A bioelectric neural interface towards intuitive prosthetic control for amputees
JOURNAL OF NEURAL ENGINEERING
Authors: Anh Tuan Nguyen; Xu, Jian; Jiang, Ming; Diu Khue Luu; Wu, Tong; Tam, Wing-kin; Zhao, Wenfeng; Drealan, Markus W.; Overstreet, Cynthia K.; Zhao, Qi; Cheng, Jonathan; Keefer, Edward; Yang, Zhi
Objective. While prosthetic hands with independently actuated digits have become commercially available, state-of-the-art human-machine interfaces (HMI) only permit control over a limited set of grasp patterns, which does not enable amputees to experience sufficient improvement in their daily activities to make an active prosthesis useful. Approach. Here we present a technology platform combining fully-integrated bioelectronics, implantable intrafascicular microelectrodes and deep learning-based artificial intelligence (AI) to facilitate this missing bridge by tapping into the intricate motor control signals of peripheral nerves. The bioelectric neural interface includes an ultra-low-noise neural recording system to sense electroneurography (ENG) signals from microelectrode arrays implanted in the residual nerves, and AI models employing the recurrent neural network (RNN) architecture to decode the subject's motor intention. Main results. A pilot human study has been carried out on a transradial amputee. We demonstrate that the information channel established by the proposed neural interface is sufficient to provide high accuracy control of a prosthetic hand up to 15 degrees of freedom (DOF). The interface is intuitive as it directly maps complex prosthesis movements to the patient's true intention. Significance. Our study layouts the foundation towards not only a robust and dexterous control strategy for modern neuroprostheses at a near-natural level approaching that of the able hand, but also an intuitive conduit for connecting human minds and machines through the peripheral neural pathways. Clinical trial: DExterous Hand Control Through Fascicular Targeting (DEFT). Identifier: NCT02994160.
Steady state solutions in a model of a cholesteric liquid crystal sample
Authors: da Costa, Fernando P.; Grinfeld, Michael; Mottram, Nigel J.; Pinto, Joao T.; Xayxanadasy, Kedtysack
Motivated by recent mathematical studies of Freedericksz transitions in twist cells and helix unwinding in cholesteric liquid crystal cells [(da Costa et al. in Eur J Appl Math 20:269-287, 2009), (da Costa et al. in Eur J Appl Math 28:243-260, 2017), (McKay in J Eng Math 87:19-28, 2014), (Millar and McKay in Mol Cryst Liq Cryst 435:277/-286/, 2005)], we consider a model for the director configuration obtained within the framework of the Frank-Oseen theory and consisting of a nonlinear ordinary differential equation in a bounded interval with non-homogeneous mixed boundary conditions (Dirichlet at one end of the interval, Neumann at the other). We study the structure of the solution set using the depth of the sample as a bifurcation parameter. Employing phase space analysis techniques, time maps, and asymptotic methods to estimate integrals, together with appropriate numerical evidence, we obtain the corresponding novel bifurcation diagram and discuss its implications for liquid crystal display technology. Numerical simulations of the corresponding dynamic problem also provide suggestive evidence about stability of some solution branches, pointing to a promising avenue of further analytical, numerical, and experimental studies.