Engineering
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A High Performance Impedance-based Platform for Evaporation Rate Detection
Summary October 17th, 2016
This paper presents an impedance-based apparatus for evaporation rate detection of solutions. It offers clear advantages over a conventional weight loss approach: a fast response, high-sensitivity detection, a small sample requirement, multiple sample measurements, and easy disassembly for cleaning and reuse purposes.
Transcript
The overall goal of this experiment is to measure the evaporation rates of solutions, using an impedance-based system. This method can help answer key questions in the analytical chemistry fields such as moisturizing competitive of cosmetics. The main advantage of this technique are faster detection response, small sample size, high sensitivities, management of multiple samples, and easy disassembly for cleaning and reuse.
This method can provide insight into the evaporation process. It can also be applied to other laces such as biomolecular dissection and cellular behavior. We first had the idea for the method when we found the time-consuming nature of the standard way those measurements system to be troublesome.
To begin building the experimental chip module, use a glass cutter to cut an indium tin oxide-coated glass substrate to the appropriate dimensions. Sonicate the ITO glass in acetone. And then in deionized water for 15 minutes each.
Then dry the ITO glass with dry air. Apply five milliliters of positive photoresist liquid to the ITO glass and spin-coat the glass for 30 seconds. Keep the glass at 90 degrees Celsius for five minutes.
Then cover the glass with a film photo mask and expose the glass to 14 milliwatts of 436-nanometer ultraviolet light for 3.1 seconds. Allow the glass to cool to room temperature. Then develop the glass in developer solution for 30 seconds.
Heat the developed glass on a hot plate at 120 degrees Celsius for 10 minutes. Allow the glass to cool to 80 degrees Celsius. Place the glass in etching solution at 80 degrees for three minutes.
Then place the glass in acetone for one minute to remove residual photoresist material. Using a glass cutter, trim the excess ITO glass from the chip. Next, sonicate an 8-well silicone array and the ITO chip in detergent, deionized water, 95%ethanol, and deonized water again for 15 minutes each.
Dry the array and chip with dry air. Carefully place the clean, dry silicone array on the surface of the ITO chip so the electrode fingers on the chip are all within the wells of the silicone array. Finally, press the silicone array onto the ITO chip to form the experimental chip module.
To begin preparation for the experiment, connect a lock-in amplifier to a computer. Then connect a switch relay circuit to the lock-in amplifier. Insert the experimental chip module into the switch relay circuit socket.
In the software, set the signal frequency, the sample well numbers, the execution cycle, and the name of the file. Then prepare 4-milliliter solutions of varying concentrations of hyaluronic acid in tap water. Transfer 2.5 milliliters of each solution to a small vial.
To begin the experiment, for each sample transfer 0.5 milliliters to a well of the experimental chip module. Then weigh each sample vial with a precision balance and record the weights. In the software, begin collecting resistance and signal phase data.
Record the weights of the vials at regular time intervals throughout the evaporation experiment. Continue collecting data until the evaporation rate can be accurately determined by the change in weight of the sample vials. The rate of evaporation of hyaluronic acid solutions relative to water could be calculated from the impedance data after an hour of data collection.
The weighing method required half a day of data collection to determine the rate of evaporation. The impedance data, when normalized and converted to rate of weight loss, indicated that the evaporation rate of the solution of 0.05 weight to volume percent hyaluronic acid is 12%lower relative to water. The conventional weighing method displayed the same trend of decreased relative evaporation rate.
But the sensitivity of the precision balance was less than that of the impedance detector. Once mastered, this technique can be done in a hour if it is performed properly. After its development, this technique pave the way for researchers in the field of biomedicine to improve biomedication detection and cellular behavior using a constant microchip.
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