Iwan Roberts - Academia.edu (original) (raw)
Papers by Iwan Roberts
Annals of Biomedical Engineering
As the first clinically translated machine-neural interface, cochlear implants (CI) have demonstr... more As the first clinically translated machine-neural interface, cochlear implants (CI) have demonstrated much success in providing hearing to those with severe to profound hearing loss. Despite their clinical effectiveness, key drawbacks such as hearing damage, partly from insertion forces that arise during implantation, and current spread, which limits focussing ability, prevent wider CI eligibility. In this review, we provide an overview of the anatomical and physical properties of the cochlea as a resource to aid the development of accurate models to improve future CI treatments. We highlight the advancements in the development of various physical, animal, tissue engineering, and computational models of the cochlea and the need for such models, challenges in their use, and a perspective on their future directions.
Biosensors
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
IEEE Transactions on Biomedical Engineering
Goal: Advances in computational models of biological systems and artificial neural networks enabl... more Goal: Advances in computational models of biological systems and artificial neural networks enable rapid virtual prototyping of neuroprostheses, accelerating innovation in the field. Here, we present an end-to-end computational model for predicting speech perception with cochlear implants (CI), the most widely-used neuroprosthesis. Methods: The model integrates CI signal processing, a finite element model of the electrically-stimulated cochlea, and an auditory nerve model to predict neural responses to speech stimuli. An automatic speech recognition neural network is then used to extract phoneme-level speech perception from these neural response patterns. Results: Compared to human CI listener data, the model predicts similar patterns of speech perception and misperception, captures between-phoneme differences in perceptibility, and replicates effects of stimulation parameters and noise on speech recognition. Information transmission analysis at different stages along the CI processing chain indicates that the bottleneck of information flow occurs at the electrode-neural interface, corroborating studies in CI
IEEE Transactions on Biomedical Engineering, 2021
Cochlear implants use electrical stimulation of the auditory nerve to restore the sensation of he... more Cochlear implants use electrical stimulation of the auditory nerve to restore the sensation of hearing to deaf people. Unfortunately, the stimulation current spreads extensively within the cochlea, resulting in "blurring" of the signal, and hearing that is far from normal. Current spread can be indirectly measured using the implant electrodes for both stimulating and sensing, but this provides incomplete information near the stimulating electrode due to electrodeelectrolyte interface effects. Here, we present a 3D-printed "unwrapped" physical cochlea model with integrated sensing wires. We integrate resistors into the walls of the model to simulate current spread through the cochlear bony wall, and "tune" these resistances by calibration with an in-vivo electrical measurement from a cochlear implant patient. We then use this model to compare electrical current spread
Materials Science and Engineering: C, 2018
Carbon nanotubes (CNTs) with exceptional physical and chemical properties are attracting signific... more Carbon nanotubes (CNTs) with exceptional physical and chemical properties are attracting significant interest in the field of tissue engineering. Several reports investigated CNTs biocompatibility and their impact in terms of cell attachment, proliferation and differentiation mainly using polymer/CNTs membranes. However, these 2D membranes are not able to emulate the complex in vivo environment. In this paper, additive manufacturing (3D printing) is used to create composite 3D porous scaffolds containing different loadings of multi-walled carbon nanotubes (MWCNT) (0.25, 0.75 and 3 wt. %) for bone tissue regeneration. Preprocessed and processed materials were extensively characterised in terms of printability, morphological and topographic characteristics and thermal, mechanical and biological properties. Scaffolds with pore sizes ranging between 366 m and 397m were successfully produced and able to sustain early-stage human adipose-derived mesenchymal stem cells attachment and proliferation. Results show that MWCNTs enhances protein adsorption, mechanical and biological properties. Composite scaffolds, particularly the 3 wt. % loading of MWCNTs, seem to be good candidates for bone tissue regeneration. Polyester materials are widely used in the fabrication of scaffolds due to their biocompatible, degradable and flexibility in processing characteristics [11]. Among them, poly(caprolactone) (PCL) is one of the most popular due to its biocompatibility, ease of processing, and controlled degradation rate [12]. However, PCL presents poor cellular affinity, high hydrophobicity, lacks bioactivity, and poor mechanical properties for load bearing applications. A strategy to overcome these limitations is to prepare composites with other materials such as ceramics (e.g. hydroxyapatite and tri-calcium phosphates), metals, and carbon nanomaterials such as graphene or CNTs [13-19]. CNTs have been used in tissue engineering including neural, cardiac, muscle, and bone applications [20-23]. Cytotoxicity effects strongly depend on their physio-chemical characteristics such as length, diameter, surface area, tendency for agglomeration, and the presence and nature of catalyst residuals generated during the fabrication process [24]. If CNTs are not internalised by cells they can considered to be biocompatible and contribute to better cell affinity (proliferation and osteogenic differentiation) [25-27]. Moreover, combined with degradable polymers, CNT incorporation can allow the fabrication of electro-active structures with improved mechanical properties [28]. Electro-active constructs have been explored by Supronowicz et al. [29], who demonstrated that osteoblasts exposed to electrical stimulation present increased cell proliferation, accelerated extracellular calcium formation, and mRNA expression for collagen type-I. Similarly, Shao et al. [30] reported that osteoblasts grew along the direction of the electrical current whilst the presence of direct current enhanced cell proliferation and directed the outgrowth of osteoblasts. Despite these observations, the biocompatibility and toxicology of CNTs are still being debated [31, 32]. Studies have reported that CNTs are similar to asbestos fibres, inducing inflammation and causing fibrosis when inhaled [33, 34]. Toxicity issues have been also associated with CNT impurities with the presence of metal nanoparticles via the chemical vapour deposition
Annals of Biomedical Engineering
As the first clinically translated machine-neural interface, cochlear implants (CI) have demonstr... more As the first clinically translated machine-neural interface, cochlear implants (CI) have demonstrated much success in providing hearing to those with severe to profound hearing loss. Despite their clinical effectiveness, key drawbacks such as hearing damage, partly from insertion forces that arise during implantation, and current spread, which limits focussing ability, prevent wider CI eligibility. In this review, we provide an overview of the anatomical and physical properties of the cochlea as a resource to aid the development of accurate models to improve future CI treatments. We highlight the advancements in the development of various physical, animal, tissue engineering, and computational models of the cochlea and the need for such models, challenges in their use, and a perspective on their future directions.
