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Impedance-based protein detection sensors for point-of-care diagnostics require quantitative specificity, as well as rapid or real-time operation. Furthermore, microfabrication of these sensors can lead to the formation of factors suitable for in vivo operation. Herein, we present microfabricated needle-shaped microwell impedance sensors for rapid-sample-to-answer, label-free detection of cytokines, and other biomarkers. The microneedle form factor allows sensors to be utilized in transcutaneous or transvascular sensing applications. In vitro, experimental characterization confirmed sensor specificity and sensitivity to multiple proteins of interest. Mechanical characterization demonstrated sufficient microneedle robustness for transcutaneous insertion, as well as preserved sensor function postinsertion. We further utilized these sensors to carry out real-time in vivo quantification of human interleukin 8 (hIL8) concentration levels in the blood of transgenic mice that endogenously express hIL8. To assess sensor functionality, hIL8 concentration levels in serum samples from the same mice were quantified by ELISA. Excellent agreement between real-time in vivo sensor readings in blood and subsequent ELISA serum assays was observed over multiple transgenic mice expressing hIL8 concentrations from 62 pg/mL to 539 ng/mL.

Bottom-up-fabricated crossbars promise superior circuit density and 3-D integrability compared with the traditional CMOS-based implementations. However, their inherent stochasticity presents difficulties in building complex circuits from components that demand precise patterning and high registration accuracies. With fewer terminals than active devices, passive components offer higher device densities and registration tolerances, making them amenable to bottom-up synthesized nanocrossbars. Motivated by this preference for passivity, we explore, in this article, neuromorphic classifiers based on passive neurons and passive synapses. We demonstrate via SPICE simulations how a shallow network of the diode-resistor-based passive rectifier neurons and resistive voltage summers, despite its inherent inability to buffer, amplify, and negate signals, can recognize MNIST digits with 95.4% accuracy. We introduce weight-to-conductance mappings that enable negative weights to be implemented in hardware without excessive memory overheads. The influences of soft and hard defects on the classification performance are evaluated, and the methods to boost fault-tolerance are proposed. The first-order evaluation of the area, speed, and power consumption of the passive multilayer perceptron classifiers is undertaken, and the results are compared with a benchmark study in neuromorphic hardware.

This article presents an implantable low-power wireless integrated system for tactile sensing applications. The reported application-specified integrated circuit (ASIC) uses a low-loss magnetic human body communication channel for both wireless power and data transfer. The chip is hybrid-integrated with an in-house fabricated MEMS capacitive force sensor to form an implantable artificial mechanoreceptor. An on-chip correlated double sampling capacitance to time converter (CTC) consumes 750 nW from a 1.2-V on-chip regulated supply, achieving a 2.0-fF resolution for an input capacitance of 14 pF and a FoM of 49 fJ/c-s while occupying an area of only 0.04 mm2. The CTC has a time-multiplexed mode to interface with four input capacitors. Wireless power management feedback is used to ensure robust operation in the presence of hand gesture changes and process–voltage–temperature variations. The on-chip data transmitter can operate in ON–OFF keying (OOK) or frequency-shift keying modulation formats, where it consumes only $7.8~\mu \text{W}$ in the OOK mode. The 1.62-mm2 chip is fabricated in a standard 180-nm CMOS process and consumes $110.3~\mu \text{W}$ .

Portable and autonomous microdevices often require on-board power sources such as thin film microbatteries. Air microbatteries are an attractive power source for such devices due to their high specific energy density. One particularly appropriate air chemistry is based on Zn, due to the multiple microfabrication approaches compatible with Zn anode formation. We demonstrate fabrication approaches to realize Zn film anodes in different thickness regimes using microelectromechanical systems based fabrication techniques—evaporation, electrodeposition, and laser micromachining; and evaluate their relative performance as power sources in a primary battery configuration. These fabrication techniques enable films in thickness regimes ranging from the micron scale to hundreds of microns. The fabricated films have been characterized using scanning electron microscopy and energy dispersive x-ray spectroscopy, and were found to be dense and reasonably free from impurities. The electrochemical and discharge properties of the fabricated films were studied in an air battery configuration comprising a Zn anode-alkaline hydrogel electrolyte-metal catalyst stack, in which the anode had a surface area of 0.78 cm2. Evaporated Zn anodes (1–10 µms) yielded Zn utilizations of 96.5% and 82% at 10 and 1 mA discharge rates, respectively. The specific capacity of the evaporated Zn anodes was 791 mAh g−1 when discharged at 10 mA, close to the Zn theoretical specific capacity of 820 mAh g−1. Electrodeposited Zn anodes (10–100 µms) yielded utilizations of 90.2% and 75.6% at 10 and 1 mA discharge rates, respectively. Laser micromachined Zn anodes (250 µms) yielded Zn utilization of 90% when discharged at 10 mA. These fabrication techniques offer the potential to realize high energy density Zn anodes of different thickness ranges for thin film microbatteries, which can be tailored to microdevice-based applications of interest.

