Its mechanical transmission converts the up-and-down stroke of heel movement into rotation of a rotor. As the rotor turns, its magnets move within the electromagnetic generating system, producing voltage through electromagnetic induction. A second conversion mechanism operates alongside the electromagnetic branch.

A driven magnet and a tip magnet couple the device’s motion into vibration of a piezoelectric cantilever beam, allowing the piezoelectric component to generate electrical voltage. The design therefore uses two energy-conversion approaches within a single heel-strike harvester rather than relying on only one physical effect. Researchers built the EPHEH prototype and performed detailed performance tests.

The reported maximum average output power of 8.5 milliwatts applied specifically to the electromagnetic branch at a pressing frequency of 1.5 hertz. At that same excitation frequency, the measured electromagnetic output power density was 23.3 microwatts per cubic centimetre. The supplied study abstract does not report a combined output value for the electromagnetic and piezoelectric branches.

The investigators also evaluated how the electrical output could be stored and used. Under excitation at 1.5 hertz, a 0.22-farad capacitor charged from 0 to 3.3 volts in four minutes. They then incorporated the harvester into an energy-harvesting shoe and carried out application experiments in which a microcontroller controlled the lighting state of an LED, while another configuration powered a thermohygrometer.

These demonstrations show that the prototype’s electrical output can operate low-power electronic components. They do not establish how much power the shoe would recover from unrestricted human walking, because the reported maximum output and power density came from tests conducted at a specified pressing frequency. The frequency-up-conversion design is central to the prototype’s operation.

Mechanical movement associated with heel strike is transferred into rotor rotation for electromagnetic generation, while magnet coupling excites the piezoelectric cantilever. These two branches are intended to make use of the same movement through distinct conversion pathways, although the reported headline performance figure concerns only the electromagnetic component. The capacitor-charging measurement and the operation of the LED and thermohygrometer move beyond instrument-only output tests, while the reported laboratory values quantify the prototype’s performance under controlled excitation.

The study’s scope remains centered on a constructed prototype and shoe-based demonstrations, and the available evidence does not quantify longer-term operation or harvesting from continuous, unconstrained walking.

Subject of Research: Electromagnetic and piezoelectric energy harvesting from human heel-strike movement

Article Title: Design and analysis of a frequency up-conversion electromagnetic-piezoelectric hybrid energy harvester for human heel strike movement energy harvesting

Article References: Xie, Z., Zhang, S., Zhu, Y., Fu, B., & Huang, W. (2026). Design and analysis of a frequency up-conversion electromagnetic-piezoelectric hybrid energy harvester for human heel strike movement energy harvesting. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13926-y

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13926-y

Keywords: energy harvesting, heel strike, piezoelectricity, electromagnetic induction, frequency up-conversion, wearable electronics, prototype testing, energy storage, Design, analysis, frequency, up-conversion

Collagen is the most abundant protein in the human extracellular matrix, providing structural integrity to bones, skin, tendons, and virtually every connective tissue. What makes it scientifically extraordinary is its non-centrosymmetric triple-helical structure. Unlike materials whose molecular arrangement is symmetric in all directions, collagen’s helical architecture lacks a center of symmetry, which is the fundamental prerequisite for piezoelectricity. When mechanical force deforms the helix, the displacement of charged molecular groups within the structure creates a net electrical polarization. This means collagen can convert mechanical energy from body movement directly into localized electrical signals without any external power source, a property that has profound implications for how cells behave in their microenvironment.

The review, which surveyed literature from January 2000 to June 2026 across PubMed, Scopus, and Web of Science, identified that collagen-based piezoelectric biomaterials have shown promise across multiple tissue types, including bone, neural, skin, and cardiac tissue engineering. The key insight is that piezoelectric scaffolds can harness the body’s own endogenous mechanical stimuli, such as walking, breathing, or cardiac pulsation, and convert them into localized electrical cues at the implant site. These electrical signals influence cell adhesion, migration, differentiation, and extracellular matrix remodeling, all without the need for batteries, wires, or external stimulators. This self-powered approach represents a fundamental shift from traditional electrically active implants that require external energy.

At the nanoscale, the origins of collagen piezoelectricity have been progressively uncovered through advanced characterization techniques. Piezoresponse force microscopy has revealed nanoscale electromechanical heterogeneity within the subfibrillar structure of collagen fibrils, meaning that piezoelectric properties vary across the molecular building blocks of the protein. Molecular dynamics simulations have further clarified the polarization mechanisms within the super-twisted collagen structure, showing how the specific amino acid sequence and the spatial arrangement of alanine, hydroxyproline, and glycine residues contribute to the net piezoelectric response. These studies demonstrate that collagen’s piezoelectricity is not a uniform bulk property but emerges from the precise molecular geometry of its triple helix.

Fabrication strategies for collagen-based piezoelectric biomaterials have evolved considerably. Electrospinning, a technique that uses electrical forces to draw polymer solutions into nanofibers, has emerged as a leading method for creating collagen-containing piezoelectric scaffolds with controlled fiber alignment and porosity. Near-field electrospinning allows even greater precision in fiber placement, enabling researchers to pattern scaffolds that mimic the anisotropic architecture of native tissues. The alignment of electrospun fibers matters enormously, because the direction of fiber orientation determines the direction of piezoelectric response, which in turn influences how cells orient and migrate on the scaffold surface.

Hybrid systems that combine collagen with other piezoelectric or conductive materials have demonstrated enhanced electromechanical performance beyond what collagen alone can achieve. Barium titanate, a ceramic piezoelectric material with a high piezoelectric coefficient, has been incorporated into composite scaffolds to boost the overall electrical output. Conductive polymers have also been integrated to improve charge transport within the scaffold matrix. These hybrid approaches address one of the key limitations of pure collagen, which is that its piezoelectric coefficient is relatively modest compared to synthetic ceramics. By combining collagen’s biocompatibility and biodegradability with the superior piezoelectric performance of synthetic materials, researchers can create scaffolds that are both biologically compatible and electrically potent.