Biosensors
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
IEEE Transactions on Biomedical Engineering
Goal: Advances in computational models of biological systems and artificial neural networks enabl... more Goal: Advances in computational models of biological systems and artificial neural networks enable rapid virtual prototyping of neuroprostheses, accelerating innovation in the field. Here, we present an end-to-end computational model for predicting speech perception with cochlear implants (CI), the most widely-used neuroprosthesis. Methods: The model integrates CI signal processing, a finite element model of the electrically-stimulated cochlea, and an auditory nerve model to predict neural responses to speech stimuli. An automatic speech recognition neural network is then used to extract phoneme-level speech perception from these neural response patterns. Results: Compared to human CI listener data, the model predicts similar patterns of speech perception and misperception, captures between-phoneme differences in perceptibility, and replicates effects of stimulation parameters and noise on speech recognition. Information transmission analysis at different stages along the CI processing chain indicates that the bottleneck of information flow occurs at the electrode-neural interface, corroborating studies in CI
IEEE Transactions on Biomedical Engineering, 2021
Cochlear implants use electrical stimulation of the auditory nerve to restore the sensation of he... more Cochlear implants use electrical stimulation of the auditory nerve to restore the sensation of hearing to deaf people. Unfortunately, the stimulation current spreads extensively within the cochlea, resulting in "blurring" of the signal, and hearing that is far from normal. Current spread can be indirectly measured using the implant electrodes for both stimulating and sensing, but this provides incomplete information near the stimulating electrode due to electrodeelectrolyte interface effects. Here, we present a 3D-printed "unwrapped" physical cochlea model with integrated sensing wires. We integrate resistors into the walls of the model to simulate current spread through the cochlear bony wall, and "tune" these resistances by calibration with an in-vivo electrical measurement from a cochlear implant patient. We then use this model to compare electrical current spread
Materials Science and Engineering: C, 2018
Carbon nanotubes (CNTs) with exceptional physical and chemical properties are attracting signific... more Carbon nanotubes (CNTs) with exceptional physical and chemical properties are attracting significant interest in the field of tissue engineering. Several reports investigated CNTs biocompatibility and their impact in terms of cell attachment, proliferation and differentiation mainly using polymer/CNTs membranes. However, these 2D membranes are not able to emulate the complex in vivo environment. In this paper, additive manufacturing (3D printing) is used to create composite 3D porous scaffolds containing different loadings of multi-walled carbon nanotubes (MWCNT) (0.25, 0.75 and 3 wt. %) for bone tissue regeneration. Preprocessed and processed materials were extensively characterised in terms of printability, morphological and topographic characteristics and thermal, mechanical and biological properties. Scaffolds with pore sizes ranging between 366 m and 397m were successfully produced and able to sustain early-stage human adipose-derived mesenchymal stem cells attachment and proliferation. Results show that MWCNTs enhances protein adsorption, mechanical and biological properties. Composite scaffolds, particularly the 3 wt. % loading of MWCNTs, seem to be good candidates for bone tissue regeneration. Polyester materials are widely used in the fabrication of scaffolds due to their biocompatible, degradable and flexibility in processing characteristics [11]. Among them, poly(caprolactone) (PCL) is one of the most popular due to its biocompatibility, ease of processing, and controlled degradation rate [12]. However, PCL presents poor cellular affinity, high hydrophobicity, lacks bioactivity, and poor mechanical properties for load bearing applications. A strategy to overcome these limitations is to prepare composites with other materials such as ceramics (e.g. hydroxyapatite and tri-calcium phosphates), metals, and carbon nanomaterials such as graphene or CNTs [13-19]. CNTs have been used in tissue engineering including neural, cardiac, muscle, and bone applications [20-23]. Cytotoxicity effects strongly depend on their physio-chemical characteristics such as length, diameter, surface area, tendency for agglomeration, and the presence and nature of catalyst residuals generated during the fabrication process [24]. If CNTs are not internalised by cells they can considered to be biocompatible and contribute to better cell affinity (proliferation and osteogenic differentiation) [25-27]. Moreover, combined with degradable polymers, CNT incorporation can allow the fabrication of electro-active structures with improved mechanical properties [28]. Electro-active constructs have been explored by Supronowicz et al. [29], who demonstrated that osteoblasts exposed to electrical stimulation present increased cell proliferation, accelerated extracellular calcium formation, and mRNA expression for collagen type-I. Similarly, Shao et al. [30] reported that osteoblasts grew along the direction of the electrical current whilst the presence of direct current enhanced cell proliferation and directed the outgrowth of osteoblasts. Despite these observations, the biocompatibility and toxicology of CNTs are still being debated [31, 32]. Studies have reported that CNTs are similar to asbestos fibres, inducing inflammation and causing fibrosis when inhaled [33, 34]. Toxicity issues have been also associated with CNT impurities with the presence of metal nanoparticles via the chemical vapour deposition