Graphene-based ion sensitive field effect transistors (GISFETs) with high sensitivity and selectivity for K + ion detection have been demonstrated utilizing valinomycin based ion selective membrane. The performance of the GISFET for K + ion detection was studied in various media over a concentration range of 1 µM-2 mM. The sensitivity of the sensor was found to be > 60 mV/decade, which is comparable to the best Si-based commercial ISFETs, with negligible interference found from Na + and Ca 2+ ions in high concentration. The sensor performance did not change significantly in Tris-HCl solution or with repeated testing over a period of two months highlighting its reliability and effectiveness for physiological monitoring. The performance of the sensor also remained unchanged when fabricated on biocompatible polyethylene terephthalate (PET) substrate, showing significant potential for developing flexible bio-implantable graphenebased ISFETs.

We report on the fabrication and characterization of a highly sensitive pressure sensor using a Au film patterned on a polydimethylsiloxane (PDMS) membrane. The strain-induced change in the film resistance was utilized to perform the quantitative measurement of absolute pressure. The highest sensitivity obtained for a 200 µm thick PDMS film sensor was 0.23/KPa with a range of 50 mm Hg, which is the best result reported so far, over that range, for any pressure sensor on a flexible membrane. The noise-limited pressure resolution was found to be 0.9 Pa (0.007 mm Hg), and a response time of ∼200 ms, are the best reported results for these sensors. The ultrahigh sensitivity is attributed to the strain-induced formation of microcracks, the effect of which on the resistance change was found to be highly reversible within a certain pressure range. A physical model correlating the sensitivity with the sensor parameters and crack geometry has been proposed.

Benefitting from the coalescence-induced droplet jumping on superhydrophobic surfaces, the condensing droplets on heat exchangers can be removed efficiently, significantly improving the condensation heat-transfer performance of various thermal applications. However, the enhancement of droplet jumping height and self-removal to further improve the condensation heat-transfer performance of the thermal applications remains a challenge due to considerable interfacial adhesion caused by the inevitable partial-Wenzel state condensing droplets on superhydrophobic surfaces. In this study, a biphilic nanostructure is developed to effectively improve the droplet jumping height by decreasing the interfacial adhesion with the formation of Cassie-like droplets. Under atmospheric conditions, ∼28% improvement of droplet jumping height is achieved on a biphilic surface compared to that of a superhydrophobic surface. Additionally, the droplet contact electrification on biphilic surfaces discovered in this work allows the droplets to jump ∼137% higher compared with that under atmospheric conditions. Furthermore, the droplet jumping and electrification mechanisms on the biphilic surface are revealed by building a theoretical model that can predict the experimental results well. Apart from being a milestone for the droplet jumping physics development on biphilic nanostructures, this work also provides new insights into the micro-droplet discipline.

Cell-based screening assays are now widely used for identifying compounds that serve as ion channel modulators. However, instrumentation for the automated, real-time analysis of ion flux from clonal and primary cells is lacking. This study describes the initial development of an ion-sensitive field effect transistor (ISFET)-based screening assay for the acquisition of K+ efflux data from cells cultured in multi-well plates. Silicon-based K+-sensitive ISFETs were tested for their electrical response to varying concentrations of KCl and found to display a linear response relationship to KCl in the range of 10 µM to 1 mM. The ISFETs, along with reference electrodes, were inserted into fast-flow chambers containing either human colonic T84 epithelial cells or U251-MG glioma cells. Application of the Ca2+ ionophore A23187 (1 µM), to activate Ca2+-activated non-selective cation (NSC) channels (T84 cells) and large conductance Ca2+-activated K+ (BK) channels (U251 cells), resulted in time-dependent increases in the extracellular K+ concentration ([K+]o) as measured with the ISFETs. Treatment of the cells with blockers of either the NSC or BK channels, caused a strong inhibition of the A23187-induced increase in [K+]o. These results were consistent with ion current measurements obtained using the whole-cell arrangement of the patch clamp procedure. In addition, K+ efflux data could be acquired in parallel from multiple cell chambers using the ISFET sensors. Given the non-invasive properties of the probes, the ISFET-based assay should be adaptable for screening ion channels in various cell types.

No abstract

No abstract

Herein, a novel coalescence–jumping phase transition thermal diode using hybrid nanofluids, an emerging thermal fluid with proven supreme thermal properties, is first proposed and investigated. The thermal rectification enhancement mechanism is investigated by the evaporation performances of a working fluid‐filled superhydrophilic porous tank. Furthermore, a developed mathematical model is well‐matched with the experimental results in terms of the heat transfer and thermal rectification performance of the thermal diodes using hybrid nanofluids. It is worth noting that increasing the volume fraction of the hybrid nanofluids does not necessarily improve the thermal rectification performance of the thermal diodes due to the aggregative nanoparticle deposition on the evaporation surface. In addition, there is a need to balance the thermal conductivity (higher copper proportion) and stability (higher alumina proportion) of the hybrid nanofluids used in the thermal diodes for long‐term operation. The experimental results show that the thermal rectification performance of the thermal diode using Cu‐Al2O3 hybrid nanofluid can be increased to 637.4, showing a nearly 300% improvement compared with the thermal diode using water. Overall, the remarkable results in this study promote the applications and studies of thermal diodes using hybrid nanofluids in various engineering systems for thermal management.

No abstract