Amine Miled

Towards a Multifunctional Electrochemical Sensing and Niosome Generation Lab-on-Chip Platform Based on a Plug-and-Play Concept

In this paper, we present a new modular lab on a chip design for multimodal neurotransmitter (NT) sensing and niosome generation based on a plug-and-play concept. This architecture is a first step toward an automated platform for an automated modulation of neurotransmitter concentration to understand and/or treat neurodegenerative diseases. A modular approach has been adopted in order to handle measurement or drug delivery or both measurement and drug delivery simultaneously. The system is composed of three fully independent modules: three-channel peristaltic micropumping system, a three-channel potentiostat and a multi-unit microfluidic system composed of pseudo-Y and cross-shape channels containing a miniature electrode array. The system was wirelessly controlled by a computer interface. The system is compact, with all the microfluidic and sensing components packaged in a 5 cm × 4 cm × 4 cm box. Applied to serotonin, a linear calibration curve down to 0.125 mM, with a limit of detection of 31 μM was collected at unfunctionalized electrodes. Added sensitivity and selectivity was achieved by incorporating functionalized electrodes for dopamine sensing. Electrode functionalization was achieved with gold nanoparticles and using DNA and o-phenylene diamine polymer. The as-configured platform is demonstrated as a central component toward an “intelligent” drug delivery system based on a feedback loop to monitor drug delivery.

Recent Advancements towards Full-System Microfluidics

Microfluidics is quickly becoming a key technology in an expanding range of fields, such as medical sciences, biosensing, bioactuation, chemical synthesis, and more. This is helping its transformation from a promising R&D tool to commercially viable technology. Fuelling this expansion is the intensified focus on automation and enhanced functionality through integration of complex electrical control, mechanical properties, in situ sensing and flow control. Here we highlight recent contributions to the Sensors Special Issue series called “Microfluidics-Based Microsystem Integration Research” under the following categories: (i) Device fabrication to support complex functionality; (ii) New methods for flow control and mixing; (iii) Towards routine analysis and point of care applications; (iv) In situ characterization; and (v) Plug and play microfluidics.

Miniaturized FDDA and CMOS Based Potentiostat for Bio-Applications

A novel fully differential difference CMOS potentiostat suitable for neurotransmitter sensing is presented. The described architecture relies on a fully differential difference amplifier (FDDA) circuit to detect a wide range of reduction-oxidation currents, while exhibiting low-power consumption and low-noise operation. This is made possible thanks to the fully differential feature of the FDDA, which allows to increase the source voltage swing without the need for additional dedicated circuitry. The FDDA also reduces the number of amplifiers and passive elements in the potentiostat design, which lowers the overall power consumption and noise. The proposed potentiostat was fabricated in 0.18 µm CMOS, with 1.8 V supply voltage. The device achieved 5 µA sensitivity and 0.99 linearity. The input-referred noise was 6.9 µVrms and the flicker noise was negligible. The total power consumption was under 55 µW. The complete system was assembled on a 20 mm × 20 mm platform that includes the potentiostat chip, the electrode terminals and an instrumentation amplifier for redox current buffering, once converted to a voltage by a series resistor. the chip dimensions were 1 mm × 0.5 mm and the other PCB components were off-chip resistors, capacitors and amplifiers for data acquisition. The system was successfully tested with ferricyanide, a stable electroactive compound, and validated with dopamine, a popular neurotransmitter.

High accuracy and sensitivity differential potentiostat with amplifier-based error cancellation feedback loop

We present a low-current, high sensitivity and high linearity biosensor dedicated to neurotransmitter detection. The design is based on a fully-differential amplifier for enhanced sensitivity and wide dynamic range. Moreover, an error cancellation loop composed of high gain and rejection ratio amplifiers subtracts the voltage drop created by the sense resistor, thus enabling the use of high resistance values for low current sensing with no adverse effect on the biosensors dynamic range; as a result, the sensitivity of the circuit is considerably improved. Implementing this biosensor with discrete components led to a current sensitivity of 10 nA, an accuracy of 0.1 % and a CMRR of 83 dB.

A Portable Wireless Communication Platform Based on a Multi-Material Fiber Sensor for Real-Time Breath Detection

In this paper, we present a new mobile wireless communication platform for real-time monitoring of an individual’s breathing rate. The platform takes the form of a wearable stretching T-shirt featuring a sensor and a detection base station. The sensor is formed by a spiral-shaped antenna made from a multi-material fiber connected to a compact transmitter. Based on the resonance frequency of the antenna at approximately 2.4 GHz, the breathing sensor relies on its Bluetooth transmitter. The contactless and non-invasive sensor is designed without compromising the user’s comfort. The sensing mechanism of the system is based on the detection of the signal amplitude transmitted wirelessly by the sensor, which is found to be sensitive to strain. We demonstrate the capability of the platform to detect the breathing rates of four male volunteers who are not in movement. The breathing pattern is obtained through the received signal strength indicator (RSSI) which is filtered and analyzed with home-made algorithms in the portable system. Numerical simulations of human breath are performed to support the experimental detection, and both results are in a good agreement. Slow, fast, regular, irregular, and shallow breathing types are successfully recorded within a frequency interval of 0.16–1.2 Hz, leading to a breathing rate varying from 10 to 72 breaths per minute.

