Mark G. Allen

We demonstrate a fully integrated magnetooptomechanical MEMS modulator for current-induced optical switching in high-EMI environments, with application as an overcurrent protection ‘circuit breaker’ in switching power converters. The device is realized by postprocess micromachining of magnetically soft suspensions over waveguides on a foundry-fabricated silicon photonic chip. Overcurrent in a switching converter line causes magnetic actuation of the suspensions, bringing the magnetic material in proximity to the waveguide and attenuating the guided light through evanescent-field absorption. This modulated light signal can then be used to control the converter; since the control signal is optical, it has reduced susceptibility to the high-EMI environment. Two magnetic architectures - a cantilever with a magnetic flux concentrator and a folded-beam suspension - are presented. The modulator achieves 6 dB of attenuation within <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3 \mu \mathrm{s}$</tex> under overcurrent pulse excitation, validating its potential as a photonic circuit breaker for optically driven, EMI-immune power systems.

Modern wireless systems demand compact, power-efficient radio frequency (RF) front-end components that support wideband tunability and nonreciprocity. We present a class of miniature bandpass filter that achieves both continuously tunable frequency operation (4.0-17.7 GHz) and high nonreciprocity ( > 25 dB), all within a compact size of 1.07 cm³. The filter employs a microfabricated 18 µm thick Yttrium Iron Garnet (YIG) waveguide with meander-line aluminum transducers, enabling low-loss unidirectional propagation via magnetostatic surface waves. Leveraging a benzocyclobutene planarization fabrication process, this study enables a dispersion profile unique to thick YIG films, resulting in enhanced filter skirt performance with minimal spurious modes. Frequency tuning is enabled by a zero-static-power magnetic bias circuit using transient current pulses, eliminating continuous power consumption. The filter demonstrates low insertion loss (3-5 dB), high out-of-band rejection ( > 30 dB), narrow bandwidth (100-200 MHz), robust power handling ( > 10.4 dBm), and high linearity (IIP3 > 26 dBm).

This paper presents the design, fabrication, and characterization of through-silicon via (TSV) coupled inductors for vertical power delivery. The inductors are implemented by electrodepositing thin-film magnetic material onto via sidewalls and forming two coaxial Cu layers inside vias as coupled windings. The unique coaxial winding arrangement eases fabrication constraints. Many coupled inductors can be interconnected in a fabric-like fashion and scaled to larger inductance values and current ratings. As a proof of concept, TSV coupled inductors are fabricated, achieving an inductance density of 162 nH/mm2, an L/RDC ratio of 597 nH/Ω, a coupling factor of 0.97, and a peak Q of 9 at 5.5 MHz. Inductor performance with different core thicknesses and via diameters is evaluated, showing the potential to exceed 1000 nH/mm2 in inductance density and 2500 nH/Ω in L/RDC ratio.

OBJECTIVE: Real-time measurement of tissue lactate levels is critical for diagnosing and monitoring metabolic disorders yet remains a challenge in dynamic physiological environments. Traditional wearable lactate sensors can provide non-invasive monitoring but are limited in their ability to capture tissue-specific information and thus diagnostic accuracy in systemic metabolic assessments. This study aims to develop an implantable microsensor for direct measurement of lactate within target tissues for continuous, real-time tracking. Recognizing that the ambient oxygen concentration in these environments may be depleted relative to oxygen concentration in, e.g., wearables, the limits of oxygen dependence of sensor operation are probed. METHODS: A miniaturized enzymatic lactate sensor (0.7×1.0×0.12 mm) was fabricated on gold electrodes with immobilized lactate oxidase, leveraging biochemical surface modifications for enhanced enzyme stability and a permselective membrane for regulation of analyte diffusion and prolonged operational lifetime in simulated biological environments. Sensor performance was evaluated electrochemically across a range of lactate concentrations. RESULTS: This sensor, tested across pathophysiological conditions, provides an expanded linear range of response (LRR) from 0.2 to 50 mM, enabling precise tracking of metabolic fluctuations with a response time of 8 s in oxygen-deficient disease microenvironments, validated by computational modelling. CONCLUSION: The sensor enables continuous monitoring of lactate levels for implantable deployment, overcoming key limitations of traditional systems in capturing local metabolic activity when tissue oxygen availability is reduced. SIGNIFICANCE: The sensor provides a platform for real-time metabolic assessment to support diagnostics, longitudinal health monitoring, and evaluation of therapeutic response in conditions such as ischemia and cancer.

Small-scale quadrotors, typically defined as centimeter-scale in size and tens of grams in weight, are increasingly being utilized in applications such as agricultural monitoring or search and rescue operations. These vehicles are typically powered with lithium-ion batteries. However, vehicle operational efficiency and capability are often compromised by the limited energy density of these batteries, resulting in short operational duration. This work explores a high-energy chemistry, aluminum-air (Al-air), as a power source to significantly extend the operational duration of small-scale quadrotors. Rapid corrosion of the aluminum anode in existing Al-air systems has been a barrier to adoption in applications where long-term operation is required. However, corrosion is less of a concern in the small-scale quadrotor application, where the battery is typically under continuous use over a short period of time. The electrochemical and packaging design of a micro-Al-air pouch cell battery is optimized for two operating points: an energy density of 325 [Formula: see text] above a power density of 500 [Formula: see text], and an energy density of [Formula: see text] [Formula: see text] above a power density of 800 [Formula: see text], both of which far surpass the performance of equivalent commercial lithium-ion batteries. A 3D-printed small-scale quadrotor platform is used to evaluate flight duration. The micro Al-air battery delivers 13.1 min of flight time, compared to the 4.5 min of flight time provided by the commercial micro lithium-ion battery. This work demonstrates the feasibility of Al-air batteries that simultaneously possess sufficiently high power density to achieve small-scale quadrotor flight, and sufficiently high energy density to achieve extended duration of that flight.

