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Microsystems & Nanoengineering volume 12, Article number: 244 (2026)
Continuous and real-time monitoring of the subtle spatio-temporal changes in human physiological states are essential for daily diagnosis and treatment. Additionally, the capacity for monitoring is frequently restricted by available materials and specific application contexts. Wearable Flexible Ultrasound Biosensors (WFUBs) can be comfortably applied to the human body and have the functions of continuous monitoring and interventional therapy. The review summarized recent advances in the way WFUBs acquire vital data from particular biological tissue, the structural design and material selection, including the substrate, electrical connection, electrode, and the material synthesis of biosensors. In addition, the aspects of performance improvement of WFUBs were summarized, and the applications of wearable ultrasound systems in health care, diagnostic imaging, and interventional therapy were further discussed. Finally, the challenges and future research directions in the field of next generation WFUBs were explored.
By the collaborative efforts of medicine and engineering, wearable ultrasound diagnosing and treating illnesses has become a reality1. Wearable ultrasound had made diagnosing and treating illnesses, extended to continuous monitoring of electrophysiology, arterial flow, intracranial pressure, and various other indicators2,3. However, the interface of signal acquisition and processing is still relatively rudimentary, resulting in constraints in duration work and poor resolution. For example, the ultrasonic probe used for signal monitoring had the problem of poor coupling between the skin and the probe. And another example was the poor resolution response of wearable ultrasound for the heart due to the limited probing depth. In practice, the difficulty of wearable ultrasound is also that the wearer is mobile, such as jogging and walking, and the application scenarios of wearable ultrasound are significantly limited.
The WFUBs are new type of wearable devices that combine flexible electronic technology, ultrasonic function and biomedical sensing. Its primary function is to utilize ultrasonic transducer units with flexible/stretchable materials to achieve real-time and continuous monitoring of physiological parameters. The performance of WFUBs is positively correlated with wearable ultrasound systems. Most of the sensing probes use traditional rigid materials to communicate with the biological tissue, such as organic materials and polysulfone. However, the rigid and non-biological properties of the traditional probe are in contradiction with the compatibility and biosafety of biological tissues. The WFUBs are ultra-thin and have low modulus, allowing ideal coupling to the biological tissue interface. Recently, with the rise of wearable ultrasound systems, ultrasonic biosensors are made into flexible, secure structures to improve the coupling between the sensor and the biological tissue4. The tensility and biodegradability of sensors were optimized without changing the original functions of the sensor. However, the approach also faces challenges such as a lack of conformal contact, unstable adhesion, and tissue damage formation. In addition, even if these sensors had flexible and stretchable structures, biological tissues might recognize them as foreign bodies, resulting in undesirable foreign body reactions. The allogeneic reaction leads to the isolation of surrounding tissue from the WFUBs, which can seriously compromise the long-term reliability and effectiveness of communication between the biological tissue and the WFUBs.
The optimized WFUBs are characterized by low power consumption, miniaturization, sufficient penetration depth, and high spatial resolution. In the emerging field, some impressive achievements are emerging, with WFUBs naturally emerging as promising options for wearable ultrasound as an alternative to traditional probes for wearable ultrasound system applications, serving as a vital link between the biological tissue and the machine. The WFUBs are rapidly emerging for a wide range of applications, both in academic research and as commercial products5. For example, ultrasound-coupled hydrogels were already in clinical use and serving as an optimal interface between wearable ultrasound devices and human skin for disease imaging and therapy6,7,8. Ultrasound stimulates the release of drugs9, acoustic electrical conversion stimulates neurons10. The WFUBs take advantage of the fact that they are usually compatible with biological tissues and biodegradable, capable of enabling sustained operation over the medium to long term in vivo, becoming a promising carrier for continuous diagnosis and treatment. Moreover, WFUBs with electromechanical properties and composite flexible material have been shown to significantly improve the biocompatibility of implantable sensors by facilitating a closely coupled human-machine interface11,12 and reducing rejection responses13,14. The enhanced biocompatibility paves the way for implantable WFUBs to form a long-term and reliable functional interface with the human body.
The new generation of flexible wearable acoustic probe uses utilizes softer and more elastic materials. The material is able to mitigate mechanical conflict between WFUBs and human tissues, thereby preventing tissue damage or immune responses that may be caused. The new material can not only flex and stretch like skin, but also has the ability to self-heal and biodegrade, providing unprecedented flexibility and safety for medical devices15. Despite the great promise and recent achievements of wearable ultrasound, stretching wearable ultrasound patches still suffer from the limitations of low imaging resolution, unstable imaging quality during body movement, short continuous working time, susceptible to external interference. Figure 1 illustrates the evolution of wearable ultrasound transducer development. The wearable ultrasound has progressed from portable ultrasound. In 2000, the application of flexible piezoelectric materials in ultrasonic transducers laid the foundation for the manufacturing of WFUBs16. The flexible ultrasonic sensors were developed, and the initial inception of wearable ultrasound occurred in 201517. Subsequently, the first wearable ultrasound device capable of non-invasive blood pressure measurement was proposed, indicating the initial phase of wearable ultrasound to the functionalization stage18. From 2019 to 2022, the performance and functions of wearable ultrasound had seen continuous optimization and continuous real-time monitoring was achieved, including advancements in composite materials and piezoelectric ceramics19,20, imaging stability and the movement of biological tissues21,22. Recent advancements, the performance of wearable ultrasound has been confirmed effective in clinical environments and has gradually moved from laboratories to hospitals and homes23,24. Recently, some studies on acoustic piezoelectric sensors had been reviewed. Existing reviews generally do not consider the requirements and principles of providing flexible ultrasound biosensor design, nor do they address the diagnostic and interventional therapy application interface. Such a systematic discussion is essential for driving future advancements of wearable ultrasound sensors and systems25,26,27,28. For instance, Wu et al. reviewed the progress made by flexible electronic devices in promoting the detection and imaging of wearable ultrasound equipment, but did not consider account the core performance optimization of flexible wearable ultrasound electronic sensors and insight into the current status of interventional therapy27. Guo et al. summarized the design and application of flexible ultrasonic transducers, but overlooked the impact of flexible ultrasonic sensors on diagnostic accuracy and treatment efficacy at the human-body contact interface28. However, the data reviewed showed a lack of discussion flexible biosensors based on wearable ultrasound systems integrated with wearable ultrasound systems for clinical diagnosis, treatment, and health management. Meanwhile, the discussion on the acquisition methods of vital sign information and the performance of wearable ultrasonic sensors was valuable. Therefore, summarizing the progress of WFUBs is deemed essential.
