Aerogels are one of the most interesting materials of the 21st century owing to their high porosity, low density, and large available surface area. Historically, aerogels have been used for highly efficient insulation and niche applications, such as interstellar particle capture. Recently, aerogels have made their way into the composite universe. By coupling nanomaterial with a variety of matrix materials, lightweight, high-performance composite aerogels have been developed for applications ranging from lithium-ion batteries to tissue engineering materials. In this paper, the current status of aerogel composites based on nanomaterials is reviewed and their application in environmental remediation, energy storage, controlled drug delivery, tissue engineering, and biosensing are discussed.

We demonstrate a new fabrication technology to realize ``intelligent'', transdermal, minimally invasive microneedle array (iμNA) by crosslinking a hydrogel, Polyethylene Glycol Diacrylate (PEGDA) by photo-polymerization using Digital Light Processing (DLP) based 3D printing. The photo-polymerization conditions have been optimized so that the mutually exclusive requirements of excellent mechanical strength while retaining hydrogel properties of PEGDA are met which would allow swelling/delivery of therapeutic cargo of diclofenac sodium via diffusion. An array having 100 microneedles arranged in a 10x 10 array was successfully 3D printed which efficiently penetrated human skin during ex vivo characterization. In vitro drug release studies demonstrated that the PEGDA based iμNA behaves as a stimuli responsive device showing distinct release characteristics from external stimuli such as temperature and pH. [2020-0133]

We demonstrate new fabrication technologies for 3D microelectrode platforms, fully realized for several 3D multi-functional biosystems. The microfabrication technology involves 3D metallized microtowers realized by 3D printing, metal evaporation, and coarse biocompatible lamination to insulate the traces. Electrospun 3D nanofiber scaffolds (NFSs) are coupled to the microelectrodes to provide additional functionality. The scaffolds were formed via electrospinning two types of nanofibers: ~ 200-500 nm PET, a hydrophobic polymer, and ~ 100 nm PVA/PAA, a hydrophilic co-polymer. PVA/PAA nanofibers had consistent diameters without beading and were used in subsequent experiments. Impedance measurements before, 651.3 kΩ , and after, 659.4 kΩ , deposition of PVA/PAA remains unchanged, indicating enhanced functionality without interfering with the electrical characteristics of the 3D MEAs. Silver nanoparticles (Ag NP) were embedded as model drug compounds in the PVA/PAA-NFS to demonstrate the potential of the 3D MEA as a biosensor and drug delivery system. TEM and antimicrobial studies demonstrated ~ 5-15 nm Ag NP within the PVA/PAA-NFS, which was potent to Acinetobacter baumannii and Escherichia coli. Fine 3D insulation atop the microtowers is achieved using a drop-casted/spin-coated 3D layer of Polystyrene (PS), which is laser micromachined to realize 50x 50 μm² 3D microelectrodes with impedance properties similar to other reported approaches. [2019-0043]

Microelectrode Arrays are established platforms for biosensing applications; however, limitations in electrode impedance and cell-electrode coupling still exist. In this paper, the SNR of 25 μm diameter gold (Au) microelectrodes was improved by decreasing the impedance with precision electrodeposition. SEM determined that N-P Pt. microelectrodes had nano-porous structures that filled the insulation cylinders. EIS, CV, and RMS noise measurements concluded that the optimized electrodeposition of N-P Pt. led to a lowered impedance of 18.36 kΩ ± 2.6 kΩ at 1 kHz, a larger double layer capacitance of 73 nF, and lowered RMS noise of 2.08 ± 0.16 μV as compared to the values for Au of 159 kΩ ± 28 kΩ at 1 kHz, 17nF, and 3.14 ± 0.42 μ V, respectively. Human motoneurons and human cardiomyocytes were cultured on N-P Pt. devices to assess their biocompatibility and signal quality. In order to improve the cell-electrode coupling, a precision plating technique was used. Both cell types were electrically active on devices for up to 10 weeks, demonstrated improved SNR, and expected responses to precision chemical and electrical stimulation. The modification of Au microelectrodes with nanomaterials in combination with precision culturing of human cell types provides cost effective, highly sensitive, well coupled and relevant biosensing platforms for medical and pharmaceutical research. [2018-0187]

Four-dimensional printing refers to a process through which a 3D printed object transforms from one structure into another through the influence of an external energy input. Self-folding structures have been extensively studied to advance 3D printing technology into 4D using stimuli-responsive polymers. Designing and applying self-folding structures requires an understanding of the material properties so that the structural designs can be tailored to the targeted applications. Poly(N-iso-propylacrylamide) (PNIPAM) was used as the thermo-responsive material in this study to 3D print hydrogel samples that can bend or fold with temperature changes. A double-layer printed structure, with PNIPAM as the self-folding layer and polyethylene glycol (PEG) as the supporting layer, provided the mechanical robustness and overall flexibility to accommodate geometric changes. The mechanical properties of the multi-material 3D printing were tested to confirm the contribution of the PEG support to the double-layer system. The desired folding of the structures, as a response to temperature changes, was obtained by adding kirigami-inspired cuts to the design. An excellent shape-shifting capability was obtained by tuning the design. The experimental observations were supported by COMSOL Multiphysics^® software simulations, predicting the control over the folding of the double-layer systems.

In this work, we report on the implementation of a closed-loop liquid-loaded resonant mass sensor as a test vehicle for the realization of highly sensitive miniaturized biomarker assays. Using thin-film piezoelectric-on-silicon (TPoS) contour-mode disc resonators that are specifically designed and optimized for liquid-phase operation, a liquid-loaded low power (~1.6 mW) oscillator at ~17 MHz is demonstrated with a single transistor. By proper placement of the electrodes and the supporting tethers, a high liquid-loaded quality factor (~380) and a low insertion loss (~19 dB) are concurrently achieved which enable the accurate frequency tracking of the potential mass microbalance. The frequency shifts due to the liquid-loading and the preliminary characterized frequency stability of the oscillator imply a minimum mass detection resolution in the picograms range. [2020-0177]