The review, led by Mohammed Nabeel and Ali J. Addie of the Scientific Research Commission in Baghdad, together with Nabil Kadhim Taieh of Middle Technical University, László Vanyorek of the University of Miskolc, and Ying Li of Chengdu University, takes a deliberately morphology-centered view. Instead of sorting bio-inspired pressure sensors by the transduction mechanism they use, the authors organize the literature by the engineered structural motifs that govern how those devices deform, make contact, and adapt at their interfaces. This reframing matters because, as the authors point out, reported performance is too often discussed through isolated sensitivity values, while the structural origins of the signal, the pressure regime in which that signal is valid, and the reliability limits of the architecture beneath it are examined separately, if at all.

The logic of the bio-inspired approach is straightforward in principle. Biological structures such as the microhairs on insect cuticles, the dermal papillae of human skin, the interlocking scales of reptiles, and the hierarchical porosity of plant tissues have all been refined by evolution to regulate deformation, contact evolution, and interfacial adaptation under load. Materials scientists have translated these motifs into engineered architectures: surface-relief and contact-engineered topographies that concentrate stress at designed asperities, porous and three-dimensional frameworks that compress reversibly under pressure, interfacial and interlocking systems that convert normal loads into lateral deformation, and hierarchical or discontinuity-driven designs that amplify small displacements into measurable electrical changes. Each motif is a mechanical decision, and each decision leaves a fingerprint on the sensor’s electrical response.

That fingerprint is where the review’s central insight emerges. The authors trace how these structural classes couple with the major transduction pathways in the field, including piezoresistive, capacitive, iontronic, triboelectric, piezoelectric, and hybrid mechanisms, and then follow the consequences across the full set of performance dimensions: sensitivity, operating range, dynamic response, hysteresis, drift, durability, and failure behavior. The pattern that emerges is uncomfortable but clarifying. Features designed to amplify signal, such as sharp surface spikes, fragile porous skeletons, or engineered discontinuities, often also set the boundaries for reversibility and long-term stability. The very geometry that produces a spectacular sensitivity number in a fresh device may be the geometry that collapses, flattens, or fatigues after thousands of press cycles.

Consider the piezoresistive case, the most common transduction route in wearable prototypes. A porous conductive elastomer achieves high sensitivity because compression dramatically changes the density of conductive pathways, producing a large resistance change per unit of pressure. But the same porosity concentrates strain locally, invites viscoelastic creep in the polymer skeleton, and creates hysteresis as air and polymer recover at different rates. A capacitive device built on a dielectric layer patterned with micropyramids gains sensitivity because the pyramids increase the effective contact area change under load, yet the sharp tips are precisely where plastic deformation and delamination begin. In iontronic sensors, the enormous interfacial capacitance at electrode-electrolyte junctions yields exquisite sensitivity at low pressures, but the operating range and the drift behavior are dictated by how the engineered interface deforms and rehydrates over time.

Tribioelectric and piezoelectric architectures tell a parallel story from a different angle. Triboelectric pressure sensors depend on contact electrification between engineered surfaces, so their output is exquisitely sensitive to surface morphology, humidity, and the evolution of that morphology through repeated contact and separation. Hierarchical textures borrowed from natural surfaces can boost charge generation, but abrasion gradually erases the texture, and with it the signal. Piezoelectric devices convert dynamic pressure directly into charge, making them ideal for pulse and motion sensing, yet their response to static loads is inherently limited, and the alignment and connectivity of the active phase, itself a morphological property, determines both sensitivity and fatigue resistance. Hybrid designs that combine mechanisms inherit the strengths of each but also the coupled failure modes, which is precisely why the authors insist that structure and mechanism cannot be evaluated in isolation.

The review’s second major contribution is its diagnosis of the field’s benchmarking problem. Because sensitivity is usually reported as a slope measured in a narrow, favorable pressure window, two sensors with wildly different architectures can post similar headline numbers while behaving completely differently in the low-pressure regime relevant to pulse monitoring, the mid-range relevant to grip force, or the high-pressure regime relevant to gait analysis. Without morphology-traceable reporting, meaning documentation of the structural features that generate the response and the pressure regimes over which those features behave reversibly, comparisons between studies become nearly meaningless. The authors call for the structural origins of the signal to be stated explicitly, so that a reader can tell whether a sensitivity figure comes from contact-area amplification, porosity collapse, interfacial charge trapping, or some combination of all three.