This work presents the development of a magnetic rheostat, a dynamically tunable magnetic circuit element analogous to a variable resistor, leveraging the stress-dependent permeability of magnetostrictive materials. Dynamic and precise control of a magnetic field is increasingly critical for diverse applications, yet traditional methods such as electromagnets suffer from power consumption and size limitations. This magnetic rheostat offers a nonvolatile, energy-efficient alternative. The device utilizes Galfenol (Fe1−xGax, x = 0.17 − 0.19), whose permeability decreases under compressive stress to demonstrate stress-induced modulation of the magnetic flux density within an air gap. A fabricated prototype, comprising a Galfenol flux conduction element mechanically coupled to a lead-zirconate-titanate piezoelectric actuator for stress application, exhibits a magnetoelectric coupling coefficient of −0.659 mT/V and tuning of the flux density from 176.6 to 85.5 mT within a gap element. This multiferroic approach, based on stress-mediated permeability changes, demonstrates the feasibility of dynamic, non-current based flux control and opens new avenues for designing tunable magnetic circuits for diverse applications requiring precise magnetic field manipulation. The inherent nonlinearity of ferromagnetic materials, while presenting design challenges related to saturation effects, also offers opportunities for performance optimization through tailored geometry and stress application methods.

Abstract Sensing oxygen levels in living tissues can be utilized in multiple applications ranging from monitoring exercise state to informing disease severity or clinical diagnosis. To enhance clinical utility, oxygen sensors must be both minimally invasive and amenable to scalable, low-cost fabrication. We report a freestanding, miniaturized electrochemical oxygen sensor designed to meet these needs. The sensor features a circular, flat sensing area (2.4 mm in diameter and ∼100 μ m thick), along with metal traces and contact pads that enable connection. The sensor design incorporates a three-electrode (working, counter, and reference) electrochemical system, an electrolyte reservoir, and a polydimethylsiloxane (PDMS) oxygen-permeable membrane, all fabricated on a flexible polyimide substrate. The electrolyte itself comprises a poly-vinyl alcoho hydrogel between the PDMS membrane and the electrodes. Structural and electrochemical characterization demonstrated that the hydrogel electrolyte simplifies fabrication while preserving sensor performance, including selectivity and sensitivity of −8.45 nA Torr −1 . In vivo validation in a zebrafish animal model demonstrated the ability of the sensors to reliably measure intramuscular tissue oxygen levels within the physiological range of 20–50 Torr. These results suggest that hydrogel-based, PDMS dip-coated, oxygen sensors offer a practical and scalable platform for minimally-invasive monitoring of tissue oxygen levels.

Image sensors and photodetectors manufactured using colloidal quantum dots (CQDs) as the photon absorbing layer have been heralded as offering cost-efficiency in production, tailorable spectral response, and scalability in pixel size owing to direct wet-processing onto the CMOS wafer surface without the need for bump bonding alignment and other hybridization steps. The CQD approach affords greater freedom and flexibility for optimizing the pixel size and shape according to application requirements; it is possible to pattern the pixel electrodes for push-broom type geometries or as a combination of different pixel sizes for snapshot multispectral sensing on top of a CMOS ROIC having a fixed pixel pitch. Here, we provide experimental and theoretical results on the pixel size scaling for Emberion’s CQD image sensor stack under reverse-bias photocurrent and voltage-sensing read-out modes. We demonstrate sensitivity vs pixel size interdependency for a custom-designed image sensor array comprising a range of pixel sizes and shapes from 7x7 μm2 to 100 x 40 μm2. We conclude with design considerations for optimizing CQD-based image sensors and cameras according to specific performance requirements relevant for industrial machine vision and defense applications.

This paper presents the design and digital control of a $\mathbf{1 M H z}$ LLC resonant converter targeted for high power density, universal input ($85-265 \mathrm{~V}_{\mathrm{AC}}$) power adapters. To sustain high efficiency across the full line and load range, a multi-mode digital control strategy is implemented. The controller utilizes variable-frequency modulation (VFM) for regulation at medium to heavy loads. For operation at high input lines, the controller transitions to an asymmetric duty-cycle scheme to regulate the output while preserving soft-switching. A pulse-skipping mode is also integrated to extend the operation to very light loads. This hybrid approach reduces switching losses, minimizes circulating current, and broadens the efficiency range. A hardware prototype validates the proposed strategy, demonstrating stable regulation and seamless transitions between different modes, confirming the method’s suitability for compact, high-density adapters.