The development history of wearable ultrasound transducers16,17,18,19,20,21,22,23,24. The schematic illustration of WFUBs showing: key stages including ultrasound origin, material innovation, transducer development, device manufacturing, clinical application, and multimodal continuous monitoring
In this review, we outline recent advances in WFUBs. Firstly, the way WFUBs acquire vital sign data from biological tissues had been discussed, and the achievements of WFUBs are summarized from the aspects of structure design and material selection, including the substrate, electrical connection and electrode, and material synthesis. In addition, the aspects of performance improvement and enhancement of WFUBs are summarized, and the latest applications of wearable ultrasound systems in healthcare, diagnostic imaging, and interventional therapy are further discussed (Fig. 2). Finally, the challenges and future research directions in the field of next-generation wearable acoustic biosensing systems are anticipated.
The key aspects of wearable flexible ultrasound biosensors, including material selection, device performance, implantation method, and application scenarios, are outlined. Material selection of flexible piezoelectric materials, flexible substrate material, electrical connection and backing and matching layers; Device performance of image resolution, transmission rate, coupling of bandwidth and degree of curvature; Implantation method of Invasive and non-invasive；The application of diagnosis, personalized treatment and health management
Unlike rigid probes, the WFUBs need to adapt to irregular surfaces of biological tissues for a long time to ensure optimal contact. Thus, consideration of the extensibility of biological tissues was necessary when WFUBs making contact with them, such as bends and skin stretching29. WFUBs must ensure ideal coupling with human tissue and maintain stability of the detected target during movement. The WFUBs can be attached to the skin surface. And then ultrasonic energy directly interacts with biological tissues to obtain vital sign information. With the advancement of wearable ultrasound technology, the diagnostic and therapeutic approach combining WFUBs with passive targets has been developed. WFUBs are non-invasive device that adheres to the skin surface, which acquire vital sign information or interventional treatment by passive target substances as a medium. Among them, the target substances lack a power supply and circuitry, as well as the complete functionality of a dedicated device. After a period of time, the passive target substances can be degraded or absorbed within biological tissue. The strategy consists of a wearable, non-invasive monitoring system primarily based on WFUBs, supplemented by passive target substances, which overcome the limitations of pure wearable ultrasound devices, such as poor positioning and low resolution. At present, both approaches promote the progress of wearable ultrasound medicine, which can be tailored solutions for specific monitoring and diagnostic and treatment purposes.
The ultrasonic energy of WFUBs directly interacts with the monitored biological tissues to obtain vital sign information is a commonly used monitoring method, known for its advantages of few side effects and convenience. Currently, it has been applied in fields of postoperative rehabilitation monitoring30, thyroid diagnosis31,32 and cardiovascular diseases33,34,35.
Imaging of cardiac function is an important method to evaluate cardiovascular and cardiac function diseases. Conventional ultrasound equipment was bulky and could not provide continuous measurement, which posed a great challenge to the diagnosis and management of cardiovascular diseases. For example, the sudden onset of myocardial infarction, if effective measures were not taken in time, the life safety of patients with such diseases would be greatly threatened. In the past, the signal resolution and detection depth of WFUBs could not meet the diagnostic requirements, and wearable echocardiography equipment could only detect skin signals. Xu et al. developed a wearable ultrasound system for continuous and real-time cardiac function assessment by innovative structure design and material fabrication, and the results showed that the system had a good signal-to-noise ratio and resolution (Fig. 3a)33. Subsequently, the team published findings on an integrated wearable ultrasound patch by combining wireless data communication and machine learning. The patch could continuously monitor blood pressure and heart rate for up to 12 h, with a detection depth of 164 mm (Fig. 4a)35. It was a sign of remarkable strides in the integration of information technology and medicine. In addition, recent transcranial Doppler ultrasound biosensors have also contributed to the application of wearable ultrasound systems. The WFUBs showed advantages in 3D network vascular imaging, the adaptive flexible patch could accurately record the systolic velocity, mean flow velocity and end-diastolic velocity of cerebral arteries, and the performance was similar to that of traditional transcranial doppler ultrasound (Fig. 4b)29. And it was noteworthy that the patch allowed continuous monitoring of vascular sign status.