In bone tissue engineering, piezoelectric scaffolds have shown particular promise because bone itself is a naturally piezoelectric tissue. The review identified that piezoelectric signals play a role in vascularized bone regeneration, and that electrical stimulation can promote osteogenic differentiation of stem cells. Ultrasound-activated piezoelectric scaffolds have been developed to target specific intracellular signaling pathways, including calcium ion and NF-κB signaling, to orchestrate immunomodulation and osteogenesis for accelerated bone regeneration. The converse piezoelectric effect, where an applied electrical field produces mechanical deformation, has also been explored as a novel approach for applying mechanical stimulation to bone tissue without external loading.

In neural tissue engineering, electrospun piezoelectric scaffolds have been shown to support neurite extension of primary neurons, suggesting that the localized electrical cues generated by these materials can guide nerve regeneration. Biodegradable piezoelectric sensors have been developed for real-time evaluation of motor function recovery after nerve injury, demonstrating that the same materials used for tissue regeneration can also serve as diagnostic tools. In skin wound healing, piezoelectric film scaffolds have promoted healing with enhanced collagen deposition and blood vessel regeneration through upregulation of the PI3K/AKT signaling pathway. Three-dimensional printed piezoelectric wound dressings have been developed with dual piezoelectric response models for scar-prevention wound healing, and self-powered piezoelectric nanofibrous hydrogels have been designed for synergistic electro-pharmacological therapy of chronic wounds.

Beyond tissue regeneration, the review highlights the emerging potential of collagen-based piezoelectric materials for biosensing and energy harvesting applications. Piezoelectric nanogenerators can convert human motion into electrical energy for powering wearable and implantable devices, and self-powered sensors based on these materials can monitor physiological signals in real time without batteries. Collagen-gold nanoparticle conjugates have been developed for versatile biosensing, and collagen-based biopiezoelectric nanogenerators have been prepared from biological waste materials such as fish skin, demonstrating the sustainability potential of these approaches. Flexible pressure sensors, wearable patches for sweat analysis, and implantable BioMEMS devices all represent potential integration points for collagen-based piezoelectric platforms in next-generation healthcare systems.

Despite the remarkable progress, the review emphasizes that clinical translation of collagen-based piezoelectric biomaterials requires further advancement in several critical areas. Performance variability remains a challenge, as the piezoelectric properties of collagen can differ depending on source, processing method, and environmental conditions. Degradation stability must be improved to ensure that scaffolds maintain their electromechanical performance throughout the tissue regeneration process. Seamless integration with flexible electronic systems is essential for combining tissue engineering with biosensing functionality. The review concludes that standardized fabrication protocols, rigorous in vivo validation, and careful consideration of regulatory requirements will be essential for advancing these materials toward practical biomedical use. As research continues to unravel the molecular mechanisms of collagen piezoelectricity and refine fabrication strategies, these materials stand poised to redefine the interface between biology and electricity in medicine.

Subject of Research: Bio-piezoelectric mechanisms and biomedical applications of collagen-based piezoelectric biomaterials

Article Title: Bio-Piezoelectricity of Collagen: Mechanisms, Tissue Engineering Applications, and Biosensing Potential

Article References: Pan, C.-T., Laya, S., Shiue, Y.-L., & Paudel, T. (2026). Bio-Piezoelectricity of Collagen: Mechanisms, Tissue Engineering Applications, and Biosensing Potential. Journal of Medical and Biological Engineering. https://doi.org/10.1007/s40846-026-01059-1

Image Credits: AI Generated

DOI: 10.1007/s40846-026-01059-1

Keywords: collagen, piezoelectricity, tissue engineering, regenerative medicine, biosensors, electrospinning, nanogenerators, biomaterials, bone regeneration, wound healing, energy harvesting, extracellular matrix

Piezoelectric materials convert mechanical strain into electrical signals, and piezoelectric polymers are prized wherever flexibility matters: flexible electronics, wearable sensors, energy harvesters, and electrically active biomaterial scaffolds. PLLA occupies a special niche in this landscape because it is biocompatible, biodegradable, mechanically compliant, and intrinsically piezoelectric. The Connecticut groups have previously used PLLA nanofiber systems for biodegradable transducers, cartilage repair, wound healing, and osteoinductive scaffolds, exploiting the materials’ ability to generate therapeutic electrical cues under mechanical or ultrasound stimulation.

The team’s fabrication method of choice was electrospinning, one of the most widely used techniques for producing polymer nanofibers. In this process, a high electric field pulls a droplet of polymer solution out of a needle toward a grounded collector, drawing continuous fibers that range from micro- to nanoscale diameter. Electrospun nanofiber mats resemble the native extracellular matrix more closely than bulk films, and the elongation the polymer jet experiences during spinning can induce the molecular alignment and crystallinity that underpin piezoelectricity in PLLA.

Among the many parameters that shape nanofiber performance, fiber alignment has attracted particular interest because it governs mechanical anisotropy, crystal organization, and piezoelectric response. Randomly deposited fibers yield isotropic mats, whereas aligned fibers offer enhanced directionality in mechanical properties and more uniform electromechanical behavior. In PLLA, tighter alignment is thought to facilitate enhanced chain orientation, improved stress transfer, and greater piezoelectric output under load. Rotating collectors are a common alignment tool, but the authors note that specifics — solution preparation, ambient environment, collector configuration, speed determination, alignment quantification, and piezoelectric validation — are often omitted or relegated to supplementary material, hampering reproducibility and cross-study comparison.