This study investigates the impact of transformer parasitic capacitance on Zero Voltage Switching (ZVS) performance in ultra-compact, high-power-density Active Clamp Flyback (ACF) converters operating at high frequencies. The research focuses on a 5 W, 5 V ACF converter with a wide input voltage range (85–265 V) and an operating frequency of 500 kHz, targeting increased switching frequency. Results reveal that increasing the frequency to 700 kHz causes ZVS loss beyond 170 V due to capacitive parasitic effects. To address this issue, a new transformer with reduced parasitic capacitance is designed and tested. Simulation results confirm that the modified transformer effectively restores ZVS operation at higher input voltages. Experimental validation further demonstrates stable performance at 700 kHz. This work provides valuable insight into mitigating ZVS challenges caused by parasitics in compact ACF designs and highlights the importance of transformer optimization for high-frequency applications.

Lactate monitoring is essential for the diagnosis and management of metabolic disorders, such as mitochondrial myopathies. To detect these conditions, assessment of lactate levels during dynamic physiological states such as exercise is a promising approach. However, conventional metabolite sensors can be limited by poor stability under mechanical stress, including muscle contractions, and slow response times, hindering their utility in capturing real-time lactate dynamics. We report a biocompatible, acutely implantable lactate sensor on a flexible substrate embedded with a lactate oxidase enzyme layer for electrochemical detection of physiologically relevant lactate concentrations (0.2-40 mM). The performance of the sensor was evaluated using a hydrogel model mimicking the biomechanical environment of muscle tissue, including resting and contracting states. The sensor demonstrates robust mechanical stability and rapid response times for monitoring of lactate diffusion dynamics under simulated muscle contractions. This platform enables real-time insights into tissue metabolism and advances precision medicine for metabolic disorders.Clinical Relevance-This work supports the use of lactate microsensors for diagnosing and monitoring metabolic disorders by enabling screening of metabolite imbalances and guiding therapeutic interventions.

This paper presents the fabrication of through-silicon-via (TSV) inductors for high-frequency vertical power delivery. To fabricate such inductors, magnetic material is introduced into TSVs by electrodepositing magnetic film onto the TSV sidewalls. A self-aligned process defines the electrodeposited magnetic film to form the cores of the TSV inductors without requiring photolithography. Subsequent copper filling of the vias provides a low-resistance vertical current path, completing the inductor structure. Compared to conventional on-silicon inductors, the TSV inductor efficiently utilizes footprint area, enabling higher inductance density and reduced resistance.

Magnetic materials are widely utilized in induction-based wireless energy harvesting for MEMS. However, the volume of these magnetic materials often comprises a large fraction of the total volume of the MEMS device; this can be challenging in many applications where the overall volume of the device is constrained by application. We present a new geometry of a wireless energy harvester (WEH) magnetic core that achieves a 43% volume reduction compared with a single solid core, while largely maintaining total harvested energy, thus improving output power density per unit volume of magnetic material by approximately 80%. The WEH design features a centrally vacant hollow magnetic core with the core sidewalls wound by two series-connected solenoids. The central hollow region is thus available for integration of other components, providing an efficient solution for volume-constrained applications.

Colloidal quantum dot (CQD) image sensors are an attractive technology, which offers cost-effective processing, tailorable spectral response and scalable pixel size. The first commercial infrared cameras based on CQDs have entered the market and are being deployed in machine vision and surveillance applications by early adopters. Emberion, a pioneer of this technology with an entirely in-house designed and produced CQD camera, recently published a detailed introduction to their custom-designed image sensor platform and CQD manufacturing process. Here, we extend the aforementioned report with further experimental results of high-speed SWIR imaging and introduce Emberion’s latest image sensor ROIC platform comprising two variants: (i) a MegaPixel resolution imager with 10 &mu;m pixel size and (ii) a push-broom sensor optimized for hyperspectral imaging at above 1000 fps. We report on the dynamic response of the CQD stack as a function of operating temperature and discuss the performance of CQD-based image sensors for high-speed imaging. We conclude by presenting selected application cases showcasing the high-speed performance of the Emberion VS20 camera at extended SWIR wavelengths.

Modern wireless systems demand compact, power-efficient RF front-end components that support wideband tunability and nonreciprocity. We present a new class of miniature bandpass filter that achieves both continuously tunable frequency operation (4-17.7 GHz) and high nonreciprocity (&gt;25 dB), all within a compact size of 1.07 cm3. The filter employs a microfabricated 18 micrometer thick Yttrium Iron Garnet waveguide with meander-line aluminum transducers, enabling low-loss unidirectional propagation via magnetostatic surface waves. Leveraging a benzocyclobutene planarization fabrication process, this study enables a dispersion profile unique to thick YIG films, resulting in enhanced filter skirt performance with minimal spurious modes. Frequency tuning is enabled by a zero-static-power magnetic bias circuit using transient current pulses, eliminating continuous power consumption. The filter demonstrates low insertion loss (3-5 dB), high out-of-band rejection (&gt;30 dB), narrow bandwidth (100-200 MHz), robust power handling (&gt;10.4 dBm), and high linearity (IIP3 &gt; 26 dBm).

