The epithelial sodium channel (ENaC) is a transmembrane protein that regulates the balance of sodium salt levels in the body through its expression in various tissues. The increase in sodium salt in the body is related to the expression of ENaC, thereby increasing blood pressure. Therefore, overexpression of the ENaC protein can be used as a biomarker for hypertension. The detection of ENaC protein using anti-ENaC in the biosensor system has been optimized with the Box-Behnken experimental design. The steps carried out in this research are screen-printed carbon electrode modification with gold nanoparticles, then anti-ENaC was immobilized using cysteamine and glutaraldehyde. Optimum conditions of the experiment, such as anti-ENaC concentration, glutaraldehyde incubation time, and anti-ENaC incubation time, were optimized using the Box-Behnken experimental design to determine the factors that influence the increase in immunosensor current response and the optimum conditions obtained were then applied to variations in ENaC protein concentrations. The optimum experimental conditions for anti-ENaC concentration were 2.5 µg/mL, the glutaraldehyde incubation time was 30 minutes, and the anti-ENaC incubation time was 90 minutes. The developed electrochemical immunosensor has a detection limit of 0.0372 ng/mL and a quantification limit of 0.124 ng/mL for the ENaC protein concentration range of 0.09375 to 1.0 ng/mL. Thus, the immunosensor generated from this study can be used to measure the concentration of normal urine samples and those of patients with hypertension.

In this research a portable potentiostat was built for electrochemical sensing measurements with three electrodes, specifically SPCEs. The circuit uses a microcontroller as the main controller to manage all activities, starting from adjusting the input voltage for the SPCEs, setting measurement parameters, measuring the resulting current, displaying graphics on the touch screen, sending data to the computer via the USB port, and connecting to the SD card. Measurements and errors with cyclic voltammetry techniques have been compared with commercial potentiostats. The measurement results on a dummy circuit and commercial SPCEs have an accuracy of more than 90% compared to commercial potentiostats. In addition, measurement data can also be saved to an SD card in .CSV format for further purposes.

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Infrared Guitar is a musical instrument that belongs to the Digital Musical Instruments (DMI). This guitar uses infrared light instead of strings and chords. This guitar is one of the Human-Computer Interaction (HCI), which can result in the form of MIDI sound in real-time.Infrared Guitar input consists of two parts, namely the strings and the chord. Both parts are used as an infrareds transmitter and photodiodes as a receiver. When your finger blocking infrared rays received by photodiodes, the output will change. The combination of these two parts of the input will be processed by a microcontroller and then the data is sent to the computer. The computer will process the data and will produce guitar tones in the form of MIDI sound on the speakers.The advantages of Infrared Guitar is easy to play, because one guitar chord can be played using one finger to press a virtual button (infrared). Players do not need to memorize chord guitar to play songs. Another advantage is the players are not feeling the pressure of strong strings as in conventional guitar, so it does not cause pain to the fingers after playing for long.