Search Results (8)

Nowadays, due to improvements in living standards, more attention is reserved to all-around disease prevention and health care. In particular, research efforts have been made for developing novel methods and treatments for anti-cancer therapy. Self-powered nanogenerators have emerged in recent years as an attractive cost-effective technology to harvest energy or for biosensing applications. Bioelectronic nanogenerators can be used for inducing tissue recovery and for treating human illness through electrical stimulation. However, there is still a lack of comprehensive cognitive assessment of these devices and platforms, especially regarding which requirements must be satisfied and which working principles for energy transduction can be adopted effectively in the body. This review covers the most recent advances in bioelectronic nanogenerators for anti-cancer therapy, based on different transducing strategies (photodynamic therapy, drug delivery, electrical stimulation, atomic nanogenerators, etc.), and the potential mechanisms for tissue repair promotion are discussed. The prospective challenges are finally summarized with an indication of a future outlook. Full article

Wound dressing production represents an important segment in the biomedical healthcare field, but finding a simple and eco-friendly method that combines a natural compound and a biocompatible dressing production for biomedical application is still a challenge. Therefore, the aim of this study is to develop wound healing dressings that are environmentally friendly, low cost, and easily produced, using natural agents and a physical crosslinking technique. Hydrogel wound healing dressings were prepared from polyvinyl alcohol/carboxymethyl cellulose and sericin using the freeze–thawing method as a crosslinking method. The morphological characterization was carried out by scanning electron microscopy (SEM), whereas the mechanical analysis was carried out by dynamic mechanical analysis (DMA) to test the tensile strength and compression properties. Then, the healing property of the wound dressing material was tested by in vitro and ex vivo tests. The results show a three-dimensional microporous structure with no cytotoxicity, excellent stretchability with compressive properties similar to those of human skin, and excellent healing properties. The proposed hydrogel dressing was tested in vitro with HaCaT keratinocytes and ex vivo with epidermal tissues, demonstrating an effective advantage on wound healing acceleration. Accordingly, this study was successful in developing wound healing dressings using natural agents and a simple and green crosslinking method. Full article

Nanogenerators are a recently emerging technology which is able to cost-effectively harvest energy from renewable and clean energy sources at the micro/nano-scale. Their applications in the field of self-powered sensing systems and portable power supplying devices have been increasing in recent years. Wearable and implantable electromechanical/electrochemical transducers for energy harvesting represent a novel alternative to chemical batteries for low-power devices and to exploit the energy conveyed by human biomechanics. The human heart, in particular, is a compelling in vivo source of continuous biomechanical energy and is a natural battery which can power implantable or wearable medical devices. This review describes the recent advances in cardiac wearable/implantable soft and flexible devices and nanogenerators for energy harvesting (piezoelectric nanogenerators, triboelectric nanogenerators, biofuel cells, solar cells, etc.), as well as cardiovascular implantable electronic devices in a more general sense, as components of more complex self-sustainable bioelectronic systems for controlling irregular heartbeats or for interventional therapy for cardiac diseases. The main types of soft heart energy harvesters (HEHs) and heart bioelectronic systems (HBSs) are covered and classified, with a detailed presentation of state-of-the-art devices, and the advances in terms of materials choice, chemical functionalization, and design engineering are highlighted. In vivo bioelectronic cardiac interfaces are outlined as well as soft devices for in vitro cardiac models (patch and organoids). Cutting-edge 3D/4D bioprinting techniques of cardiac tissue are also mentioned. The technical challenges for the practical application and commercialization of soft HBSs are discussed at the end of this paper. Full article

Nanogenerators, based on piezoelectric or triboelectric materials, have emerged in the recent years as an attractive cost-effective technology for harvesting energy from renewable and clean energy sources, but also for human sensing and biomedical wearable/implantable applications. Advances in materials engineering have enlightened new opportunities for the creation and use of novel biocompatible soft materials as well as micro/nano-structured or chemically-functionalized interfaces. Hybridization is a key concept that can be used to enhance the performances of the single devices, by coupling more transducing mechanisms in a single-integrated micro-system. It has attracted plenty of research interest due to the promising effects of signal enhancement and simultaneous adaptability to different operating conditions. This review covers and classifies the main types of hybridization of piezo-triboelectric bio-nanogenerators and it also provides an overview of the most recent advances in terms of material synthesis, engineering applications, power-management circuits and technical issues for the development of reliable implantable devices. State-of-the-art applications in the fields of energy harvesting, in vitro/in vivo biomedical sensing, implantable bioelectronics are outlined and presented. The applicative perspectives and challenges are finally discussed, with the aim to suggest improvements in the design and implementation of next-generation hybrid bio-nanogenerators and biosensors. Full article