The diagnostic and therapeutic methods of wearable ultrasound. a Wireless wearable ultrasound patch33. b The image of the textile-based probe attached to clothing (left), the schematic diagram and cross-sectional image of fabric probe (right)39. c Principle of continuous monitoring of carotid vessels by multi-sensors40. d Flexible piezoelectric composites monitor blood pressure74. e Injectable degradable ultrasonic sensor43. f, g Acoustic transparent skull window was constructed44. h Ultrasound intervention in neuromodulation and drug release49
The structure and shape characterization of the flexible ultrasonic sensor. a Ultrasound-system-on-patch sensor, including stretchable probe, flexible control circuit, and battery35. b Transcranial angiography and schematic representation of structures. The patch was attached to the scalp and used for volumetric imaging of major arteries in the brain (left). The patch is connected by a five-layer stretchable electrode and a common ground electrode, using a copper mesh as an electromagnetic shield(right)29. c Biodegradable implantable piezoelectric sensors based on PLA nanofibers55. d A flexible cardiac ultrasound patch33. e Schematic representation of the cross-section of the flexible ultrasonic transducer. Top: Included in the polyimide foil and molybdenum aluminum electrode, P (VDF-TrFE) film, bottom: Picture of the foil of the bendable ultrasonic transducer62. f Degradable sensor, left: photos of the metagel sample and puncture needle(left), microscopic images of the metagel structure (right)43
Beyond applications in cardiovascular diseases, WFUBs had proven effective in the areas of fingertip blood pressure monitoring, personalized reproductive hormone monitoring36 and continuous monitoring of bladder urine volume (Fig. 5a)37. Previously, continuous blood pressure monitoring typically required invasive insertion of an arterial tube, presenting risks to patients. Researchers at the California Institute of Technology introduced a novel approach utilizing resonance acoustic measurement. The method enabled real-time calculation of absolute arterial blood pressure by analyzing arterial dimensions and resonance frequencies, thereby enhancing patient safety and comfort38. An innovative wearable fabric ultrasound device had also been created to monitor carotid artery pulsations and internal jugular vein diameter changes. Noteworthy for its outstanding stability during 24-h continuous monitoring (Fig. 3b)39. In addition, a cervical artery monitoring technology with automatic phase calibration of multiple flexible ultrasonic sensors was introduced. The imaging resolution was introduced improved and the monitoring error was reduced to 0.34 mm (Fig. 3c)40. The achievement facilitates the future integration for the application of human-machine interfaces in prosthetic hand control.
The types and internal structures of WFUBs. a The ultrasound patch placed in the lower abdomen and the working mechanism(left), front view of the ultrasonic transducer. (right)37. b The structural profile of the glycine-PCL ultrasonic transducer56. c The structure diagram of the flexible PUEH sensor. d the profile diagram of the components in the piezoelectric element68. e Wearable ultrasound with a single flexible sensor continuously monitors the EMG system77. f Structural diagram of the CW Doppler patch assembly, the patch has translucent tape and clear label, and was fitted to the skin85
On the other hand, wearable ultrasound had made valuable progress in the continuous monitoring of bladder volume. Similar to the frequency of abdominal ultrasound, the frequency of the wearable ultrasound transducer for bladder volume monitoring was manufactured within the range of 2–5 MHZ. Levent Beker et al. designed an air wearable ultrasonic transducer with Bluetooth data transmission function. The integrated and miniaturized equipment could operate continuously for 12 h, which had been tested to achieve good imaging results after 500 bends37. In addition, bladder volume monitoring transducers adaptively coupled with non-curved skin have been developed, and the elastic tensile rate reached 40%. The volume of the balloon was innovatively reconstructed by using the least squares ellipsoid fitting method. The measurement data of the designed sensor array had an error of a minimal 9.4% compared with the actual bladder volume41. To better balance the contradiction between imaging resolution and stretchability, the Sm/La-doped PN-PT ceramic flexible ultrasonic transducer with high electrical performance was proposed. The 64-element multiphased array transducer demonstrated high resolution in both the transverse and longitudinal dimensions, and with a detection depth of 15 cm, which was sufficient for bladder imaging of most people. The experimental results also showed that the dielectric constant and electromechanical coupling coefficient of the doped PMN-PT material had been significantly increased42. Looking ahead, advancements in technology may soon bring about wearable devices such as mobile phone terminals and smartwatches capable of not only monitoring heart rate but also tracking vital signs throughout the day. The evolution of WFUBs holds promise for delivering more precise and convenient monitoring tools to patients with chronic diseases, as well as healthcare and postoperative patients, to enhance disease prevention and management.
The ultrasonic energy of WFUBs is applied to implant the target into biological tissues to obtain vital sign data. The method mainly employs non-invasive WFUBS, with the artificial implantation of target substances serving as the medium, to enhance the ultrasonic penetration depth and resolution. The method involves artificially implanting target substances near biological tissues and using WFUBs to monitor the status of the target substances, thereby indirectly obtaining vital sign information of biological tissues. The artificial implantation of the implanted substances not only enhances the depth and resolution of the continuous monitoring signal of WFUBs43,44, but also has been applied in the fields of acoustically promoted drug release and interventional therapy45,46,47,48. The research team from Huazhong University of Science and Technology had recently introduced a meta-structured hydrogel sensor for injection, could be implanted into the brain via a probe for the continuous monitoring of intracranial pressure, temperature, pH, and other parameters. The material exhibited degradability, with near-complete degradation occurring within 18 weeks (Fig. 3e)43. Additionally, Mikhail G. Shapiro et al. developed transparent acoustic signal skull replacements utilizing polymethyl methacrylate and titanium mesh materials. The acoustic signal-to-noise ratio of the acoustic signal for various substitute materials was analyzed, demonstrating that functional ultrasound could achieve a resolution of 200 μm (Fig. 3f, g)44.