MEMS-enabled multilayer composites, in which microfabrication is used to create micron-scale thickness layers within the volume of meso-scale thickness structures, can be exploited to create materials with highly anisotropic electromagnetic properties. Such materials have utility in both sensing and energy applications, including electrostatic and magnetic energy storage and conversion. A fabrication challenge in realizing these classes of materials lies in the size-scale disparity between the thickness of an individual layer and the desired thickness of the final anisotropic material. We demonstrate a fully additive sequential electrochemical deposition approach for such structures, which enables scalable composite volume while maintaining micron-scale individual layer thicknesses. Alternating metal and polymer layers, which exhibit very different electrical conductivities, are continuously electrodeposited in batch-scale. Individual layer thicknesses are controlled by deposition currents and times, while lateral extents are defined by lithographically defined molds. The fabrication process is illustrated using electrodeposited NiFe alloys and polypyrrole, and the anisotropy of electrical conductivity is assessed for potential use of these structures as magnetic cores for high frequency switching converters. Due to the relatively resistive polypyrrole layers, electrical anisotropy of lateral to vertical conductivity exceeding 106 was achieved. This approach offers a solution-based, microfabrication compatible, and manufacturable route to functional composite materials that exhibit high electrical anisotropies. [2020-0256]

We report a biodegradable, self-powered sensor for measurement of dissolved oxygen in the body. The principle of operation is the competition of an oxygen reduction reaction against the ordinarily dominant hydrogen reduction reaction at the cathode of a corroding electrochemical couple. Because the relative contribution of the oxygen reduction reaction to the overall electrochemical reaction depends on the local oxygen concentration, the output voltage of the couple is also dependent on local oxygen concentration. The sensor is formed by embedding the biodegradable metals magnesium and molybdenum within a biodegradable poly(lactic acid) substrate using lamination; external physiological solution is utilized as the electrolyte. The output voltage of the sensor (i.e., the voltage generated across the corroding couple) was measured as a function of oxygen concentration over typical physiological oxygen concentration ranges of 0–60% that of atmospheric oxygen. A linear output voltage response of approximately 6 mV per percentage point oxygen concentration was observed; oxygen concentrations above this range resulted in sensor saturation. [2020-0192]

1. Small‐bodied freshwater fishes are commonly overlooked in threatened species management despite being highly imperilled. Before this study, the newly described little pygmy perch (Nannoperca pygmaea ) was known from only 0.06 km2 of habitat in a single catchment in south‐western Australia and a lack of knowledge prevented an understanding of its conservation status and priority actions. 2. The present study determined the distribution, biology, and movement patterns of N. pygmaea and compared these with other small, sympatric percihthyids to assess its conservation status and likely resilience to threatening processes. 3. The current ‘extent of occurrence' of N. pygmaea was determined to be 3,420 km2 and the ‘area of occupancy' was 10 km2. Nannoperca pygmaea inhabited permanent refuge pools in the main stem of an ephemeral, secondarily salinized catchment where salinities remained

We present a novel method for label-free detection of tumor necrosis factor alpha (TNF-α) in serum after immobilization by electric field. Detection of proteins in blood using label-free impedance-based techniques is difficult due to high salt concentration of the matrix, which results in charge screening. The nanowell array sensor provides enhanced electrochemical sensitivity by electric field focusing in the nanoscale volume wells. Here, an on-chip multiwell plate sensing platform was fabricated and tested. The sensor performance through testing in mouse serum at protein concentrations between 10 and 500 ng/l has been demonstrated. This detection modality is advantageous to many label-free electronic sensors in that signal power scales will increase in salt concentration, thus improving the sensitivity of the platform.

