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The electrosynthesis of PEDOT in an aqueous dispersion of rGO results in the formation of composite films having a fully open surface morphology.

We describe a hand-held sensing system using a transistor based multiplexed platform and a detector that couples the electrochemical information wirelessly to a smartphone. The custom disposable platform exploits the ion-sensitive FET (ISFET) technology. Via simple surface modifications the design allows a broad range of analytes to be tested with low cost. We compared our read-out device to a commercial potentiometer using K+ as an example species analyte. The developed sensing system has a slightly better limit of detection and is notably less susceptible to external noise which is commonly observed with potentiometers. The designed platform is fabricated using standard electronic processes with gold surface and we used commercial discrete transistors as the transducing element. It can be mass produced with high yield and low cost. To circumvent the drift that typically occurs with modified solid state electrodes we incorporated a transducing layer between the electric conductor (gold pad) and the ionically conducting ion-selective membrane. The polyaniline doped with dinonylnaphtalene sulfonic acid (PANI-DNNSA) was used as a transducing layer for the first time. The PANI-DNNSA layer significantly reduces the drift of the electrodes compared to a configuration without the transducing layer. The system is easy to use with a transistor based detection that can be modified for a vast variety of existing potentiometric tests.

Out of 463 million people currently with diabetes, 232 million remain undiagnosed. Diabetes is a threat to human health, which could be mitigated via continuous self-monitoring of glucose. In addition to blood, interstitial fluid is considered to be a representative sample for glucose monitoring, which makes it highly attractive for wearable on-body sensing. However, new technologies are needed for efficient and noninvasive sampling of interstitial fluid through the skin. In this report, we introduce the use of Lorentz force and magnetohydrodynamics to noninvasively extract dermal interstitial fluid. Using porcine skin as an ex-vivo model, we demonstrate that the extraction rate of magnetohydrodynamics is superior to that of reverse iontophoresis. This work seeks to provide a safe, effective, and noninvasive sampling method to unlock the potential of wearable sensors in needle-free continuous glucose monitoring devices that can benefit people living with diabetes.

We demonstrate an electrochemical sensor for detection of unlabeled single-stranded DNA using peptide nucleic acid (PNA) probes coupled to the field-effect transistor (FET) gate. The label-free detection relies on the intrinsic charge of the DNA backbone. Similar detection schemes have mainly concentrated on sensitivity improvement with an emphasis on new sensor structures. Our approach focuses on using an extended-gate that separates the FET and the sensing electrode yielding a simple and mass fabricable device. We used PNA probes for efficient hybridization in low salt conditions that is required to avoid the counter ion screening. As a result, significant part of the target DNA lies within the screening length of the sensor. With this, we achieved a wash-free detection where  typical gate potential shifts are more than 70 mV with 1 µM target DNA. We routinely obtained a real-time, label- and wash-free specific detection of target DNA in nanomolar concentration with low-cost electronics and the responses were achieved within minutes after introducing targets to the solution. Furthermore, the results suggest that the sensor performance is limited by specificity rather than by sensitivity and using low-cost electronics does not limit the sensor performance in the presented sensor configuration.

Electrically conductive composite nanofibers were fabricated using poly­(3,4-ethylenedioxythiophene) doped with poly­(styrenesulfonate) (PEDOT–PSS) and cellulose nanofibrils (CNFs) via the electrospinning technique. Poly­(ethylene oxide) (PEO) was used to assist the electrospinning process, and poly­(ethylene glycol) diglycidyl ether was used to induce chemical cross-linking, enabling stability of the formed fibrous mats in water. The experimental parameters regarding the electrospinning polymer dispersion and electrospinning process were carefully studied to achieve a reproducible method to obtain bead-free nanofibrous mats with high stability after water contact, with an electrical conductivity of 13 ± 5 S m–1, thus making them suitable for bioelectrochemical applications. The morphology of the electrospun nanofibers was characterized by scanning electron microscopy, and the C/S ratio was determined with energy dispersive X-ray analysis. Cyclic voltammetric studies showed that the PEDOT–PSS/CNF/PEO composite fibers exhibited high electroactivity and high stability in water for at least two months. By infrared spectroscopy, the slightly modified fiber morphology after water contact was demonstrated to be due to dissolution of some part of the PEO in the fiber structure. The biocompatibility of the PEDOT–PSS/CNF/PEO composite fibers when used as an electroconductive substrate to immobilize microalgae and cyanobacteria in a photosynthetic bioelectrochemical cell was also demonstrated.

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