Quantum Nature of Charge Transport in Inkjet-Printed Graphene Revealed in High Magnetic Fields up to 60T.

Inkjet-printing of graphene, iGr, provides an alternative route for the fabrication of highly conductive and flexible graphene films for use in devices. However, the contribution of quantum phenomena associated with 2D single layer graphene, SLG, to the charge transport in iGr is yet to be explored. Here, the first magneto-transport study of iGr in high magnetic fields up to 60 T is presented. The observed quantum phenomena, such as weak localization and negative magnetoresistance, are strongly affected by the thickness of the iGr film and can be explained by a combination of intra- and inter-flake classical and quantum charge transport. The quantum nature of carrier transport in iGr is revealed using temperature, electric field, and magnetic field dependences of the iGr conductivity. These results are relevant for the exploitation of inkjet deposition of graphene, which is of particular interest for additive manufacturing and 3D printing of flexible and wearable electronics. It is shown that printed nanostructures enable ensemble averaging of quantum interference phenomena within a single device, thereby facilitating comparison between experiment and underlying statistical models of electron transport.

Wireless electrical-molecular quantum signalling for cancer cell apoptosis.

Quantum biological tunnelling for electron transfer is involved in controlling essential functions for life such as cellular respiration and homoeostasis. Understanding and controlling the quantum effects in biology has the potential to modulate biological functions. Here we merge wireless nano-electrochemical tools with cancer cells for control over electron transfer to trigger cancer cell death. Gold bipolar nanoelectrodes functionalized with redox-active cytochrome c and a redox mediator zinc porphyrin are developed as electric-field-stimulating bio-actuators, termed bio-nanoantennae. We show that a remote electrical input regulates electron transport between these redox molecules, which results in quantum biological tunnelling for electron transfer to trigger apoptosis in patient-derived cancer cells in a selective manner. Transcriptomics data show that the electric-field-induced bio-nanoantenna targets the cancer cells in a unique manner, representing electrically induced control of molecular signalling. The work shows the potential of quantum-based medical diagnostics and treatments.

Towards OPM-MEG in a virtual reality environment.

Virtual reality (VR) provides an immersive environment in which a participant can experience a feeling of presence in a virtual world. Such environments generate strong emotional and physical responses and have been used for wide-ranging applications. The ability to collect functional neuroimaging data whilst a participant is immersed in VR would represent a step change for experimental paradigms; unfortunately, traditional brain imaging requires participants to remain still, limiting the scope of naturalistic interaction within VR. Recently however, a new type of magnetoencephalography (MEG) device has been developed, that employs scalp-mounted optically-pumped magnetometers (OPMs) to measure brain electrophysiology. Lightweight OPMs, coupled with precise control of the background magnetic field, enables participant movement during data acquisition. Here, we exploit this technology to acquire MEG data whilst a participant uses a virtual reality head-mounted display (VRHMD). We show that, despite increased magnetic interference from the VRHMD, we were able to measure modulation of alpha-band oscillations, and the visual evoked field. Moreover, in a VR experiment in which a participant had to move their head to look around a virtual wall and view a visual stimulus, we showed that the measured MEG signals map spatially in accordance with the known organisation of primary visual cortex. This technique could transform the type of neuroscientific experiment that can be undertaken using functional neuroimaging.

Novel regimes of electron dynamics in superlattices.

A superlattice (SL) is an artificial crystal in which alternating nanometre-thick layers of two or more different semiconductor materials provide a periodic potential for conduction electrons. Strong magnetic and electric fields applied to this type of structure provide a means of exploring novel regimes of electron dynamics. The applied fields lower the dimensionality of the electronic states and lead to qualitative changes in the electronic conduction. This discovery is of fundamental interest and highly relevant to the properties of other low-dimensional conductors, such as nanowires and quantum dot SLs, which are presently attracting the attention of the physics and device communities. In addition, a rare type of chaotic electron dynamics, called non-Kolmogorov-Arnold-Moser (KAM) chaotic motion, which has been theoretically studied for several decades, is observed experimentally in SLs. The onset of chaos at discrete values of the applied electric and magnetic fields is observed as a large increase in the current flow due to the creation of unbound electron orbits, which propagate through intricate web patterns in phase space. Therefore, non-KAM chaos could provide a new mechanism for controlling the electrical conductivity of the electronic devices with extreme sensitivity.

Chaotic ray dynamics in slowly varying two-dimensional photonic crystals.

We use Hamiltonian optics to investigate chaotic ray dynamics in a photonic crystal whose lattice parameters vary slowly with position. The ray dynamics are chaotic even in regimes where only stable motion has been found in previous studies of energy band transport. Stable ray paths provide dynamical barriers that localize chaotic motion to certain regions of the photonic crystal.