A method for sintering nanoparticles by applying voltage is presented. This electrical sintering method is demonstrated using silver nanoparticle structures ink-jet-printed onto temperature-sensitive photopaper. The conductivity of the printed nanoparticle layer increases by more than five orders of magnitude during the sintering process, with the final conductivity reaching 3.7 × 10(7) S m(-1) at best. Due to a strong positive feedback induced by the voltage boundary condition, the process is very rapid-the major transition occurs within 2 µs. The best obtained conductivity is two orders of magnitude better than for the equivalent structures oven-sintered at the maximum tolerable temperature of the substrate. Additional key advantages of the method include the feasibility for patterning, systematic control of the final conductivity and in situ process monitoring. The method offers a generic tool for electrical functionalization of nanoparticle structures.

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Organic and printed electronics integration has the potential to revolutionise many technologies, including biomedical diagnostics. This work demonstrates the successful integration of multiple printed electronic functionalities into a single device capable of the measurement of hydrogen peroxide, and total cholesterol. The single-use device employed printed electrochemical sensors for hydrogen peroxide electroreduction integrated with printed electrochromic display and battery. The system was driven by a conventional electronic circuit designed to illustrate the complete integration of silicon ICs via pick and place, or using organic electronic circuits. The device was capable of measuring 8 µL samples of both hydrogen peroxide (0 to 5 mM, 2.72×10 -6 A.mM -1 ) and total cholesterol in serum from 0 to 9 mM (1.34×10 -8 A.mM -1 , r 2 =0.99, RSD <10%, n=3) which was output on a semi-quantitative linear bar display. The device could operate for 10 minutes via a printed battery and display the result for many hours or days. A mobile phone 'app' was also capable of reading the test result and transmitting this to a remote health care provider. Such a technology could allow improved management of conditions such as hypercholesterolemia.Printed electronics is being hailed as a technological revolution, equal in importance to the emergence of microelectronics over 50 years ago. The combined qualities of print-processable organic, inorganic and hybrid (semi)conductive materials which can be deposited onto flexible polymeric substrates using a range of additive, high throughput printing methodologies offer the prospect of low cost mass production capability and the potential for unprecedented levels of technological integration.

The fabrication process and the operation characteristics of a fully roll-to-roll printed resistive write-once-read-many memory on a flexible substrate are presented. The low-voltage (<10 V) write operation of the memories from a high resistivity '0' state to a low resistivity '1' state is based on the rapid electrical sintering of bits containing silver nanoparticles. The bit ink is formulated by mixing two commercially available silver nanoparticle inks in order to tune the initial square resistance of the bits and to create a self-organized network of percolating paths. The electrical performance of the memories, including read and write characteristics, is described and the long-term stability of the less stable '0' state is studied in different environmental conditions. The memories can find use in low-cost mass printing applications.

A method for rapid electrical sintering (RES) of nanoparticle structures on temperature-sensitive substrates is presented. For an inkjetted silver nanoparticle conductor, a conductance increase of five orders of magnitude is demonstrated to occur in a timescale that typically varies between a few and one hundred milliseconds depending on process parameters. Furthermore, most of the conductance change takes only a few microseconds. The achievable final conductivities are within a factor of two from the bulk silver conductivity, as calculated using the external geometric dimensions of the structure ignoring porosity. The method is also applicable to other inorganic conductors such as indium-tin-oxide (ITO). More generally, the method offers a versatile tool in nanotechnology for electrical functionalization of nanoparticle structures. The method is also potentially suited for mass production.

Wearable device technologies for sweat analytics present a versatile application for monitoring physiological state, which can circumvent the requirement for inconvenient and invasive blood sampling. This paper reports a miniature electrochemical sensor platform for non-invasive and wireless real-time monitoring of lactate in exercise-induced human sweat. The conformal and low profile sensor platform is composed of (a) a flexible electronic readout tag with wireless charging and data acquisition, and (b) a disposable enzymatic amperometric biosensor patch with electrodes fabricated using high throughput roll-to-roll processing. Data were generated in real time from sensor response to lactate in exercise-induced sweat from multiple body regions simultaneously. The biosensor demonstrates current response proportional to lactate at physiological concentration range between 5 and 30 mM. This developed platform can be adapted for sensing of other sweat constituents including ions or metabolites, and therefore advances wearable technology for personalized physiological monitoring