It is worth noting that target-based WFUBs have been increasingly utilized in the field of interventional therapy in recent years47. The Devices that utilized implanted stimulators and regulated the intensity of the stimulator’s current intensity by WFUBs to achieve pain treatment had been developed48. The barium titanate is a non-toxic, sound-sensitive material. Barium titanate can generate electrical signals to regulate neuronal potentials when stimulated by acoustic signals, facilitating healing processes (Fig. 3h)49,50. The technologies are crafted utilizing ultrasonic systems, such as ultrasonic systems like the Vantage 64 and pulse receiver systems. The system is capable of connecting to an external transducer for converting acoustic and electrical signals. Despite the demonstrated benefits of wearable ultrasound biosensors in continuous monitoring and therapeutic applications, challenges such as low signal strength and biosafety concerns remain; skull signal attenuation and tissue rejection of implants are notable factors impacting monitoring accuracy.
The selection of flexible materials and structural design are key factor in the performance of WFUBs. This section provides a detailed discussion on the structure of WFUBs, summarizes recent research progress, and discusses the material choices. WFUBs differ from rigid probes in terms of manufacturing techniques, electrodes, and substrates. The distinctions involve: (a) Energy transducing materials for bidirectional conversion of acoustic and electrical signals; (b) Flexible substrate material for conducting electricity between biological tissue and device; (c) Electrical connections within biosensors. Additionally, significant attention is directed towards the material selection for WFUBs.
Piezoelectric materials play a vital role in WFUBs. When piezoelectric materials are subjected to external forces, they undergo a charge transfer process, enabling the energy conversion between mechanical and electrical. Material flexibility, impedance, piezoelectric coefficient, and coupling are important factors in material selection, including piezoelectric ceramics and polymers. An ideal flexible piezoelectric material exhibits high coupling and low impedance characteristics. Piezoelectric polymers have garnered attention as a means to produce nearly ideal flexible piezoelectric materials, exemplified by PVDF51, PVDFTrEF52,53, etc. They exhibit low acoustic impedance and high-quality Young’s modulus. Recently, researchers have been focused on enhancing the properties of PVDF and PVDF-Tref, particularly in terms of stability and coupling54. Furthermore, piezoelectric polymers have shown promise as biocompatible materials and have been developed as materials for implantable WFUBs (Fig. 4c)55. Researchers developed a biodegradable ultrasound detector by blending the piezoelectric properties of amino acid crystals with the hydrophobicity of polycaprolactone (Fig. 5b)56. It provided a new idea for the development of implantable ultrasound biosensors. The piezoelectric principle involves energy transformation via the coupling between the electrical and mechanical properties of the material, establishing an energy relationship between these variables57:
Where S is the strain tensor, T is the stress tensor, E represents the electric field vector, and d is the electric displacement vector. (S^{E}) is the elastic compliance matrix under a constant electric field (superscript E denotes a constant electric field), D is the piezoelectric constant matrix, and eT is the dielectric constant measured under a constant stress.
Enhancing the performance of flexible piezoelectric sensors can be achieved through the production of composite materials. The combination of the characteristics of different materials constitutes an ideal flexible sensor that is superior to a single material, such as the utilization of flexible low-density polymer piezoelectric materials. Dai et al. were able to modify the acoustic impedance of the sensor from 6.50 to 9.47MRayl by adjusting the compression pressure and the composition ratio of the aluminum-epoxy composite58. Piezoelectric materials like PZT-5H41,59 and PMN-PT60,61, known for their high sensitivity and broad bandwidth, were also incorporated in WFUBs. Moreover, in applications where the use of lead is restricted due to patient interaction, lead-free piezoelectric ceramics and piezoelectric film materials function as suitable substitutes for PZT. The development of future polymer-piezoelectric composites is vital for the effective enhancement of WFUBs (Fig. 4d)62. Table 1 shows the properties of several classes of flexible piezoelectric materials; the sensitivity, stability, coupling property, resistance to fatigue, and electrical conductivity were the key indicators of interest.
The choice of substrate determines the mechanical properties of the WFUBs. In the application, the substrate material is required to have the characteristics of low impedance, strong tensile and high tortuosity63,64. The thin-film sensor methods using thin films as substrates enable many design thinking and engineering applications. Therefore, the existing process makes the film’s thickness than the wavelength, which facilitates the incidence and reflection of sound waves. Implantable WFUBs also must consider the degradability and biocompatibility to minimize the adverse effects of the implant on the human body. Like other flexible sensors, common substrate materials include polydimethylsiloxane65, polyethylene terephthalate66,67, etc. The choice of substrate material can be tailored based on intended usage. For example, polydimethylsiloxane exhibits good elasticity and enables effective skin coupling. Polyethylene terephthalate’s non-toxic nature makes it suitable for developing implantable acoustic biosensors.
It is crucial for the WFUBs to maintain a stable conductivity when the flexible biosensor is subjected to deformation, such as stretching, compression and bending. In order to ensure a reliable electrical connection, researchers designed anisotropic conductive film electrode to realize reliable electrical connection. It was noteworthy that the flexible sensor was reusable after disinfection, and the experiment showed that the monitoring data remained unbiased throughout human interaction35. In addition, the design of multi-layer flexible electrodes enhanced resolution and electrical output stability, showing potential application in wearable miniature ultrasound devices (Fig. 5c, d)68. Innovative structural design and composite material synthesis are favorable measures for the development of a high-density, stable, stretchable electrode. Thus, advancements in WFUBs technology are keeping pace with developments in electrical impedance, positioning them at the forefront of the next generation of miniature ultrasound devices.
