On-Demand Printing of Wearable Thermotherapy Pad.

Thermotherapy is an effective method for pain relief, recovery from injury, and general healthcare. The ordinary heat pad used for thermotherapy at home is not usually tailored to the individual but supplied in a few different pre-fixed sizes and shapes for mass marketing. A customized wearable heat pad often requires expert support. Herein, an instant, custom-fit, and on-demand heat pad for thermotherapy is demonstrated. The heater is directly printed using silver nanoparticle ink on an off-the-shelf medical grade tape by inkjet technology. By coating the tape with silica nanoparticles as ink-absorbing layer and chloride ions as chemical sintering agent, stable heater patterns are printed without the need for subsequent high temperature sintering process. A 3D scanner is used to acquire body information, and a customized heater is produced using the information. The printed heat pad is attached to the shoulder and the effect of thermotherapy is verified objectively through electroencephalography and subjectively through survey. This printed heat pad produced by simple and low-cost fabrication provides wearable medical devices for personal thermotherapy.

Joule-Heated and Suspended Silicon Nanowire Based Sensor for Low-Power and Stable Hydrogen Detection.

We developed self-heated, suspended, and palladium-decorated silicon nanowires (Pd-SiNWs) for high-performance hydrogen (H2) gas sensing with low power consumption and high stability against diverse environmental noises. To prepare the Pd-SiNWs, SiNWs were fabricated by conventional complementary metal-oxide-semiconductor (CMOS) processes, and Pd nanoparticles were coated on the SiNWs by a physical vapor deposition method. Suspended Pd-SiNWs were simply obtained by etching buried oxide layer and Pd deposition. Joule heating of Pd-SiNW (<1 mW) enables the detection of H2 gas with a faster response and without the reduction of sensitivity unlike other Pd-based H2 gas sensors. We proposed a H2 sensing model using oxygen adsorption on the Pd nanoparticle-coated silicon oxide surface to understand the H2 response of Joule-heated Pd-SiNWs. A suspended Pd-SiNW showed a similar transient sensing response with around four times lower Joule heating power (147 µW) than the substrate-bound Pd-SiNW (613 µW). The effect of interfering gas on the Pd-SiNW was investigated, and it was found that the Joule heating of Pd-SiNW helps to maintain the H2 sensing performance in humid or carbon monoxide environments.

Porphyrin-silicon hybrid field-effect transistor with individually addressable top-gate structure.

A conductance-controllable hybrid device that utilizes the photoinduced charge transfer behavior of a porphyrin in a field-effect transistor (FET) with a nanogap is proposed and analyzed. A conventional metal-oxide-semiconductor (MOS) structure is modified to form a nanogap in which the porphyrin can be embedded. The conductance of an inversion channel is controlled by the negatively charged, optically activated porphyrin molecules. The proposed nanogap-formed MOSFET structure solves the conventional dilemma that a top-gate cannot be used for an organic-inorganic hybrid device because the top-gate blocks an entire area of a channel where organic material should be immobilized. The top-gate structure has much practicality compared with the back-gate structure because each device can be controlled individually. Furthermore, the device is highly compatible with the chip-based integrated system because the fabrication process follows the standard complementary metal-oxide-semiconductor (CMOS) technology. The charge transfer mechanisms between silicon and porphyrin are analyzed using devices with different doping polarities and geometrical parameters. The results show that the influence of the negative charge of the porphyrin in the device is reversed when opposite doping polarities are used. The device characteristics can be comprehensively evaluated using the energy band diagram analysis and simulation. The possible application of the proposed device for nonvolatile memory is demonstrated using the optical charging and electrical discharging behavior of the porphyrins.

A polydimethylsiloxane (PDMS) sponge for the selective absorption of oil from water.

We present a sugar-templated polydimethylsiloxane (PDMS) sponge for the selective absorption of oil from water. The process for fabricating the PDMS sponge does not require any intricate synthesis processes or equipment and it is not environmentally hazardous, thus promoting potential in environmental applications. The proposed PDMS sponge can be elastically deformed into any shape, and it can be compressed repeatedly in air or liquids without collapsing. Therefore, absorbed oils and organic solvents can be readily removed and reused by simply squeezing the PDMS sponge, enabling excellent recyclability. Furthermore, through appropriately combining various sugar particles, the absorption capacity of the PDMS sponge is favorably optimized.