Karen Twomey

Swallowable-Capsule Technology

Annually, over 3 million people in the US alone suffer gastrointestinal (GI) disease serious enough to require hospitalization. In over one-third of these cases, the cause is never found. Despite standard invasive examination techniques, much of the GI tracts inner workings remain a mystery. Procedures exist for examining the esophagus and stomach (gastroscopy) and the colon (colonoscopy), delivering some information at a cost of much distress to the patient. However, the small intestine remains inaccessible. Swallowable capsules have been evolving for almost half a century and are now helping uncover GI tract mysteries in diagnostic and therapeutic applications. Here, we briefly review the history of the technology, present the state of the art, and describe ongoing research.

On-chip electrochemical microsystems for measurements of copper and conductivity in artificial seawater

The fabrication and characterisation of microelectrochemical sensors for Cu(2+) and conductivity suitable for operation in the marine environment are presented. The impact of the designs on sensor performance and their adequacy to operate in real conditions are discussed. The sensors, tailored to voltammetric and impedimetric measurements, are fabricated on silicon using photolithographic and thin film deposition techniques. The impedimetric sensor is made of Pt interdigitated electrodes which are used for the measurement of conductivity. The voltammetric sensors are based on a three electrode electrochemical cell with on-chip Ag|AgCl reference and Pt counter and working electrodes, used for detection of copper by underpotential deposition-stripping voltammetry at microelectrode array. The sensors operated in the Cu(2+) concentrations ranging from 0.48 to 3.97 µM with a limit of detection of 0.115 μM. The impact of the temperature, the pH and the salinity of the artificial seawater on the sensitivity for Cu(2+) detection are also considered. Measurements of copper concentration and conductivity are validated using certified reference materials and standard solutions.

Fabrication and Electrochemical Characterization of Micro- and Nanoelectrode Arrays for Sensor Applications

This paper describes the fabrication of microelectrode arrays, with two different geometries: disc (Designs d1 and d2) and band (Designs b1, b2 and b3) using three critical dimensions (100 nm, 1 μm and 10 μm) leading to 5 different designs, fabricated by the combination of UV photolithographic and e-beam lithographic techniques. Three silicon nitride layer thicknesses (200, 300 and 500 nm) were chosen to determine an optimized transducer design and fabrication process. Cyclic voltammetry characterisation using a simple redox probe ion, ferreocenecarboxylic acid in phosphate buffered saline electrolyte solution, demonstrated steady-state voltammetric curves for d1, d2, b1 and b2. A good agreement between experimental and theoretical data is found for devices d1, d2, b1 and b2. The experimental current for b3, on the other hand, is much lower compared to the calculated one- perhaps due to the overlapping of the diffusion layers of neighbouring microelectrodes in the array.

Development of an Integrated Electrochemical Sensing System to Monitor Port Water Quality Using Autonomous Robotic Fish

The development of autonomous systems for environmental monitoring is a great challenge posed to scientists. Robots might offer an interesting solution for monitoring where access is difficult such as oceans and seas. Here, we describe the approach envisaged for pollution monitoring in port waters based on robot fish equipped with chemical sensors. We will briefly review the state of the art of environmental sensors before describing the electrochemical sensors and instrumentation developed to be integrated inside a robot fish. Finally, we will present laboratory and real sample tests obtained with the developed electrochemical microsystems.

Investigation into the packaging and operation of an electronic tongue sensor for industrial applications

Purpose – The purpose of this paper is to describe the packaging and operation of an electronic tongue sensor. The sensor will be used in an industrial setting and the packaging needs to withstand the harsh clean‐in‐place (CIP) routines that are commonly employed. A suitable epoxy, Loctite FP4450 HYSOL, was identified from a number of packaging materials. The sensor was validated by carrying out cyclic voltammetry in a number of reference solutions including sulphuric acid solution and ferrocyanide in potassium chloride solution, which gave well‐defined reduction and oxidation peaks that could be compared with the literature. The operation of the sensor in mixtures of salt and citric acid solutions was also investigated and it was seen that by applying a carefully selected voltage window and scan rate to each electrode, the sensor could distinguish between the different mixtures. Further experimentation and the application of principle component analysis have shown the sensor to have good repeatability.De...

