Low-power organic transistors: For internet-of-things applications, transistors that deliver high signal amplification (high gain) at low power will help conserve power and extend battery life. Jiang et al. used inkjet printing to fabricate an organic transistor in which silver metal contacts form a low Schottky barrier (less than 0.2 electron volt) with an organic semiconductor. The transistor delivered gain near the theoretical limit at a power below 1 nanowatt and detected electrophysiological signals from the skin with a wearable device. Science , this issue p. 719

In this paper, all-solution-processed low-voltage organic thin-film transistor inverters on polyethylene naphthalate plastic substrate were achieved in the bottom-gate bottom-contact device configuration. In the devices, 6,13-bis(triisopropylsilylethynyl)-pentacene blended with polystyrene was used as the channel layer, and ultraviolet cross-linked polyvinyl alcohol was used as the gate dielectric layer. With optimized inkjet jetting process parameters and a proper polymer dielectric substrate surface, fine silver electrodes were formed as the source, drain, and gate electrodes. The maximum processing temperature was 150°C. The devices show promising performance with a mobility of 0.8 cm²/(V·s), a subthreshold swing of 100 mV/decade and an ON/OFF ratio of about 10⁴. The fabricated diode-load inverter has a high dc voltage gain up to 67.3 at a supply voltage of 3 V.

A conductometric sensor for potassium ions in solution is presented. Interdigitated, planar gold electrodes were coated with a potassium-selective polymer membrane composed of a poly(vinyl chloride) matrix with about 65 wt% of plasticiser and 2-5 wt% of a potassium-selective ionophore. The impedance of the membrane was measured, using the electrodes as a transducer, and related to the concentration of potassium in a sample solution in contact with the membrane. Sensitivity was optimised by varying the sensor components, and selectivity for potassium over sodium was also shown. The resulting devices are compact, miniature, robust sensors which, by means of impedance measurements, eliminate the need for a reference electrode. The sensor was tested for potassium concentration changes of 2 mM across the clinically relevant range of 2.7-18.7 mM.

We present an active-matrix digital microfluidics platform for bio-sample handling, which demonstrates extension of the ubiquitous and highly-scalable flat-panel technology from displays to bio-applications, and leverage the well-established a-Si thin-film transistor (TFT) manufacturing facilities and excess capacity. The fabricated chip contains 32 × 32 pixels in an active area of 10 cm ² , which can be individually or simultaneously addressed. Generation and manipulation of liquid droplets at single pixel level with the volume coefficient of variation around 1% is demonstrated. Such performance is substantial improvement over current state-of-the-art (9-pixel resolution and 4% variation). This work opens new possibilities for on-chip in vitro diagnostics in point-of-care testing.