Unsafe Stimulation Correlates with Oxide Reduction Onset in Unbuffered Saline

Damage mechanisms in electrical stimulation must be better understood to address the demands of new electrode technologies. In this work, we studied the effect of pH on the charge injection mechanisms in a repeated pulsing experiment. We show that damage occurs when the electrode potential enters the oxide reduction region

An active microchannel neural interface with artifact reduction

High-density neural electrodes in microchannel interfaces require in-situ amplification of the neural signals and rejection of high-voltage stimulus pulses leaking to the channel in order to adequately detect neural signals in the presence of concurrent stimulation. This paper presents the design of an active microchannel neural interface in 0.18 μm CMOS employing neural recording and stimulation. To reduce stimulus artifacts, a novel method is proposed that disconnects the recording module during concurrent channel stimulation and automatically applies detection and reduction of stimulus artifacts from adjacent channels using a tunable filter. Simulations show that the method provides at least 54 dB artifact attenuation

Stem Cell Interventions for Bone Healing: Fractures and Osteoporosis

With the ageing population, musculoskeletal conditions are becoming more inherent. Delayed union is defined as a slower than normal fracture healing response, with no healing after 4 to 6 months; however, union is anticipated given sufficient time. In the context of delayed/non-union, fragility fractures in osteoporotic populations carry significant patient morbidity and socioeconomic costs. Multiple mechanisms hinder fracture healing in osteoporotic patients, imbalanced bone remodelling leads to impaired bone microarchitecture due to reduced osteoblast number and activity and as such, callus formation is diminished. Since stem cells can self-renew and differentiate into various tissue lineages, they are becoming very popular in tissue regeneration in musculoskeletal conditions. In this review we discuss the role of stem cells in physiological fracture healing and their potential therapeutic use following a fracture. We explore the potential of stem cells, the release of chemokines and cytokines to reduce fracture risk in osteoporosis

Characterisation of a multi-channel multiplexed EMG recording system: towards realising variable electrode configurations

First steps towards osseointegrated myoelec-trically-controlled prostheses: Bone anchor conduit conveys EMG signals from implanted electrodes [1]. In vivo selection of electrode configurations would improve signal-to-noise ratio (SNR) of EMG recordings [2]; optimal electrode config-urations are not known before implantation. The CAPITel system: Control of Active Prostheses using Implant-able Telemetry [3,4]. Implantable EMG amplifier with a novel multi-plexed frontend. In vivo selection of monopolar, bipolar or tripolar configurations. Designed using commercially available com-ponents for use in animal models. After further research design will be imple-mented as an ASIC

In vitro biocompatibility and electrical stability of thick-film platinum/gold alloy electrodes printed on alumina

OBJECTIVE: High-density electrode arrays are a powerful tool in both clinical neuroscience and basic research. However, current manufacturing techniques require the use of specialised techniques and equipment, which are available to few labs. We have developed a high-density electrode array with customisable design, manufactured using simple printing techniques and with commercially available materials. APPROACH: Electrode arrays were manufactured by thick-film printing a platinum-gold alloy (Pt/Au) and an insulating dielectric on 96% alumina ceramic plates. Arrays were conditioned in serum and serum-free conditions, with and without 1kHz, 200µA, charge balanced stimulation for up to 21 days. Array biocompatibility was assessed using an extract assay and a PC-12 cell contact assay. Electrode impedance, charge storage capacity and charge injection capacity were before and after array conditioning. MAIN RESULTS: The manufactured Pt/Au electrodes have a highly porous surface and exhibit electrical properties comparable to arrays manufactured using alternative techniques. Materials used in array manufacture were found to be non-toxic to L929 fibroblasts by extract assay, and neuronal-like PC-12 cells adhered and extended neurites on the array surfaces. Arrays remained functional after long-term delivery of electrical pulses while exposed to protein-rich environments. Charge storage capacities and charge injection capacities increased following stimulation accounted for by an increase in surface index (real surface area) observed by vertical scanning interferometry. Further, we observed accumulation of proteins at the electrode sites following conditioning in the presence of serum. SIGNIFICANCE: This study demonstrates the in vitro biocompatibility of commercially available thick-film printing materials. The printing technique is both simple and versatile, with layouts readily modified to produce customized electrode arrays. Thick-film electrode arrays are an attractive tool that may be implemented for general tissue engineering and neuroscience research

Logical design of yield pillar base in longwall mining

Longwall is one of the most widely used methods in mining horizontal and gently dipping coal seams. It is a high production method that requires high initial capital investment. Such characteristics enhance the importance of initial design and hence design process. The entries on both sides of the face are integral parts of the method whose accurate design adds to increased profitability and safety of the mining operation. In this paper, two strain-softening models based on analytical fundamentals have been adopted. These models have been applied to a series of yield chain pillars in a coal seam with the depth of 700 meters. Results obtained from this analysis show that such models can be used in deep coal mining and they produce optimum design dimensions and hence they could be adopted as a valid base for logical design of chain pillars. Finally, sensitivity analysis of the results shows that the final design is highly sensitive to the pillar behavior after the coal peak strength. This further demonstrates the validity of the method as a useful tool in designing pillars in longwall deep coal mining

Myoelectric Signal Transmission from Implanted Epimysial Electrodes Using a Bone-Anchor as a Conduit

Introduction Current Upper-limb myoelectric prostheses rely on only 2 control signals from surface electrodes, placed over antagonistic muscles in the amputation stump, for limb control. While this has benefits over the traditional body-powered control, there are disadvantages; electrode lift-off, impedance variation, cross-talk, reliability, and limitations in intuitive control. To address these problems, electrodes can be implanted directly on individual muscles responsible for specific actions. Not only does this address skin-related issues, it reduces cross-talk and greatly increases the number of control channels for multi degrees of freedom intuitive control. Bone-anchored devices can be used to overcome problems with prosthetic attachment and additionally used to transfer control signals from these implantable electrodes to the prosthesis. [1] In above-elbow amputees, targeted muscle reinnervation (TMR) enables more signal generation by redirecting nerves previously controlling the amputated muscles in the forearm, to surrogate muscles in the torso (e.g. pectoralis major). [2] We describe in vivo model using implantable electrodes to record myoelectric signals (MES) in normal muscles and following TMR, utilizing a bone-anchor as a conduit to carry signals across the skin barrier. Materials and Methods An in vivo n=6 ovine model was used. A bone-anchor was placed trans-tibially and bipolar electrodes sutured to M. Peroneus Tertius (PT). In a further n=1, motor nerve to PT was divided and coapted with a motor branch from peroneal nerve. MES were recorded over a 12-week period. Functional recovery in the TMR model was assessed by MES and force-plate analysis (FPA). Results In the n=6 group, there was a positive correlation between signal to noise ratio (SNR) and time since implantation (p < 0.005), with a mean SNR of 7 by week 12. In the TMR model, functional recovery was observed after 6 weeks. Difference between legs returned to normal (pre-op: left 4.7 N/kg, right 4.8 N/kg; 80 days post-op: left 4.1 N/kg, right 4.3 N/kg). Recorded MES from TMR muscle compared favourably with healthy muscle. Conclusions We have demonstrated that a bone-anchor is a reliable and robust conduit for transmitting MES over a period of 12 weeks. The combination of implanted electrodes & direct skeletal fixation offers clear advantages over current systems for prosthetic attachment & control. This system forms the basis of a complete solution for prosthetic rehabilitation, which can also be used in the context of TMR. References 1. Al Ajam et. al., 2013. PMID: 23358938 2. Kuiken et. al., 2004. PMID: 1565863