The backing layer and matching layer were essential components of WFUBs that enhance the performance by improving bandwidth and spatial resolution69. Previously, some flexible bioprobes utilized an air interface as the backing layer, which had problems such as excessive signal pulses and reduced spatial resolution. The backing layer helped decrease back reflection and spatial pulse length (Fig. 4e)33. The decoupling of the sensor and skin interfaces resulted in acoustic impedance, leading to information loss and interference in transfer. Incorporating a matching layer between the skin and the sensor interface was a crucial strategy for addressing these issues. Frequently employed backing layer materials, like polyimide, feature thin interfaces that effectively transmit incident and reflected waves, thereby enhancing transmission efficiency70. Therefore, incorporating backing and matching layers is an optimal design choice to enhance WFUB performance, improve transmission efficiency, and increase detection depth.
The resolution of ultrasonic imaging is typically categorized as axial resolution and lateral resolution. Axial resolution refers to the minimum distance that can be differentiated parallel to the direction of the ultrasonic beam, and lateral resolution represents the minimum distance that can be distinguished perpendicular to that of the ultrasonic beam. The ultrasound patch emitted a signal that was reflected back and detected, enabling the identification of lesions based on signal differences. Various factors impact imaging resolution, including attenuation, interference, and others in ultrasonic signal transmission, such as the attenuation of ultrasonic signals from the skull and the movement of the subject being monitored, typically disrupts imaging resolution71. Optical markers and trackers were employed by Ding to monitor probe geometry, and a polygon fitting algorithm was utilized to estimate transducer position. The outcomes demonstrated high accuracy of the scheme (error <0.5 mm)72. In addition, the resolution could be significantly improved by correcting the geometric phase of the ultrasonic piezoelectric transducer (Fig. 6a)73. Optimizing pulse delivery wavelength, wave number, and the characteristics and size of the flexible patch can further improve imaging resolution. For instance, Peng et al. developed adjustable, flexible piezo-composite ultrasonic patches that accurately captured blood pressure readings below 2 mmHg in vivo (Fig. 3d)74. Adequate skin-to-patch coupling and comfort are crucial for achieving precise imaging, as evidenced by complete contact with irregular and curved skin. Various factors influencing the quality of ultrasonic imaging are diverse, including the focusing performance of the sound field, frequency, coupling, etc. These should be taken into account when manufacturing WFUBs and the application scenarios.
The performance characterization and simulation of WFUBs. a Flexible ultrasonic patch with high bending. Left: Photograph of patch appearance, right: The samples were ultrasonically scanned with the patch, as well as their axial and transverse resolutions73. b The transmission dynamics of the wireless acoustic sensor when the testers were at different speeds for 20 s, top: v = 1.2 m/s, bottom: v = 2 m/s76. c–e High-resolution tissue imaging map of a flexible polymer array sensor (c Function of transmitted and received signals as a function of frequency. d The flexible transducer had a peak transmission area uniformity at 8.2 MHz. e Plane wave composite images were captured)62
The WFUBs are designed to non-invasively observe the structure of biological tissues and analyze tissue dynamics. Low signal transmission rate and suboptimal imaging quality are common drawbacks. The differences in the structural organization of animals lead to partial reflection of the transmitted ultrasonic wave and shielding of the remaining reflected wave. Incorporating a flexible matching layer exhibiting a gradient acoustic impedance proved effective in enhancing ultrasound transmission through the skull. Kim et al. enhanced the transmission rate by optimizing the center frequency and bandwidth of the flexible patch, achieving heart rate monitoring with a dual-modality sensor incorporating photoacoustics75. Additionally, optimization of the signal transmission and receiver performance substantially improved transmission efficiency and sensitivity (Fig. 6b)76. Moving forward, wearable devices will enable the acquisition of in vivo signals, wireless transmission between devices and terminals, and enhanced transmission efficiency of flexible acoustic sensors (Fig. 5e)77.
Signal bandwidth and circuit matching of flexible patches are critical parameters of WFUBs. The degree of matching is closely associated with waveform integrity and signal loss. To conserve energy, many wearable flexible acoustic sensors have utilized piezoelectric materials, leading to devices with narrow bandwidths that directly impact image resolution78. Thus, selecting wideband materials and organic piezoelectric polymers for composite materials could optimize both bandwidth and energy efficiency, while enhancing transmission efficiency and acoustic impedance. Recently, the TNO Institute in the Netherlands employed hot stamping technology to fabricate a soft, lightweight, and large-area ultrasonic array utilizing the lead-free piezoelectric polymer P(VDF-TrFE). The array was employed for imaging the carotid artery, with the 78% bandwidth at −6 dB, a maximum transmit efficiency of 1.3 kPa/V, and a receive sensitivity of 150 μV/Pa (Fig. 6c–e)62. Furthermore, a backing layer was introduced to the active layer to enhance the absorption of backpropagating ultrasound from the active layer, aiming to enhance bandwidth, such as a composite composed of a mixture of metal powder and epoxy resin79,80.
