A three-dimensional electrochemical paper-based analytical device for low-cost diagnostics.

Paper-based microfluidic devices with screen-printed electrodes (SPEs) for electrochemical sensing are popular for low-cost point-of-care diagnostics. The electroactive sensing area in these devices is always the irregular, bottom-SPE surface which is in contact with the analyte flowing within the paper substrate. Unfortunately, this results in an electroactive area which varies widely from sensor to sensor. In this paper, we present a three-dimensional paper-based analytical device with a hollow 3D fluid reservoir which allows for use of a more uniform top-SPE surface as the electroactive sensing area. The use of this isolated reservoir eliminates the need for dielectric inks used in conventional SPEs on paper. Our sensors are fabricated using a combination of wax-printing, screen-printing and simple folding via a cleanroom free process without the need for expensive equipment. Additionally, for the first time, we demonstrate an electrochemical paper-based analytical device with a custom designed potentiostat integrated circuit (IC) as a miniaturized reader. The versatility of the sensor is demonstrated through voltammetric, amperometric and potentiometric measurements of important biochemical analytes such as dopamine, glucose and pH. The 3D ePAD together with a custom CMOS potentiostat demonstrates a low-cost, versatile, self-contained system suitable for point-of-care diagnostic devices.

Laterally Confined Microfluidic Patterning of Cells for Engineering Spatially Defined Vascularization.

A biofabrication strategy for creating planar multiscale protein, hydrogel, and cellular patterns, and simultaneously generating microscale topographical features is developed that laterally confines the patterned cells and direct their growth in cell permissive hydrogels.

Hard polymeric porous microneedles on stretchable substrate for transdermal drug delivery.

Microneedles offer a convenient transdermal delivery route with potential for long term sustained release of drugs. However current microneedle technologies may not have the mechanical properties for reliable and stable penetration (e.g. hydrogel microneedles). Moreover, it is also challenging to realize microneedle arrays with large size and high flexibility. There is also an inherent upper limit to the amount and kind of drugs that can be loaded in the microneedles. In this paper, we present a new class of polymeric porous microneedles made from biocompatible and photo-curable resin that address these challenges. The microneedles are unique in their ability to load solid drug formulation in concentrated form. We demonstrate the loading and release of solid formulation of anesthetic and non-steroidal anti-inflammatory drugs, namely Lidocaine and Ibuprofen. Paper also demonstrates realization of large area (6 × 20 cm2) flexible and stretchable microneedle patches capable of drug delivery on any body part. Penetration studies were performed in an ex vivo porcine model supplemented through rigorous compression tests to ensure the robustness and rigidity of the microneedles. Detailed release profiles of the microneedle patches were shown in an in vitro skin model. Results show promise for large area transdermal delivery of solid drug formulations using these porous microneedles.

A review on 3D printing functional brain model.

Modern neuroscience increasingly relies on 3D models to study neural circuitry, nerve regeneration, and neural disease. Several different biofabrication approaches have been explored to create 3D neural tissue model structures. Among them, 3D bioprinting has shown to have great potential to emerge as a high-throughput/high precision biofabrication strategy that can address the growing need for 3D neural models. Here, we have reviewed the design principles for neural tissue engineering. The main challenge to adapt printing technologies for biofabrication of neural tissue models is the development of neural bioink, i.e., a biomaterial with printability and gelation properties and also suitable for neural tissue culture. This review shines light on a vast range of biomaterials as well as the fundamentals of 3D neural tissue printing. Also, advances in 3D bioprinting technologies are reviewed especially for bioprinted neural models. Finally, the techniques used to evaluate the fabricated 2D and 3D neural models are discussed and compared in terms of feasibility and functionality.

Design and implementation of magnetically-tunable quad-band filter utilizing split-ring resonators at microwave frequencies.

In this article, we present a magnetically-tunable quad-band filter with high tunability in the frequency range of 2.1-3.9 GHz. A multi-band filter with four stop-bands comprises of a microstrip line coupled to four frequency-selective split-ring resonators (SRRs). We achieve tuning of individual frequency bands using magnetic reed switches connected in between the capacitive gaps of each split-ring resonator. Application of magnetic field tunes this capacitance affecting its resonance frequency. The measured reflection spectrum of the proposed device matches well with the simulation results. The results show more than 25% tunability for each of the four bands with bandwidth values in the range of 30-70 MHz with over 100% overall tunability in the 2.1-3.9 GHz frequency spectrum.

Three dimensional printing of metamaterial embedded geometrical optics (MEGO).

Three-dimensional printers have revolutionized many scientific fields with its low-cost, accessibility and ease of printing. In this paper, we show how stereolithography (SLA) based 3D printers can enable realization of innovative 3D optical devices formed through the fusion of metamaterials with geometrical optics or MEGO. It utilizes a combination of desktop SLA 3D printer and metal deposition/coating systems. Using this approach, we present innovative metamaterial embedded optical components such as mushroom-type metamaterials, curved wide-angle metamaterial absorbers/reflectors and a frequency selective moth eye hemispherical absorber. Finally a unique MEGO device formed through the fusion of a frequency selective metamaterial with an optical parabolic reflector has been demonstrated that combines their individual properties in a single device. The fabricated MEGO devices operate in the millimeter wave frequency range. Simulation and measurement results using terahertz continuous-wave spectrometer validate their functionality and performance. With improving resolution in 3D printing, MEGO devices will be able to reach Terahertz and optical frequencies in the near future.

Highly Flexible Transistor Threads for All-Thread Based Integrated Circuits and Multiplexed Diagnostics.

Physically intimate, real-time monitoring of human biomarkers is becoming increasingly important to modern medicine and patient wellness. Such monitoring is possible due to advances in soft and flexible materials, devices and bioelectronics systems. Compared to other flexible platforms, multifilament textile fibers or threads offer superior flexibility, material diversity, and simple ambient processing to realize a wide range of flexible devices such as sensors, electronics, and microfluidics. In this paper, we realize unique flexible transistors on threads and interconnect them to realize logic gates and small-scale integrated circuits. Compared to prior textile-based transistors, the proposed thread-based transistors (TBTs) are realized with a readily shaped, colloidally dispersed gel consisting of silica nanoparticles and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI TFSI) ionic liquid for all-around electrolyte gating of a carbon nanotube (CNT) semiconducting network assembled on the thread. We interconnect TBTs with thread-based electrochemical sensors (TBEs) to realize an all-thread based multiplexed diagnostic device. All-thread based platforms are thin, highly flexible and conformal, allowing them to be worn directly on the skin without any polymeric substrate, or sutured transdermally using a needle.