Additively Manufactured Microfluidic Enzymatic Biofuel Cell with Comb -like Bioelectrodes

3D printing is a growing processing technology, which offers manufacturing of tailored, portable and integrable electrochemical energy harvesting device for realising next generation bioelectronics devices. Enzymatic biofuel cells (EBFCs) associated with biocatalysis uses biofriendly alternatives for energy harvesting. Also at microscale, the precision design and assembling of the bioelectrodes are complex procedures. The combination of computer-assisted design and 3D printing has enabled the realization of customized electrochemical miniaturized devices for various applications. In this work, a completely 3D printed EBFC at a micro level configuration, names as 3D-µEBFC, integrated with new precise bioelectrode configuration has been demonstrated. The 3D-µEBFC consists of bioelectrode with comb-like structures with carbon black which helps in increasing the active surface to volume ratio available for electrocatalysis by 80 times higher than plain electrodes. This micro-device produced an output power density of 13 µW/cm2 with an open circuit voltage of 570 mV. The 3D printed bioelectrodes show high stability, which may transform the fabrication methodology by decreasing production costs and time, letting the development of complex-shaped and purely 3D printed micro-devices.

Self-selective formation of ordered 1D and 2D GaBi structures on wurtzite GaAs nanowire surfaces

Scaling down material synthesis to crystalline structures only few atoms in size and precisely positioned in device configurations remains highly challenging, but is crucial for new applications e.g., in quantum computing. We propose to use the sidewall facets of larger III–V semiconductor nanowires (NWs), with controllable axial stacking of different crystal phases, as templates for site-selective growth of ordered few atoms 1D and 2D structures. We demonstrate this concept of self-selective growth by Bi deposition and incorporation into the surfaces of GaAs NWs to form GaBi structures. Using low temperature scanning tunneling microscopy (STM), we observe the crystal structure dependent self-selective growth process, where ordered 1D GaBi atomic chains and 2D islands are alloyed into surfaces of the wurtzite (Wz) $$\{11{\bar{2}}0\}$$ { 11 2 ¯ 0 } crystal facets. The formation and lateral extension of these surface structures are controlled by the crystal structure and surface morphology uniquely found in NWs. This allows versatile high precision design of structures with predicted novel topological nature, by using the ability of NW heterostructure variations over orders of magnitude in dimensions with atomic-scale precision as well as controllably positioning in larger device structures.

Time-Resolved FDTD and Experimental FTIR Study of Gold Micropatch Arrays for Wavelength-Selective Mid-Infrared Optical Coupling

Infrared radiation reflection and transmission of a single layer of gold micropatch two-dimensional arrays, of patch length ∼1.0 μm and width ∼0.2 μm, have been carefully studied by a finite-difference time-domain (FDTD) method, and Fourier-transform infrared spectroscopy (FTIR). Through precision design of the micropatch array structure geometry, we achieve a significantly enhanced reflectance (85%), a substantial diffraction (10%), and a much reduced transmittance (5%) for an array of only 15% surface metal coverage. This results in an efficient far-field optical coupling with promising practical implications for efficient mid-infrared photodetectors. Most importantly we find that the propagating electromagnetic fields are transiently concentrated around the gold micropatch array in a time duration of tens of ns, providing us with a novel efficient near-field optical coupling.

Precision Design of Antimicrobial Surfaces

The overall expectation from an antimicrobial surface has been high considering the need for efficiency in preventing the attachment and growth of pathogenic microbes, durability, safety to both humans and environment as well as cost-effectiveness. To date, antimicrobial surface design has been mostly conducted liberally, without rigorous consideration of establishing robust structure-activity relationships for each design strategy or of the use intended for a specific antimicrobial material. However, the variability among the domain bacteria, which is the most diverse of all, alongside the highly dynamic nature of the bacteria-surface interface have taught us that the likelihood of finding universal antimicrobial surfaces is low. In this perspective we discuss some of the current hurdles faced by research in this promising field, emphasizing the relevance and complexity of probing the bacteria-surface interface, and explain why we feel it would greatly benefit from a more streamlined ad-hoc approach.