The new protocol closes that gap with a fully specified workflow. The researchers dissolved PL38 polymer in chloroform — a validated replacement for methylene chloride, whose research and consumer uses the EPA banned as of May 5, 2025 — and spun the solution at 14 kV from a 20-gauge needle positioned a fixed 8.573 centimeters from a foil-wrapped rotating drum. Humidity was held between 25 and 35 percent inside the spinning chamber, adjusted with dry air or ultrapure water as needed, while flow rate, polymer concentration, and tip-to-collector distance were kept constant so that collector speed stood as the only deliberate variable.

After spinning, the films underwent an overnight evaporation step on the drum, followed by a two-stage annealing sequence: first at 105 °C to drive off residual solvent, then sandwiched between Teflon films at 160 °C to stabilize the material. For some applications the team cryosectioned the annealed sheets into individual nanofibers, embedding them in O.C.T. compound, freezing at −80 °C, and cutting 0.25-micrometer sections perpendicular to the fiber direction before washing away the embedding medium and lyophilizing the product.

Alignment was quantified rather than eyeballed. Scanning electron microscopy images taken at ×5 kV and ×5000 magnification were processed with a MATLAB two-dimensional structure tensor approach, producing normalized orientation histograms from 0 to 180 degrees. The key metric was orientation spread, where lower values indicate tighter alignment. When the drum spun at 1000 rpm, the fibers were visibly more random, and the orientation spread measured 19.57 degrees. At 2000 rpm it narrowed to 14.68 degrees, and at 4000 rpm the mats displayed aligned fiber bundles with a spread of just 11.23 degrees. The authors attribute this trend to stronger directional pull and increased shear forces on the polymer jet at higher speeds, which suppress the jet oscillations responsible for random deposition.

Structural analysis supported the mechanistic story. Fourier transform infrared spectroscopy showed consistent chemical composition across all samples, but within the 850–940 per centimeter region associated with piezoelectric activity, films spun at 2000 and 4000 rpm showed stronger beta-phase peaks. Quantified by integrating spectral regions, the relative beta-phase content rose from 56 percent at 1000 rpm to 61 percent at 2000 rpm and 62 percent at 4000 rpm, at the expense of the alpha phase. By contrast, X-ray diffraction revealed no differences in peak position or intensity across samples, and differential scanning calorimetry showed similar thermal behavior in all films, each with a characteristic melting endotherm near 180 °C — suggesting the piezoelectric gains arise from molecular packing and phase organization rather than changes in bulk crystallinity.

The functional payoff was unambiguous. Measured with a quasi-static d33 meter under a 0.05 newton compressive force, the effective piezoelectric coefficient climbed from 3.37 pC/N at 1000 rpm to 4.13 pC/N at 2000 rpm and 5.92 pC/N at 4000 rpm — roughly a 76 percent increase across the speed range. Open-circuit voltage output, recorded with an oscilloscope while ultrasound at 1 MHz and 0.5 W/cm² pressed on gel-coupled samples fitted with aluminum foil electrodes, rose from 15 mV to 20 mV to 35 mV. Samples were soaked in deionized water before testing to suppress triboelectric artifacts, ensuring the signals reflected genuine piezoelectric response.

The authors are candid about the method’s limits. Collector speed does not act alone: polymer concentration, solvent system, flow rate, applied voltage, tip-to-collector distance, temperature, and humidity all influence final fiber morphology, so each system requires systematic optimization. At extremely high rotational speeds, fibers can suffer instability, breakage, or nonuniform deposition, degrading mat quality. Alignment also does not correlate linearly with piezoelectricity — crystalline phase content, dipole alignment, fiber diameter, and device design all contribute — so morphological evaluation must be paired with structural and functional characterization. Practical troubleshooting guidance, from drum release coatings to syringe pump replacement every three years and desiccator storage that keeps performance stable for roughly two months, rounds out the protocol. With those caveats, the team argues the framework offers a simple, reproducible dial for designing tunable scaffolds, wearable sensors, and mechanically triggered energy harvesters, and could extend to other polymers, piezoelectric composites, multilayer structures, and scaled-up setups.

Subject of Research: Collector speed-controlled fiber alignment and piezoelectric properties of electrospun PLLA nanofibers

Article Title: Tuning the structure-piezoelectric property relationship in electrospun PLLA nanofibers through collector-induced fiber alignment

Article References: Muhammad, I., Miller, K., Ge, G., Nguyen, T. D., & Lo, K. W.-H. (2026). Tuning the structure-piezoelectric property relationship in electrospun PLLA nanofibers through collector-induced fiber alignment. Frontiers in Biomaterials Science, 5, Article 1967187. https://doi.org/10.3389/fbiom.2026.1967187

Image Credits: AI Generated

DOI: 10.3389/fbiom.2026.1967187

Keywords: electrospinning, PLLA, nanofibers, piezoelectricity, fiber alignment, biomaterials, energy harvesting, wearable sensors, tissue scaffolds, rotating collector, beta phase, biodegradable polymers

The achievement matters because multifunctionality is one of the central goals of nanomedicine. Most therapeutic nanoparticles are designed to perform a single task: deliver a drug, generate heat, or provide electrical stimulation. Combining several functions in one biocompatible structure means that a single implanted or injected material could, in principle, be switched between different modes of action depending on what the surrounding tissue needs. The IIT team’s nanotubes offer exactly this kind of programmable versatility, responding to two completely external and non-invasive triggers, light and sound, that can be applied from outside the body with careful control of dose and location.

