Abstract.A Wheatstone bridge-giant magnetoresistance (GMR) sensor was successfully developed for a potential biomaterial detection. In order to achieve this, a giant magnetoresistive [Co(1.5nm/Cu(1.0nm)] 20 multilayer structures have been fabricated by DC magnetron sputtering method, showing a magnetoresistance (MR) of 2.7%. The X-Ray diffraction (XRD) patterns showed that Co/Cu film multilayer has a high degree of crystallinity with a single peak corresponding to face-centered cubic (111) structure at 2 = 44.1 . Co/Cu multilayers exhibit a soft magnetic behavior with the saturation magnetization (Ms) of 1489 emu/cc and the coercivity (Hc) of 11.2 Oe. The magnetite Fe 3 O 4 nanoparticles used as a bimolecular labels (nanotags) were synthesized via co-precipitation method, exhibiting a soft magnetic behavior with Ms of 77.16 emu/g and Hc of 49 Oe. XRD patterns and transmission electron microscopy (TEM) images showed that Fe 3 O 4 was well crystallized and it grew in their inverse spinel structure with an average size of around 10 nm. The GMR sensor design was used to detect a biomolecules of streptavidin magnetic particles with concentration 10, 20, 30, and 40 l/ml and -amylase enzyme with consentration 10, 20, 30, and 40 l/ml captured using polyethylene glycol (PEG)/ Fe 3 O 4 nanoparticles. Various applied magnetic fields of 0-650 Gauss have been performed using electromagnetic with the various currents of 0-5 A. Here, the final value of the output voltage signals for the streptavidin magnetic particles concentration is 1.2 mV (10 l/ml). The output voltage changes with the increase of concentration. It was reported that the output voltage signal of the Wheatstone bridge exhibits log-linear function in real time measurement of the concentration of streptavidin magnetic particles and -amylase enzyme respectively, making the sensor suitable for use as a biomolecule concentration detector. Thus, the combination of Co/Cu multilayer, Wheatstone bridge, magnetite and PEG polymer has potential application to be used in bio-detection applications where ultra-small bio-labels are needed.

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Indonesia's strong economic growth is expected to continue, thus increasing electricity consumption to reach 491 Tera Watt hours (TWh) in 2030. Significant electricity savings can be obtained by increasing the electrical energy efficiency of homes. The aim of this study is to design a household electrical control system (KENDIL) by using the RLC circuit to reduce the flow in order to achieve more efficient home electricity distribution. The Data collection was carried out at Wisma Kertonegaran as a residential house consisting of 50 rooms. After using KENDIL, The PLN electricity bills per month was decreased from Rp. 176,601.82 / kwh to Rp. 107,294.85 / kwh. It can save electricity bill costs by 60%. This device is an application of electronic skills courses.

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Nanopartikel Fe3O4 yang berasal dari pasir besi pantai Glagah Kulon Progo telah berhasil disintesis menggunakan metode kopresipitasi dengan berbagai variasi konsentrasi HCl (10%, 15%, 25% dan 37%). Pengaruh konsentrasi HCl terhadap mikrostruktur dan sifat kemagnetan dari Fe3O4 dilihat dengan menggunakan XRD, SEM EDX serta VSM. Hasil XRD menunjukkan bahwa Fe3O4 yang dihasilkan memiliki struktur kristal kubik invers spinel. Semakin besar konsentrasi HCl, semakin baik derajat kristalinitasnya. Hasil SEM EDX untuk sampel Fe3O4 dengan konsentrasi HCl 37% menunjukkan ukuran butir (grain) yang hampir sama serta tingkat kemurnian sampel Fe3O4 yang dihasilkan sebesar 100% (Fe 72,42% dan O 27,58%). Hasil VSM menunjukkan Fe3O4 hasil sintesis memiliki sifat superparamagnetik serta bersifat soft magnetic. Nanopartikel Fe3O4 dengan konsentrasi HCl 25% memiliki Hc, Mr dan Mmax masing-masing sebesar 0,0215 T, 11,60 emu/gr dan 36,51 emu/gr. Sedangkan Nanopartikel Fe3O4 dengan konsentrasi HCl 37% memiliki Hc dan Mr yang lebih kecil yaitu masing-masing sebesar 0,0017 T dan 10,83 emu/gr serta Mmax yang lebih besar yaitu 36,82 emu/gr.