We study the ionization and excitation structure of the interstellar medium in the late-stage gas-rich galaxy merger NGC 6240 using a suite of emission line maps at $\sim$25 pc resolution from the Hubble Space Telescope, Keck NIRC2 with Adaptive Optics, and ALMA. NGC 6240 hosts a superwind driven by intense star formation and/or one or both of two active nuclei; the outflows produce bubbles and filaments seen in shock tracers from warm molecular gas (H$_2$ 2.12$\mu$m) to optical ionized gas ([O III], [N II], [S II], [O I]) and hot plasma (Fe XXV). In the most distinct bubble, we see a clear shock front traced by high [O III]/H$\beta$ and [O III]/[O I]. Cool molecular gas (CO(2-1)) is only present near the base of the bubble, towards the nuclei launching the outflow. We interpret the lack of molecular gas outside the bubble to mean that the shock front is not responsible for dissociating molecular gas, and conclude that the molecular clouds are partly shielded and either entrained briefly in the outflow, or left undisturbed while the hot wind flows around them. Elsewhere in the galaxy, shock-excited H$_2$ extends at least $\sim$4 kpc from the nuclei, tracing molecular gas even warmer than that between the nuclei, where the two galaxies' interstellar media are colliding. A ridgeline of high [O III]/H$\beta$ emission along the eastern arm aligns with the south nucleus' stellar disk minor axis; optical integral field spectroscopy from WiFeS suggests this highly ionized gas is centered at systemic velocity and likely photoionized by direct line-of-sight to the south AGN., Comment: 27 pages, 18 figures; accepted for publication in ApJ

Single-step label-free nanowell array immunoassay accurately detects serum stress hormones within minutes at small volumes., A non-faradaic label-free cortisol sensing platform is presented using a nanowell array design, in which the two probe electrodes are integrated within the nanowell structure. Rapid and low volume (≤5 μl) sensing was realized through functionalizing nanoscale volume wells with antibodies and monitoring the real-time binding events. A 28-well plate biochip was built on a glass substrate by sequential deposition, patterning, and etching steps to create a stack nanowell array sensor with an electrode gap of 40 nm. Sensor response for cortisol concentrations between 1 and 15 μg/dl in buffer solution was recorded, and a limit of detection of 0.5 μg/dl was achieved. Last, 65 human serum samples were collected to compare the response from human serum samples with results from the standard enzyme-linked immunosorbent assay (ELISA). These results confirm that nanowell array sensors could be a promising platform for point-of-care testing, where real-time, laboratory-quality diagnostic results are essential.

Monitoring cytokine profiles plays a crucial role in predictive medicine and early disease diagnosis, as well as enables basic research in many biological fields. Although single cytokine measurement can be very useful, simultaneous assessment of multiple biomolecular signatures can more fully illuminate complex biological function. To this end, multiplexing technologies for simultaneous assessment of multiple cytokines on a single measurement device have recently attracted significant interest. Despite the promise of these techniques, many still require specialized instrumentation or do not function in real-time, impeding their clinical adoption as point-of-care systems. Microfabrication can be exploited to create impedance-based cytokine sensors that can supply realtime assessment information; further, microfabrication can lead to device form factors suitable for in vivo operation. We present microfabricated needle-shaped microwell impedance sensors for rapid, label-free multiplexing detection of multiple cytokines. The sensor utilizes a microwell array configuration in which multiple microwell sensors are distributed along the needle shank. Multiplexed detection of multiple cytokines in vitro using these devices is demonstrated.

We present a vacuum packaging process based on standard fused silica wafer bonding combined with laser-assisted simultaneous localized fusion bonding and dicing technology. Direct bonding of fused silica wafer stacks results in an optically transparent package without introducing intermediate bonding layers. The temperature inside the package is maintained lower than 400 °C during the fabrication process to preserve CMOS compatibility. To characterize the vacuum level inside the package, white light interferometery is introduced to observe the surface topography of the package. Simulation and experimental results indicate that the vacuum level inside the package is at or below 1 Torr. Such fused silica vacuum and hermetic packages have many favorable features such as vacuum for encapsulating resonating devices, optical transparency for packaging MOEMS, biocompatibility and hermeticity for implantation applications, and transparency at radio frequencies for encapsulating electronics for wireless power and signal transmission.

