Mapping of Small Nerve Trunks and Branches Using Adaptive Flexible Electrodes.

Selective stimulation is delivered to the sciatic nerve using different paris of contacts on a split-ring electrode, while simulatneous recordings are acquired by the neural ribbon electrodes on three different branches. Two hook electrodes are also implanted in the muscle to monitor the activated muscle responses. It shows that the high precision implantation of electrodes, increases the efficacy and reduces the incidence of side effects.

Progress of Flexible Electronics in Neural Interfacing - A Self-Adaptive Non-Invasive Neural Ribbon Electrode for Small Nerves Recording.

A novel flexible neural ribbon electrode with a self-adaptive feature is successfully implemented for various small nerves recording. As a neural interface, the selective recording capability is characterized by having reliable signal acquisitions from the sciatic nerve and its branches such as the peroneal nerve, the tibial nerve, and the sural nerve.

A flexible three-dimensional electrode mesh: An enabling technology for wireless brain-computer interface prostheses.

The neural interface is a key component in wireless brain-computer prostheses. In this study, we demonstrate that a unique three-dimensional (3D) microneedle electrode on a flexible mesh substrate, which can be fabricated without complicated micromachining techniques, is conformal to the tissues with minimal invasiveness. Furthermore, we demonstrate that it can be applied to different functional layers in the nervous system without length limitation. The microneedle electrode is fabricated using drawing lithography technology from biocompatible materials. In this approach, the profile of a 3D microneedle electrode array is determined by the design of a two-dimensional (2D) pattern on the mask, which can be used to access different functional layers in different locations of the brain. Due to the sufficient stiffness of the electrode and the excellent flexibility of the mesh substrate, the electrode can penetrate into the tissue with its bottom layer fully conformal to the curved brain surface. Then, the exposed contact at the end of the microneedle electrode can successfully acquire neural signals from the brain.

Flexible Epineural Strip Electrode for Recording in Fine Nerves.

This paper demonstrates flexible epineural strip electrodes (FLESE) for recording from small nerves. Small strip-shaped FLESE enables us to easily and closely stick on various sized nerves for less damage in a nerve and optimal recording quality. In addition, in order to enhance the neural interface, the gold electrode contacts were coated with carbon nanotubes, which reduced the impedance of the electrodes. We used the FLESEs to record electrically elicited nerve signals (compound neural action potentials) from the sciatic nerve in rats. Bipolar and differential bipolar configurations for the recording were investigated to optimize the recording configuration of the FLESEs. The successful results from differential bipolar recordings showed that the total length of FLESEs could be further reduced, maintaining the maximum recording ability, which would be beneficial for recording in very fine nerves. Our results demonstrate that new concept of FLESEs could play an important role in electroceuticals in near future.

A convection-driven long-range linear gradient generator with dynamic control.

We developed a novel gradient generator to achieve long range and linear chemical gradients with a dynamic control function. The length of the gradient can be on the centimetre scale. The gradient profile can be tuned by changing the flow rates. The device can work in both high flow rate regimes with large shear stress and low flow rate regimes with minimum shear stress. The drug screening function was demonstrated by the viability test of PC-9 cancer cells.

Flexible and self-adaptive neural ribbon with three-dimensional electrodes for sciatic nerve recording.

Various peripheral nerve interfaces have been developed in the last decades and transferred into neuroscientific researches or clinical applications. In this study, we present a novel flexible neural ribbon electrode that can achieve self-adaption to nerves in various diameters and have three dimensional (3D) contacts. Impedance spectroscopy of the neural ribbon electrode was carried out to determine its electrochemical characteristics during the recording. The recording capability of the neural ribbon on sciatic nerves with different diameter was demonstrated by successful signal acquisitions.

Development of stretchable membrane based nanofilters using patterned arrays of vertically grown carbon nanotubes.

A unique process which utilizes membrane based vertically grown carbon nanotubes (CNTs) as nanofilters for a mass transport study is presented here. By using ions, ss-DNA and haemagglutinin as testing molecules of different dimensions, the mass transport function of the CNT membrane is investigated under pressure difference and/or electric field.

Development of vertical SU-8 microtubes integrated with dissolvable tips for transdermal drug delivery.

Polymer-based microneedles have drawn much attention in the transdermal drug delivery resulting from their flexibility and biocompatibility. Traditional fabrication approach deploys various kinds of molds to create sharp tips at the end of needles for the penetration purpose. This approach is usually time-consuming and expensive. In this study, we developed an innovative fabrication process to make biocompatible SU-8 microtubes integrated with biodissolvable maltose tips as novel microneedles for the transdermal drug delivery applications. These microneedles can easily penetrate the skin's outer barrier represented by the stratum corneum (SC) layer. The drug delivery device of mironeedles array with 1000 µm spacing between adjacent microneedles is proven to be able to penetrate porcine cadaver skins successfully. The maximum loading force on the individual microneedle can be as large as 7.36 ± 0.48N. After 9 min of the penetration, all the maltose tips are dissolved in the tissue. Drugs can be further delivered via these open biocompatible SU-8 microtubes in a continuous flow manner. The permeation patterns caused by the solution containing Rhodamine 110 at different depths from skin surface were characterized via a confocal microscope. It shows successful implementation of the microneedle function for fabricated devices.

Development of vertical SU-8 microneedles for transdermal drug delivery by double drawing lithography technology.

Polymer-based microneedles have drawn much attention in transdermal drug delivery resulting from their flexibility and biocompatibility. Traditional fabrication approaches are usually time-consuming and expensive. In this study, we developed a new double drawing lithography technology to make biocompatible SU-8 microneedles for transdermal drug delivery applications. These microneedles are strong enough to stand force from both vertical direction and planar direction during penetration. They can be used to penetrate into the skin easily and deliver drugs to the tissues under it. By controlling the delivery speed lower than 2 µl/min per single microneedle, the delivery rate can be as high as 71%.