The starting material is as surprising as the result. The nanoparticles are made from polydopamine, a polymer formed when dopamine, the neurotransmitter that carries chemical signals in the human brain, binds into long chains. On its own, dopamine is a small molecule, but polymerised it becomes a strongly adhesive, biocompatible material that is already widely used in biomedical research because it integrates well with human tissues. Polydopamine has a long track record in applications ranging from surface coatings to drug delivery vehicles, which makes it an attractive foundation for a new class of therapeutic nanodevices.

What changed in this study was the geometry. Until now, polydopamine had typically been studied in the form of spherical nanoparticles. Ciofani’s group instead shaped the polymer into nanotubes: hollow cylinders approximately one-seventieth the length of a grain of sand, with a diameter about 500 times smaller than that of a human hair. That structural decision proved decisive. Changing the shape of the material changed its physical properties, and one property in particular emerged that had never been seen in this substance before: piezoelectricity.

Piezoelectricity is the ability of a material to generate an electric current in response to mechanical deformation. It is common in certain ceramics and crystals but rare in organic, biocompatible nanomaterials, which is precisely why the observation is significant. The researchers induced vibrations in the nanotubes using ultrasound, causing the tubular structures to deform rhythmically and produce electrical output. In effect, the nanotubes behave as wireless electrodes: once placed in tissue, they can be activated remotely by an ultrasound beam, without wires, batteries or surgical replacement of power sources. The same principle could be exploited to build bioelectronic devices at the nanoscale or microscale.

The tubular geometry is what unlocks this behaviour. As Ciofani explains, the ability to generate an electric current in response to mechanical stimulation is a very rare and important property for an organic, biocompatible nanomaterial, and piezoelectricity had never previously been observed in polydopamine. In his account, the tubular shape allowed a property that is absent in spherical nanoparticles made from the same material to emerge. The lesson for materials science is a familiar one but strikingly demonstrated here: in nanomaterials, form and function are inseparable, and simply reshaping a known polymer can reveal entirely new physics.

The other two functions of the nanotubes derive directly from the chemistry of polydopamine. First, the material absorbs infrared light and converts it into heat, a photothermal effect. Delivered in a controlled way, localised warming can stimulate cellular activity in tissues; one example highlighted by the researchers is the release of intracellular calcium, the ionic signal that underlies communication between cells. Photothermal heating is also a well-established strategy in oncology research, where gentle, targeted heating of tumour tissue can damage cancer cells while sparing healthy ones, although the current study focuses on cellular modulation rather than cancer therapy itself.

Second, when the nanotubes are stimulated with ultrasound, they release individual dopamine molecules in a controlled manner. Dopamine is not only a neurotransmitter but also an antioxidant, meaning it can neutralise reactive molecules that damage cells. Released at a target site, the dopamine therefore produces a protective antioxidant effect, shielding cells from oxidative stress and promoting their survival. Oxidative stress is implicated in a wide range of pathologies, including neurodegenerative diseases, which is one reason the researchers see the nervous system as a particularly promising arena for this technology, alongside regenerative medicine and neurostimulation.

Matteo Battaglini, first author of the study, summarises the platform concept: the nanotubes release dopamine in a controlled manner and respond to external stimuli such as ultrasound and infrared light, integrating multiple functions into a single platform. That integration is the key selling point. A clinician or researcher working with these particles would not need to choose between electrical stimulation, thermal activation and antioxidant protection; the same material could provide all three, selected and timed through external triggers. Before any such use, however, safety had to be established, and the team addressed this directly.

To assess biocompatibility, the researchers tested the nanotubes on cultured cells and observed that the nanostructures were incorporated by the cells without interfering with their normal activity. That is an encouraging early result, though it represents the first step of a long translational path from laboratory cultures to clinical applications. The study was conducted within IIT’s flagship programme Technologies for Healthy Living, which aims to develop health technologies capable of precisely activating and delivering therapies, with contributions from PhD students enrolled at the Sant’Anna School of Advanced Studies in Pisa and researchers from the Italian National Institute of Metrological Research in Turin.

Taken together, the results establish polydopamine nanotubes as a new class of multifunctional nanomaterials. Their potential applications span regenerative medicine, neurostimulation and the development of bioelectronic devices, as well as the controlled delivery of therapeutic molecules to the nervous system. The work also carries a broader message for the field: the next generation of nanomedicines may come not from exotic new chemicals but from familiar, body-friendly polymers re-engineered at the nanoscale, where a change as simple as rolling a sphere into a tube can turn a passive material into an active, remotely controlled therapeutic tool.

Subject of Research: Multifunctional polydopamine nanotubes combining piezoelectric, photothermal and antioxidant properties for nanomedicine

Article Title: They heat, heal and stimulate cells: IIT’s new nanoparticles for nanomedicine

Article References: They heat, heal and stimulate cells: IIT’s new nanoparticles for nanomedicine. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: nanomedicine, polydopamine, nanotubes, piezoelectricity, photothermal therapy, antioxidant, dopamine, ultrasound, infrared light, neurostimulation, biocompatibility, Italian Institute of Technology

To appreciate why this matters, it helps to understand what a phononic integrated circuit, or PnIC, actually is. Just as photonic integrated circuits guide light through nanoscale channels, phononic circuits guide mechanical vibrations—phonons—through engineered waveguides. At gigahertz frequencies, these vibrations have wavelengths measured in mere hundreds of nanometers, roughly five orders of magnitude shorter than electromagnetic waves of the same frequency. That enormous shrinkage factor means acoustic devices can pack resonators, filters, and delay lines into a footprint far smaller than any radio-frequency electromagnetic equivalent. This is precisely why acoustic filters already sit inside nearly every smartphone, converting crowded radio signals into clean channels. The catch has been that most existing acoustic platforms force engineers to choose: they can have low-loss waveguides, or high-quality resonators, or efficient transducers, but rarely all of these on one chip.