Abstract A significant challenge for power sources of small-scale quadrotors is the simultaneous need for high gravimetric energy density and high power density. While aluminum–air batteries (AABs) can provide the high energy density, achieving high power density typically necessitates expensive catalysts such as platinum, which can be a significant cost driver. We present microfabricated silver-based air-cathodes for high-power AABs that are suitable for small-scale quadrotor applications. Experimental results, supported by a diffusion–reaction model, indicate that the power performance of the Ag-based cathode is largely determined by the electrochemically active catalyst surface area. To maximize the surface area, we exploit a microfabrication technique involving co-sputtering of a silver–copper alloy on a carbon paper substrate, followed by selective etching of the copper. This process results in a Ag-based paper cathode that delivers a power density of 202 mW cm −2 with 0.3 mg-silver cm −2 catalyst loading. Under battery discharge conditions relevant to small-scale quadrotor operations, the discharge performance of the silver-based AAB is examined. The silver-based cathode achieves a discharge peak power density of 1000 W/kg battery , which is 70% that of the platinum-based cathode. Notably, when discharging above the 800 W/kg battery threshold required for the small-scale quadrotor, the silver-based cathode achieves a comparable discharge duration compared with the platinum-based cathode. The cost analysis reveals a significant economic advantage, with this high-power silver-based cathode being 460 times less expensive than the commercial platinum-based cathode on a materials basis.

Abstract A 200 mm processing platform for the large-scale production of graphene field-effect transistor-quantum dot (GFET-QD) hybrid photodetectors is demonstrated. A comprehensive statistical analysis of the electrical data revealed a high yield (96%) and low variation in the 200 mm scale fabrication. The GFET-QD devices deliver responsivities of 10 5 to 10 6 V/W in the wavelength range from 400 to 1800 nm with a response time of 10 ms. The spectral sensitivity compares well to that obtained via similar GFET-QD photodetectors. The device concept enables gate-tunable suppression or enhancement of the photovoltage, which may be exploited for electric shutter operation by toggling between the signal capture and shutter states. The devices show good stability over a wide operation range. Furthermore, an integration solution with complementary metal-oxide-semiconductor technology is presented to realize image-sensor-array chips and a proof-of-concept image system. This work demonstrates the potential for the volume manufacture of infrared photodetectors for a wide range of imaging applications.

For a bounded open set $Ω\subset \mathbb{R}^n$ with the same volume as the unit ball, the classical Faber-Krahn inequality says that the first Dirichlet eigenvalue $λ_1(Ω)$ of the Laplacian is at least that of the unit ball $B$. We prove that the deficit $λ_1(Ω)- λ_1(B)$ in the Faber-Krahn inequality controls the square of the distance between the resolvent operator $(-Δ_Ω)^{-1}$ for the Dirichlet Laplacian on $Ω$ and the resolvent operator on the nearest unit ball $B(x_Ω)$. The distance is measured by the operator norm from $L^{\infty}$ to $L^2$. As a main application, we show that the Faber-Krahn deficit $λ_1(Ω)- λ_1(B)$ controls the squared $L^2$ norm between $k$th eigenfunctions on $Ω$ and $B(x_Ω)$ for every $k \in \mathbb{N}.$ In both of these main theorems, the quadratic power is optimal.

Communication-assisted line protection schemes can face unexpected breaker failure (BF) trip time delays. This paper examines an actual event where a Permissive Overreach Transfer Trip (POTT) line protection scheme operated for a close-in fault as expected with the local relay issuing a permit to the remote relay. This resulted in a remote end BF initiation and subsequent longer than expected BF trip operation for a failed remote end breaker. In this event, the local breaker opened successfully causing the local relay to stop sending a permit to assert the remote end breaker failure initiate input. After a time delay, the remote end relay Zone 2 reach operated and its BF input re-asserted due to the echo key logic from the local relay. This resulted in an overall delayed response of the BF scheme to operate for the remote end failed breaker. The investigation of this event concluded that this was a slow breaker failure operation in a POTT scheme. Through detailed analysis of relay events, oscillography data, and post-event simulations, the root cause of this rare occurrence was uncovered. Three solutions were proposed to improve the BF scheme response time. This paper presents simulated solutions of the event and provides the preferred solution based on ease of implementation with improved security. In conclusion, this case study serves as a reminder that even well-designed systems can face unexpected challenges with field application. By sharing these insights, this paper aims to contribute to the ongoing improvement of power system reliability and the education of protection engineers.

Cells are diverse systems with unique molecular profiles that support vital functions, such as energy production and nutrient absorption. Advances in omics have provided valuable insights into these cellular processes, but many of these tools rely on cell lysis, limiting the ability to track dynamic changes over time. To overcome this, methods for longitudinal profiling of living cells have emerged; however, challenges such as low throughput and genetic manipulation still need to be addressed. Nanomaterials, particularly nanowires, offer a promising solution due to their size, high aspect ratios, low cost, simplicity, and potential for high-throughput manufacturing. Here, we present a nanowire-based platform for longitudinal mRNA profiling in living cells using vertically aligned nickel nanowire arrays for efficient mRNA extraction with minimal cellular disruption. We demonstrate its ability to track enhanced green fluorescent protein expression and transcriptomic changes from drug responses in the same cells over time, showcasing the platform's potential for dynamic cellular analysis.

