We report the fabrication of a flexible, lightweight and disposable multi walled carbon nanotube (MWCNT)-zinc oxide (ZnO) nanofiber based chemiresistive biosensor for label free detection of the malaria biomarker, histidine rich protein II (HRP2). The sensing platform is formed by depositing nanofibers in between the source and drain electrodes patterned on a thin, flexible polyethylene terephthalate (PET) substrate. MWCNT-ZnO nanofibers are synthesized via the electrospinning technique followed by a calcination process. This approach creates functional groups on the nanofiber surface that are used for the one step immobilization of HRP2 antibodies without further surface modification. The device exhibits a good sensitivity of 8.29 kΩ g mL and a wide detection range of 10 fg mL-10 ng mL, and it is specific towards the targeted HRP2 biomarker. To the best of our knowledge, this is the first report on a flexible chemiresistive biosensor explored for the detection of the malaria biomarker and can be extended in the future to several other biomarker detection systems towards smart point-of-care (POC) diagnostics.

We report fabrication of a fully integrated plastic based microfluidic biochip for biosensing application. The microfluidic channels were fabricated by tune transfer method and integrated with the prefunctionalized sensing platform. This approach to assembling microchannels into prefunctionalized sensing substrate facilitates controlled functionalization and prevents damages on the functionalized surface. The sensing platform comprised a three-electrode system, in which the sensing electrode was integrated with antibody immobilized carbon nanotubes-zinc oxide (C-ZnO) nanofibers. Electrospinning technique was used to synthesize C-ZnO nanofibers and the surface of the nanofibers was covalently conjugated with histidine rich protein II antibodies (AntiHRP II) toward detection of infectious malarial specific antigen, namely histidine-rich protein II (HRP II). The analytical performance of the fabricated biochip was evaluated by differential pulse voltammetry method. The device exhibited a high sensitivity of 1.19 mA/((g mL)/cm) over a wide detection range (10 fg/mL to 100 μg/mL) with a low detection limit of 7.5 fg/mL toward HRP II detection. This fully integrated biochip offers a promising cost-effective approach for detection of several other infectious disease biomarkers.

Abstract-In this paper, we report a low temperature, finepitch, bump-less, damascene compatible Cu-Cu thermocompression bonding, using an optimized ultra-thin passivation layer, Constantan, which is an alloy (CopperNickel) of 55% Cu and 45% Ni. Surface oxidation and its roughness are the major bottlenecks in achieving high quality, low temperature, and fine-pitch Cu-Cu bonding. In this endeavor, we have used Cu rich alloy (Constantan) for passivation of Cu surface prior to bonding. We have systematically optimized the constantan passivation layer thickness for high quality low temperature, low pressure, bump-less Cu-Cu bonding. Also, we have studied systematically the efficacy of Cu surface passivation with optimized ultra-thin constantan alloy passivation layer. After rigorous trial and optimization, we successfully identified 2 nm passivation layer thickness, at which very high quality Cu-Cu bonding could be accomplished at sub 200 ˚C with a nominal contact pressure of 0.4 MPa. Post-bonding, electrical and mechanical characterization were validated using four-probe IV measurement and bond strength measurement respectively. Furthermore, Cu-Cu bonding interface was analyzed using IR wafer bonder inspection tool. Very high bond strength of 163 MPa and defect free interface observed by WBI-IR clearly suggests, Cu-Cu fine-pitch bonding with optimized ultra-thin alloy of 2 nm thick constantan, is of very high quality and reliable. Moreover, this novel bonding approach with alloy based interconnect passivation technique is the prime contestant for future heterogeneous integration.

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