The Virginia Tech and University of Virginia collaboration set out to break that trade-off. Their ideal platform, as described in the paper, should simultaneously support four building blocks: low-loss acoustic waveguides, high-quality-factor resonators, high-performance modulators, and efficient electromechanical transducers. The material pairing they chose is chemically and mechanically elegant. Lithium niobate is a ferroelectric crystal famous for its strong piezoelectric properties, meaning it converts electrical signals into mechanical motion—and back again—with exceptional efficiency. It also possesses large electro-optic and acoustic velocities that make it a favorite in modern integrated photonics. Silicon nitride, by contrast, is one of the lowest-loss optical materials known, forms ultrasmooth films, and is compatible with standard semiconductor foundry processes. By patterning thin-film silicon nitride directly on lithium niobate, the team created a hybrid structure in which each material does what it does best: lithium niobate drives and senses the vibrations, while the carefully shaped silicon nitride confines and directs them.

The headline performance metric of the new platform is the propagation frequency-quality factor product of its acoustic waveguides, which reached 4.22 × 10^13. In the world of resonant and wave-based systems, the quality factor, or Q, measures how many oscillation cycles a wave or resonator completes before its energy dissipates. Multiplying Q by frequency yields a figure of merit that is largely independent of scale, allowing fair comparison across platforms. A frequency-Q product above 10^13 places these acoustic waveguides in an elite class of coherent information carriers, comparable to the best optical waveguides in relative terms. Practically, it means that a gigahertz sound wave traveling through the team’s circuits retains its energy over distances long enough to build complex, multi-element circuits—delays, filters, interferometers—without the signal fading into heat. For quantum applications, where a single phonon must survive long enough to be manipulated and read out, such low loss is not a luxury but a prerequisite.

Waveguides alone do not make a circuit, however; engineers also need ways to split and combine acoustic signals with minimal waste. The team demonstrated directional couplers—devices in which two waveguides run close enough that vibrational energy gradually transfers from one to the other through evanescent coupling, the same physics that lets a vibrating tuning fork set a neighboring fork ringing. Their couplers achieved controllable power transfer at an insertion loss of just 3.5 dB. Insertion loss quantifies how much signal is lost simply by passing through a component, and every decibel counts when signals are weak or when photons and phonons must be conserved at the quantum level. A 3.5 dB figure means that roughly 55 percent of the acoustic power survives the coupling process, a level the authors identify as a key enabler for routing phonons between resonators, delay lines, and transducers on the same chip.

Storage is the third pillar, and here the platform delivered ring resonators with a loaded quality factor of up to 17,925. An acoustic ring resonator is a closed loop of waveguide in which sound circulates, resonating at frequencies whose wavelengths fit an integer number of times around the ring. The loaded Q includes the coupling losses to the outside world, not just the intrinsic material loss, making it the number that matters in real systems. A loaded Q near 18,000 at gigahertz frequencies corresponds to phonons persisting for microseconds—a long time on the scale of microwave electronics. Long-lived acoustic resonances are the heart of the spectral processing that makes radio-frequency acoustic filters so selective, and they are equally the heart of proposed quantum memories, where mechanical modes would buffer quantum states between optical photons or superconducting qubits.

The team then assembled these building blocks into a showcase application: a 1-gigahertz phononic oscillator built around one of their ring resonators. An oscillator is the metronome of electronics—a device that produces a perfectly periodic signal used to time everything from radio transmitters to radar systems to quantum logic gates. The best electronic oscillators achieve their stability by referencing a high-Q mechanical or electromagnetic resonance, and the new phononic oscillator leverages the platform’s 17,925 loaded Q to spectacular effect. It reached a phase noise of −159.0 dBc/Hz at a 100-kilohertz offset from the carrier. Phase noise describes the rapid, random fluctuations in an oscillator’s timing; lower is better, and the decibel scale here means the noise power is 159 billion times smaller than the carrier power within a one-hertz bandwidth at that offset. That figure rivals the performance of much bulkier, power-hungry microwave oscillators, in a device etched onto a chip.

The implications ripple outward across several fields at once. For microwave acoustics, the platform offers a path toward integrated radio-frequency processors that are smaller, cleaner, and more stable than today’s surface-acoustic-wave and bulk-acoustic-wave components, which typically rely on suspended or bulky geometries. For quantum phononics, low-loss gigahertz phonons are a sought-after resource: they can couple to superconducting qubits through piezoelectric transduction, interface with solid-state defects such as those in diamond or silicon carbide, and bridge to optical photons in hybrid quantum networks. Lithium niobate’s piezoelectricity makes that electromechanical link natural, while silicon nitride’s optical excellence makes the photonic link equally promising. The authors point to integrated hybrid systems combining phonons, photons, superconducting qubits, and solid-state defects as the long-term destination—and this platform is designed from the outset to host all of them.

The research was conducted with support from several major United States funding programs, including the Air Force Office of Scientific Research, the Defense Advanced Research Projects Agency’s OPTIM, SynQuaNon, and GRYPHON programs, and fabrication was performed at the Center for Nanophase Materials Sciences, a Department of Energy Office of Science user facility. The work also reflects a growing trend in which Virginia’s university ecosystem—through the Commonwealth Cybersecurity Initiative—invests in the intersection of quantum devices and secure communications. The paper, received in March 2026 and accepted in September 2026, is open access, allowing engineers and physicists worldwide to build on its results immediately.