We present a carbon dioxide (CO2) laser-assisted simultaneous localized fusion bonding and dicing technology on fused silica wafer. 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 below 400 °C during the fabrication process to preserve complementary metal-oxide-semiconductor (CMOS)- compatibility. Such fused silica packages have many favorable features such as optical transparency for packaging micro-opto-electro-mechanical systems (MOEMS), biocompatibility and hermeticity for implantation applications, and transparency at radio frequencies for encapsulating electronics for wireless power and signal transmission. We applied this localized fusion bonding technology to encapsulate humidity sensors, evaluating the hermeticity and suggesting an implantation lifespan of over 70 years in the human body. Furthermore, we extended its application to vacuum packages and implantable tactile sensing systems to restore hand function for individuals with paralysis.

We introduce a flyback transformer with a laminated NiFe magnetic core, fabricated using a CMOS-compatible microfabrication technique involving sequential multilayer electrodeposition, and demonstrate its application in a flyback AC/DC converter with constant output voltage control operating at 500 kHz. The core adopts a 'UT' shape to facilitate winding, as opposed to the traditional EI shape. The transformer includes a 45-turn primary winding and a 3-turn secondary winding, featuring a magnetizing inductance of 317 µH and a coupling coefficient of 0.98. The total transformer core thickness was 4.2mm. Electrical performance was evaluated using a customized flyback circuit on a printed circuit board (PCB), which provided a stable isolated 5 V, 1 A DC output from a 60 Hz sinusoidal AC input ranging from 80 V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</inf> to 220 V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</inf>. The system achieved an end-to-end efficiency of 80% with a 120 V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</inf> input and maintained over 68% efficiency across the entire input range.

BACKGROUND: Stroke remains a leading cause of death and disability, underscoring the urgent need for treatments that enhance recovery. GDF11 (growth differentiation factor 11), a member of the TGF-β (transforming growth factor-β) superfamily, is a circulating protein involved in cellular development and tissue repair. GDF11 has gained attention for its potential regenerative properties in aging and disease contexts, making it a candidate for stroke recovery therapies. METHODS: The therapeutic benefits of rGDF11 (recombinant GDF11) were evaluated using a rat ischemic stroke model, in which focal cerebral infarcts were induced in 8- to 10-week-old young adult male Sprague-Dawley rats by permanently occluding the proximal right middle cerebral artery. Rats received single or multiple doses of rGDF11 (0.1-4 mg/kg) or vehicle from 24 to 72 hours post-injury. Sensorimotor functions were evaluated, and brain and serum samples were examined to determine the mechanisms of action and identify biomarkers, using immunofluorescence, target-specific ELISAs, and an aptamer-based proteomics platform. RESULTS: We confirmed rGDF11 activity in vitro and in established in vivo mouse models of cardiac hypertrophy and glucose metabolism and assessed the efficacy of rGDF11 treatment in 6 preclinical stroke studies using independent Contract Research Organizations, with all study animals and treatment groups blinded. All 6 studies revealed consistent improvement in sensorimotor outcomes with rGDF11. rGDF11-treated rats showed increased cortical vascularization and radial glia in the ventricular zone. Serum analysis revealed that rGDF11 caused dose-dependent decreases in CRP (C-reactive protein) and identified novel pharmacodynamic biomarkers and pathways associated with potential mechanisms of action of rGDF11. CONCLUSIONS: These results demonstrate that systemically delivered rGDF11 enhances neovascularization, reduces inflammation, promotes neurogenesis, and improves sensorimotor function post-injury in a rat model of ischemic stroke. More importantly, these data define an optimized and clinically feasible rGDF11 dosing regimen for therapeutic development in ischemic stroke and identify a panel of candidate pharmacodynamic and mechanistic biomarkers to support clinical translation.

Quasi-static magnetic fields can be used to modulate the magnetic and electrical properties of many magnetic materials, thereby enabling the operation of various magnetic devices, such as multiferroic magnetic field sensors and ferro/ferrimagnetic magneto-static wave filters. We present a magnetic circuit designed to produce a tunable dc magnetic bias field and detail its operating principle. The magnitude of the bias field can be electrically tuned to achieve a desired magnetic field; when not being switched, the achieved field is maintained with zero static power consumption. The magnetic circuit comprises two distinct types of permanent magnets: an NdFeB magnet with relatively high coercivity and an AlNiCo V magnet with relatively low coercivity combined with a tuning coil for adjusting its magnetization. Soft magnetic yoke pieces link the permanent magnets and also define an air gap. Pulses of current through the coil will adjust the remanence of the AlNiCo magnet, thereby changing the flux and field in the air gap. A magnetic bias circuit with a compact volume of 0.27 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> has been constructed, providing an adjustable dc magnetic field with a tuning range of 3.7 to 288.5 mT within a 1 mm air gap.

This work presents biodegradable, wax-encapsulated zinc–air batteries for sustainable, long-term IoT applications like precision agriculture and environmental science.