Reliability assessment receives equally pointed criticism. Real applications subject flexible sensors to cyclic loading, temperature swings, humidity, sweat, abrasion against skin or textile, and mechanical deformation of the substrate itself, yet many published durability tests consist of a single cyclic-press experiment under ideal laboratory conditions. The review argues for realistic reliability evaluation that connects observed drift, hysteresis growth, and eventual failure to specific pressure-responsive structural features, so that failure is understood as a morphological event rather than an anecdote. A sensor whose microstructured surface flattens after ten thousand cycles fails for a different reason than one whose porous filler network fractures, and the remedies are correspondingly different: surface stiffening and material selection in the first case, tougher composites and graded architectures in the second.

What the authors ultimately propose is a shift from intuition-driven mimicry to structure-guided design rules. Nature-inspired morphology should not be copied for its visual appeal but selected for the mechanical function it performs, matched deliberately to the transduction mechanism and the target pressure regime, and validated against the reliability demands of the intended application. In that framing, the trade-off between signal amplification and reversibility becomes a design variable to be managed rather than a surprise to be discovered. For a field racing toward electronic skin, human-machine interfaces, and soft robotics, the message is that the next generation of flexible pressure sensors will be won not by the highest single sensitivity number but by architectures whose shapes, mechanisms, and lifetimes are understood as one connected story.

Subject of Research: Bio-inspired flexible pressure sensors and morphology-guided structure-function relationships

Article Title: Bio-inspired flexible pressure sensors: morphology-guided structure–function relationships, reliability, and future perspectives

Article References: Nabeel, M., Addie, A. J., Taieh, N. K., Vanyorek, L., & Li, Y. (2026). Bio-inspired flexible pressure sensors: morphology-guided structure–function relationships, reliability, and future perspectives. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02119-5

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02119-5

Keywords: flexible pressure sensors, bio-inspired materials, morphology, wearable electronics, electronic skin, soft robotics, piezoresistive, triboelectric, reliability, structure-function relationships, biomimetic architectures, flexible electronics

The clinical motivation is stark. Myopia has become one of the fastest-growing public health problems in the world, particularly among children and adolescents, and it is far more than a simple refractive error that glasses can fix. Progressive myopia involves excessive elongation of the eyeball, driven by a cascade that begins in the retina and ends in structural weakening of the sclera, the tough outer coat of the eye. Genetic susceptibility combines with environmental pressures such as prolonged near work, insufficient outdoor light exposure and abnormal retinal defocus to alter retinal neurotransmission, including dopamine signalling. These changes disturb the release of growth modulators such as retinoic acid, TGF-β and insulin-like growth factor, which in turn destabilize the balance of collagen synthesis and degradation in the sclera, mediated by matrix metalloproteinases and activated fibroblasts. The result is a thinner, softer sclera that deforms under normal intraocular pressure, stretching the eye axially and predisposing patients to retinal detachment, myopic macular degeneration and optic neuropathy.

SENGs attack this problem from a fundamentally different angle than conventional optical correction. The review divides the technology into two complementary classes. Piezoelectric nanogenerators, or PENGs, exploit materials such as zinc oxide nanowires, barium titanate nanoparticles and piezoelectric polymers like PVDF and its copolymer P(VDF-TrFE), in which mechanical deformation shifts internal charge distributions and creates a piezoelectric potential that drives current through an external circuit. Triboelectric nanogenerators, or TENGs, instead harvest charge generated when two materials with different electron affinities make contact and separate, an effect amplified by electrostatic induction. PENGs deliver moderate voltages with relatively higher current and suit implantable stimulation scenarios, while TENGs produce high open-circuit voltages at very low currents and excel in flexible wearable formats such as contact lenses and eyeglass-mounted sensors. Both operate comfortably within the mechanical regime of the eye, where a normal blink imposes roughly 2 to 5 kilopascals of pressure and forceful blinking can exceed 10 kilopascals.

The most striking preclinical demonstrations come from device prototypes that translate these physics into therapy. One electro-driven drug delivery system integrates barium titanate nanoparticles coated with atropine into an orthokeratology lens. When the wearer closes their eyes, eyelid pressure triggers the piezoelectric effect, generating transient microvoltages that are proposed to perturb the interfacial electrostatic equilibrium of the nanoparticles and promote atropine desorption. Release rates reach approximately 80 percent within 12 hours, with more release accumulating the longer the eyes remain closed, effectively synchronizing drug delivery with natural physiology. In guinea pig myopia models, this system achieved superior reversal of refractive error compared with atropine eye drops alone or combined lens-plus-drop regimens, increased choroidal blood flow velocity, and raised ocular tissue drug concentrations more than twenty-fold above blood levels without detectable systemic toxicity or ocular surface irritation.

