A high aspect ratio Fin-Ion Sensitive Field Effect Transistor: compromises towards better electrochemical bio-sensing

The development of next generation medicines demand more sensitive and reliable label free sensing able to cope with increasing needs of multiplexing and shorter times to results. Field effect transistor-based biosensors emerge as one of the main possible technologies to cover the existing gap. The general trend for the sensors has been miniaturisation with the expectation of improving sensitivity and response time, but presenting issues with reproducibility and noise level. Here we propose a Fin-Field Effect Transistor (FinFET) with a high heigth to width aspect ratio for electrochemical biosensing solving the issue of nanosensors in terms of reproducibility and noise, while keeping the fast response time. We fabricated different devices and characterised their performance with their response to the pH changes that fitted to a Nernst-Poisson model. The experimental data were compared with simulations of devices with different aspect ratio, stablishing an advantage in total signal and linearity for the FinFETs with higher aspect ratio. In addition, these FinFETs promise the optimisation of reliability and efficiency in terms of limits of detection, for which the interplay of the size and geometry of the sensor with the diffusion of the analytes plays a pivotal role.Comment: Article submitted to Nano Letter

Low power cmos potentiometric circuit design for label-free DNA detection

DNA detector is one of the main way to use in order to detect diseases, preventing crime and so on. The DNA detecting process is limited due to the bulky and expensive existing DNA detector machine. As the demand of the small, portable and inexpensive biosensor for point-of-care testing aid and medical diagnostic, the research and development of biosensor are increasing exponentially every year. The aim of this work is to develop an on-chip Complementary Metal Oxide Semiconductor (CMOS) biosensor circuit based on the charge-modulated field effect transistor (CMFET) for a label-free deoxyribonucleic acid (DNA) detection. This project focusing on low voltage and low power design potentiometric DNA detection circuit. Overall of detection circuit consists of two main circuits which are self-cascode source drain follower and two-stage differential amplifier. The proposed detection circuit is designed and simulates using 0.13 µm Silterra CMOS fabrication with 1.2 V supply. The power consumption of the improved source-drain follower circuit is 1.36 µW and with gain of 0.998 dB. The two-stage differential amplifier achives a voltage gain of 56.02 dB and high common mode rejection ration (CMRR) of 90 dB

Field-effect based chemical and biological sensing : theory and implementation

Electrochemical sensors share many properties of an ideal (bio)chemical sensor. They can be easily miniaturized with high parallel sensing capabilities,with rugged structure and at low cost. The response obtained from thetarget analyte is directly in electrical form allowing convenient data post-processing and simple interfacing to standard electrical components. With field-effect transistor (FET) based sensors, the transducing principle relies on direct detection of interfacial charge allowing detection of various ions and charged macromolecules. This thesis investigates FET based sensors for biological and chemical sensing. First, an ion-sensitive floating gate FET (ISFGFET) structure is studied and modeled. The proposed model reveals novel abilities of the structure not found in conventional ion-sensitive FETs (ISFETs). With IS-FGFET, we can simultaneously optimize the transistor operating point and modulate the charging of the surface and the ionic screening layer via the field effect. This control is predicted to allow reduced electric double layer screening as well as the possibility to enhance charged molecule attachment to the sensing surface. The model can predict sensor characteristic curves in pH sensing in absolute terms and allows any potential to be computed in the sensor including the electrical part and the electrolyte solution. Furthermore, a compact ISFGFET variant is merged into electric circuit simulator, which allows it to be simulated as a standard electrical component with electrical simulations tools of high computational efficiency, and allows simple modifications such as addition of parasitic elements, temperature effects, or even temporal drifts. Next, another transistor based configuration, the extended-gate ISFET is studied. The simplicity of the proposed configuration allows a universal potentiometric approach where a wide variety of chemical and biological sensors can be constructed. The design philosophy for this sensing structure is to use the shelf electric components and standard electric manufacturing processes. Such an extended-gate structure is beneficial since the dry electronics can be completely separated from the wet sensing environment. The extended-gate allows simple functionalization towards chemical and biological sensing. A proof-of-concept of this structure was verified through organo modified gold platforms with ion-selective membranes. A comparison with standard open-circuit potentiometry reveals that the sensing elements in a disposable sensing platform arrays provide comparable performance to traditional electrodes. Finally, a universal battery operated hand-held electrical readout device is designed for multiplexed detection of the disposable sensors with wireless smartphone data plotting, control, and storage. Organic polymers play an important role in the interfacial properties of sensors studied in this thesis. The polymer coating is attractive in chemical sensing because of its redox sensitivity, bio-immobilization capability, ion-to-electron transducing capability, and applicability, for example via a simple low-cost drop-casting. This structure simplifies the design of the sensor substantially and the coating increases the amount of possible target applications.Siirretty Doriast

Ion-Sensitive Field-Effect Transistor for Biological Sensing

In recent years there has been great progress in applying FET-type biosensors for highly sensitive biological detection. Among them, the ISFET (ion-sensitive field-effect transistor) is one of the most intriguing approaches in electrical biosensing technology. Here, we review some of the main advances in this field over the past few years, explore its application prospects, and discuss the main issues, approaches, and challenges, with the aim of stimulating a broader interest in developing ISFET-based biosensors and extending their applications for reliable and sensitive analysis of various biomolecules such as DNA, proteins, enzymes, and cells

Recent trends in field-effect transistors-based immunosensors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Immunosensors are analytical platforms that detect specific antigen-antibody interactions and play an important role in a wide range of applications in biomedical clinical diagnosis, food safety, and monitoring contaminants in the environment. Field-effect transistors (FET) immunosensors have been developed as promising alternatives to conventional immunoassays, which require complicated processes and long-time data acquisition. The electrical signal of FET-based immunosensors is generated as a result of the antigen-antibody conjugation. FET biosensors present real-time and rapid response, require small sample volume, and exhibit higher sensitivity and selectivity. This review brings an overview on the recent literature of FET-based immunosensors, highlighting a diversity of nanomaterials modified with specific receptors as immunosensing platforms for the ultrasensitive detection of various biomolecules.Immunosensors are analytical platforms that detect specific antigen-antibody interactions and play an important role in a wide range of applications in biomedical clinical diagnosis, food safety, and monitoring contaminants in the environment. Field-effec44FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)2013/22127-2; 2016/04739-9sem informação: The authors acknowledge the financial assistance provided by The São Paulo Research Foundation (FAPESP, project #2013/22127-2 and grant #2016/04739-9) and the National Council for Scientific and Technological Development (CNPq

Micro- and nano-devices for electrochemical sensing

Electrode miniaturization has profoundly revolutionized the field of electrochemical sensing, opening up unprecedented opportunities for probing biological events with a high spatial and temporal resolution, integrating electrochemical systems with microfluidics, and designing arrays for multiplexed sensing. Several technological issues posed by the desire for downsizing have been addressed so far, leading to micrometric and nanometric sensing systems with different degrees of maturity. However, there is still an endless margin for researchers to improve current strategies and cope with demanding sensing fields, such as lab-on-a-chip devices and multi-array sensors, brain chemistry, and cell monitoring. In this review, we present current trends in the design of micro-/nano-electrochemical sensors and cutting-edge applications reported in the last 10 years. Micro- and nanosensors are divided into four categories depending on the transduction mechanism, e.g., amperometric, impedimetric, potentiometric, and transistor-based, to best guide the reader through the different detection strategies and highlight major advancements as well as still unaddressed demands in electrochemical sensing