We report a cost-effective microfabricated silver-based air-cathode for high-discharge-rate aluminum-air batteries which are suitable for micro-drone applications. A challenge for batteries for aerial drones is that both high gravimetric energy density and power density are required for extended operation. While air batteries can address the energy density issue, achieving high power density necessitates high loadings of expensive catalytic materials such as platinum (Pt), which can constitute over 99% of the cost in commercial air batteries. [1] Building upon prior research that studied the power performance of an aluminum-air battery (AAB) system with a silver-based cathode, this study further explores the influence of silver (Ag) sputtering conditions and Ag loadings on AAB power performance. [2] The power performance of AAB is significantly influenced by both air flux through the air cathode and electrochemically active catalyst surface area ratio (ECSA). The ECSA is the ratio of the electrochemically active catalyst surface area to its cathode area. Sputtered Ag cathodes with catalyst loadings ranging from 0.03 mg-Ag/cm 2 to 0.3 mg-Ag/cm 2 consistently show high porosity, indicating good air flux for the microfabricated cathode. Increasing the loading of the sputtered Ag catalyst further can lead to particle agglomeration. To improve power performance and ECSA, a silver-copper (AgCu) co-sputtering technique has been developed, significantly increasing the surface area and power performance. Figure 1 shows cathodes with Ag loadings ranging from 0.038 mg-Ag/cm 2 to 0.267 mg-Ag/cm 2 under two silver sputtering conditions: 400W+5mTorr and 100W+10mTorr. Within the examined range, the latter sputtering condition shows superior power performance compared to the former. For Ag loadings exceeding 0.1 mg-Ag/cm 2 , both conditions show decreasing power performance as Ag loading increases, and the 100W+10mTorr curve shows a maximum power at 0.088 mg-Ag/cm 2 . Figure 2 shows SEM images of 0.038 mg-Ag/cm 2 , 0.088 mg-Ag/cm 2 , and 0.19 mg-Ag/cm 2 films, using the 100W+10mTorr sputtering condition. Ag particle size increases with higher Ag loading, which can result from particle agglomeration. Figure 3 shows the catalyst layer porosity and the ECSA calculated from the SEM images. All samples show porosity over 90%, indicating good air flux for the microfabricated Ag cathode. The trend of ECSA for different Ag loading correlates well with the power performance, suggesting that the power performance of the microfabricated Ag cathode primarily depends on the ECSA. Further enhancement of the ECSA through AgCu co-deposition is investigated, involving two parent alloy compositions (at%): Ag 28 Cu 72 and Ag 16 Cu 84 . Following the co-sputtering, the parent alloy undergoes selective etching of Cu using hydrochloric acid (HCl). Figure 4 compares power performance between Ag 28 Cu 72 and Ag 16 Cu 84 . Both curves exhibit an upward trend as the silver loading increases from 0.09 mg-Ag/cm 2 to 0.4 mg-Ag/cm 2 , with Ag 28 Cu 72 samples showing superior power performance. Figure 5 shows an SEM image of Ag 28 Cu 72 parent alloy with 0.32 mg-Ag/cm 2 loading after Cu etching, demonstrating that the ECSA increased to 47.52 while maintaining a high porosity of 90.2%. The peak power of Ag 28 Cu 72 0.32 mg-Ag/cm 2 sample is increased to 200 mW/cm 2 . By comparison, a 4mg-Pt/cm 2 commercial cathode shows a peak power of 280 mW/cm 2 . Figure 6 compares the discharge performance of the 0.088 mg-Ag/cm 2 cathode with a commercial 4 mg-Pt/cm 2 cathode. Both cells can discharge under 1.1 Amp with a power density exceeding 500 W/kg battery , a threshold sufficient to lift a quadrotor drone. [3] Battery weight encompasses anode, cathode, electrolyte and battery packaging. The 0.088 mg-Ag/cm 2 cathode shows a discharge power plateau above 600 W/kg battery (86% of the 4 mg-Pt/cm 2 ) and an energy density of 228 Wh/kg battery when discharge power density exceeding 500 W/kg battery (95% of the 4 mg-Pt/cm 2 ). Remarkably, the material cost of the 0.088 mg-Ag/cm 2 cathode is 5000 times less than the 4 mg-Pt/cm 2 cathode. References: Huang, Lei, et al. "An integrated platinum-nanocarbon electrocatalyst for efficient oxygen reduction." nature communications 13.1 (2022): 6703. Huang, Yanghang, et al. "Microfabrication-Enhanced Carbon Fiber Cathodes for High Discharge Rate Aluminum-Air Batteries." 2022 21st International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS). IEEE, 2022. Mulgaonkar, Yash, et al. "Power and weight considerations in small, agile quadrotors." Micro-and Nanotechnology Sensors, Systems, and Applications VI. Vol. 9083. SPIE, 2014. Figure 1