What makes this demonstration genuinely exciting is its completeness. Many platform papers showcase a single impressive component; this one delivers waveguides, couplers, resonators, and a working oscillator, all on the same material system, all at gigahertz frequencies, and all with numbers that stand up against the best specialized devices in each category. The phonon, long treated as the awkward cousin of the photon, now has an integrated circuit platform worthy of its ambitions. If the trajectory of silicon photonics is any guide, the coming years could see these sound-based circuits shrink radar front ends, sharpen quantum sensors, and serve as the mechanical backbone of hybrid quantum machines—proof that sometimes the future of computing hums at a frequency we cannot hear, in a material we cannot see, on a chip smaller than a fingernail.

Subject of Research: Low-loss gigahertz phononic integrated circuits on a silicon nitride–lithium niobate platform

Article Title: Low-loss phononic integrated circuits based on a silicon nitride-lithium niobate platform

Article References: Ji, J., Thomas, J. G., Xi, Z., Liu, R., Fang, K., Qin, Y., Beling, A., Yi, X., Zhu, Y., & Shao, L. (2026). Low-loss phononic integrated circuits based on a silicon nitride-lithium niobate platform. Communications Engineering. https://doi.org/10.1038/s44172-026-00795-1

Image Credits: AI Generated

DOI: 10.1038/s44172-026-00795-1

Keywords: phononics, integrated circuits, silicon nitride, lithium niobate, acoustic waveguides, ring resonators, quality factor, oscillators, phase noise, quantum phononics, microwave acoustics, piezoelectricity

P(VDF-co-TrFE) is the most technologically important member of the PVDF copolymer family, and the reason lies in a single fluorine atom. Poly(vinylidene fluoride), or PVDF, is famous for its piezoelectricity — a property discovered in mechanically poled films by Heiji Kawai in 1969 — but its most useful crystalline form, the all-trans beta phase, does not form easily from the melt. In the beta phase the carbon backbone adopts a planar zig-zag conformation that points every carbon–fluorine bond dipole to the same side of the chain, producing the largest spontaneous polarization of any known polymer, roughly 0.13 coulombs per square metre. Ordinary PVDF instead crystallizes preferentially into the non-polar alpha phase, whose trans-gauche-trans-gauche-prime conformation cancels those dipoles, forcing manufacturers to stretch or electrically pole their films to convert them.

The trifluoroethylene (TrFE) unit solves this problem chemically. Its extra fluorine substituent adds steric and electrostatic hindrance to gauche conformations, locking the backbone into the all-trans geometry and stabilizing the ferroelectric beta phase directly upon melt crystallization, with no stretching or poling required. The copolymer also undergoes a sharp Curie transition from ferroelectric to paraelectric well below its melting point — a feature absent in neat PVDF — making it an ideal model system for studying ferroelectric switching in organic materials. Thin films of P(VDF-TrFE) now appear in ferroelectric transistors, non-volatile memories, piezoelectric nanogenerators, flexible pressure sensors and photovoltaic devices where the polarization modulates charge transport.

To probe the molecular origins of this behaviour, the team first had to decide how long a chain to simulate. An energy-convergence analysis over oligomers of one to twenty monomer units showed that the energy per monomer stabilizes at about eight repeat units, so an eight-unit oligomer became the standard model for all subsequent calculations. Seven compositions were examined — 0, 12.5, 25, 50, 75, 87.5 and 100 mol% TrFE — spanning the entire composition range. The optimized geometries confirmed in every case the near-planar, all-trans zig-zag backbone that is the structural signature of the beta phase, with fluorine atoms directed predominantly to one side of the chain and hydrogens to the other, so that all the carbon–fluorine bond dipoles reinforce one another perpendicular to the chain axis.

The conformational analysis quantified exactly why TrFE is such an effective beta-phase stabilizer. Scanning the rotational energy of a pure VDF dimer and a VDF-co-TrFE dimer across the full 0–360 degree range of the backbone dihedral angle revealed double-minimum profiles with trans conformations as the global minima in both cases. Crucially, the TrFE-containing dimer did not shift the position of the preferred conformation; instead it raised the energetic penalty for rotating away from it, with the largest differences of roughly one to two kilojoules per mole appearing in the gauche-like regions. The extra fluorine atom therefore increases the effective torsional rigidity of the chain and suppresses gauche defects — the molecular-level origin of TrFE’s celebrated ability to deliver the ferroelectric phase straight from the melt.

The electronic structure told an equally systematic story. The highest occupied molecular orbital energy fell almost linearly from −9.36 electron-volts at zero TrFE to −10.13 electron-volts at full TrFE, while the lowest unoccupied orbital dropped much more steeply, from +0.65 to −1.77 electron-volts. Because the LUMO falls faster than the HOMO, the HOMO–LUMO gap narrowed progressively from 10.01 electron-volts to 8.35 electron-volts across the series. The orbital isosurfaces showed why: as TrFE content increased, both frontier orbitals became increasingly localized on the TrFE-rich segments, with the LUMO developing a pronounced lobe near the chain terminus — evidence that TrFE units act as the electron-accepting parts of the copolymer. The authors caution that these finite, gas-phase gaps exceed the experimental optical band gap of about five to six electron-volts for beta-phase thin films, as expected for short oligomers lacking inter-chain screening, but the relative trend should persist in the solid.

Conceptual DFT descriptors distilled from those orbital energies painted a consistent reactivity picture. The chemical potential became more negative with rising TrFE content, meaning electronegativity climbed from 4.36 to 5.95 electron-volts, while chemical hardness fell steadily from 5.01 to 4.18 electron-volts and softness rose in parallel. In plain terms, TrFE-rich chains are softer, more electronegative and more electrophilic than VDF-rich chains. The global electrophilicity index more than doubled, from 1.89 to 4.24 electron-volts, with the sharpest rise between 50 and 75 mol% TrFE. From the standpoint of the radical copolymerization mechanism, this means VDF behaves as the relatively electron-donating monomer and TrFE as the electron-accepting one — information that helps rationalize the head-to-head and tail-to-tail sequence defects observed in diffraction studies of real copolymers.