In this work, a new flexible and biocompatible microfluidic pH sensor based on surface acoustic waves (SAWs) is presented. The device consists of polyethylene naphthalate (PEN) as a flexible substrate on which aluminum nitride (AlN) has been deposited as a piezoelectric material. The fabrication of suitable interdigitated transducers (IDTs) generates Lamb waves (L-SAW) with a center frequency ≈500 MHz traveling in the active region. A SU-8 microfluidics employing ZnO nanoparticles (NPs) functionalization as a pH-sensitive layer is fabricated between the IDTs, causing a shift in the L-SAW resonance frequency as a function of the change in pH values. The obtained sensitivity of ≈30 kHz/pH from pH 7 to pH 2 demonstrates the high potential of flexible SAW devices to be used in the measurement of pH in fluids and biosensing. Full article

Innovative biocompatible organic materials with piezoelectric properties have great potential for the development of wearable sensors for monitoring physiological parameters. Among them, Chitosan (CS) is a natural, biodegradable, antibacterial and low cost biopolymer that shows interesting piezoelectric behaviour. In this context, this work reports on a protocol where plain chitosan films (CS-F) are exploited to easily create a flexible, wearable piezoelectric patch. By adapting a previously reported simple drop casting method, we here demonstrate that a 70 μm thick CS-F can exhibit good piezoelectric properties. The structure of CS-F was analysed via the XRD technique: the spectrum reveals peaks of partially crystalline chitosan film, indicating the presence of organized polymeric chains (Suppl. Ppt. Slide 8). Piezoresponse Force Microscopy scans confirmed the presence of domains with opposite polarization directions with an extrapolated value of the piezoelectric coefficient d₃₃ of 2.54 pC/N. A microfabrication process for patch realization has been set up. The top electrode was created by the simple thermal evaporation of gold directly onto the free-standing CS-F (Suppl. Ppt. Slide 10). This bilayer was then precisely cut using a cutting plotter and assembled on the copper bottom electrode (Suppl. Ppt. Slide 11). The complete patch can be conformally applied on the skin. The ability of the device to sense physiological movements was validated by an ad hoc measurement set up generating strain pulses; open circuit voltage peaks up to 20 mV were detected (Suppl. Ppt. Slide 13). This sensor represents an important step towards totally biocompatible and biodegradable wearable devices. Full article

Triboelectric nanogenerators (TENGs) have recently become a powerful technology for energy harvesting and self-powered sensor networks. One of their main advantages is the possibility to employ a wide range of materials, especially for fabricating inexpensive and easy-to-use devices. This paper reports the fabrication and preliminary characterization of a novel flexible triboelectric nanogenerator which could be employed for driving future low power consumption wearable devices. The proposed TENG is a single-electrode device operating in contact-separation mode for applications in low-frequency energy harvesting from intermittent tapping loads involving the human body, such as finger or hand tapping. The novelty of the device lies in the choice of materials: it is based on a combination of a polysiloxane elastomer and a poly (para-xylylene). In particular, the TENG is composed, sequentially, of a poly (dimethylsiloxane) (PDMS) substrate which was made porous and rough with a steam-curing step; then, a metallization layer with titanium and gold, deposited on the PDMS surface with an optimal substrate–electrode adhesion. Finally, the metallized structure was coated with a thin film of parylene C serving as friction layer. This material provides excellent conformability and high charge-retaining capability, playing a crucial role in the triboelectric process; it also makes the device suitable for employment in harsh, wet environments owing to its inertness and barrier properties. Preliminary performance tests were conducted by measuring the open-circuit voltage and power density under finger tapping (~2 N) at ~5 Hz. The device exhibited a peak-to-peak voltage of 1.6 V and power density peak of 2.24 mW/m² at ~0.4 MΩ. The proposed TENG demonstrated ease of process, simplicity, cost-effectiveness, and flexibility. Full article

Electronic devices used for marine applications suffer from several issues that can compromise their performance. In particular, water absorption and permeation can lead to the corrosion of metal parts or short-circuits. The added mass due to the absorbed water affects the inertia and durability of the devices, especially for flexible and very thin micro-systems. Furthermore, the employment of such delicate devices underwater is unavoidably subjected to the adhesion of microorganisms and formation of biofilms that limit their reliability. Thus, the demand of waterproofing solutions has increased in recent years, focusing on more conformal, flexible and insulating coatings. This work introduces an evaluation of different polymeric coatings (parylene-C, poly-dimethyl siloxane (PDMS), poly-methyl methacrylate (PMMA), and poly-(vinylidene fluoride) (PVDF)) aimed at increasing the reliability of piezoelectric flexible microdevices used for sensing water motions or for scavenging wave energy. Absorption and corrosion tests showed that Parylene-C, while susceptible to micro-cracking during prolonged oscillating cycles, exhibits the best anti-corrosive behavior. Parylene-C was then treated with oxygen plasma and UV/ozone for modifying the surface morphology in order to evaluate the biofilm formation with different surface conditions. A preliminary characterization through a laser Doppler vibrometer allowed us to detect a reduction in the biofilm mass surface density after 35 days of exposure to seawater. Full article