Small-scale quadcopters are increasingly used in various fields, including rescue, surveillance and precision agriculture. The predominant energy storage system for such quadcopters has been the micro lithium-ion battery (mLIB). Two of the most important design metrics for power sources used in quadcopters are specific power and specific energy. The specific energy determines the flight duration of the quadcopters, while specific power is necessary for maneuverability and takeoff. The mLIB can easily meet the power requirement of small scale quadcopters; however, the limited energy density of mLIBs (exacerbated by the packaging overhead of these batteries as scales shrink) constrains their flight duration. To increase the flight time, aluminum-air batteries (AABs), with a theoretical energy density twenty times greater than conventional lithium-ion batteries, are being explored. [1] Despite AAB’s high theoretical energy density, the conventional AAB lacks the high-power performance of LIBs. [2] To fulfill the demanding power requirements of small scale quadcopters, the AAB cell has been re-engineered to enhance power capability while maintaining high energy density. To maximize AAB energy and power density at the cell level, it is imperative to address the issue of battery packages that add weight without contributing to electrochemical performance. A light-weight battery packaging approach is developed for the micro-AAB (mAAB). In the context of AABs, the primary function of the battery package is to retain the aqueous electrolyte within the cell. Typically, the cathode of an AAB is constructed using a carbon cloth, doped with a layer of polytetrafluoroethylene (PTFE). This hydrophobic carbon cloth cathode effectively retains the aqueous electrolyte. In order to increase the mechanical integrity of mAAB pouch cells, 3D printed polypropylene is utilized as the body frame of mAABs, providing a robust and lightweight structure. The carbon cloth cathode is affixed to the 3D printed polypropylene using epoxy, as shown in Figure 1A. An image of an assembled 2-gram mAAB pouch cell is shown in Fig 1B. Remarkably, the electrochemically inactive packaging materials contribute to less than 13% of the total cell weight, achieving the goal of minimizing packaging material to enhance battery performance. As a comparison, the packaging material of gram-scale mLIBs can contribute to over 30% of total cell weight. Furthermore, in contrast to traditional aluminum-air battery designs, the pouch cell architecture optimizes cathode area exposure, which is advantageous for high-power applications. The anode structure is also engineered for high power capability. Figure 2A shows that increasing the anode/cathode area ratio can augment areal power density. Therefore, a multi-layer anode structure, supported by 3D printed polypropylene, is developed for mAAB pouch cells. This design effectively increases the anode/cathode surface area ratio and enables rapid ion and electron transport within the multi-layer anode, optimizing power performance. A schematic of a 3D printed polypropylene supported multi-layer anode structure is shown in Figure 2B. The electrochemical performance of assembled mAAB pouch cells is evaluated to assess their suitability for the demanding requirements of small scale quadcopter applications. Figure 3A provides a comparative analysis of power densities between mAABs and commercial micro-quadcopter mLIBs. Notably, mAABs exhibit a peak power density exceeding 1500 Wh/kg battery at 4 Amp, surpassing that of mLIBs. Battery weight encompasses anode, cathode, electrolyte and all necessary battery packaging, confirming that mAABs can meet the power demands of micro-quadcopters. In Figure 3B, the energy density of mAABs is compared to commercial mLIBs. When the power density is above 500 W/kg battery , a threshold sufficient to lift a quadrotor drone, mAABs exhibit an energy density of 320 Wh/kg battery , which is multiple times higher than that of mLIBs. [3] Notably, the anode utilization of the mAAB exceeds 85%, underscoring the effectiveness of the multi-layer anode design. This superior electrochemical performance emphasizes the superior capability of mAABs, indicating their potential as an advanced power source for long flight duration small scale quadcopters. References: Li, Yanguang, and Jun Lu. "Metal–air batteries: will they be the future electrochemical energy storage device of choice?." ACS Energy Letters 2.6 (2017): 1370-1377. Cao, Ruiguo, et al. "Recent progress in non‐precious catalysts for metal‐air batteries." Advanced Energy Materials 2.7 (2012): 816-829. Mulgaonkar, Yash, et al. "Power and weight considerations in small, agile quadrotors." Micro-and Nanotechnology Sensors, Systems, and Applications VI. Vol. 9083. SPIE, 2014. Figure 1

Magnetic field sensors that can operate at temperatures above 300 °C are necessary for sensing in harsh environments. A strain-modulated sensor composed of AlN and FeCo paired with an AlNiCo magnetic bias circuit and FeCoV flux concentrators capable of operation from 25 to 500 °C is presented. The total package size, including the bias circuit and flux concentrators, is 0.4 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>, and at 500 °C, the noise spectral density of this sensor is 26 nT/√Hz for a 100 Hz signal. At 500 °C, the sensor has a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> factor of 1366 and a theoretical bandwidth of 2.5 kHz. The noise spectral density and sensitivity are reported for various temperatures as the temperature is heated from 25 to 500 °C and subsequently cooled from 500 to 25 °C.

Internet of Things (IoT) devices and small robots would benefit from higher-energy-density and disposable primary Al–air batteries, but corrosion and side reactions on the Al anode limit the widespread application of this chemistry. This paper studies how the physical and chemical characteristics of double-network hydrogel (DNH) electrolytes affect the anode oxidation, discharge morphology, and performance of Al–air batteries. The chemically crosslinked and physical–chemical crosslinked DNHs were made from biodegradable materials and showed enhanced corrosion inhibition compared to aqueous KOH solution, reducing the corrosion rate by 58% to 21 mmpy. An Al–air battery with a PVA-PAAM DNH extracted over 300 mAh cm−2 from Al at 10 mA cm−2.

