Micro-/Nano-Structured Biodegradable Pressure Sensors for Biomedical Applications

Analysis of Tribological and Cytotoxicity Assays of a Biocompatible Mg-Zn-Ca-Pr Alloy

This work covers a Mg-Zn-Ca-Pr alloy fabricated by a novel method of mechanical alloying and spark plasma sintering (SPS). Currently, magnesium alloys used as biomaterials are mostly commercial alloys without consideration of cytotoxicity from the perspective of biosafety. So far, the tribological and cytotoxic properties of Mg-Zn-Ca-Pr alloys have not been investigated. Hence, in the article, the tribological properties, considering wear rate, wear resistance, coefficient of friction, and the roughness of the sintered Mg-Zn-Ca-Pr alloy, are investigated. Cytotoxicity assays have also been carried out. The ball-on-a-disc method is used in the tribological test. Samples before sintering by the SPS method are milled at varying times of 13, 20, and 70 h. Results show that increasing the milling time affects tribology and cytotoxic tests. The longer the milling time, the lower the cell survival rate. The conducted tests reveal cell survival of 90, 82, and 61% for 13, 20, and 70 h, respectively. A reduction of cell viability by over 30% is considered a cytotoxic effect, which was observed only in the 70 h milling-time samples.

Catheter-Free Urodynamics Testing: Current Insights and Clinical Potential

Lower urinary tract dysfunction not only interferes with the health-related quality of life of patients but may also lead to acute kidney injury and infections. To assess the bladder, urodynamic studies (UDS) have been implemented but the use of catheters leads to discomfort for the patient. Catheter-free long-term UDS would be useful and a potential solution could be ambulatory wireless devices that communicate via telemetry. Such sensors can detect pressure or volume. Numerous types of potential catheter-free sensors have been proposed for bladder monitoring. Despite substantial innovation in the manufacturing of implantable biomedical electronic systems, such sensors have remained at the laboratory stage due to a number of critical challenges. These challenges primarily concern hermeticity and biocompatibility, sensitivity and artifacts, drift, telemetry, and energy management. Having overcome these challenges, catheter-free ambulatory urodynamic monitoring could combine a synchronized intravesical pressure sensor with a volume analyzer but only the steps of cystometry and volume measurement are currently sufficiently reproducible to simulate UDS results. The measurement of volume by infrared optical sensors, in the form of abdominal patches, appears to be promising and studies are underway to market a telemetric ambulatory urodynamic monitoring system that includes an intravesical pressure sensor. There has been considerable progress in wearable and conformable electronics on many fronts, and continued collaboration between engineers and urologists could quickly overcome current challenges. In addition, to the diagnosis of UDS, such sensors could be useful in the development of a long-term closed-loop neuromodulation system. In this review, we explore the various types of catheter-free bladder sensors, inherent challenges and solutions to overcome these challenges, and the clinical potential of such long-term implantable sensors.

Bioinspired nanoplatforms for human-machine interfaces: Recent progress in materials and device applications

The panoramic characteristics of human-machine interfaces (HMIs) have prompted the needs to update the biotechnology community with the recent trends, developments, and future research direction toward next-generation bioelectronics. Bioinspired materials are promising for integrating various bioelectronic devices to realize HMIs. With the advancement of scientific biotechnology, state-of-the-art bioelectronic applications have been extensively investigated to improve the quality of life by developing and integrating bioinspired nanoplatforms in HMIs. This review highlights recent trends and developments in the field of biotechnology based on bioinspired nanoplatforms by demonstrating recently explored materials and cutting-edge device applications. Section 1 introduces the recent trends and developments of bioinspired nanomaterials for HMIs. Section 2 reviews various flexible, wearable, biocompatible, and biodegradable nanoplatforms for bioinspired applications. Section 3 furnishes recently explored substrates as carriers for advanced nanomaterials in developing HMIs. Section 4 addresses recently invented biomimetic neuroelectronic, nanointerfaces, biointerfaces, and nano/microfluidic wearable bioelectronic devices for various HMI applications, such as healthcare, biopotential monitoring, and body fluid monitoring. Section 5 outlines designing and engineering of bioinspired sensors for HMIs. Finally, the challenges and opportunities for next-generation bioinspired nanoplatforms in extending the potential on HMIs are discussed for a near-future scenario. We believe this review can stimulate the integration of bioinspired nanoplatforms into the HMIs in addition to wearable electronic skin and health-monitoring devices while addressing prevailing and future healthcare and material-related problems in biotechnologies.

A Review of Single-Cell Microrobots: Classification, Driving Methods and Applications

Single-cell microrobots are new microartificial devices that use a combination of single cells and artificial devices, with the advantages of small size, easy degradation and ease of manufacture. With externally driven strategies such as light fields, sound fields and magnetic fields, microrobots are able to carry out precise micromanipulations and movements in complex microenvironments. Therefore, single-cell microrobots have received more and more attention and have been greatly developed in recent years. In this paper, we review the main classifications, control methods and recent advances in the field of single-cell microrobot applications. First, different types of robots, such as cell-based microrobots, bacteria-based microrobots, algae-based microrobots, etc., and their design strategies and fabrication processes are discussed separately. Next, three types of external field-driven technologies, optical, acoustic and magnetic, are presented and operations realized in vivo and in vitro by applying these three technologies are described. Subsequently, the results achieved by these robots in the fields of precise delivery, minimally invasive therapy are analyzed. Finally, a short summary is given and current challenges and future work on microbial-based robotics are discussed.

MXene-Based Nanocomposites for Piezoelectric and Triboelectric Energy Harvesting Applications

Due to its superior advantages in terms of electronegativity, metallic conductivity, mechanical flexibility, customizable surface chemistry, etc., 2D MXenes for nanogenerators have demonstrated significant progress. In order to push scientific design strategies for the practical application of nanogenerators from the viewpoints of the basic aspect and recent advancements, this systematic review covers the most recent developments of MXenes for nanogenerators in its first section. In the second section, the importance of renewable energy and an introduction to nanogenerators, major classifications, and their working principles are discussed. At the end of this section, various materials used for energy harvesting and frequent combos of MXene with other active materials are described in detail together with the essential framework of nanogenerators. In the third, fourth, and fifth sections, the materials used for nanogenerators, MXene synthesis along with its properties, and MXene nanocomposites with polymeric materials are discussed in detail with the recent progress and challenges for their use in nanogenerator applications. In the sixth section, a thorough discussion of the design strategies and internal improvement mechanisms of MXenes and the composite materials for nanogenerators with 3D printing technologies are presented. Finally, we summarize the key points discussed throughout this review and discuss some thoughts on potential approaches for nanocomposite materials based on MXenes that could be used in nanogenerators for better performance.

Zinc hybrid sintering for printed transient sensors and wireless electronics

Transient electronics offer a promising solution for reducing electronic waste and for use in implantable bioelectronics, yet their fabrication remains challenging. We report on a scalable method that synergistically combines chemical and photonic mechanisms to sinter printed Zn microparticles. Following reduction of the oxide layer using an acidic solution, zinc particles are agglomerated into a continuous layer using a flash lamp annealing treatment. The resulting sintered Zn patterns exhibit electrical conductivity values as high as 5.62 × 106 S m-1. The electrical conductivity and durability of the printed zinc traces enable the fabrication of biodegradable sensors and LC circuits: temperature, strain, and chipless wireless force sensors, and radio-frequency inductive coils for remote powering. The process allows for reduced photonic energy to be delivered to the substrate and is compatible with temperature-sensitive polymeric and cellulosic substrates, enabling new avenues for the additive manufacturing of biodegradable electronics and transient implants.