Design and analysis of a reservoir-based controllable microneedle for transdermal drug delivery applications.

Microneedle has made excellent contribution in the era of biomedical sector. This paper presents a reservoir-based out-of-plane silicon carbide (SiC) microneedle which has two lumens for delivering drug. The total height of the designed microneedle is 451 µm where the conical tip area is about 69.39 µm2. The additional part of this microneedle is a reservoir which is trapezium in shape having a height of 150 µm. This work use COMSOL Multiphysics software for the structural analysis and Ansys Workbench software to investigate the fluid analysis. The flow analyses are performed by releasing drugs from the reservoir where different viscosity based sample drugs are included. Although reservoir-based microneedles are existing, however, there is no system to control the fluid in those microneedles. Thus, this work proposes a controllable microneedle which able to control the drug flow by using a valve. For both the case of valveless and with a valve, the drug velocities are determined. As paracetamol has highest viscosity among other drugs, it provides lowest velocities. Conversely, the flow of aspirin shows high velocity of 6.51E-2 m/s without a valve and 4.26E-2 m/s with a valve. To analyze the skin insertion performance, a skin model including six layers is designed. The simulation results ensure that the proposed microneedle can penetrate the human skin successfully with less stress and deformation.

Modeling and simulation of a split and recombination-based passive micromixer with vortex-generating mixing units.

As a state-of-the-art technology, micromixers are being used in various chemical and biological processes, including polymerization, extraction, crystallization, organic synthesis, biological screening, drug development, drug delivery, etc. The ability of a micromixer to perform efficient mixing while consuming little power is one of its basic needs. In this paper, a passive micromixer having vortex-generating mixing units is proposed which shows effective mixing with a small pressure drop. The micromixer works on the split and recombination (SAR) flow principle. In this study, four micromixers are designed with different arrangements of mixing units, and the effect of the placement of connecting channels is evaluated in terms of mixing index, pressure drop, and mixing performance. The channel width of 200 µm, height of 300 µm, and size of mixing units are maintained constant for all the micromixers throughout the evaluation process. The numerical simulation is performed for the Reynolds number (Re) range of 0.1-100 using Comsol Multiphysics software. By categorizing the flow patterns into three regimes based on the range of Re, the fluid flow throughout the length of the micromixer is visualized. The micromixer with dislocated connecting channels provides a satisfactory result with the mixing index of 0.96 and 0.94, and the pressure drop of 2.5 Pa and 7.8 kPa at Re = 0.1 and Re = 100 respectively. It also outperformed the other models in terms of the mixing performance. The proposed micromixer might very well be used in microfluidic devices for a variety of analytical procedures due to its straightforward construction and outstanding performance.

Radio frequency energy harvesting from a feeding source in a passive deep brain stimulation device for murine preclinical research.

This paper presents the development of an energy harvesting circuit for use with a head-mountable deep brain stimulation (DBS) device. It consists of a circular planar inverted-F antenna (PIFA) and a Schottky diode-based Cockcroft-Walton 4-voltage rectifier. The PIFA has the volume of π × 10(2) × 1.5 mm(3), resonance frequency of 915 MHz, and bandwidth of 16 MHz (909-925 MHz) at a return loss of -10 dB. The rectifier offers maximum efficiency of 78% for the input power of -5 dBm at a 5 kΩ load resistance. The developed rectenna operates efficiently at 915 MHz for the input power within -15 dBm to +5 dBm. For operating a DBS device, the DC voltage of 2 V is recorded from the rectenna terminal at a distance of 55 cm away from a 26.77 dBm transmitter in free space. An in-vitro test of the DBS device is presented.

Design and analysis of a low actuation voltage electrowetting-on-dielectric microvalve for drug delivery applications.

This paper presents a low actuation voltage microvalve with optimized insulating layers that manipulates a conducting ferro-fluid droplet by the principle of electrowetting-on-dielectric (EWOD). The proposed EWOD microvalve contains an array of chromium (Cr) electrodes on the soda-lime glass substrate, covered by both dielectric and hydrophobic layers. Various dielectric layers including Su-8 2002, Polyvinylidenefluoride (PVDF) and Cyanoethyl pullulan (CEP), and thin (50 nm) hydrophobic Teflon and Cytonix are used to analyze the EWOD microvalves at different voltages. The Finite Element Method (FEM) based software, Coventorware is used to carry out the simulation analysis. It is observed that the EWOD microvalve having a CEP dielectric layer with dielectric constant of about 20 and thickness of 1 µm, and a Cytonix hydrophobic layer with thickness of 50 nm operated the conducting ferro-fluid droplet at the actuation voltage as low as 7.8 V.