Stretchable Wireless Research Articles

Stretchable wireless optoelectronic synergistic patches for effective wound healing

Physiotherapies play a crucial role in noninvasive tissue engineering for wound healing. However, challenges such as the implementation of complex interventions and unsatisfactory treatment outcomes impede widespread application. Here, we proposed a stretchable and wirelessly-powered optoelectronic synergistic patch with a dual-layer serpentine wireless receiver circuit to drive the optoelectronic modulation component. Optimized structure and impedance matching enable the patch to seamlessly attach to irregular skin surfaces and operate robustly over a 30% tensile strain range. Based on Sprague-Dawley rat wound model. The wound closure rate of the optoelectronic synergistic group significantly outperformed both monointervention and blank control groups. Mechanistically, optoelectronic synergistic intervention enhances the secretion of vascular endothelial marker proteins and growth factors, and stabilizes mitochondrial function during oxidative stress. Overall, the scalable amalgamation of flexible electronics, wireless transmission, and synergistic interventions promise to improve wound care.

Phase-separated porous nanocomposite with ultralow percolation threshold for wireless bioelectronics.

Realizing the full potential of stretchable bioelectronics in wearables, biomedical implants and soft robotics necessitates conductive elastic composites that are intrinsically soft, highly conductive and strain resilient. However, existing composites usually compromise electrical durability and performance due to disrupted conductive paths under strain and rely heavily on a high content of conductive filler. Here we present an in situ phase-separation method that facilitates microscale silver nanowire assembly and creates self-organized percolation networks on pore surfaces. The resultant nanocomposites are highly conductive, strain insensitive and fatigue tolerant, while minimizing filler usage. Their resilience is rooted in multiscale porous polymer matrices that dissipate stress and rigid conductive fillers adapting to strain-induced geometry changes. Notably, the presence of porous microstructures reduces the percolation threshold (Vc = 0.00062) by 48-fold and suppresses electrical degradation even under strains exceeding 600%. Theoretical calculations yield results that are quantitatively consistent with experimental findings. By pairing these nanocomposites with near-field communication technologies, we have demonstrated stretchable wireless power and data transmission solutions that are ideal for both skin-interfaced and implanted bioelectronics. The systems enable battery-free wireless powering and sensing of a range of sweat biomarkers-with less than 10% performance variation even at 50% strain. Ultimately, our strategy offers expansive material options for diverse applications.

A stretchable wireless wearable bioelectronic system for multiplexed monitoring and combination treatment of infected chronic wounds.

Chronic nonhealing wounds are one of the major and rapidly growing clinical complications all over the world. Current therapies frequently require emergent surgical interventions, while abuse and misapplication of therapeutic drugs often lead to an increased morbidity and mortality rate. Here, we introduce a wearable bioelectronic system that wirelessly and continuously monitors the physiological conditions of the wound bed via a custom-developed multiplexed multimodal electrochemical biosensor array and performs noninvasive combination therapy through controlled anti-inflammatory antimicrobial treatment and electrically stimulated tissue regeneration. The wearable patch is fully biocompatible, mechanically flexible, stretchable, and can conformally adhere to the skin wound throughout the entire healing process. Real-time metabolic and inflammatory monitoring in a series of preclinical in vivo experiments showed high accuracy and electrochemical stability of the wearable patch for multiplexed spatial and temporal wound biomarker analysis. The combination therapy enabled substantially accelerated cutaneous chronic wound healing in a rodent model.

Stretchable thin film inductors for wireless sensing in wearable electronic devices

The unique soft and elastic nature of stretchable electronics has potential to advance wearable devices as human-machine interfaces. The integration of wireless power and data communication technology into stretchable electronics, which could be realised by inductive coupling and oscillator circuits, is key to achieve continuous monitoring of body signals with minimally invasive devices. As one of the main components for inductive coupling and oscillator circuits, the development of stretchable inductors is therefore compelling. The most common strategy to fabricate stretchable inductors is to add periodic waves to a spiral conductor, which provides mechanical robustness but inevitably increases resistance. In this work, we introduce a method to fabricate stretchable inductors, which relies on creating a wrinkled thin film inductor on a polystyrene substrate, functionalizing the inductor surface with an adhesive layer, and then transferring the structure onto a polydimethylsiloxane (PDMS) elastomer. Contrary to inductors created through the addition of periodic wave patterns, the wrinkled inductor features low resistance while providing high stretchability. The wrinkled inductors fabricated using this approach exhibited 30% decrease in resistance compared to their flat counterparts of the same size and geometry. Resistance and inductance under uniaxial stretching remained unchanged up to 45% strain, revealing exceptional electrical and mechanical stability. The strong chemical bonding between the functionalized wrinkled inductor and the PDMS elastomer contributes to the robustness and long-term stability of the device. This method provides an added advantage of miniaturization of the stretchable inductor, as it is shrunk to 16% of its original size during the wrinkling process. This technology has potential for building high performance stretchable inductors for stretchable wireless electronic devices and can eventually benefit the design of electronics for implants, health care monitoring and wearable communication.