Miniaturization of modern devices, including the advent of highly distributed Internet of Things nodes, has created a need for miniaturization in energy systems. Air batteries can be an attractive power source for such small-scale devices. This paper investigates fabrication of thin zinc anodes for zinc-air batteries using a thermal evaporation technique. Zinc anodes produced by thermal evaporation are found to be of high purity, approximately 96% dense, and smooth (roughness less than 0.1 micron). Anodes up to 8 microns in thickness are demonstrated. The structural characterization of the evaporated zinc films was performed by profilometry and scanning electron microscopy. The purity of the evaporated film was determined by the energy dispersive X-ray spectroscopy. Thin zinc anodes fabricated by evaporation exhibited utilization of 96.5% at 10 mA (5C rate) discharge. Specific capacity was 791mAh/g, approaching the theoretical limit of zinc-air batteries (820mAh/g). The anodes produced by evaporation offer the potential to fabricate high energy density thin film microbatteries.

A laminated magnetic core is comprised of alternating metallic magnetic layers and electrically insulating interlamination insulation layers, due to which eddy current losses in the core are suppressed. In practice, the nonzero conductivity of the interlamination insulation can lead to additional eddy current losses due to the electrical currents that travel across the layers. We present quantitative models which enable the determination of the necessary insulation quality of the interlamination insulation layers for various applications. For a given operating frequency range and given geometries/material properties of the magnetic material, the maximum tolerable conductivity of the interlamination material is calculated; this maximum is defined in such a way that the total eddy current losses, including the interlayer-induced losses, do not exceed the intrinsic material hysteresis losses. Understanding these maximum tolerable losses may open new design spaces for magnetic components; for example, allowing the use of interlamination insulation materials with finite conductivities may lead to a manufacturable, yet effective lamination approach for dc/dc converters based on integrated magnetics that can operate at RF switching frequencies (>3 MHz).

Hermetic packages compatible with complementary metal–oxide–semiconductor (CMOS) processes and capable of transmitting RF and optical energy are in high demand. A hermetic packaging process based on the localized fusion bonding of patterned and stacked fused silica wafers to encapsulate a CMOS chip has been successfully demonstrated. The process also allows for feedthroughs to be fabricated within the package for wired interconnection to encapsulated devices. A carbon dioxide laser is applied to achieve localized fusion bonding of the fused silica stack. Exploiting vector motion of the laser, simultaneous bonding and dicing is achieved within 2 s. The low thermal conductivity of fused silica thermally isolates the CMOS chip from the bond area. The heat diffusion during the process is examined both experimentally and using finite element analysis. The temperature falls to CMOS compatibility levels (under 400°C) within a distance of 660 $\mu \text{m}$ from the bond line. The viability of the packaging process and the hermeticity of the package are simultaneously evaluated by encapsulating a commercial MEMS humidity sensor within the package and monitoring the internal package humidity as a function of time. The packaged sensor was placed in an external relative humidity environment of 85% at 24°C and the relative humidity change inside the package was measured over a time span of 300 days. A water vapor leakage rate less than $4.6\times 10^{-14}$ atm $\cdot $ cm3/s was observed. These preliminary results suggest that the hermeticity of the package can meet the criterion of implantation in human body for more than 70 years for a package with an inner volume of 0.0012 cm3. [2018-0280]

A freestanding, miniaturized electrochemical oxygen sensor for biomedical implantation has been microfabricated and characterized. The sensor is fabricated on a flexible and biocompatible polyimide substrate using lithographic techniques and singulated with an excimer laser. The sensor consists of a round-shaped planar sensing portion (diameter: 2.4 mm and thickness: $180~\mu \text{m}$ ) and metal lines and contact pads for connection with external analytical tools. The sensing portion is comprised of three electrodes (working, counter, and reference electrodes), an electrolyte reservoir filled with liquid electrolyte, and a semipermeable membrane for oxygen introduction. The electrodes are patterned using a single layer of gold without the adhesion layer to eliminate any multilayer metallic structure in the sensing region. Both polydimethylsiloxane and fluorinated ethylene propylene semipermeable membranes are characterized. The fabricated sensor demonstrated an oxygen response of −14 nA/atm.% and good linearity (correlation coefficient exceeding 0.99). This device can potentially be incorporated into physiological applications, including monitoring oxygen tension in biomedical-related applications over semi-chronic time periods. [2019-0004]