Ultra-high-molecular-weight polyethylene (UHMWPE) components for orthopedic implants have historically been integrated into metal backings by direct-compression molding (DCM). However, metal backings are costly, stiffer than cortical bone, and may be associated with medical imaging distortion and metal release. Hybrid-manufactured DCM UHMWPE overmolded additively manufactured polyetheretherketone (PEEK) structural components could offer an alternative solution, but are yet to be explored. In this study, five different porous topologies (grid, triangular, honeycomb, octahedral, and gyroid) and three surface feature sizes (low, medium, and high) were implemented into the top surface of digital cylindrical specimens prior to being 3D printed in PEEK and then overmolded with UHMWPE. Separation forces were recorded as 1.97-3.86 kN, therefore matching and bettering the historical industry values (2-3 kN) recorded for DCM UHMWPE metal components. Infill topology affected failure mechanism (Type 1 or 2) and obtained separation forces, with shapes having greater sidewall numbers (honeycomb-60%) and interconnectivity (gyroid-30%) through their builds, tolerating higher transmitted forces. Surface feature size also had an impact on applied load, whereby those with low infill-%s generally recorded lower levels of performance vs. medium and high infill strategies. These preliminary findings suggest that hybrid-manufactured structural composites could replace metal backings and produce orthopedic implants with high-performing polymer-polymer interfaces.

This study introduces a novel miniature Magnetostatic Wave Filter (MSWF) based on micromachined Yttrium Iron Garnet (YIG) with meander line transducers. The MSWF achieves a low insertion loss of 2.1-3 dB and over 35 dB isolation while tuning from 3.3-9.7 GHz. Utilizing a zero-static-power miniature magnetic bias circuit, the filter is continuously electrically tunable, compact (1.7 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>), and consumes no static power. Meander line transducers enhance resonator Q-factor and Figure of Merit (FoM), reducing filter insertion loss compared to straight line transducers. The device also exhibits superior linearity and increased power handling eanabifity.

Image sensors made using colloidal quantum dots (CQDs) as the optical absorber material are breaking through as a viable competing technology within the SWIR and MWIR imaging domains. The CQD-based absorber material stack is processed directly onto the surface of the CMOS wafer providing advantages in scalability, cost and flexibility regarding pixel size and dimensions. The absorption spectrum can be tailored by choice of quantum dot size and material system for the same underlying read-out integrated circuit (ROIC). Here, we introduce the Emberion image sensor platform and report our recent results on image sensor development using Lead Sulfide (PbS) CQDs processed onto our custom-designed ROIC. The optoelectronic characteristics of the CQD photosensitive stack are analyzed and the optimal interface to the ROIC is discussed. We also address challenges related to manufacturability such as the planarity requirements of the ROIC surface to facilitate wet-processing via spin-cast CQD thin-film layers. We demonstrate wavelength response from 400 nm out to beyond 2000 nm with noise equivalent irradiance (NEI) below 1e-3 W/m2 over the entire spectral range. Selected illustrative application demonstrations are showcased including detection of water content at SWIR wavelengths, high-speed imaging of a moving target at 400 fps and camouflage detection.

A single tunable filter simplifies complexity, reduces insertion loss, and minimizes size compared to frequency switchable filter banks commonly used for radio frequency (RF) band selection. Magnetostatic wave (MSW) filters stand out for their wide, continuous frequency tuning and high-quality factor. However, MSW filters employing electromagnets for tuning consume excessive power and space, unsuitable for consumer wireless applications. Here, we demonstrate miniature and high selectivity MSW tunable filters with zero static power consumption, occupying less than 2 cc. The center frequency is continuously tunable from 3.4 GHz to 11.1 GHz via current pulses of sub-millisecond duration applied to a small and nonvolatile magnetic bias assembly. This assembly is limited in the area over which it can achieve a large and uniform magnetic field, necessitating filters realized from small resonant cavities micromachined in thin films of Yttrium Iron Garnet. Filter insertion loss of 3.2 dB to 5.1 dB and out-of-band third order input intercept point greater than 41 dBm are achieved. The filter's broad frequency range, compact size, low insertion loss, high out-of-band linearity, and zero static power consumption are essential for protecting RF transceivers from interference, thus facilitating their use in mobile applications like IoT and 6 G networks.

Abstract Soft robots and wearable technologies benefit significantly from stretchable batteries, yet the rigid nature of high‐capacity electrodes creates large trade‐offs in battery performance and stretchability. This study introduces a new approach for realizing stretchable batteries by allowing the electrodes to slide along a stretchable electrolyte. When the sliding‐electrodes battery is stretched, the forces are transmitted through the hydrogel electrolyte and elastomeric enclosure, while the rigid electrodes slide relative to the hydrogel to maintain interfacial contact. The sliding‐electrodes approach allows 100% of the unstretched battery area to be covered by thick electrodes so that the battery areal capacity and power are improved by up to 10X of prior stretchable designs. Three metal‐air batteries achieve areal capacities of up to 104 mWh cm −2 . Further mechanical testing, electrochemical characterization, and integration into soft robotic systems demonstrate the potential of these stretchable batteries in practical applications. The sliding‐electrodes battery can stably power multiple servo motors and sensing circuits under stretching, twisting, bending, and after impact.

This paper presents a miniature (1.7 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) and zero static power magnetostatic surface wave tunable notch filter with a tuning range from 3.3 GHz – 10.3 GHz. The notch frequency can be directly tuned by transient voltage pulses applied to a magnetic bias circuit, eliminating the need for bulky, power-hungry electromagnets. Aluminium transducers were designed to achieve strong spin wave coupling by direct placement on yttrium iron garnet magnetostatic wave resonators. Low insertion loss was achieved by absorbing the parasitic inductance of the magnetostatic wave resonator transducers into an on-chip LC transmission line. The filter exhibits less than 1.8 dB of insertion and a notch rejection of more than 38 dB.