Characterization of the Electrochemical Behavior of Gastrointestinal Fluids Using a Multielectrode Sensor Probe

A characterization of gastrointestinal fluids has been performed by means of an electrochemical sensor that has potential for clinical in vivo and in vitro monitoring applications. The sensor comprised a three-electrode cell with a counter, reference, and four working electrodes, Au, Pt, Ir, and Rh. Cyclic voltammetry was used to obtain chemical information from faecal water (in vitro) and gut model (in vivo ) fluids. Stable voltammetric responses were obtained for both fluids at these noble metal working electrodes. The responses differed in shape that demonstrated the discrimination capability and the potential for practical use as a tool for gastrointestinal fluid investigation. The analysis of the stability profiles in faecal water over a 14-h duration has indicated a possible adsorption mechanism with the formation of a biolayer on the sensor surface. The stability in gut model fluids over a 42-h duration has demonstrated a more stable profile, but the mechanisms involved are more complicated to determine.

A swallowable diagnostic capsule with a direct access sensor using Anisotropic Conductive Adhesive

Technological developments in biomedical microsystems are opening up new opportunities to improve healthcare procedures. Swallowable diagnostic sensing capsules are an example of this. In this paper, a novel direct access sensor (DAS) has been demonstrated which uses Flip Chip (FC) technology to expose the sensor to the liquid medium. An electrochemical study showed that the Anisotropic Conductive Adhesive (ACA) joint provides good connection and does not impair the sensor functionality. The reliability test results showed that most of the samples survived the humidity aging test and that only 2 out of 9 ACA connections of the same electrode failed. For the failed samples, the failure analysis showed that the tensile stress at the chip/epoxy interface caused a delamination at this interface.

Multi-parameter system for marine environmental applications

The contamination of sea waters by pollutants is a subject of growing public concern. The existing monitoring process is costing an estimated 350 million Euros/year in the EU. Most of the detection methods are laboratory-based, which require extensive sample preparation prior to analysis and, hence are not suitable for on-site analysis. Here a multi-sensor system is described for eventual deployment in a port. The system can provide an accurate assessment of the water quality through monitoring a variety of different parameters. Copper detection, conductivity measurements and redox potential measurements are described, and the stability of each sensor in artificial seawater is estimated.

A Portable Sensing System for Impedance based Detection of Biotoxin Substances.

The study describes the development of a portable autonomous biosensing platform for impedance based detection of biotoxin substances. The platform implements a label-free approach, which is based on detection of the biosensor interfacial changes due to a bio recognition reaction. The interfacial changes are sensed by means of Electrochemical Impedance Spectroscopy in a frequency range from 10 Hz to 100 kHz. The platform comprises of an electrochemical biosensor, portable low-noise mix signal hardware and associated software incorporating signal processing algorithms for extraction biotarget concentration from the biosensor response. The biosensor is realized as an on-chip package-free three electrode micro electrochemical cell consisted of a counter electrode (CE), a reference electrode (RE) and a working electrode (WE) patterned on a single silicon chip. WE represents an array of 40 um diameter gold disks with 400 m center-to-center distance, which were undergone of corresponding surface modification for antibody immobilisation. The developed system was validated by an example of T-2 toxin detection. Performed calibration in the range of 0 – 250 ppm of T2 toxin concentrations confirmed that the system can provide successful detection of the toxin at the levels

Fabrication and characterization of microfabricated on-chip microelectrochemical cell for biosensing applications

The fabrication of on-chip microelectrochemical cell on Si wafer by means of photolithography is described here. The single on-chip microelectrochemical cell device has dimensions of 100 × 380 mm with integrated Pt counter electrode (CE), Ag/AgCl reference electrode (RE) and gold microelectrode array of 500 nm recess depth as the working electrode (WE). Two geometries of electrode array were implemented, band and disc, with fixed diameter/width of 10 µm; and varied centre-to-centre spacing (d) and number of electrodes (N) in the array. The on-chip microelectrochemical cell structure has been designed to facilitate further WE biomodifications. Firstly, the developed microelectrochemical cell does not require packaging hence reducing the production cost and time. Secondly, the working electrode (WE) on the microelectrochemical cell is positioned towards the end of the chip enabling modification of the working electrode surface to be carried out for surface bio-functionalisation without affecting both the RE...