Independent spectroscopic checks supported the structural conclusions. The simulated infrared spectra of all seven compositions showed the intense carbon–fluorine stretching envelope between 1450 and 700 wavenumbers and, tellingly, none displayed the alpha-phase doublet near 615 and 766 wavenumbers that would betray a trans-gauche backbone. The simulated X-ray diffraction patterns were likewise dominated by a single intense reflection near 2-theta of 17–18 degrees, the fingerprint of the overlapping (110)/(200) planes of the orthorhombic beta-phase unit cell, with weaker higher-order reflections whose relative intensities shifted modestly as hydrogen atoms were replaced by the larger fluorine atoms of TrFE.

Perhaps the most striking result was the non-monotonic behaviour of the electric properties. The computed dipole moment rose only slightly from 5.06 debye at zero TrFE, then climbed sharply to 10.10 debye at 25 mol% and reached a maximum of 11.93 debye at 50 mol%, before falling back to 4.86 debye for the pure TrFE chain. The polarization density followed the same pattern, peaking at 20.84 in units of ten-thousand microcoulombs per square metre at equimolar composition. The explanation is geometric: in the pure homopolymers the regular repetition of equivalent units allows partial cancellation of transverse dipole components, whereas near-alternating VDF and TrFE sequences reinforce one another most effectively. The authors are careful to stress that these single-chain values overestimate bulk polarization — the figure at 50 mol% exceeds the experimental remnant polarization of real films because inter-chain depolarizing fields and dipole cancellation in the semicrystalline solid are absent from the model — so only the composition-dependent trend is physically meaningful.

That trend, however, aligns neatly with experiment. Commercial P(VDF-TrFE) copolymers with roughly 20 to 50 mol% TrFE show some of the largest piezoelectric coefficients among PVDF-based materials, and recent work has linked the strongest responses near equimolar composition to a morphotropic-phase-boundary-like competition between the trans-planar and 3/1-helical phases. The dipole maximum found here is therefore a necessary molecular ingredient of, but not a sufficient predictor of, the optimum piezoelectric composition, since crystallinity, domain structure and packing also govern device performance. The team suggests that extending the analysis to periodic crystalline models and direct Berry-phase calculations of the piezoelectric tensor is the natural next step. For now, the study offers materials designers a coherent, atomistic rule of thumb: if you want the strongest ferroelectric fluoropolymer, aim for chains where vinylidene fluoride and trifluoroethylene alternate almost one for one.

Subject of Research: Density functional theory study of the structure, conformation, reactivity and electronic properties of the ferroelectric copolymer β-P(VDF-co-TrFE)

Article Title: DFT study of the structure, conformation, reactivity and electronic properties of β-P(VDF-co-TrFE) copolymer

Article References: Riwa, I. O., Veved, A., Banyikwa, A. T., Costa, R., Sahini, M. G., & Babu, N. S. (2026). DFT study of the structure, conformation, reactivity and electronic properties of β-P(VDF-co-TrFE) copolymer. Discover Chemistry, 3(1), Article 528. https://doi.org/10.1007/s44371-026-00972-3

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00972-3

Keywords: P(VDF-co-TrFE), ferroelectric polymer, density functional theory, beta phase, piezoelectricity, HOMO-LUMO gap, conceptual DFT, conformational analysis, trifluoroethylene, poly(vinylidene fluoride), dipole moment, flexible electronics

The research, led by Chloé Melin of the École de Technologie Supérieure in Montreal and INSA-Lyon, together with Jean-Fabien Capsal, Ricardo Zednik, Angelo Pommella, Nicole Demarquette, and Jean-Marc Chenal, set out to answer a question that has lingered in the literature for years: does PLA actually help PVDF become a better piezoelectric material, or does it merely look like it does on a spectroscopy plot? The team attacked the problem from two processing directions at once. They melt-blended PVDF with PLA at weight ratios of 95/05 and 60/40 using a twin-screw extruder at 210 degrees Celsius, then compression-molded films and stretched them uniaxially at draw ratio 3 across a range of temperatures. In parallel, they prepared the same blend compositions as electrospun fibrous membranes using a semi-industrial twenty-needle unit, with both polymers dissolved together in a dimethyl sulfoxide and acetone mixture.

The central character in this story is the crystal structure of PVDF. The polymer can solidify into several distinct lattice forms, and they are not equal partners. The alpha phase, which forms readily when PVDF cools from the melt, is non-polar and piezoelectrically useless. The beta phase, in which polymer chains adopt an all-trans conformation, is highly polar and delivers the strongest piezoelectric response when the molecular dipoles are aligned by a high-voltage poling treatment. Converting alpha to beta is therefore the name of the game, and the two classic routes are uniaxial stretching of solid films and electrospinning, in which a jet of polymer solution is whipped by intense electric fields into nanometer- and micrometer-scale fibers, combining extreme elongational deformation with rapid solvent evaporation.

Morphology turned out to be the first fork in the road. In the melt-processed blends, scanning electron microscopy revealed that the 95/05 formulation produced a beaded, droplet-in-matrix structure, with discrete PLA domains dispersed in the PVDF, while the 60/40 blend formed a co-continuous architecture in which both polymers formed interpenetrating networks. Differential scanning calorimetry showed that adding PLA left the overall crystallinity of PVDF essentially unchanged at roughly 42 percent, before and after stretching, a consequence of the micrometric PLA domain size and the fact that PVDF crystallizes at a higher temperature than PLA. But the phase composition told a very different story. In the stretched 95/05 blend, the beta-phase fraction matched that of pure PVDF, whereas in the co-continuous 60/40 blend the beta fraction collapsed to 36 percent from the 86 percent achievable in well-processed samples, leaving the material dominated by the inert alpha phase.

