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ISFET Applications Introduction to ISFET Ion-Sensitive Field-Effect Transistor G8 鄭向均 鍾建陽 翁華揚 History • The first transistor was invented in 1947 • ISFET was first reported in 1970 Evolution MOSFET vs. ISFET • Insulator interface is key point • ISFET is usually operated at triode region Site Binding Model • The response of the ISFET to pH can be explained by using site-binding model • The exchange of hydrogen ions between the electrolyte and the reactive sites at the insulator surface causes the change in potential at the electrolyte insulator interface Fundamental Sum • As the pH changes the electrolyte oxide interface potential also change and due to this the threshold voltage of the ISFET changes. This variation of threshold voltage causes the change in drain current which is observed in this figure. ISFET Applications 8 Why ISFET? • Small size, low weighted • Suitable for use in miniaturized measurement systems • High input resistance, low output resistance • Direct contact with electrolyte solution • Fast response • Similar process with CMOS • Sensitive to H+ (pH-sensitive) 9 Direct Application: pH measurement • Site – Binding Model • Ions form a well-confined electric double layer close to the surface • A diffuse layer of outer charges exists between the Helmholtz planes and the neutral bulk of the solution Fig. 1 Fig. 2 Fig1: Biotecnolgy Advances[2003] Ion sensitive field effect transducer-based biosensors Fig2. https://www.mt.com/tw/zt/home/products/Process-Analytics/pH-probe/non-glass-ISFET-electrode.html 10 EnFET: Enzy field effect transistor • Glucose • Urea • Penicillin • Pesticides • Phenolic compounds • Steroidal glycoalkaloids • Creatinine 11 Glucose GOx FAD + Glucose → GOx FADH2 + Gluconolactone GOx FADH2 + O2 → GOx FAD + H2O2 + − H2O2 → O2 + 2H + 2e • Traditional Measurement Method Same procedure but measures by the current Need testing strips (can be damped if long time exposed to air) Fig. 3 Fig.3 [2009]The development of a glucose sensor chip using Enzyme-based FETs and micro-valves 12 Urea • Enzyme: Urease • Traditional Measurement Method Enzyme-coupled assay Photometric method High accuracy and cost, too CO(NH2)2 + H2O → CO2 + 2NH3 + − NH3 (aq) + H2O → NH4 (aq) + OH (aq) • Related Disease Hepatic enceohalopathy Fig.4 Fig.4 http://140.122.142.231/~wzlee/research.htm 13 Key Point Immobilize enzyme 14 Case Study: Immobilize enzyme • enzyme capsules Sodium Alginate + CaCl2 Enzyme Magnetic powder Fig.5 微系統暨奈米科技協會會刊 第二十六期: 血糖、尿素、肌酐酸 ISFET 微流體感測晶片 Fig5. http://www.ntcu.edu.tw/scigame/chemistry/chemistry-019.html 15 DNA-based ISFET (Ion semiconductor sequencing /Ion Torrent sequencing) Operating principle • DNA hybridization: single-strand (ss) DNA to double-strand (ds) DNA • Use hydrogen ions to indicate nucleotide insertion • ISFET detect the pH/potential changes Operating principle(cont’d) • Oligonucleotide (寡核苷酸) probes are immobilized on the gate surface • Complementary target DNA is hybridized with these probes • DNA polymerase • deoxynucleotide (dCTP, dATP, dGTP, or dTTP) • Phosphate buffer solution Operating principle(cont’d) • Negative charges increases at the gate surface cause a shift in the threshold voltage (푉푇) of the FET • 푉푇was determined from the gate voltage–drain current (푉퐺–퐼퐷) characteristics • Sequencing Applications • DNA Sequencing • Single nucleotide polymorphisms (SNPs) detection Result & Limitations • Result by Ion Torrent: Accuracy: 99.6% Reads length: 600 nucleotides per read. 100 Mb per run • Limitations System is difficult to enumerate long repeats (Homopolymer, e.g. TTTTT) Short read length(Debye length) Comparison Cost per 1 Accura Reads per Time per Method Read length million cy run run bases up to 600 Ion semiconductor 99.6% ~80 million 2 hours $1 bp Pyrosequencing (454) 700 bp 99.9% 1 million 24 hours $10 Sequencing by HiSeq X: 1 to 11 $0.05 to 99.9% 3 billion synthesis (Illumina) 300 bp days $0.15 Chain termination 400 to 900 20 minutes 99.9% N/A $2400 (Sanger sequencing) bp to 3 hours Comparison Advantages • Less expensive equipment • No need of technically trained operator • Portable • Fast • Compatibility with CMOS processes Other Sequencing method • Single-molecule real-time sequencing • Sequencing by ligation (SOLiD sequencing) • Nanopore Sequencing References 1. Biotecnolgy Advances[2003] Ion sensitive field effect transducer-based biosensors 2. [2009]The development of a glucose sensor chip using Enzyme-based FETs and micro-valves 3. Urea cycle disorders: http://web.tfrd.org.tw/genehelp/article.html?articleID=Urea%2520cycle%2520di sorders&submenuIndex=0 4. Urease Active site Modeling: http://140.122.142.231/~wzlee/research.htm 5. Kazuo Nakazato. An Integrated ISFET Sensor Array. Sensors 2009, 9, 8831- 8851. 6. Toshiya Sakata and Yuji Miyahara. DNA Sequencing Based on Intrinsic Molecular Charges. Angew. Chem. Int. Ed. 2006, 45, 2225 –2228 7. Jonathan M. Rothberg et al. An integrated semiconductor device enabling non- optical genome sequencing. Nature volume475, pages348–352 Thanks for listening! Q&A.
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