Introducing the pressure-sensing palatograph - the next frontier in electropalatography

Primary Objective. To extend the capabilities of current electropalatography (EPG) systems by developing a pressure-sensing EPG system. An initial trial of a prototype pressure-sensing palate will be presented. Research Design. The processes involved in designing the pressure sensors are outlined, with Hall effect transistors being selected. These units are compact, offer high sensitivity and are inexpensive. An initial prototype acrylic palate was constructed with five embedded pressure sensors. Syllable repetitions were recorded from one adult female. Main Outcomes, Results and Future Directions. The pressure-sensing palate was capable of recording dynamic tongue-to-palate pressures, with minimal to no interference to speech detected perceptually. With a restricted number of sensors, problems were encountered in optimally positioning the sensors to detect the consonant lingual pressures. Further developments are planned for various aspects of the pressure-sensing system. Conclusions. Although only in the prototype stage, the pressure-sensing palate represents the new generation of EPG. Comprehensive analysis of tongue-to-palate contacts, including pressure measures, is expected to enable more specific and effective therapeutic techniques to be developed for a variety of speech disorders.

Novel hardwired distributive tactile sensing system for medical applications

This thesis described the research carried out on the development of a novel hardwired tactile sensing system tailored for the application of a next generation of surgical robotic and clinical devices, namely a steerable endoscope with tactile feedback, and a surface plate for patient posture and balance. Two case studies are examined. The first is a one-dimensional sensor for the steerable endoscope retrieving shape and ‘touch’ information. The second is a two-dimensional surface which interprets the three-dimensional motion of a contacting moving load. This research can be used to retrieve information from a distributive tactile sensing surface of a different configuration, and can interpret dynamic and static disturbances. This novel approach to sensing has the potential to discriminate contact and palpation in minimal invasive surgery (MIS) tools, and posture and balance in patients. The hardwired technology uses an embedded system based on Field Programmable Gate Arrays (FPGA) as the platform to perform the sensory signal processing part in real time. High speed robust operation is an advantage from this system leading to versatile application involving dynamic real time interpretation as described in this research. In this research the sensory signal processing uses neural networks to derive information from input pattern from the contacting surface. Three neural network architectures namely single, multiple and cascaded were introduced in an attempt to find the optimum solution for discrimination of the contacting outputs. These architectures were modelled and implemented into the FPGA. With the recent introduction of modern digital design flows and synthesis tools that essentially take a high-level sensory processing behaviour specification for a design, fast prototyping of the neural network function can be achieved easily. This thesis outlines the challenge of the implementations and verifications of the performances.

A novel actuated digit with tactile feedback for clinical applications

This thesis describes the work carried out on the development of a novel digit actuator system with tactile perception feedback to a user and demonstrated as a master-slave system. For the tactile surface of the digit, contrasting sensor elements of resistive strain gauges and optical fibre Bragg grating sensors were evaluated. A distributive tactile sensing system consisting of optimised neural networking schemes was developed, resulting in taxonomy of artificial touch. The device is suitable for use in minimal invasive surgical (MIS) procedures as a steerable tip and a digit constructed wholly from polymers makes it suitable for use in Magnetic Resonance Imaging (MRI) environments enabling active monitoring of the patient during a procedure. To provide a realistic template of the work the research responded to the needs of two contrasting procedures: palpation of the prostate and endotracheal intubation in anaesthesia where the application of touch sense can significantly assist navigation. The performance of the approach was demonstrated with an experimental digit constructed for use in the laboratory in phantom trials. The phantom unit was developed to resemble facets of the clinical applications and digit system is able to evaluate reactive force distributions acting over the surface of the digit as well as different descriptions of contact and motion relative to the surface of the lumen. Completing control of the digit is via an instrumented glove, such that the digit actuates in sympathy with finger gesture and tactile information feedback is achieved by a combination of the tactile and visual means.

Fibre Bragg grating sensors for distributive tactile sensing

Distributive tactile sensing is a method of tactile sensing in which a small number of sensors monitors the behaviour of a flexible substrate which is in contact with the object being sensed. This paper describes the first use of fibre Bragg grating sensors in such a system. Two systems are presented: the first is a one-dimensional metal strip with an array of four sensors, which is capable of detecting the magnitude and position of a contacting load. This system is favourably compared experimentally with a similar system using resistive strain gauges. The second system is a two-dimensional steel plate with nine sensors which is able to distinguish the position and shape of a contacting load, or the positions of two loads simultaneously. This system is compared with a similar system using 16 infrared displacement sensors. Each system uses neural networks to process the sensor data to give information concerning the type of contact. Issues and limitations of the systems are discussed, along with proposed solutions to some of the difficulties.