Flexible wearable ultrasound patch needs to adapt to the irregular shape and non-stop motion of the monitored tissue surface. The WFUBs with good tissue coupling and bending ability can obtain high-quality ultrasound images. The flexible wearable ultrasound biosensor is required to bend tens of thousands of times without significant damage during the application process. Sometimes the bending angle was even greater than 90°, which is a great challenge for the design of the sensor. Recent studies had incorporated an optical shape-sensing fiber into a 128-element flexible linear array sensor. The sensor’s smallest concave and convex bending diameters were about 20 mm and 25 mm, respectively, sustained 2000 bends without compromising performance81. Chen et al. reported a scalable flexible ultrasound transducer that coupled large curvature surfaces and maintains superior imaging quality. The flexible transducer had shown excellent flexibility and stretchability, and could be applied to in vitro phantom imaging and in vivo ultrasound imaging of thyroid, brachial artery and carotid artery82. In addition, the thickness of the backing layer film is closely related to the tortuosity. The deflection of the backing layer film was caused by the lateral strain generated by the piezoelectric effect, and the lateral dynamic strain should be avoided83. Thin-film-based devices were prone to deformation under low stress and had better fatigue resistance. Notably, when the ultrasonic transducer membrane vibrates in the bending mode, they had lower mechanical impedance and better matches acoustically with biological tissues84. For the application of wearable acoustic devices, ideal acoustic coupling is essential to achieve optimal acoustic matching with the wearable device and the skin. The need for acoustic coupling can be minimized by designing compliant flexible structures (Fig. 5f)85. Table 2 summarizes the performance characterization of several types of WFUBs, including resolution, transmission rate, bandwidth coupling, piezoelectric coefficient, center frequency.
Flexible ultrasound probes that continuously and in real time monitor internal tissues show promise for early disease detection, diagnosis, and interventional therapy. Since the flexible sensor material was proposed in 2000, wearable devices have been extensively utilized with diverse technologies and application scenarios.
Wearable ultrasound systems are increasingly being utilized in healthcare for preventive care and health management. When used by patients outside the clinic, wearable ultrasound enables continuous monitoring of their condition, tracking post-surgery recovery. Additionally, wearable ultrasound devices can provide diagnostic and monitoring capabilities in emergency medical situations like earthquakes and tsunamis, ensuring timely assessments. The health management of diabetic patients has always been a topic of concern. Real-time, continuous monitoring of blood glucose markers is beneficial for assessing the patient’s condition. A flexible ultrasound patch based on a chemical–physical method was introduced. A multi-modal platform provided continuous monitoring of glucose, lactic acid and alcohol, enhancing the diabetes management and related cardiovascular risks86. In addition, multi-modal sensors attached to human skin, including ultrasonic patches, chemical sensors and biosensors and others, which can continuously monitor various physiological signals related to strain and vital signs, represent the evolutionary trajectory of the next generation of wearable sensors87. With the ongoing improvement in WFUBs performance, the wearable ultrasound system is poised to be seamlessly integrated into daily life for monitoring hypertension, heart failure, and enabling early detection of cerebral thrombosis.
Wearable ultrasound is a commonly imaging method and serves to diagnose and monitor various diseases. The development of WFUBs has expanded the application scope of ultrasound. The use of acoustic signals to generate 2D/3D images of the lesion site enables physicians to visualize the conditions of various cardiovascular, abdominal and other multiple body parts88,89,90. Hypertension is one of the pathogenic mechanisms of cardiovascular diseases, and ultrasound is a good means to monitor cardiovascular health. A wearable ultrasound device that could directly quantify vascular parameters was developed. The device accurately measures blood pressure by continuously analyzing important parameters of blood vessels and applying mathematical models and algorithms specific to the measurement site90. The new device offered advantages in imaging deep tissues and organs compared to traditional diagnostic methods. Zang et al. introduced a novel approach for monitoring intracranial signs through the design of an implantable polymer hydrogel. The results demonstrated the effectiveness of hydrogels in monitoring intracranial pressure, pH and flow rate, providing insight for the formulation of treatment strategies (Fig. 4f)43. Furthermore, transcranial arterial blood pressure monitoring significantly improves the accuracy and management of diagnosing, intracranial diseases, especially in patients with neurovascular disorders like vasospasm, stenosis, aneurysm, and embolism. It could offer diagnostic data for the early detection of significant29. The applications of wearable ultrasound driven by advances in WFUBs are aimed to address challenges in clinical applications.
The regulation of neurons mainly included electrical91,92, light93,94, and acoustic stimulation95, among which acoustic stimulation has high safety and significant therapeutic effects. Ultrasound signals have been used as a method to activate and inhibit neuronal, and modulating neuronal activity and treating diseases through regulation. Currently, a series of WFUBs had been developed for the treatment of Parkinson’s disease, neuronal modulation, and cardiovascular diseases, which showing promise for clinical implementation. Recent studies had explored the effects of wearable ultrasound stimulation on the motor cortex in awake and anesthetized animals, laying the groundwork for the development of additional new neuromodulatory devices96. In addition to new neuromodulatory devices, capacitive micromechanical ultrasound transducers (cMUTs) had also been tried for ultrasound stimulation97. However, the majority of acoustic biosensors were non-implantable, and the type and depth of disease treated are limited. Although some semi-implantable acoustic biosensors had been developed, the ability to perform interventional therapy at deep sites was still insufficient. Therefore, further efforts should be devoted to creating WFUBs for use in deep sites. On the other hand, ultrasound drug infiltration and drug release were equally novel pathways. In conclusion, wearable acoustics devices might be a promising route for disease treatment and drug delivery in clinical medicine and healthcare.
