Hydrogel optimization towards fibroblast-friendly biomimetic coatings for implantable devices

In this paper we present our investigations related to the optimization of hydrogels for the coating/packaging of biomedical devices. In order for hydrogels to be a viable interface/packaging material, a number of conditions must be met. We outline the tailoring of the mechanical properties of a HEMA based hydrogel by exploiting the influence of individual hydrogel components to achieve these requirements. The water sorption, the elasticity and the porosity of various hydrogel materials were tested and the effects of the different hydrogel components was determined. These components include gelatin (used as a pore generator or porogen), alginate (to influence mechanical properties) and collagen (to improve cell adhesion). We also report the results of in vitro fibroblast testing on various hydrogel types.

Two-dimensional multi-channel neural probes with electronic depth control

This paper presents multi-electrode arrays for in vivo neural recording applications incorporating the principle of electronic depth control (EDC), i.e., the electronic selection of recording sites along slender probe shafts independently for multiple channels. Two-dimensional (2D) arrays were realized using a commercial 0.5- μm complementary-metal-oxide-semiconductor (CMOS) process for the EDC circuits combined with post-CMOS micromachining to pattern the comb-like probes and the corresponding electrode metallization. A dedicated CMOS integrated front-end circuit was developed for pre-amplification and multiplexing of the neural signals recorded using these probes.

Out-of-plane, high strength, polymer microneedles for transdermal drug delivery

This paper reports on the high strength of high-aspect ratio (> 50) hollow, polymer microneedles fabricated out-of-plane using a fairly repeatable fabrication process. Further, these microneedle tips were sharpened by a molding principle, with a simple anisotropic etch of silicon wafer. Also, an enhanced elegant process was explored to incorporate the mounting of the microneedle onto a platform without using any additional material, such that the bore of the microneedle is continuous with the bore of the platform in order to facilitate microfluidic delivery through the hollow needles. The high aspect ratio microneedles undergo failure at the critical load of around 4 N, while the insertion force for such a needle into agar gel, which is a fairly good equivalent of the human skin due to its inherent visco-elastic properties, is 7 mN, which translates into a safety factor (ratio of critical loading force to the maximum applied force) of greater than 500 thus, making it adequately strong for skin penetration.

Tuning electrode impedance for the electrical recording of biopotentials

Tuning the electrode impedance through the DC biasing of iridium oxide is presented. Impedance reduction of up to two orders of magnitude was reproducibly observed in 20 microm diameter microelectrodes at a biasing of 1V.

A 3D slim-base probe array for in vivo recorded neuron activity

This paper introduces the first experimental results of a new implantable slim-base three-dimensional (3D) probe array for cerebral applications. The probes are assembled perpendicularly into the slim-base readout platform where electrical and mechanical connections are achieved simultaneously. A new type of micromachined interconnect has been developed to establish electrical connection using extreme planarization techniques. Due to the modular approach of the platform, probe arrays of different dimensions and functionality can be assembled. The platform is only several hundred microns thick which is highly relevant for chronic experiments in which the probe array should be able to float on top of the brain. Preliminary tests were carried out with the implantation of a probe array into the auditory cortex of a rat.

Powering an inorganic nanodevice with a biomolecular motor

Biomolecular motors such as F1-adenosine triphosphate synthase (F1-ATPase) and myosin are similar in size, and they generate forces compatible with currently producible nanoengineered structures. We have engineered individual biomolecular motors and nanoscale inorganic systems, and we describe their integration in a hybrid nanomechanical device powered by a biomolecular motor. The device consisted of three components: an engineered substrate, an F1-ATPase biomolecular motor, and fabricated nanopropellers. Rotation of the nanopropeller was initiated with 2 mM adenosine triphosphate and inhibited by sodium azide.