Another angle on contact lens surface analysis

Purpose: Dynamic contact angle (DCA) methods have advantages over other contact angle methodologies, not least that they can provide more than single contact angle values. Here we illustrate the use of DCA analysis to provide “fingerprint” characterisation of contact lens surfaces, and the way that different materials change in the early stages of wear. Method: The DCA method involves attaching to a microbalance weighted strips cut from a lens. The strips are then cyclically inserted into and removed from an aqueous solution. Conventionally, readings of force taken from linear portions of the resultant dipping curves are translated into advancing (CAa) and receding contact (CAr) angles. Additionally, analysis of the force versus immersion profile provides a “fingerprint” characterisation of the state of the lens surface. Results: CAa and CAr values from DCA traces provide a useful means of differentiating gross differences in hydrophilicity and molecular mobility of surfaces under particular immersion and emersion conditions, such as dipping rate and dwell times. Typical values for etafilcon A (CAa:63.1; CAr:37) and balafilcon B (CAa:118.4; CAr:36.4) illustrate this. Surface modifications induced in lens manufacture are observed to produce not only changes in these value, which may be small, but also changes in the DCA “fingerprint” (slope, undulations, length of plateau). Interestingly, similar changes are induced in the first few hours of lens wear with some lens-patient combinations. Conclusions: Although single parameter contact angles are useful for material characterisation, information of potential clinical interest can be obtained from more detailed analysis of DCA traces.

A smart sensing platform for the discrimination of human movement

This thesis documents the design, implementation and testing of a smart sensing platform that is able to discriminate between differences or small changes in a persons walking. The distributive tactile sensing method is used to monitor the deflection of the platform surface using just a small number of sensors and, through the use of neural networks, infer the characteristics of the object in contact with the surface. The thesis first describes the development of a mathematical model which uses a novel method to track the position of a moving load as it passes over the smart sensing surface. Experimental methods are then described for using the platform to track the position of swinging pendulum in three dimensions. It is demonstrated that the method can be extended to that of real-time measurement of balance and sway of a person during quiet standing. Current classification methods are then investigated for use in the classification of different gait patterns, in particular to identify individuals by their unique gait pattern. Based on these observations, a novel algorithm is developed that is able to discriminate between abnormal and affected gait. This algorithm, using the distributive tactile sensing method, was found to have greater accuracy than other methods investigated and was designed to be able to cope with any type of gait variation. The system developed in this thesis has applications in the area of medical diagnostics, either as an initial screening tool for detecting walking disorders or to be able to automatically detect changes in gait over time. The system could also be used as a discrete biometric identification method, for example identifying office workers as they pass over the surface.

A smart sensing platform for the classification of ambulatory patterns

This paper describes an innovative sensing approach allowing capture, discrimination, and classification of transients automatically in gait. A walking platform is described, which offers an alternative design to that of standard force plates with advantages that include mechanical simplicity and less restriction on dimensions. The scope of the work is to investigate as an experiment the sensitivity of the distributive tactile sensing method with the potential to address flexibility on gait assessment, including patient targeting and the extension to a variety of ambulatory applications. Using infrared sensors to measure plate deflection, gait patterns are compared with stored templates using a pattern recognition algorithm. This information is input into a neural network to classify normal and affected walking events, with a classification accuracy of just under 90 per cent achieved. The system developed has potential applications in gait analysis and rehabilitation, whereby it can be used as a tool for early diagnosis of walking disorders or to determine changes between pre- and post-operative gait.

Distributive tactile sensing using fibre Bragg grating sensors

Two distributive tactile sensing systems are presented, based on fibre Bragg grating sensors. The first is a onedimensional metal strip with an array of 4 sensors, which is capable of detecting the magnitude and position of a contacting load. This system is compared experimentally with a similar system using resistive strain gauges. The second is a two-dimensional steel plate with 9 sensors which is able to distinguish the position and shape of a contacting load. This system is compared with a similar system using 16 infrared displacement sensors. Each system uses neural networks to process the sensor data to give information concerning the type of contact.

Femtosecond laser-induced microstructures on diamond for microfluidic sensing devices applications

This paper reported a three-dimensional microfluidic channel structure, which was fabricated by Yb:YAG 1026?nm femtosecond laser irradiation on a single-crystalline diamond substrate. The femtosecond laser irradiation energy level was optimized at 100?kHz repetition rate with a sub-500 femtosecond pulse duration. The morphology and topography of the microfluidic channel were characterized by a scanning electron microscope and an atomic force microscope. Raman spectroscopy indicated that the irradiated area was covered by graphitic materials. By comparing the cross-sectional profiles before/after removing the graphitic materials, it could be deduced that the microfluidic channel has an average depth of ~410?nm with periodical ripples perpendicular to the irradiation direction. This work proves the feasibility of using ultra-fast laser inscription technology to fabricate microfluidic channels on biocompatible diamond substrates, which offers a great potential for biomedical sensing applications.

