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2010 | Book

Introduction Read chapter Read first chapter

CMOS Capacitive Sensors for Lab-on-Chip Applications

A Multidisciplinary Approach

Authors: Ebrahim Ghafar-Zadeh, Mohamad Sawan

Publisher: Springer Netherlands

Book Series : Analog Circuits and Signal Processing

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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About this book

1.1 Overview of Lab-on-Chip Laboratory-on-Chip (LoC) is a multidisciplinary approach used for the miniaturization, integration and automation of biological assays or procedures in analytical chemistry [1–3]. Biology and chemistry are experimental sciences that are continuing to evolve and develop new protocols. Each protocol offers step-by-step laboratory instructions, lists of the necessary equipments and required biological and/or chemical substances [4–7]. A biological or chemical laboratory contains various pieces of equipment used for performing such protocols and, as shown in Fig. 1.1, the engineering aspect of LoC design is aiming to embed all these components in a single chip for single-purpose applications. 1.1.1 Main Objectives of LoC Systems Several clear advantages of this technology over conventional approaches, including portability, full automation, ease of operation, low sample consumption and fast assays time, make LoC suitable for many applications including. 1.1.1.1 Highly Throughput Screening To conduct an experiment, a researcher fills a well with the required biological or chemical analytes and keeps the sample in an incubator for some time to allowing the sample to react properly. Afterwards, any changes can be observed using a microscope. In order to quickly conduct millions of biochemical or pharmacolo- cal tests, the researchers will require an automated highly throughput screening (HTS) [8], comprised of a large array of wells, liquid handling devices (e.g., mic- channel, micropump and microvalves [9–11]), a fully controllable incubator and an integrated sensor array, along with the appropriate readout system.

Table of Contents

Frontmatter
Chapter 1. Introduction
Abstract
Laboratory-on-Chip (LoC) is a multidisciplinary approach used for the miniaturization, integration and automation of biological assays or procedures in analytical chemistry [1-3]. Biology and chemistry are experimental sciences that are continuing to evolve and develop new protocols. Each protocol offers step-by-step laboratory instructions, lists of the necessary equipments and required biological and/or chemical substances [4-7]. A biological or chemical laboratory contains various pieces of equipment used for performing such protocols and, as shown in Fig. 1.1, the engineering aspect of LoC design is aiming to embed all these components in a single chip for single-purpose applications.
Ebrahim Ghafar-Zadeh, Mohamad Sawan
Chapter 2. Capacitive Sensing Electrodes
Abstract
The capacitive sensing electrodes on the top of a CMOS chip serve as an interface between the microelectronic readout system and the biological/chemical analyte. These electrodes are directly exposed to the analyte or an intermediate layer which will be described in Chapter 3 (Fig. 2.1). The sensing electrode can be realized by a standard CMOS process. However for some applications, further micromachining procedure may be necessary.
Ebrahim Ghafar-Zadeh, Mohamad Sawan
Chapter 3. Capacitive Bio-interfaces
Abstract
In Chapter 2, we discussed the design and implementation of sensing electrodes atop CMOS chip. The sensing electrodes are incorporated with biological substances for sensing purposes as shown in Fig. 3.1.
Ebrahim Ghafar-Zadeh, Mohamad Sawan
Chapter 4. Capacitive Interface Circuits for LoC Applications
Abstract
The design criteria of capacitive interface circuits for LoC applications differs from conventional MEMS based applications such as acceleration, vibration or pressure [238]. As already mentioned in Chapter 2, a movable sensing electrode should be implemented through MEMS procedures and then bonded to an interface circuit for measurement purposes, but the surface electrodes can be directly realized atop integrated circuit chip fabricated through standard CMOS technology [240]. The emphasis of this chapter is placed on describing the difference between a MEMS based capacitive sensor (MBCS), a Lab-on-Chip based capacitive sensor (LBCS) and on introducing various circuit design techniques for LBCSs.
Ebrahim Ghafar-Zadeh, Mohamad Sawan
Chapter 5. Microfluidic Packaging Process
Abstract
A CMOS-based LoC system would require efficient microfluidic packaging to protect the circuitry from the biological and chemical analytes, as well as the external environment. Microfluidic packaging is also critical to direct the fluids towards the embedded sensors or actuators for analysis. Ideally, these microfluidic packaging components, including micro-channels, -chambers, -fittings, -valves and -pumps should be performed using a low temperature process with reliable hermetic bonding [278]. The leakage of analytes (especially of charged molecules, as is the case with many bioanalytes) from microfluidic components may increase the parasitic capacitances or resistances and thus affect the circuit characteristics.
Ebrahim Ghafar-Zadeh, Mohamad Sawan
Chapter 6. Current Technology and Future Works
Abstract
The capacitive measurements of deposable sensing electrodes are conventionally performed using Electrochemical Impedance Spectroscopy (EIS) [331, 332]. As shown in Fig. 6.1a, such a measurement device is connected to an array of electrodes which are exposed to analyte. Recently handheld EIS systems have received much attention as opposed to conventional EIS systems. A handheld system featuring an array of sensing sites (Fig. 6.1b) can be used for several point-of-care applications such as blood analysis (e.g. minilab, Abaxis Inc. [333]) or environmental monitoring such as bacteria detection [334]. However, researchers involved in circuit and system design and relevant biotechnological studies are willing to embed such portable systems in a single chip in the near future. In this direction, a CMOS based capacitive sensing LoC can be implemented in a syringe style package as shown in Fig. 6.1c. The biological or chemical analyte is directed by syringe towards the sensing sites through the nozzle. After each measurement, the nozzle and sensing site will be cleaned using the appropriate solutions which are directed into the channel and sensing sites in the same manner.
Ebrahim Ghafar-Zadeh, Mohamad Sawan
Backmatter
Metadata
Title
CMOS Capacitive Sensors for Lab-on-Chip Applications
Authors
Ebrahim Ghafar-Zadeh
Mohamad Sawan
Copyright Year
2010
Publisher
Springer Netherlands
Electronic ISBN
978-90-481-3727-5
Print ISBN
978-90-481-3726-8
DOI
https://doi.org/10.1007/978-90-481-3727-5