Lab-on-chip devices and bio-fluidic microsystems are emerging technologies that exhibit the required fluidic transport, bio chemical detection and control functions to enhance the detection resolution and accuracy within a single miniaturised portable instrument for bio-diagnostic and bio-synthesis applications. These devices impact a number of markets, including medical diagnostics, pharmacology, environmental monitoring and industrial control. Example applications are DNA extraction from blood and detection of pathogens or genetically modified organisms. Electrode technology is fundamental to numerous actuation and sensing functions within these microsystems. Reliability is a key component of these microsystems and most applications require extremely low probabilities of false positives or negatives. New methods of validating the functionality and integrity of measurements are hence required. Embedded test and condition monitoring are crucial technologies for delivering these capabilities. This thesis makes significant contributions to knowledge in these areas to further the development and viability of accurate test equipment. The work in this thesis focuses on delivering novel solutions and methodologies that can be used to increase the reliability of electrode-based bio-fluidic mi'crosystems and cellbased biosensors. Three self-test solutions have been developed to address surface degradation within the sensing interface of a cell-based biosensor system and microfluidic chips. The first solution, a mid-frequency oscillation test approach, is based on the sensitivity of the interface capacitance to degradation, contamination and fouling. The second solution proposes a new fault diagnosis approach using an Artificial Neural III F -=---';~I_---- Abstract Network for detecting degradation in electrodes that interface to fluidic or biological systems. The third solution studies the feasibility of scanning the strength of a test signal over an array of electrodes to monitor degradation. The design of the monitoring structures has been validated through physical characterisation involving data extracted for both a single electrode and an array of electrodes where a micro controller, an analogue multiplexer, a test circuit, and an LeD have been used to achieve a real-time condition monitoring system. The novel test techniques provide analogue values directly related to the degradation of the electrode, so have the ability to provide accurate on-line degradation detection for a range of conditions across the electrode surface. Optimising the design of the microfluidic chips to maximise flow rate and the investigation into new methods for validating functionality and integrity of the readings have also been studied numerically. In addition, this thesis concretely examines potential research directions for future bio-fluidic microsystems.