The reason for that collapse is a lesson in mechanics. In a co-continuous blend, the macroscopic deformation applied during stretching is shared between the two continuous polymer networks, so the PVDF phase simply never sees enough local stress to drive the alpha-to-beta conformational transformation. Meanwhile, in the beaded 95/05 blend, the team observed cavitation, tiny voids opening at the PVDF-PLA interfaces during stretching, which relaxed local stresses and prevented the hoped-for enhancement of stress transfer to PVDF crystals. Earlier hypotheses in the literature had suggested that PLA could act as a stress concentrator, boosting beta formation through cavitation and heterogeneous deformation. This study’s data call that idea sharply into question: the beta fraction in the stretched blend was no better than in neat PVDF, and in some conditions worse.

Then came the electrical measurements, and the results were even more striking. After poling at 100 volts per micrometer for one hour in dielectric oil, the stretched 95/05 blend showed a piezoelectric coefficient d33 that was 34 to 45 percent lower than pure PVDF stretched under equivalent conditions, despite having a nearly identical beta-phase fraction. The culprit, the researchers showed, is dielectric mismatch. PVDF has a relative permittivity of about 10.8, while PLA’s is only 2.7. During poling, electric field lines preferentially route through the low-permittivity PLA inclusions and through the air-filled cavities left by stretching-induced voids, starving the surrounding PVDF matrix of the field it needs to rotate its dipoles. Finite element simulations in COMSOL Multiphysics, built on a representative volume element containing a PLA inclusion surrounded by an air ellipse, reproduced exactly this field concentration. When the team measured the piezoelectric response of pure PVDF poled at the reduced effective field of roughly 65 volts per micrometer, they obtained a d33 of about 6 piconewtons per coulomb, in close agreement with the blend’s measured value. The physics, in other words, checks out.

The co-continuous 60/40 blend, being overwhelmingly alpha phase, registered no measurable piezoelectric response at all, a d33 of zero. But the electrospinning results added their own twist. Pure electrospun PVDF membranes outperformed their stretched-film counterparts, delivering a d33 roughly 30 percent higher, thanks to about 29 percent greater overall beta-phase content and the superior chain alignment imparted by the enormous elongational forces inside the spinning jet. Interestingly, electrospinning also introduced a significant gamma-phase fraction, an intermediate polar conformation rarely seen in the stretched films, which the authors attribute to the rapid solvent evaporation and extreme deformation rates preserving the initially beta-nucleated chains only partially, letting them relax toward the gamma conformation rather than all the way to alpha.

Yet even electrospinning could not rescue the blend. The electrospun PVDF/PLA 95/05 membranes, despite achieving an electroactive phase fraction of about 86 percent, essentially identical to neat electrospun PVDF, showed a d33 of exactly zero after poling. The team points to a convergence of factors: the finely dispersed, highly elongated PLA domains formed during fiber formation disrupt the local electric field and hinder chain and lamellar orientation; the vastly increased interfacial area places PLA, which is stiffer than amorphous PVDF at the poling temperature, immediately adjacent to the crystal-amorphous interfaces where dipole switching initiates; and interfacial interactions locally stiffen the material, impeding the conformational kinks that must propagate through PVDF chains during poling. Raising the poling temperature triggered electrical breakdown, and lowering the field produced no effective dipole alignment, leaving the membranes piezoelectrically mute.

The study also challenges another widespread assumption. None of the electrospun membranes in this work showed measurable piezoelectric activity before an external poling step, even though the poling field used was nearly twice that of most previous studies reporting self-poled electrospun PVDF. The through-thickness dipole orientation required for a d33 response, the authors note, evidently does not emerge from the electrospinning process alone under these conditions, contradicting a body of literature that has treated self-poling as an intrinsic benefit of the technique.

The broader takeaway is a warning against a seductive shortcut. In the drive toward sustainable, flexible sensors and energy harvesters, blending PVDF with biobased PLA seems like an obvious win: PLA is renewable, biodegradable, stiff, and easy to process. But this work demonstrates that a high beta-phase fraction alone does not guarantee functional piezoelectricity. Electric field distribution, interfacial cavitation, domain size, chain mobility, and processing route all conspire to determine whether a material that looks piezoelectric under an infrared spectrometer actually produces a measurable voltage under stress. For engineers designing the next generation of self-powered wearables and structural health monitors, the message is clear: composition, morphology, and processing must be engineered together, and the role of PLA in enhancing the beta phase of PVDF, once considered promising, is now very much in doubt.

Subject of Research: Piezoelectric performance of PVDF/PLA polymer blends prepared by melt processing and electrospinning

Article Title: Piezoelectric properties of PVDF/PLA blends prepared by melt processing and electrospinning

Article References: Melin, C., Capsal, J.-F., Zednik, R., Pommella, A., Demarquette, N., & Chenal, J.-M. (2026). Piezoelectric properties of PVDF/PLA blends prepared by melt processing and electrospinning. Journal of Materials Science: Polymers, 1(1), Article 13. https://doi.org/10.1007/s44493-026-00010-9

Image Credits: AI Generated

DOI: 10.1007/s44493-026-00010-9

Keywords: PVDF, PLA, piezoelectricity, polymer blends, electrospinning, melt processing, beta phase, energy harvesting, flexible sensors, poling, crystallinity, dielectric permittivity