technology suited for converting wet biomass, like microalgae, into biocrude oil. This study investigates the effects of temperature and reaction time on the mass yield and the properties of HTL biocrude oil such as higher heating value (HHV) and composition. Spirulina platensis, a microalgae species, is used as feedstock. Slurry prepared at 30% dry weight is processed in 5-mL mini-reactors. Temperatures are set at 280 0 C, 320 0 C, and 350 0 C using a temperature-controlled sandbath. Reaction times are varied at 15 mins, 30 mins, and 45 mins. Biocrude oil is produced and separated using dichloromethane (DCM) as solvent. The mass yield of biocrude oil varies depending on temperature and reaction time ranging from 29.6% to 44.8% by mass, dry ash-free (daf) basis. Higher mass yield is observed at the lowest temperature setting of 280 0 C. The HHV is measured using bomb calorimeter and calculated using Dulong's formula. The HHV ranges from 31.5 MJ/kg to 37 MJ/kg. Highest HHV is obtained for biocrude oil at 350 0 C and 45 mins reaction time. The highest energy recovery is 76.8%, which is attained at 280 0 C and 45 mins. Elemental analysis and GC-MS analysis are conducted to analyze the composition of biocrude oil produced. The N/C and O/C ratios of HTL biocrude oil are reduced in all experimental conditions. Nitrogen content is lowest at 350 0 C and 30 mins to 45 mins reaction time.

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Abstract-Microfluidics involves fluid dynamics, controlled fluid manipulations, and design of devices or systems in microchannels with typical dimensions of 10 to 200 micrometers. The conventional fabrication method of polydimethylsiloxane (PDMS) microchannels is soft lithography, which involves an expensive process for the preparation of master. The study aims to fabricate microchannels using print-and-peel (PAP) method for simple and low-cost construction of microfluidic systems. Based on the PAP method, a PDMS microchannel is developed using a master based on inkjet ink relief printed on paper. The study improves on the existing methodologies for PAP method by devising a technique called "printing-over", which is reprinting of the same pattern over itself at a high precision by modifying the printing process. This can produce irregularly-shaped molds with dimensions that can reach up to 200 micrometer width and 14.8 micrometer height, with aspect ratio equal to 0.07. Moreover, the aspect ratio is found to increase proportionally with number of printing-over runs. The microchannel produced from the mold has dimensions of 155 by 10 micrometers with aspect ratio of 0.06. With a rough cost analysis, the capital and variable costs of the PAP inkjet method are significantly lower than that of photolithography.Index Terms-Low-cost microfluidics, polydimethylsiloxane, print-and-peel method, inkjet printing. I. INTRODUCTIONMicrofluidics is the science that deals with the flow of liquids inside micrometer-size channels. This technology has found applications in various areas including biomedical engineering, cell biology, drug screening, chemical reaction engineering, and electrochemistry. While the main advantage of microfluidics is the reduction of costs by reducing fluid volumes, the conventional fabrication process requires specialized equipment in laboratories; and the material used, usually silicon chips, can be expensive to produce. Inducing controlled fluid flows in microfluidic channels is done using special equipment called microsyringe pumps, but these are also too expensive and are unavailable locally. The high costs associated with the fabrication of microfluidics consequently limits accessibility and thus, hinders its development especially in low-resource settings.The conventional fabrication method of polydimethylsiloxane (PDMS) microchannels is soft lithography, which involves an expensive process for the Manuscript received October 8, 2016; revised January 18, 2017. This work was supported in part by the UP Engineering Research and Development Foundation, Inc. (ERDFI) and the College of Engineering, University of the Philippines Diliman.The authors are with University of the Philippines Diliman, Quezon City 1101, Philippines (e-mail: kristian.yap@gmail.com). preparation of master called photolithography. Photolithography is a patterning process where light is used to transfer a pattern from a mask to a photosensitive polymer layer, and this resulting pattern can either be etched into the underlying su...

This study is relevant to developing biomass, specifically microalgae, as a source for biofuel production through hydrothermal liquefaction (HTL). Hydrothermal liquefaction (HTL) is a thermochemical conversion that requires no drying of the feedstock because the whole microalgae biomass is decomposed and converted in hot compressed water. A biocrude oil is obtained as the main product, along with gaseous, aqueous and solid by-products. It was observed in different studies that catalysts, particularly alkali catalysts, improve liquefaction efficiency. This study investigated the effects of potassium carbonate (K 2 CO 3 ) on the yield and properties of biocrude oil. Different amounts of catalysts used were 5, 7.5, and 10 wt. %, respectively. Biocrude oil was produced from hydrothermal liquefaction of Arthrospira platensis (formerly referred to as Spirulina platensis) in a micro-reactor at 280 and 350 degrees Celsius for two levels of residence time, 15 and 45 minutes. The biocrude produced under these different conditions were analyzed for C, H, O, and N content. Biocrude oil yield and its calorific value were also determined. The highest biocrude oil yield with catalyst (32.18 wt. %) was obtained at 280°C with 15 minutes residence time and 5 wt. % K 2 CO 3 . Highest HHV of 39.17 MJ/kg was obtained with the addition of 10 wt. % K 2 CO 3 at 280°C and 45 minutes residence time. Biocrude oil obtained from the experiment runs had almost similar H/C, and O/C values to that of biodiesel and plant oil and was better than biomass pyrolysis oil. The N/C ratios of the biocrude oil ranged between 0.03 to 0.09.

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