This paper presents the development and characterization of biodegradable electrical interconnects for transient implantable medical devices. The interconnects comprised micropatterned biodegradable conductive polymer composites, which were developed using iron (Fe) microparticles as the conductive filler and polycaprolactone (PCL) as the insulating matrix. The electrical properties of the composites were investigated under various degradation conditions. Electrical percolation was observed at 17% Fe volume fraction, but higher volume fractions exhibited more stable electrical resistivity throughout the time course of physiological degradation. The electrical resistivity of 40%vf Fe-PCL composites increased tenfold in an emulated packaged environment under degradation. Biodegradable electrical interconnects based on 40%vf Fe-PCL composites were successfully micropatterned in daisy-chain structures, illustrating the process compatibility of Fe-PCL composites for interconnect applications. The electrical resistance of the packaged daisy-chain structures exhibited a reasonable increase under degradation. An electrical lifetime of over five days was also achieved. System integration with a commercial humidity sensor and analytical calculations supporting other application scenarios confirmed the feasibility of micropatterned Fe-PCL interconnects for use in implantable electrical systems.

We introduce the US NSF Engineering Research Center for the Internet of Things for Precision Agriculture (IoT4Ag). IoT4Ag aims to improve agricultural outcomes using highly distributed sensor technologies that monitor the soil and microclimate where plants are grown. MEMS will be a key technology enabler of this application, which requires sensing diverse measurands over large physical areas. We describe example optical and RF sensors that use large-area, low-cost fabrication technologies, are biocompatible or biodegradable, communicate from above or below the soil surface, require zero or near-zero power, and/or are powered from biodegradable batteries, wireless power, and energy harvesting.

Label-free electronic affinity based immuno-sensing is an attractive candidate as a platform technology for analyzing biomarkers due to the ease of miniaturization and minimal use of reagents. Electronic based sensing approaches, however, have lagged behind their optical counterparts in terms of detection limit, selectivity, and reliability. Also, the matrix dependent nature of electronic sensing modalities makes difficult the analysis of biomarkers in high salt concentration samples such as serum due to charge screening. We present a novel sensing platform, the micro-well sensor, that works by functionalizing nanoscale volume wells with antibodies and monitoring the impedance change inside the wells due binding of target protein. This detection modality is advantageous to many label-free electronic sensors in that signal power scales with increase in salt concentration, thus improving the sensitivity of the platform. We demonstrate rapid label-free qualitative detection of cytokines within ten minutes at femtoMolar concentrations and a dynamic range of 3 orders of magnitude in serum samples. We describe the design, fabrication, and characterization of the micro-well sensor in serum samples using inflammatory protein biomarkers.

A low-power wireless chip for an implantable tactile sensor system is presented. The reported ASIC utilizes the low-loss magnetic human body communication channel for both wireless powering and data transfer. The chip is hybrid-integrated with an in-house fabricated MEMS capacitive force sensor to form an implantable artificial mechanoreceptor (IAM). An on-chip correlated double sampling capacitance-to-time converter consumes 3.9µW from a 1.2V on-chip regulated supply and achieves a resolution of 22.8fF over an input capacitance range of 100pF, while occupying an area of only 0.04mm2. A wireless power management feedback is used to ensure robust operation for different hand gestures and under process-voltage-temperature (PVT) variations. The IAM can operate in on-off keying (OOK) or frequency-shift keying (FSK) modulation formats, where the transmitter consumes only 15.6µW in OOK mode and is more immune to hand gesture variations in FSK mode. The 1.62mm2 chip is fabricated in a standard 180nm CMOS process and consumes 104.3µW.

The development of laser wakefield accelerators (LWFA) over the past several years has led to an interest in very compact sources of X-ray radiation – such as “table-top” free electron lasers. However, the use of conventional undulators using permanent magnets also implies system sizes which are large. In this work, we assess the possibilities for the use of novel mini-undulators in conjunction with a LWFA so that the dimensions of the undulator become comparable with the acceleration distances for LWFA experiments (i.e., centimeters). The use of a prototype undulator using laser machining of permanent magnets for this application is described and the emission characteristics and limitations of such a system are determined. Preliminary electron propagation and X-ray emission measurements are taken with a LWFA electron beam at the University of Michigan.