Wearable ultrasound-enhanced drug release has been a method that uses ultrasound to promote the release of drugs within biological tissues. Drugs injected into a specific area undergo a series of dynamic processes under ultrasound action, such as vibration, contraction, expansion, and adsorption. The blood-brain barrier was composed of endothelial cells and brain microvessels, the barrier presented challenges for drug delivery into the brain. Therefore, traditional structural modification drug approaches were limited in their ability to penetrate the blood-brain barrier. Recently, the biocompatibility nano-diagnostic reagent and ultrasonic cancer immunotherapy platform have demonstrated both safety and potential therapeutic effects in treating physical diseases using acoustics (Fig. 7a)98,99. Wearable flexible acoustics have become an effective method for enhancing antitumor effects. However, it should be noted that most of the current research is still limited to the experimental stage of animal models, and further clinical investigations are required to validate the performance of wearable ultrasound devices, including indicators such as time, frequency and power settings. In recent years, with the continuous progress of WFUBs, wearable acoustic devices have been also evolving. Many clinical studies are investigating wearable acoustic devices for the treatment of benign and malignant solid tumors in various organs, such as liver, prostate, bladder, kidney, uterus, breast, and pancreas (Fig. 7b)100,101.
The several types of applications of wearable ultrasound. a Ultrasound promotes antitumor drug release mechanisms (top: ncMBs were obtained by coupling with anti-CD11b antibody and SpeDex and loading with negatively charged cGAMP. Bottom: ncMBs bind to apc and upon ultrasound, cGAMP is delivered directly into the cytoplasm of apc via acoustic resonance to activate STING and downstream antitumor immunity)99. b A schematic diagram of the application of wearable flexible ultrasound microneedle patch in cancer treatment100. c Enhancement of the mechanism of radiofrequency ablation lesions using photoacoustic imaging102. d Ultrasound-enhanced inhibition enhances the mechanism of tumor piezo catalytic immunotherapy103. e Schematic of the effect of transcranial acoustic stimulation of the hippocampus (Representative sharp wave ripple trigger spectrogram (top), representative trigger spectra during sharp wave ripples in different groups of mice (Bottom))10
The Wearable ultrasound system for collaborative therapy. Traditional non-invasive treatment methods like phototherapy and chemotherapy could inhibit the growth and division of diseased tissue through external stimulation. Nonetheless, these approaches had evident limitations such as a lack of specificity and inadequate treatment depth. On the contrary, combination therapy involving ultrasound had displayed encouraging outcomes by regulating treatment advancement temporally and spatially to address these limitations. Recent studies had demonstrated the potential utility of photoacoustic imaging systems in diagnosing and treating deep vascular conditions (Fig. 7c)102. By integrating photoacoustic imaging tomography, ultrasound detection, and beamforming, it became feasible to resolve the intricate microvascular network and quantify oxygen saturation through simultaneous ultrasound signal acquisition. Furthermore, collaborative ultrasonic and piezoelectric efforts had advanced in the realm of radiofrequency ablation. Employing novel ultrasonic and piezoelectric technology in radiofrequency ablation therapy represented a novel approach to enhance the precision of lesion boundary detection (Fig. 7d)103. Besides leveraging ultrasound’s mechanical energy for disrupting lesion tissue structure, researchers had explored ultrasound elastography-guided fine-needle aspiration procedures, including those targeting the thyroid.
In order to achieve periodic sign monitoring and treatment, a large number of researchers, clinical engineers, and institutions have been developing wearable ultrasound systems that integrate diagnosis and treatment. Therefore, the fabrication of a class of dual-mode WFUBs with integrated high-resolution imaging and accommodation modes aligned with the needs of various applications75,104,105. For example, Alzheimer’s disease was difficult to treat. It proved an effective treatment strategy to monitor biological signals by wearable systems, and intervened in time when the disease occurs (Fig. 7e)10. In addition, wearable systems also provided solutions for telemedicine, where doctors could be remotely browse postoperative patient recovery data of postoperative patients in order to make a judgment of the condition. Wearable acoustic diagnostic and therapeutic integrated systems offer promising solutions for healthcare and precision medicine. Therefore, enhancing dynamic disease detection and early intervention of a wider range of diseases was warranted to improve patient outcomes. In recent studies, the wearable applications have been expanded to include continuous bladder monitoring, fingertip blood pressure measurement, interventional therapy, and health management (Fig. 8).
The summary of wearable ultrasound applications in diagnosis and treatment and health. The application fields include preventive medicine, health management, disease diagnosis, and personalized interventional treatment, etc42,47,109,110
WFUBs have successfully addressed several of the technical challenges for medical applications of wearable ultrasound systems. However, various obstacles hinder their effectiveness in clinical diagnosis and healthcare. The barriers encompass durability, flexibility, and accuracy of WFUBs, as well as the ease of use and seamless operation of wearable ultrasound applications. Several WFUBs exhibit limited bandwidths and low resolution, as seen in pMUT arrays. Another crucial aspect is enhancing their capability to identify specific targets in intricate settings during the development of wearable acoustic biosensors. Despite some acoustic sensors for wearables achieving comparable 2D/3D resolution to conventional ultrasound through structural optimization. Nevertheless, additional clinical validation will be necessary in the future. In enhancing the performance of WFUBs and enabling their clinical utilization, the following strategies may be contemplated.
An integrated ultrasound system is crucial for enhancing the quality of imaging and expanding the application of wearable ultrasound devices, including small handheld units106. Optimization of sensor size, shape, and manufacturing parameters enhances the sensitivity and specificity of the transducer while achieving wireless miniaturization of the device, leading to increased stability and precision. Progress in ultrasonic patch system technology has advanced the development of fully integrated systems35. The next advancement in this field involves merging clinical ultrasound imaging capabilities with fully integrated, wireless, and wearable flexible biosensors.