High-frequency and intrinsically stretchable polymer diodes.

Skin-like intrinsically stretchable soft electronic devices are essential to realize next-generation remote and preventative medicine for advanced personal healthcare1-4. The recent development of intrinsically stretchable conductors and semiconductors has enabled highly mechanically robust and skin-conformable electronic circuits or optoelectronic devices2,5-10. However, their operating frequencies have been limited to less than 100 hertz, which is much lower than that required for many applications. Here we report intrinsically stretchable diodes-based on stretchable organic and nanomaterials-capable of operating at a frequency as high as 13.56 megahertz. This operating frequency is high enough for the wireless operation of soft sensors and electrochromicdisplaypixels using radiofrequency identification in which the base-carrier frequency is 6.78 megahertz or13.56 megahertz. This was achieved through a combination of rational material design and device engineering. Specifically, we developed a stretchable anode, cathode, semiconductor and current collector that can satisfy the strict requirements for high-frequency operation. Finally, we show the operational feasibility of our diode by integrating it with a stretchable sensor, electrochromicdisplay pixel and antenna to realize a stretchable wireless tag. This work is an important step towards enabling enhanced functionalities and capabilities for skin-like wearable electronics.

Fully Integrated Wireless Elastic Wearable Systems for Health Monitoring Applications

Advances in flexible and hybrid electronics promote increasing demands for wearable sensors in personal health, monitoring, and diagnostic medical gadgets. Conventional wearable devices rely on electronics based on rigid substrates and components with limited conformity to user skin. In this work, we report a fully integrated, stretchable wireless electrocardiography (ECG) system developed on highly elastic, ultra-thin ( 100 μm) thermoplastic polyurethane (TPU) film without any rigid or flexible interposer. Moreover, the circuit layout printing and component assembly are carried out through sheet-to-sheet (S2S) process directly on TPU film. This study utilizes both experimental reliability tests coupled with data acquired from finite element modeling (FEM) to assess performance and failure of the device under tensile loading. In such a complex system assembly, FEM simulation not only provides insights on the overall electromechanical performance of the device, but also facilitates localization of the failure points which are difficult to access for visual inspection. The performance of the device is also evaluated through controlled uniaxial cyclic strain at 5% and 10% elongation. The durability test shows that the assembled device can stay functional over hundreds of deformation cycles, suggesting that direct assembly of conventional components on stretchable substrate represents a promising approach for fully integrated stretchable devices, which is a step toward scalable manufacture of wearable stretchable electronics through high-throughput manufacturing processes.

Light‐Induced Swelling‐Responsive Conductive, Adhesive, and Stretchable Wireless Film Hydrogel as Electronic Artificial Skin

AbstractLight‐induced wireless soft electronic skin hydrogels with excellent mechanical and electronic properties are important for several applications, such as soft robotics and intelligent wearable devices. Precise control of reversible stretchability and capacitive properties depending on intermolecular interaction and surface characteristics remains a challenge. Here, a thin‐film hydrogel is designed based on titanium oxide (TiO2) polydopamine–perfluorosilica carbon dot‐conjugated chitosan–polyvinyl alcohol‐loaded tannic acid with controllable hydrophobic–hydrophilic transition in the presence of UV–vis light irradiation. The shifting of surface wettability from hydrophobic to hydrophilic by irradiation affects thin‐film water permeability and swelling ratio. This allows the penetration of water into the matrix to change its mechanical strength, electronic properties, and adhesive behavior. Specifically, the hydrogel displays mechanical strain as high as 278% in response to light stimuli and demonstrates the ability to regain its initial state determining the elasticity of the fabricated material. Moreover, the thin‐film hydrogel shows an increase in conductivity to 1.096 × 10−3 and 1.026 × 10−3 S cm−1 when irradiated with UV and visible light, respectively. The hydrogel exhibits capacitive reversibility that follows finger motion which can be identified directly or remotely using wireless connection, indicative of its possible applications as an artificial electronic skin.

Fractal serpentine-shaped design for stretchable wireless strain sensors

Stretchable sensors have been widely applied to biological fields due to their unique capacity to integrate with soft materials and curvilinear surfaces. The article presents the fractal serpentine-shaped design for stretchable wireless strain sensor which is operating around 1.6 GHz. The wireless passive LC sensor is formed by a fractal serpentine-shaped inductor coil and a concentric coplanar capacitor. The inductance of the fractal serpentine-shaped coil varies with the deformation of the wireless sensor, and the resonance frequency also varies with the applied strain of the wireless sensor embedded in soft substrate. The 40% stretchability of wireless sensor is verified by finite element analysis (FEA). Strain response of the stretchable wireless sensor has been characterized by experiments and demonstrates high strain responsivity about 6.74 MHz/1%. The stretchable wireless sensor has the potential to be used in biological and wearable applications.