The largest of the sawfishes is the Critically Endangered green sawfish Pristis zijsron, a species believed to have undergone a major decline (38%) in extent of occurrence. Conservation efforts are hampered by the lack of information on the habitat requirements of this species. We used passive acoustic telemetry to document the movement patterns of 37 juvenile P. zijsron (

Three-dimensional (3D) nickel hydroxide electrodes based on well-ordered and laminated structures are prepared via an electrochemical route combined with microfabrication technologies. The electrodes exhibit enhanced rate capabilities owing to their large surface area and reduced diffusion and conduction path lengths for the charge transfer. Highly laminated electrodes enable areal capacities as high as 2.43 mAh cm −2 . When charged at fast rates of 150C, the electrodes are able to deliver more than 50% of their initial capacity. The electrochemical performance of the fabricated electrodes is predicted with close approximation by means of a mathematical model developed by employing fundamental mass transport and reaction kinetics principles. This model is then used to optimize the characteristic dimensions of the electrodes and make projections of performance for various energy and power needs.

Climate change is projected to alter river discharge in every populated basin in the world. In some parts of the world, dam removal now outpaces their construction and the diminishing cost efficiency of dams in drying regions is likely to further increase the rate of removals. However, the potential influence of climate change on the impact of dam removals has received almost no consideration. Most dams have major biological and ecological impacts and their removal would greatly benefit riverine ecosystems. However, using model regions in the Southern Hemisphere, we highlight that artificial lentic habitats created by dams can act as refuges for increasingly imperiled freshwater fishes, and dams may also prevent the upstream spread of invasive alien species in rivers. We argue that, in these and other regions where the major impact of climate change will be to reduce streamflow and aquatic refuge availability, a shifting balance between the negative and positive environmental impacts of dams requires policy makers to include climate change predictions in prioritisation processes for dam removal.

We report a scheme for the integrated fabrication of MEMS-scale, series-connected battery cells. The approach exploits multilayer electrodeposition of active and sacrificial layers to generate structures that can be formed into high voltage power sources. Aqueous, non-vacuum based fabrication, via electrodeposition, enables high throughput and deterministic control of layer thicknesses and battery performance. Batteries manufactured using this technique offer the potential to match supply voltages to system needs, ranging from conventional electronics to direct drive of high voltage electrostatic or piezoelectric MEMS.

Biodegradable batteries play an important role in fully degradable biomedical or environmental systems. The development of biodegradable batteries faces many challenges including power content, device compactness, performance stability, shelf and functional lifetime. In particular, a key driver in the lifetime and overall size of microfabricated biodegradable batteries is the liquid electrolyte volume. Harnessing liquid from the environment to serve as the battery electrolyte may, therefore, be desirable; however, for stable operation, maintaining a constant electrochemical environment inside the cell is required even in the presence of changing body or environmental conditions. We report a biodegradable battery featuring a solid electrolyte of sodium chloride and polycaprolactone. This approach harnesses the body fluid that diffuses into the cell as an element of the electrolyte; however, the large excess of sodium chloride suspended in the polycaprolactone holds intracell ionic conditions constant. A constant discharge profile can then be achieved even in the presence of varying external aqueous conditions, enabling compact, stable-performing cells. This design also features easy integration and automatic activation, providing a simplified strategy to fabricate batteries with long shelf life and desirable functional life span. In addition, the polymeric skeleton of the solid electrolyte system acts as an insulating layer between electrodes, preventing the metallic structure from short-circuit during discharge.

The brain’s small-world network utilizes its short-range and long-range synaptic connections to process information in a complex and energy-efficient manner. To emulate the former, neuromorphic hardware typically leverages the conductance switching properties of thin-film dielectrics and semiconductors. Because these materials offer low ion mobilities, long-range connections built from thicker dielectrics require impractically-large forming voltages. To overcome this intrinsic shortcoming of solid-state active media, we present in this paper a simple Ag–H2O–Au cell that takes advantage of the relatively high ion mobility offered by deionized water to enable programmable connectivity switches between neurons separated by large gaps (∼40 µm). We introduce dual voltage programming schemes that allow the switch conductance to be modulated in analog and digital steps. When operating in the analog mode, the switch conductance could be potentiated and depressed over a relatively large (3.5×) range. In the digital mode, the Ag–H2O–Au switch delivered a high ON/OFF current ratio of ∼600 and sustained this margin over 200 switching cycles. Additionally, both switch states could be maintained for at least 3 h without external power. We show that unlike their solid-state counterparts, the water-gap in the Ag–H2O–Au cell can be easily refreshed without compromising the switching functionality. These attributes of Ag–H2O–Au switches in addition to their biocompatibility and simple design make them attractive for neuromorphic wetware implementations.