Reconfigurable Prototyping Microfluidic Platform for DEP Manipulation and Capacitive Sensing

In this paper, we present a new rapid prototyping platform dedicated to dielectrophoretic microfluidic manipulation and capacitive cell sensing. The proposed platform offers a reconfigurable design including 4 independently programmable output channels to be distributed across 64 electrodes. Although its range of frequency covers up to 3.4 MHz, signal amplitude accuracy ( +/-10%) was demonstrated for frequencies up to 1 MHz and channel-to-channel phase shift setting was stable up to 1.5 MHz. A test of maximum resistive load showed a 10% attenuation of a 12 V peak-to-peak signal with a 22 Ω load. The platform has an advanced capacitive sensor to measure capacitance variation between in-channel electrodes with a sampling frequency up to 5 kH z. Experimental data of capacitive sensor showed a sensitivity of 100 fF. The sensor can be extended to 4 parallel measurements with lower frequency. We also present a new assembly technique for reusable microfluidic chip based on anisotropic adhesive conductive film, epoxy and PDMS. The proposed platform provides a wide range of control signals depending on the type of manipulation as sine, rectangular or square wave. The frequency range is extendible up to 3.4 MHz, in addition to a programmable phase shift circuit with a minimum phase step of 3.6 ° for each signal.

Reconfigurable Lab-on-Chip platform for algae cell manipulation

In this paper, we present a new dielectrophoretic microfluidic technique in a modular Lab-on-Chip (LoC) platform. The proposed LoC has a reconfigurable topology. It generates a wide range of signals depending on the analyzed liquid with a variable frequency up to 1.2 MHz. In addition, a programmable phase shift circuit with a minimum phase step of 3.6° for each signal is implemented. The amplitude of each signal can be adjusted independently, and the latter can be distributed through 64 bidirectional electrodes. Each electrode can be enabled or disabled individually. Moreover, device includes capacitive sensing stage for the measurement of the in-channel capacitance change induced by algae. Furthermore, The architecture of the proposed system is versatile and can be adjusted to different cell manipulation applications. The presented LoC was tested with 15 μm algae cells.

An on-chip programmable multichannel power supply for a lab-on-chip platform

This paper presents a reprogrammable low-voltage power-supply integrated circuit for low resistive load down to 180 Ω. The achieved chip is dedicated for biomedical lab-on-chip (LoC) platforms. The proposed system includes two positive and two negative fully independent output voltage channels. Each positive and negative channel provides a reprogrammable DC output which varies from 14.23 mV to 1.42 V and -1.54 V to 0 V, respectively. Each channel is controlled through a reprogrammable reference voltage circuit with an 8-bit digital to analog converter (DAC). A wireless real-time control of output signals amplitude is performed with LabVIEW and FPGA-based interface. The proposed architecture is implemented with 0.18 μm 3.3 V 1-poly 6-metal CMOS technology. The chip area is 1.5 mm2. Post-layout simulations show that the minimum voltage step is 12.21 mV. The accuracy of output voltage is 5 mV and the measured power consumption is 35 mW.

Pseudo-Continuous Flow FTIR System for Glucose, Fructose and Sucrose Identification in Mid-IR Range

In this paper, we present a new FTIR-based microfluidic system for Glucose, Fructose and Sucrose detection. The proposed microfluidic system is based on a pseudo-continuous flow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their absorption spectrum in the wavelength range 700–1000 cm−1 of the Mid-IR region. The proposed pseudo-continuous flow system is designed to improve the uniformity of the sample distribution in the analyzed area versus conventional systems. The obtained results for different sugars concentrations, show a very low measurement error of 4.35% in the absorption peak intensity, which is ten times lower than the error obtained using the conventional measurements.

Counter/reference-based potentiostat architecture analysis and comparison

In this paper we present a counter/reference control based potentiostat architecture including the analysis and experimental results. Then, a comparison between different potentiostat architectures was achieved in order to study the effect of counter/reference (CR) voltage control in potentiostats instead of working/reference (WR) electrodes. Reported results are obtained with (Fe(CN)6)4− with a concentration range between 2 and 10 mM/L. Used voltages and frequency in all experiments and architectures were ± 1.2 V and 1 Hz, respectively. In the CR-based architecture we used 6 amplifiers while in the case of WR, 11 amplifiers have been implemented which shows the advantage of using CR-based approach. However, results in terms of detected currents are similar for both CR and WR-based architectures.