Thermotherapy Platform Based on a Highly Stretchable Wireless Heater

Thermotherapy Platform Based on a Highly Stretchable Wireless Heater

Highly Stretchable Electrodes on Wrinkled Polydimethylsiloxane Substrates.

This paper demonstrates a fabrication technology of Ag wrinkled electrodes with application in highly stretchable wireless sensors. Ag wrinkled thin films that were formed by vacuum deposition on top of pre-strained and relaxed polydimethylsiloxane (PDMS) substrates which have been treated using an O2 plasma and a surface chemical functionalization process can reach a strain limit up to 200%, while surface adhesion area can reach 95%. The electrical characteristics of components such as resistors, inductors and capacitors made from such Ag conductors have remained stable under stretching exhibiting low temperature and humidity coefficients. This technology was then demonstrated for wireless wearable electronics using compatible processing with established micro/nano fabrication technology.

Soft, stretchable, fully implantable miniaturized optoelectronic systems for wireless optogenetics.

Optogenetics allows rapid, temporally specific control of neuronal activity via targeted expression and activation of light-sensitive proteins. Implementation typically requires remote light sources and fiber-optic delivery schemes that impose significant physical constraints on natural behaviors. In this report we bypass these limitations using novel technologies that combine thin, mechanically soft neural interfaces with fully implantable, stretchable wireless radio power and control systems. The resulting devices achieve optogenetic modulation of the spinal cord and peripheral nervous system. This is demonstrated with two form factors; stretchable film appliques that interface directly with peripheral nerves, and flexible filaments that insert into the narrow confines of the spinal epidural space. These soft, thin devices are minimally invasive, and histological tests suggest they can be used in chronic studies. We demonstrate the power of this technology by modulating peripheral and spinal pain circuitry, providing evidence for the potential widespread use of these devices in research and future clinical applications of optogenetics outside the brain.

Tape transfer atomization patterning of liquid alloys for microfluidic stretchable wireless power transfer.

Stretchable electronics offers unsurpassed mechanical compliance on complex or soft surfaces like the human skin and organs. To fully exploit this great advantage, an autonomous system with a self-powered energy source has been sought for. Here, we present a new technology to pattern liquid alloys on soft substrates, targeting at fabrication of a hybrid-integrated power source in microfluidic stretchable electronics. By atomized spraying of a liquid alloy onto a soft surface with a tape transferred adhesive mask, a universal fabrication process is provided for high quality patterns of liquid conductors in a meter scale. With the developed multilayer fabrication technique, a microfluidic stretchable wireless power transfer device with an integrated LED was demonstrated, which could survive cycling between 0% and 25% strain over 1,000 times.

Self-similar design for stretchable wireless LC strain sensors

Stretchable sensors provide a foundation for applications that exceed the scope of conventional device technologies due to their unique capacity to integrate with soft materials and curvilinear surfaces. This article presents the implementation and characterization of a large-area stretchable wireless RF strain sensor, operating at around 760MHz, based on the concept of self-similar design. It has an electrical LC resonant circuit formed by a self-similar inductor coil and a capacitor to facilitate passive wireless sensor. The inductance of the wireless sensor varies with the elongation of the PDMS substrate, so is the resonance frequency of the sensor that is detected using an external coil linked to a vector network analyzer. Finite element modeling was used in combination with experimental verification to demonstrate that the wireless strain sensor with 300μm width can be stretched up to 40%. Self-similar structured coil incorporating variable inductance has been implemented to monitor the strain of artificial skin. Strain response of the stretchable wireless sensor has been characterized by experiments, and demonstrates high strain responsivity about 33.7MHz/10%, which confirms the feasibility of strain sensing for biomedical and wearable applications.

Stretchable, Wireless Sensors and Functional Substrates for Epidermal Characterization of Sweat

This paper introduces materials and architectures for ultrathin, stretchable wireless sensors that mount on functional elastomeric substrates for epidermal analysis of biofluids. Measurement of the volume and chemical properties of sweat via dielectric detection and colorimetry demonstrates some capabilities. Here, inductively coupled sensors consisting of LC resonators with capacitive electrodes show systematic responses to sweat collected in microporous substrates. Interrogation occurs through external coils placed in physical proximity to the devices. The substrates allow spontaneous sweat collection through capillary forces, without the need for complex microfluidic handling systems. Furthermore, colorimetric measurement modes are possible in the same system by introducing indicator compounds into the depths of the substrates, for sensing specific components (OH(-) , H(+) , Cu(+) , and Fe(2+) ) in the sweat. The complete devices offer Young's moduli that are similar to skin, thus allowing highly effective and reliable skin integration without external fixtures. Experimental results demonstrate volumetric measurement of sweat with an accuracy of 0.06 μL/mm(2) with good stability and low drift. Colorimetric responses to pH and concentrations of various ions provide capabilities relevant to analysis of sweat. Similar materials and device designs can be used in monitoring other body fluids.