The development and characterization of step-up transformers with high winding ratios and laminated metallic magnetic cores for MHz-range step-up transformers used in DC-DC power converters is presented. The use of metallic magnetic cores with higher saturation flux density than traditional ferrites offers the possibility of reducing the physical size of the transformers. Core eddy currents are suppressed by forming the magnetic cores in a sequential electrodeposition process through toroidal lithographic molds, followed by self-assembly. This approach results in relatively thick magnetic cores (in the hundreds of microns range), comprised of many individual laminations with micron-scale thicknesses. Transformers were formed by manual winding of primary and secondary coils on these cores. The resultant transformers, with typical dimensions in the cubic millimeter range, exhibited primary and secondary inductances in the microhenry and hundreds of microhenry ranges, respectively. Typical transformer coupling coefficients were in the range 0.85–0.95. The transformers exhibited expected voltage step-up ratios as high as 10:1 at typical operation frequencies of 1–2 MHz. These ultracompact devices exhibit up to seven times higher inductance per unit volume and five times higher inductance per weight than typical commercial coupled inductors, and show promise for use in space-constrained electronic systems.

Composite materials comprising multilayers of metal and conductive polymer can have applications in sensing, biomedical, and energy storage/conversion scenarios. One attribute of such metal/polymer composites is that they typically display highly anisotropic electrical properties, which makes them useful as materials for microelectronic or magnetic devices. However, incorporating the deposition of conductive polymers into scalable and manufacturable fabrication processes can be challenging, as the mechanisms for electropolymerization are complex. We previously demonstrated an additive approach to fabricate metal/polymer multilayer structures, using soft magnetic alloys as the metal component and polypyrrole (PPy) as the polymer component. To extend the utility of these composites, the deposition of many multiples of alternating metal/polymer pairs within specifically defined lithographic molds is highly desirable. However, since the lateral growth of electrodeposited PPy is typically faster than vertical growth, non-uniform layer geometry and growth of the polymer on and above the patterned molds are often observed. In this work, we achieve suppression of lateral PPy growth by control of electropolymerization bath counter-anions and passivation of underlying metal layers during deposition. The lateral-to-vertical growth rate uniformity ratio is reduced by a factor of six (to approximately unity) through polymerization parameter optimization and exploiting a continuous five-bath electrodeposition approach. The reduction in lateral growth rate enhances the scalability of multilayer structures that are fabricated using this additive electrodeposition-based approach and provides a manufacturable route to additive, lithographically patterned metal/polymer composites with tunable volume and geometry, without sacrificing the microstructure and properties of the composite.

Goldfish (Carassius auratus) was one of the first fishes to be domesticated and has been widely introduced across the globe, but is now considered one of the world's worst invasive aquatic species. Surprisingly, there is a dearth of information on its spatial and temporal movement patterns, which hampers the development of effective control programmes. We examined the movement patterns of an introduced population of C. auratus in a south-western Australian river using passive acoustic telemetry. The study population had a high residency index within the array (i.e. proportion of all days at liberty that, on average, each fish was detected by a receiver) with fish being detected on 64% of days. The individuals were also reasonably mobile, travelling a mean of 0.30 km (linear river kilometres).day-1 within the array, and one fish moved 231.3 km over the 365-day study period (including 5.4 km in a 24 hr period). Importantly, C. auratus displayed significant seasonal movement patterns including a clear shift in habitats during its breeding period with most mature individuals being detected in an off-channel wetland during that time. The results of this study strongly suggest that C. auratus undertook a spawning migration into a lentic habitat. These results have important implications for developing control programmes for the species, such as targeting connections to off-channel lentic systems during its breeding period.

We developed a new patch-shaped enzyme free biosensor using a micro-needle array with Pt black sensing electrode layer for painless continuous glucose monitoring applications. We fabricated the micro-needle array using a bulk micromachining technique and commercial stainless steel 316L grade substrate. Pt black and Ag/AgCl were then electroplated on the tip of each micro-needle as working and counter/reference electrodes of the sensor, respectively. The fabricated micro-needle was 650 μm high and 150 μm wide. We used 48 and 24 micro-needles for the working electrode and counter/reference electrode, respectively. The measured sensitivity was 1.62 μA mM −1 with high linearity of 0.9939, and was obtained within 13 sec, in glucose concentrations ranging up to 36 mM. The biosensor also exhibited a low detection limit of 50 μM. We tested the sensor under PBS solution over a period of 6 days. Then we partially inserted the sensor into a rabbit, to monitor the interstitial glucose level. We then induced change of interstitial glucose concentration by oral glucose tolerance test. Although we expected the sensor to perform for more than 6 days, it performed for just 4 days as a sensor, due to bio fouling.

