Teena James

3D Printed Bionic Ears

The ability to three-dimensionally interweave biological tissue with functional electronics could enable the creation of bionic organs possessing enhanced functionalities over their human counterparts. Conventional electronic devices are inherently two-dimensional, preventing seamless multidimensional integration with synthetic biology, as the processes and materials are very different. Here, we present a novel strategy for overcoming these difficulties via additive manufacturing of biological cells with structural and nanoparticle derived electronic elements. As a proof of concept, we generated a bionic ear via 3D printing of a cell-seeded hydrogel matrix in the precise anatomic geometry of a human ear, along with an intertwined conducting polymer consisting of infused silver nanoparticles. This allowed for in vitro culturing of cartilage tissue around an inductive coil antenna in the ear, which subsequently enables readout of inductively-coupled signals from cochlea-shaped electrodes. The printed ear exhibits enhanced auditory sensing for radio frequency reception, and complementary left and right ears can listen to stereo audio music. Overall, our approach suggests a means to intricately merge biologic and nanoelectronic functionalities via 3D printing.

Curving Nanostructures Using Extrinsic Stress

Many thin films develop high residual stress during deposition. These stresses develop due to grain boundaries, dislocations, voids, and impurities within the film itself, or interfacial factors such as a lattice mismatch, difference in thermal expansion, or adsorption.[1–4] It is known that these intrinsic stresses can cause the spontaneous curving of substrates on which they are deposited.[5] If the substrate is much thicker than the stressed thin film, the substrate curves with a large radius of curvature. [6] In contrast, when the stressed thin film is deposited atop or below another thin film and the films are released from the substrate, it will spontaneously curve with a micro or nanoscale radii of curvature. [7–13] However, it is challenging to get the high intrinsic stress magnitudes needed to enable assembly with small nanoscale radii of curvature; typically, heteroepitaxial deposition at elevated temperatures is required, [11–13] which limits the types of devices and structures that can be assembled.

BioMEMS –Advancing the Frontiers of Medicine

Biological and medical application of micro-electro-mechanical-systems (MEMS) is currently seen as an area of high potential impact. Integration of biology and microtechnology has resulted in the development of a number of platforms for improving biomedical and pharmaceutical technologies. This review provides a general overview of the applications and the opportunities presented by MEMS in medicine by classifying these platforms according to their applications in the medical field.

Voltage-gated ion transport through semiconducting conical nanopores formed by metal nanoparticle-assisted plasma etching.

Nanopores with conical geometries have been found to rectify ionic current in electrolytes. While nanopores in semiconducting membranes are known to modulate ionic transport through gated modification of pore surface charge, the fabrication of conical nanopores in silicon (Si) has proven challenging. Here, we report the discovery that gold (Au) nanoparticle (NP)-assisted plasma etching results in the formation of conical etch profiles in Si. These conical profiles result due to enhanced Si etch rates in the vicinity of the Au NPs. We show that this process provides a convenient and versatile means to fabricate conical nanopores in Si membranes and crystals with variable pore-diameters and cone-angles. We investigated ionic transport through these pores and observed that rectification ratios could be enhanced by a factor of over 100 by voltage gating alone, and that these pores could function as ionic switches with high on-off ratios of approximately 260. Further, we demonstrate voltage gated control over protein transport, which is of importance in lab-on-a-chip devices and biomolecular separations.

Fabrication of 3D nanostructures with lithographically patterned surfaces by self-folding

One of the important challenges in nanoscale manufacturing is the construction of simultaneously patterned three dimensional structures, materials and devices. Since we live in a three dimensional world, such capabilities are needed to fully realize the capabilities of nanotechnology. We describe self-assembly processes based on utilizing intrinsic stress and inducing grain coalescence (extrinsic stress) in thin metal films that can be used to curve or fold lithographically patterned two dimensional (2D) panels into 3D structures. We discuss the use of intrinsic chromium (Cr) stresses and extrinsic stresses based on induced grain coalescence in tin (Sn) based structures with varying material composition to create a variety of lithographically patterned curved and polyhedral structures.

Nano-scale Debye Capacitive Sensors for Highly Sensitive, Label-free, Nucleic Acid Analysis

An electrochemical capacitive sensor with electrode separation in the order of the Electrical Double Layer width (Debye length) of the analyte solution is presented for extremely sensitive and label-free analysis of Nucleic Acids. As the Electrical Double Layers (EDL) from both the capacitive electrodes interact and overlap each other in the reduced space confinement, the contribution from the electrode polarization effects and noises due to bulk sample resistance are found to be minimized. The dielectric property changes during hybridization reaction were measured using 10-mer nucleotide sequences. A 30-45% change in relative permittivity (capacitance) was observed due to DNA hybridization at 10Hz.