Artificial intelligence medical imaging modalities have been used in clinical settings to assist doctors in diagnosing medical conditions, including ultrasound images, CT and MRI imaging. However, there may be external interference in the wearable system image, which generates additional noise. AI algorithms can mitigate phase distortion, and it is ideal for improving the resolution of ultrasound imaging. An intelligent model based on neural network was constructed to reduce image noise of imaging information, improve the accuracy of continuous monitoring, and provide a reliable foundation for further examination. Artificial intelligence-guided acoustic therapy holds great promise for improving patient outcomes, optimizing disease management, and optimizing precision in disease management and efficacy. In addition, the analysis, classification and judgment of deep learning and real-time imaging of wearable ultrasound system are of great significance for improving the accuracy and efficiency of disease diagnosis, and also provide new ideas for the application of AI in the medical field107.
It is crucial to consider the transmission and reception of acoustic signals by materials when developing wearable ultrasonic biomaterials108. In order to effectively transmit and receive sound waves, the flexible bio-probe must establish a strong coupling with the skin. Some researchers created stretchable flexible sensors that can conform to the curved surface of the skin, but stretching these sensors simultaneously compromises their imaging performance. Therefore, optimizing properties are crucial, such as stability, acoustic impedance, elasticity, sensitivity and other techniques. Furthermore, it is important to prevent skin allergies and ensure biosafety, including materials like silicone encapsulants, silicone elastomers, and polyurethane.
WFUBs have advanced significantly in continuously monitoring various physiological indicators and providing interventional therapy. Further exploration of their application fields is warranted. Combining multiple imaging modalities can decrease errors and enhance the overall robustness of the imaging system. While wearable ultrasound therapy for various diseases, such as brain diseases, cardiovascular diseases, and metabolic diseases, has been documented, research in these domains remains constrained. Enhancing the device’s spatial resolution and performance is crucial for clinical applications and can be achieved through a multimodal collaborative approach.
The application of WFUBs necessitates careful consideration of biocompatibility and biodegradability. Specifically, the prolonged presence of WFUBs based on artificially implanted targets in the body may have unforeseen adverse effects on human health. Hence, there is a need for extensive research pertaining to chronic toxicity, biodegradability, and metabolic processes. The majority of implanted soft targets, which may include sound-sensitive agents, are likely to exhibit some level of toxicity, further complicated by various physical factors encountered during diagnosis and treatment, thereby introducing significant uncertainty and variability in these procedures. Currently, the evaluation of biosafety in wearable flexible acoustic biomaterials is at a nascent stage, lacking standardized assessment methodologies and comparative analyses of preclinical and clinical trial outcomes. Furthermore, a comprehensive comprehension of the biological interactions within in vivo systems is imperative. Therefore, the establishment of human biosafety research guidelines for clinical investigations is indispensable.
In summary, research on a wearable ultrasound system utilizing WFUBs demonstrates significant potential and opens up opportunities for sustainable real-time monitoring. WFUBs exhibit skin-like properties and establish robust connections with human tissues to ensure effective coupling. The innovative design of flexible sensors enhances energy absorption, minimizes energy loss from wave reflection, and optimizes the conversion of mechanical energy into electrical energy. The development of these WFUBs face various technical challenges ranging from molecular material selection to structural and system integration design, encompassing initial medical material utilization and clinical system performance validation. The resolution of current stretchable flexible materials is limited to deteriorating bending, necessitating further advancements in high-performance flexible materials. Material structural design adjustments are facilitated through characterization techniques to enhance ultrasonic capture, frequency selectivity, and mechano-electric conversion capabilities. Miniaturization of sensors and systems, material compatibility, and improved reliability are pivotal for successful commercialization. Furthermore, the device’s biocompatibility and long-term wear comfort are essential factors requiring consideration. Ultimately, the advancement of WFUBs is contingent upon interdisciplinary collaboration to establish high-performance, tightly integrated bioelectronic networks for the human body and to enhance healthcare quality.
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This paper is supported by the National Natural Science Foundation of China (62422104, 62473284, 62371115 and 62473284), the Soft Science Foundation of Sichuan Academy of Medical Sciences· Sichuan Provincial People’s Hospital (25RKX002) and Fundamental Research Funds for the Central Universities, UESTC under grant No. ZYGX2025YGLH006.
These authors contributed equally: Jia Li, Gang Li, Chaoqiong Ma.
The Medical Equipment Department, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology, Chengdu, Sichuan, China
Jia Li, Gang Li, Chaoqiong Ma & Wei Li
School of Electronics and Information Engineering, Tiangong University, Tianjin, Tianjin, China
Jia Li
Urology Department, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology, Chengdu, Sichuan, China
Gui Yu
School of Artificial Intelligence, Tiangong University, Tianjin, China
Linying Xiang
School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
Guang Yao
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G. Yao and J. Li proposed this theme, organized the skeleton, provided the raw materials, G. Li and W. Li re-organized figures and wrote the manuscript. J. Li wrote this manuscript, and L.Y. Xiang and C.Q. Ma revised the manuscript and supervised and supported the project. G. Yu edited the manuscript. All authors commented on this manuscript.
Correspondence to Linying Xiang or Guang Yao.
The authors declare no competing interests.
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Li, J., Li, G., Ma, C. et al. Flexible bioelectronic sensors promote the advancement of wearable ultrasound technology in the medicine. Microsyst Nanoeng 12, 244 (2026). https://doi.org/10.1038/s41378-026-01308-y
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DOI: https://doi.org/10.1038/s41378-026-01308-y
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Microsystems & Nanoengineering (Microsyst Nanoeng)
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