We report a scheme for the integrated fabrication of MEMS-scale, series-connected battery cells. The approach exploits multilayer electrodeposition of active and sacrificial layers to generate structures that can be formed into high voltage power sources. Aqueous, non-vacuum-based fabrication, via electrodeposition, enables high throughput and deterministic control of layer thicknesses and battery performance. Batteries manufactured using this technique offer the potential to match supply voltages to system needs, ranging from conventional electronics to direct drive of high voltage electrostatic or piezoelectric MEMS.

Using dual optical frequency comb (OFC) spectroscopy in the longwave infrared (LWIR), we demonstrate standoff detection of trace amounts of target compounds on diffusely scattering surfaces. The OFC is based on quantum cascade lasers (QCL) that emit ~1 Watt of optical power under cw operation at room temperature over coherent comb bandwidths approaching 100 cm-1. We overlap two nearly identical 1250 cm-1 QCL OFC sources so that the two interfering optical combs create via heterodyne a single comb in the radio frequency (rf) that represents the entire optical spectrum in a single acquisition. In a laboratory scale demonstration we show detection of two spectrally distinct fluorinated silicone oils, poly(methyl-3,3,3-trifluoropropylsiloxane) and Krytox™, that act as LWIR simulants for security relevant compounds whose room temperature vapor pressure is too low to be detected in the gas phase. These target compounds are applied at mass loadings of 0.3 to 90 μg/cm2 to sanded aluminum surfaces. Only the diffusely scattered light is collected by a primary collection optic and focused onto a high speed (0.5 GHz bandwidth) thermoelectrically cooled mercury cadmium telluride (MCT) detector. At standoff distances of both 0.3 and 1 meter, we demonstrate 3 μg/cm2 and 1 μg/cm2 detection limits against poly(methyl-3,3,3-trifluoropropylsiloxane) and Krytox™, respectively.

Intracortical neural microelectrodes, which can directly interface with local neural microcircuits with high spatial and temporal resolution, are critical for neuroscience research, emerging clinical applications, and brain computer interfaces (BCI). However, clinical applications of these devices remain limited mostly by their inability to mitigate inflammatory reactions and support dense neuronal survival at their interfaces. Herein we report the development of microelectrodes primarily composed of extracellular matrix (ECM) proteins, which act as a bio-compatible and an electrochemical interface between the microelectrodes and physiological solution. These ECM-microelectrodes are batch fabricated using a novel combination of micro-transfer-molding and excimer laser micromachining to exhibit final dimensions comparable to those of commercial silicon-based microelectrodes. These are further integrated with a removable insertion stent which aids in intracortical implantation. Results from electrochemical models and in vivo recordings from the rat’s cortex indicate that ECM encapsulations have no significant effect on the electrochemical impedance characteristics of ECM-microelectrodes at neurologically relevant frequencies. ECM-microelectrodes are found to support a dense layer of neuronal somata and neurites on the electrode surface with high neuronal viability and exhibited markedly diminished neuroinflammation and glial scarring in early chronic experiments in rats.

We develop a hermetic package process based on laser machining that simultaneously achieves dicing and localized fusion bonding of stacked, patterned bulk silica wafers; this process enables rapid hermetic encapsulation of foundry CMOS/MEMS. Because of the extremely low thermal diffusivity of fused silica, as well as the localized and controllable nature of the laser spot illumination, the interwafer molten bond line penetrates less than 200 microns laterally into the device, sparing the CMOS chip the extreme heat of fusion bonding. Metallic feedthroughs can be incorporated without compromising the hermeticity of the package. Furthermore, excimer laser patterning of fused silica prior to bonding had 100x shorter processing time than patterned wet etching. Such fused silica hermetic packages have many favorable attributes; for example, the excellent chemical inertness enables biocompatibility, and the transparency at radio and optical frequencies enables wireless transmission through the package.