Electrical stimulation itself may also remodel the diseased sclera. Inspired by the electrocyte discharge of electric eels, researchers developed a biomimetic piezoelectric patch called BPP@PVDF, made by spin-coating a piezoelectric PVDF membrane onto a bovine pericardium scaffold. Under physiological ocular deformation, the patch generates self-powered microcurrents that were associated with increased scleral fibroblast proliferation and type I collagen synthesis. In rabbit models of lens-induced myopia, eyes receiving the patch showed over 40 percent less axial elongation than sham-operated controls, along with denser and more regularly organized collagen fibers, 20 to 30 percent greater scleral tensile strength and no abnormalities in intraocular pressure, retina or cornea. The authors are careful to stress, however, that the intracellular signaling pathways connecting generated electricity to fibroblast activation remain incompletely defined, and long-term risks such as pathological fibrosis have not been systematically excluded.

Drug delivery to the back of the eye is a second major frontier. Intravitreal injections carry infection and retinal detachment risks, while non-invasive routes typically achieve delivery efficiencies below 5 percent. A wearable electric switch system comprising an electrically driven drug delivery lens and a flexible square-wave generator addresses this bottleneck by using electrical stimulation to transiently open junctions between retinal pigment epithelial cells, reducing resistance along the sclerochoroidal-retinal pathway. The system delivered immunoglobulin G with 14 percent efficiency, approaching the 16 percent achieved by intravitreal injection, enhanced macromolecular penetration three- to five-fold in rabbit eyes and worked across monoclonal antibodies, DNA origami and extracellular vesicles, with adjustable waveform parameters providing a controllable safety window.

The same physics also supports closed-loop sensing. Triboelectric sensors mounted on skin or eyeglasses can distinguish voluntary from involuntary blinks, decode eye movements in eight directions with micrometer spatial resolution, and monitor intraocular pressure with sensitivities of about 1.28 megahertz per millimeter of mercury. A wireless therapeutic contact lens platform integrating sensing, wireless communication and iontophoretic drug delivery has maintained stable intraocular pressure readings for up to two months in rabbits while delivering anti-glaucoma medication on demand. Combined with machine learning, such self-powered sensors could feed adaptive algorithms that adjust stimulation and drug-release parameters in real time, forming the basis of an intelligent feedback loop between the eye, external computation and therapy. The review notes that tellurium nanowire retinal nanoprostheses and the clinically validated PRIMA photovoltaic implant, while not energy harvesters themselves, provide powerful engineering templates for wireless neural interfacing and long-term biointegration that future SENG platforms can borrow.

Formidable challenges separate the laboratory from the clinic. The eye is a hostile environment for electronics: tear fluid shields surface charges, millions of blinks per year accelerate mechanical fatigue and delamination, and materials such as zinc oxide can dissolve and release cytotoxic ions, while lead-based piezoceramics pose obvious toxicity concerns that push designers toward lead-free alternatives like barium titanate and biodegradable polymers such as PLGA. A fundamental ‘power gap’ also persists, since blink-driven generators produce transient bursts rather than the continuous, tightly regulated currents needed for reliable neuromodulation, and patients with dry eye or impaired ocular motility generate too little biomechanical energy for dependable therapy. Hybrid devices that pair nanogenerators with miniature supercapacitors or thin-film batteries could buffer this variability. Regulatory pathways add another layer of complexity, because multifunctional platforms combining stimulation, drug delivery, biosensing and artificial intelligence will likely be classified as combination products requiring coordinated review of electrical safety, pharmacology, software reliability and cybersecurity. Pediatric use, the population that most needs myopia control, raises additional ethical and developmental concerns that will demand adult safety data first.

Even so, the trajectory is clear. Ophthalmic biomaterials are evolving from passive structural supports into dynamic, intelligent systems that sense, respond and adapt. By harvesting the eye’s own motion to power stimulation, drug release and continuous monitoring, self-generated electricity nanogenerators sketch a future in which myopia is actively managed as the progressive neurovascular disease it truly is, rather than passively corrected with lenses. If materials scientists, neuroscientists and clinicians can close the remaining gaps in energy stability, chronic biocompatibility and validated dosing, the review concludes, blinking may one day do far more than keep the eye wet. It could power the therapy that saves a child’s sight.

Subject of Research: Self-powered bioelectronic nanogenerators for myopia treatment and vision restoration

Article Title: Bioelectronic interfaces for restoring vision pathways

Article References: Wang, T., Zhao, B., Du, Y., Wu, S., Jiang, Y., Li, J., Miao, Y.-B., & Shi, Y. (2026). Bioelectronic interfaces for restoring vision pathways. Materials Today Bio, 40, Article 103652. https://doi.org/10.1016/j.mtbio.2026.103652

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103652

Keywords: myopia, nanogenerators, triboelectric, piezoelectric, bioelectronics, drug delivery, retina, sclera, biomaterials, energy harvesting, contact lenses, neuromodulation