Femtosecond laser-induced microstructures on diamond for microfluidic sensing device applications

This paper reported a three-dimensional microfluidic channel structure, which was fabricated by Yb:YAG 1026?nm femtosecond laser irradiation on a single-crystalline diamond substrate. The femtosecond laser irradiation energy level was optimized at 100?kHz repetition rate with a sub-500 femtosecond pulse duration. The morphology and topography of the microfluidic channel were characterized by a scanning electron microscope and an atomic force microscope. Raman spectroscopy indicated that the irradiated area was covered by graphitic materials. By comparing the cross-sectional profiles before/after removing the graphitic materials, it could be deduced that the microfluidic channel has an average depth of ~410?nm with periodical ripples perpendicular to the irradiation direction. This work proves the feasibility of using ultra-fast laser inscription technology to fabricate microfluidic channels on biocompatible diamond substrates, which offers a great potential for biomedical sensing applications.

Fibre Bragg grating sensors for distributive tactile sensing

Distributive tactile sensing is a method of tactile sensing in which a small number of sensors monitors the behaviour of a flexible substrate which is in contact with the object being sensed. This paper describes the first use of fibre Bragg grating sensors in such a system. Two systems are presented: the first is a one-dimensional metal strip with an array of four sensors, which is capable of detecting the magnitude and position of a contacting load. This system is favourably compared experimentally with a similar system using resistive strain gauges. The second system is a two-dimensional steel plate with nine sensors which is able to distinguish the position and shape of a contacting load, or the positions of two loads simultaneously. This system is compared with a similar system using 16 infrared displacement sensors. Each system uses neural networks to process the sensor data to give information concerning the type of contact. Issues and limitations of the systems are discussed, along with proposed solutions to some of the difficulties. © 2007 IOP Publishing Ltd.

Femtosecond laser-induced microstructures on diamond for microfluidic sensing devices applications

This paper reported a three-dimensional microfluidic channel structure, which was fabricated by Yb:YAG 1026?nm femtosecond laser irradiation on a single-crystalline diamond substrate. The femtosecond laser irradiation energy level was optimized at 100?kHz repetition rate with a sub-500 femtosecond pulse duration. The morphology and topography of the microfluidic channel were characterized by a scanning electron microscope and an atomic force microscope. Raman spectroscopy indicated that the irradiated area was covered by graphitic materials. By comparing the cross-sectional profiles before/after removing the graphitic materials, it could be deduced that the microfluidic channel has an average depth of ~410?nm with periodical ripples perpendicular to the irradiation direction. This work proves the feasibility of using ultra-fast laser inscription technology to fabricate microfluidic channels on biocompatible diamond substrates, which offers a great potential for biomedical sensing applications.

Flexible tactile digital feedback for clinical applications

Trauma and damage to the delicate structures of the inner ear frequently occurs during insertion of electrode array into the cochlea. This is strongly related to the excessive manual insertion force of the surgeon without any tool/tissue interaction feedback. The research is examined tool-tissue interaction of large prototype scale (12.5:1) digit embedded with distributive tactile sensor based upon cochlear electrode and large prototype scale (4.5:1) cochlea phantom for simulating the human cochlear which could lead to small scale digit requirements. This flexible digit classified the tactile information from the digit-phantom interaction such as contact status, tip penetration, obstacles, relative shape and location, contact orientation and multiple contacts. The digit, distributive tactile sensors embedded with silicon-substrate is inserted into the cochlea phantom to measure any digit/phantom interaction and position of the digit in order to minimize tissue and trauma damage during the electrode cochlear insertion. The digit is pre-curved in cochlea shape so that the digit better conforms to the shape of the scala tympani to lightly hug the modiolar wall of a scala. The digit have provided information on the characteristics of touch, digit-phantom interaction during the digit insertion. The tests demonstrated that even devices of such a relative simple design with low cost have potential to improve cochlear implants surgery and other lumen mapping applications by providing tactile feedback information by controlling the insertion through sensing and control of the tip of the implant during the insertion. In that approach, the surgeon could minimize the tissue damage and potential damage to the delicate structures within the cochlear caused by current manual electrode insertion of the cochlear implantation. This approach also can be applied diagnosis and path navigation procedures. The digit is a large scale stage and could be miniaturized in future to include more realistic surgical procedures.