MONITORING PERTUMBUHAN MIKROALGA MENGGUNAKAN SENSOR GIANT MAGNETORESISTANCE (GMR) BERBASIS LAPISAN TIPIS SPIN VALVE DAN SINGLE LAYER

LIA SAPTINI H, Dr. Edi Suharyadi, M.Eng.

2019 | Tesis | MAGISTER FISIKA

Giant Magnetoresistance (GMR) berbasis lapisan tipis spin valve dan single layer di fabrikasi dengan metode DC magnetron sputtering. Lapisan tipis spin valve terdiri atas IrMn(10 nm)/CoFe(3 nm)/Cu(2.2 nm)/CoFeB(10 nm) dan single layer terdiri atas CoFe(20 nm) digunakan untuk mendeteksi keberadaan mikroalga. Nanopartikel Fe3O4 sebagai label magnetik disintesis dengan metode co-precipitation. Kurva histerisis loop Fe3O4 dari hasil vibrating sample magnetometer (VSM) menunjukkan magnetisasi saturasi (Ms), magnetisasi remanen (Mr), dan koersifitas (Hc) masing-masing sebesar 77,7 emu/g; 7,7 emu/g; dan 50 Oe. Nanopartikel Fe3O4 difungsionalisasi dengan polyethylene glycol (PEG-4000) untuk mengurangi aglomerasi antar partikel. Hasil tegangan keluaran pada variasi konsentrasi Fe3O4 (0 mg/mL sampai 20 mg/mL) menggunakan medan magnet elektromagnetik coil menunjukkan perubahan tegangan keluaran semakin berkurang seiring bertambahnya konsentrasi Fe3O4, sebaliknya pada medan magnet Helmholtz coil perubahan tegangan keluaran semakin meningkat dengan bertambahnya konsentrasi Fe3O4. Pendeteksian durasi waktu kultur mikroalga dari hari ke-0 sampai hari ke-14 dengan menggunakan lapisan tipis spin valve menunjukkan bahwa sensitivitas yang dihasilkan medan magnet Helmholtz coil dua kali lebih tinggi dibandingkan dengan elektromagnetik coil, masing-masing 48,1 % berbanding 29,5%. Lapisan tipis single layer untuk mendeteksi mikroalga dari hari ke-0 sampai hari ke-6 menunjukkan semakin tinggi densitas sel mikroalga, perubahan tegangan keluaran semakin rendah. Berdasarkan hasil penelitian tersebut menunjukkan bahwa lapisan tipis spin valve dan single layer dapat dijadikan sebagai biosensor untuk mendeteksi keberadaan biomolekul lainnya.

Giant Magnetoresistance (GMR) spin valve and single layer structure were fabricated by DC magnetron sputtering method. Spin valve structure consisting of IrMn(10 nm)/CoFe(3 nm)/Cu(2.2 nm)/CoFeB(10 nm) and single layer structure consisting of CoFe (20nm) were used to detect microalgae growth. Fe3O4 as magnetic label in detecting microalgae was synthesized by co-precipitation method. Hysteresis curve that was measured by VSM exhibited saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) of Fe3O4 were 77.7 emu/g, 7,7 emu/g, and 50 Oe, respectively. To functionalize the surface, Fe3O4 was coated with polyethylene glycol (PEG-4000). The change of output voltage with variation concentration of Fe3O4 from 0 mg/mL to 20 mg/mL shows that the pattern of spin valve structure in electromagnetic coil was inversely proportional to Helmholtz coil. In electromagnetic coil, the change of output voltage decreased with the increasing the concentration of Fe3O4, while Helmholtz coil shows that it increased with the rising the concentration of Fe3O4. Detection of microalgae growth from day-0th to day-14th of culture time by using spin valve thin film shows sensitivity of Helmholtz coil was twice as high as the electromagnetic coil, 48,1% compared to 29,5%. Single layer thin film to detect microalgae from day-0th to day-6th exhibits the higher the density of microalgae cells, the lower change in output voltage produced. Based on the results of these studies indicate that the spin valve and single layer thin film can be used as a biosensor to detect the presence of other biomolecules.

Kata Kunci : Giant magnetoresistance (GMR) biosensor, Fe3O4, microalgae, electromagnetic coil, Helmholtz coil