patches have been recommended by physicians for patients with heart abnormalities to correlate their activities with heart signals. [2] In order for long-duration on-skin monitoring, comfort to the wearer is an important design consideration for these patches. To enable intimate attachment to the body, the package modulus and form factor should approach that of the human skin. Besides enhancing comfort, good electrical contact for high fidelity signal acquisition that is immune to the motion of wearer and environment influences are necessary. [8] Despite significant advancement in wearable electronics, [1, major tradeoffs between form-factor, performance, and functionality remain. For ultrathin skin-like material systems fabricated by ink-printing or microcontact transfer printing, [9][10][11][12][13][14][15][20][21][22][25][26][27] the complexity and signal processing capabilities are typically limited by the weaker transistors or interconnects. Ink-printed components are also limited by lower integration density compared to rigid Silicon CMOS technologies, leading to lower functionality. The increased R-C parasitic with larger and weaker components limits the scalability toward highly-energy-efficiency under low-voltage operations. In contrast, rigid CMOS chips and printed circuit boards (PCBs) require integration with soft components to interface comfortably with the human body. The need for electrical performance with soft and robust mechanical form factor leads us to the codesign of composite materials and electronic circuits/system in a monolithic form of flexible hybrid electronics. [1,3,4,12,13,25,28] In this work, we report on a novel integration of a wearable and stretchable-hybrid SEP with monolithically integrated sensor electrodes and liquid-metal interconnects. The SEP integration involves the combination of a chip-on-board embedded in a moisture-resistant elastomer matrix with microfluidic interconnects, and soft low-resistance electrodes (Figure 1). A stretchable electrocardiogram (ECG) patch (SEP) that monolithically integrates ECG monitoring chip-on-board (COB) with polydimethylsiloxane (PDMS) and liquid-metal interconnects is presented. The 4.8 × 4.8 cm 2 SEPis conformal and robust to mechanical deformation. The use of a siliconon-insulator rigid complementary-metal-oxide-semiconductor chip allows sophisticated power management and signal processing. The chip's dense inputs/output pads are interfaced with coarser liquid-metal interconnects using a dual-sided COB design. A robust ECG signal response (≈100 mV p-p up to 1 kHz), subjected to mechanical deformation and moisture is demonstrated. The SEP allows up to 10% stretch, providing sufficient pliability to enable conformal contact to the human chest. Low profile soft carbon black-PDMS nanocomposite electrodes, robust to deformation, enable good skin contact and allow for low-noise signal acquisition that is comparable to larger commercial wet electrodes.

Structural and magnetic properties of triode-sputtered epitaxial γ ′ -Fe 4 N films deposited on SrTiO 3 (001) substrates Appl.Fe 3 O 4 has been widely studied because of its great potential in spintronics and other applications. As a magnetic electrode, it is highly desired if magnetic anisotropy can be controlled. Here, we report the results from our systematic study on the magnetic properties of magnetite (Fe 3 O 4 ) thin films epitaxially grown on various MgO substrates. Strikingly, we observed a prominent perpendicular magnetic anisotropy in Fe 3 O 4 film deposited on MgO (111) substrate. When measured in out-ofplane direction, the film (40 nm thick) exhibits a well-defined square hysteresis loop with coercivity (H c ) above 1 kOe, while much lower coercivity was obtained in the in-plane orientation. In sharp contrast, the films deposited onto MgO (100) and MgO (110) substrates show in-plane magnetic anisotropy. These films exhibit a typical soft magnet characteristic-H c lies within the range of 200-400 Oe. All the films showed a clear Verwey transition near 120 K-a characteristic of Fe 3 O 4 material. In addition, a series of magnetoresistance (MR) measurements is performed and the MR results are in good agreement with the magnetic observations. The role of the substrate orientation and film thickness dependency is also investigated. V C 2015 AIP Publishing LLC.

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Electronic and structural properties of ZnO films before and after H 2 annealing treatment are studied. The initial system is smooth amorphous ZnO films that are intentionally grown at room temperature. A dramatic change is found in the crystallinity and the surface transforms to a multiple-stacked nanoporous structure upon annealing as observed by scanning electron microscopy and X-ray diffraction. Photoluminescence spectroscopy shows the presence of a new mid-gap state below the first optical transition, and the annealing treatment transforms the ZnO system to more transparent film. Interestingly, it is found that the structural evolution changes the dielectric function measured by high-resolution, angle-dependent spectroscopic ellipsometry and this generates strong emission at %2.5 eV. These results show the importance of structural modification via H 2 annealing to control the optical properties and electronic structure of ZnO films.