Ebrahim Ghafar-Zadeh

A Hybrid Microfluidic/CMOS Capacitive Sensor Dedicated to Lab-on-Chip Applications

A hybrid microfluidic/IC capacitive sensor is presented in this paper for highly integrated lab-on-chips (LoCs). We put forward the design and implementation of a charge based capacitive sensor array in 0.18-mum CMOS process. This sensor chip is incorporated with a microfluidic channel using direct-write microfluidic fabrication process (DWFP). The design, construction and experimental results as well are demonstrated using four different chemical solutions with known dielectric constants. The proposed highly sensitive CMOS capacitive sensor (ap530 mV/fF) along with low complexity DWFP emerges as clear favorite for LoC applications.

Bacteria Growth Monitoring Through a Differential CMOS Capacitive Sensor

In this paper, we present a bacteria growth monitoring technique using a complementary metal-oxide semiconductor capacitive sensor. The proposed platform features a differential capacitive readout architecture with two interdigitized reference and sensing electrodes. These electrodes are exposed to pure Luria-Bertani (LB) medium and Escherichia Coli (E. Coli) bacteria suspended in the LB medium, respectively. In order to direct the solutions toward the electrodes, two microfluidic channels are implemented atop the electrodes through a direct-write assembly technique. We thereafter demonstrate and discuss the experimental results by using two different bacteria concentrations in the order of 106 and 107 per 1 mL in the LB medium.

Charge-Based Capacitive Sensor Array for CMOS-Based Laboratory-on-Chip Applications

In this paper, we present a capacitive sensor array for highly integrated lab-on-chip (LoC) applications using the charge-based capacitance measurement method (CBCM). The core-CBCM sensor chip is designed and implemented in 0.18 micron CMOS process featuring an array of capacitive sensors; an offset cancellation module and a low complexity analog-to-digital converter (ADC). This sensor chip is incorporated with a microfluidic channel using direct-write fabrication process. We demonstrate the testing results using chemical solvents with known dielectric constants in order to show the viability of the proposed sensor chip for LoCs.

Wireless Integrated Biosensors for Point-of-Care Diagnostic Applications

Recent advances in integrated biosensors, wireless communication and power harvesting techniques are enticing researchers into spawning a new breed of point-of-care (POC) diagnostic devices that have attracted significant interest from industry. Among these, it is the ones equipped with wireless capabilities that drew our attention in this review paper. Indeed, wireless POC devices offer a great advantage, that of the possibility of exerting continuous monitoring of biologically relevant parameters, metabolites and other bio-molecules, relevant to the management of various morbid diseases such as diabetes, brain cancer, ischemia, and Alzheimer’s. In this review paper, we examine three major categories of miniaturized integrated devices, namely; the implantable Wireless Bio-Sensors (WBSs), the wearable WBSs and the handheld WBSs. In practice, despite the aforesaid progress made in developing wireless platforms, early detection of health imbalances remains a grand challenge from both the technological and the medical points of view. This paper addresses such challenges and reports the state-of-the-art in this interdisciplinary field.

A Polypyrrole-based Strain Sensor Dedicated to Measure Bladder Volume in Patients with Urinary Dysfunction

This paper describes a new technique to measure urine volume in patients with urinary bladder dysfunction. Polypyrrole – an electronically conducting polymer - is chemically deposited on a highly elastic fabric. This fabric, when placed around a phantom bladder, produced a reproducible change in electrical resistance on stretching. The resistance response to stretching is linear in 20%-40% strain variation. This change in resistance is influenced by chemical fabrication conditions. We also demonstrate the dynamic mechanical testing of the patterned polypyrrole on fabric in order to show the feasibility of passive interrogation of the strain sensor for biomedical sensing applications.

A Microfluidic Packaging Technique for Lab-on-Chip Applications

In this paper, we address the often-neglected challenges of microfluidic packaging for biochemical sensors by proposing an efficient direct-write microfluidic packaging procedure. This low-cost procedure is performed through a programmable dispensing system right after a routine electronic packaging process. In order to prove the concept, the simulation, fabrication and chemical testing results of implemented hybrid system incorporating microelectronics and microfluidics are also presented and discussed.

CMOS Capacitive Sensors for Lab-on-Chip Applications

The main components of CMOS capacitive biosensors including sensing electrodes, bio-functionalized sensing layer, interface circuitries and microfluidic packaging are verbosely explained in chapters 2-6 after a brief introduction on CMOS based LoCs in Chapter 1. CMOS Capacitive Sensors for Lab-on-Chip Applications is written in a simple pedagogical way. It emphasises practical aspects of fully integrated CMOS biosensors rather than mathematical calculations and theoretical details. By using CMOS Capacitive Sensors for Lab-on-Chip Applications, the reader will have circuit design methodologies, main important biological capacitive interfaces and the required microfluidic fabrication procedures to create capacitive biosensor through standard CMOS process.

Bacteria growth monitoring through an on-chip capacitive sensor

In this paper, a charge based capacitive biosensor is presented for bacteria growth monitoring (BGM). This sensor chip is implemented through CMOS process in order to show the applicability of the proposed on-chip capacitive technique for BGM purposes. The passivated interdigitated electrodes atop CMOS chip are exposed to Escherichia coli (Ecoli) bacteria in the channel. The presence of bacteria in proximity of electrode causes a minute change in double layer capacitance. The variation of this capacitance (DeltaC<60 pF) versus time is demonstrated and compared with conventional impedance-based technique.

A New Fully Differential CMOS Capacitance to Digital Converter for Lab-on-Chip Applications

In this paper, we present a new differential CMOS capacitive sensor for Lab-on-Chip applications. The proposed integrated sensor features a DC-input ΣΔ capacitance to digital converter (CDC) and two reference and sensing microelectrodes integrated on the top most metal layer in 0.35 μm CMOS process. Herein, we describe a readout circuitry with a programmable clocking strategy using a Charge Based Capacitance Measurement technique. The simulation and experimental results demonstrate a high capacitive dynamic range of 100 fF-110 fF, the sensitivity of 350 mV/fF and the minimum detectable capacitance variation of as low as 10 aF. We also demonstrate and discuss the use of this device for environmental applications through various chemical solvents.

Direct-Dispense Polymeric Waveguides Platform for Optical Chemical Sensors

We describe an automated robotic technique called direct-dispense to fabricate a polymeric platform that supports optical sensor arrays. Direct-dispense, which is a type of the emerging direct-write microfabrication techniques, uses fugitive organic inks in combination with cross-linkable polymers to create microfluidic channels and other microstructures. Specifically, we describe an application of direct-dispensing to develop optical biochemical sensors by fabricating planar ridge waveguides that support sol-gel-derived xerogel-based thin films. The xerogel-based sensor materials act as host media to house luminophore biochemical recognition elements. As a prototype implementation, we demonstrate gaseous oxygen (O2) responsive optical sensors that operate on the basis of monitoring luminescence intensity signals. The optical sensor employs a Light Emitting Diode (LED) excitation source and a standard silicon photodiode as the detector. The sensor operates over the full scale (0%-100%) of O2 concentrations with a response time of less than 1 second. This work has implications for the development of miniaturized multi-sensor platforms that can be cost-effectively and reliably mass-produced.