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Herein, Microfluidic Paper-based Analytical Devices (μPAD) strips, also called microstrips, have been fabricated using a fused-deposition modeling (FDM) based 3D printer. A polycaprolactone (PCL) filament on a chromatography paper was harnessed to create hydrophobic boundaries of a microchannel. A pair of screen-printed electrodes, with known separation, were integrated on the microchannel to measure the time taken for fluid automatically. A mini electronic sub-system, amenable to connect with an android smartphone, consists of an easily programmable microcontroller, Bluetooth module and voltage booster circuit. The pluggable-and-playable disposable microstrip was utilized to measure the viscosity of various biological samples with an accuracy of92% with respect to a benchtop viscometer. In particular, the protein denaturation of Bovine Serum Albumin (BSA) and Lysozyme, and viscosity variation of human saliva have been observed. With a competency to measure the viscosity between 0.5 cP to 10 cP, platform cost ofUS$ 8 and a cost-per-test of less than US$ 0.02, the present device has a strong potential to be employed as a personalized gadget for various viscosity dependent measurements.

Neuron-specific enolase (NSE) had clinical significance on diagnosis, staging, monitoring effect and judging prognosis of small cell lung cancer. Thus, there had a growing demand for the on-site testing of NSE. Here, a wireless point-of-care testing (POCT) system with electrochemical measurement for NSE detection was developed and verified. The wireless POCT system consisted of microfluidic paper-based analytical devices (μPADs), electrochemical detector and Android's smartphone. Differential pulse voltammetry (DPV) measurement was adopted by means of electrochemical detector which including a potentiostat and current-to-voltage converter. μPADs were modified with nanocomposites synthesized by Amino functional graphene, thionine and gold nanoparticles (NH2-G/Thi/AuNPs) as immunosensors for NSE detection. Combined with μPADs, the performance of the wireless POCT system was evaluated. The peak currents showed good linear relationship of the logarithm of NSE concentration ranging from 1 to 500ngmL-1 with the limit of detection (LOD) of 10pgmL-1. The detection results were automatically stored in EEPROM memory and could be displayed on Android's smartphone through Bluetooth in real time. The detection results were comparable to those measured by a commercial electrochemical workstation. The wireless POCT system had the potential for on-site testing of other tumor markers.