Advances in Medical Applications of Additive Manufacturing

In the past few decades,additive manufacturing(AM)has been developed and applied as a cost-effective and versatile technique for the fabrication of geometrically complex objects in the medical industry.In this review,we discuss current advances of AM in medical applications for the generation of pharmaceuticals,medical implants,and medical devices.Oral and transdermal drugs can be fabricated by a variety of AM technologies.Different types of hard and soft clinical implants have also been realized by AM,with the goal of producing tissue-engineered constructs.In addition,medical devices used for diagnostics and treatment of various pathological conditions have been developed.The growing body of research on AM reveals its great potential in medical applications.The goal of this review is to highlight the usefulness and elucidate the current limitations of AM applications in the medical field.

Wireless communication and wireless power transfer system for implantable medical device

Traditional magnetically coupled resonant wireless power transfer technology uses fixed distances between coils for research,to prevent fluctuations in the receiving voltage,and lead to reduce transmission efficiency.This paper proposes a closed-loop control wireless communication wireless power transfer system with a wearable four-coil structure to stabilize the receiving voltage fluctuation caused by changes in the displacement between the coils.Test results show that the system can provide stable receiving voltage,no matter how the distance between the transmitting coil and the receiving coil is changed.When the transmission distance is 20 mm,the power transfer efficiency of the system can reach 18.5%under the open-loop state,and the stimulus parameters such as the stimulation period and pulse width can be adjusted in real time through the personal computer terminal.

PNN-SVM Approach of Ti-Based Powder’s Properties Evaluation for Biomedical Implants Production

The advent of additive technologies has provided a significant breakthrough in the production of medical implants.It has reduced costs,increased productivity and accuracy of the implant manufacturing process.However,there are problems associated with assessing defects in the microstructure,mechanical and technological properties of alloys,both during their production by powder metallurgy and in the process of 3D printing.Thus traditional research methods of alloys properties demand considerable human,material,and time resources.At the same time,artificial intelligence tools create opportunities for intelligent evaluation of the conformity for the microstructure,phase composition,and properties of titanium powder’s alloys.It provides new possibilities for the efficient production of biocompatible implants for various functional purposes.However,the accuracy of the methods and models used should be as high as possible.In this paper we designed a hybrid PNN-SVM(Probabilistic Neural Network-Support Vector Machine)high-precision approach for the intelligent evaluation of alloy properties for additive manufacturing of biomedical implants.We have proposed a new approach for extending the dimensionality of input data space by the outputs of the summation layer of the modified PNN topology.Subsequent classification based on the expanded dataset is performed using SVM.We conducted experimental modeling of the proposed approach using a data set on the properties of titanium alloys Ti-6Al-4V and Ti-Al-V-Zr.We have demonstrated a significant increase in the accuracy of the PNN-SVM scheme compared to the single classifiers that form it and other machine learning methods.

Recharging method of active medical implant using wearable incoherent light source

A new method for recharging active medical implant（AMI）in vitro based on incoherent light source and results of the simulation experiments are proposed.Firstly,the models of the AMI recharging method based on incoherent light source in vitro are developed,which include the models of an incoherent light source and skin tissue.Secondly,simulation experiments of the incoherent light source of the AMI recharging process in vitro based on the Monte Carlo（MC）method are carried out.Finally,absorbed fractions of different layers and distributions of density along x axis of the tissue model and other important conclusions have been achieved.

Recent Techniques for Harvesting Energy from the Human Body

The human body contains a near-infinite supply of energy in chemical,thermal,and mechanical forms.However,the majority of implantable and wear-able devices are still operated by batteries,whose insufficient capacity and large size limit their lifespan and increase the risk of hazardous material leakage.Such energy can be used to exceed the battery power limits of implantable and wear-able devices.Moreover,novel materials and fabrication methods can be used to create various medical therapies and life-enhancing technologies.This review paper focuses on energy-harvesting technologies used in medical and health applications,primarily power collectors from the human body.Current approaches to energy harvesting from the bodies of living subjects for self-powered electronics are summarized.Using the human body as an energy source encompasses numer-ous topics:thermoelectric generators,power harvesting by kinetic energy,cardi-ovascular energy harvesting,and blood pressure.The review considers various perspectives on future research,which can provide a new forum for advancing new technologies for the diagnosis,treatment,and prevention of diseases by integrating different energy harvesters with advanced electronics.

Impact of three dimensional printing in orthopedics

The primary objective of this article is to explore effects of latest development in the area of three dimensional(3D)printing&to assess its abilities,and further undertake helpful reporting.Here the focus is to assess ad vantages of 3D printing in orthopedics and analyze how 3D printed models help solve complex 3D orthopedics distortions.This study identified that 3D models manufactured by 3D printing models reduce medical parts de velopment cost and surgical planning time.Integrating 3D printing with orthopaedics helps in understanding the conditions of problems and achieving the operation succssfully.This technology can enable doctors/surgeons to design,produce,recreate and plan operations more accurately,carefully,and economicaly.3D models can assist specialists with a visual comprehension of the patient-particular pathology and life structures.Innovation in 3D printing initiated a scaffold for the virtual outline and execution of medical procedures.This research proposes the utilisation of 3D printers as an elective procedure for the fabrication of parts.It empowers surgeons/patients for better raining,education and research.In the future,there is a foreseeable expansion of additive manufacturing in orthopedics.

A Review of Implant Intra-Body Communication

With an extending life expectancy and demand for medical healthcare,there are wide-spread and stringent requirements of implantable medical devices(IMDs)development for dia-gnostics,treatments,and therapies by emerging technologies.One of the primary targets for the IMDs is evolving a reliable,speed,and accurate communication method to provide proactive well-ness management and thereby achieve early detection,disease prevention,and even treatments.In-tra-body communication(IBC)is a potential technology envisioning a sensors/actuators network within a human body,which uses the conductive properties of a body and is categorized in the standardized IEEE 802.15.06 protocol.In the present review,the current state-of-art of implant in-tra-body communication has been surveyed.Based on the propagation mechanisms over investig-ated IBC spectrum(i.e.,0.1 MHz-100 MHz),the capacitive and galvanic coupling IBC is con-sidered,where the subfields regarding modeling method(including circuit,numerical,analytical,and filter model),measurement details(including the effect of the electrode,cable,impedance,and instrument),clinical application(including cardiac pacemaker and wireless endoscope),transceiver design(including discrete component and CMOS technology)and media access control(MAC)lay-er design have been introduced or discussed.Furthermore,the open challenges and issues have been explored as an anticipated inspiration for future development.

Review:Fabrication and Application of Zwitterion-based Functional Coatings

Zwitterion-based materials by virtue of their special physical and chemical characteristics have attracted researchers to utilize them for fabricating functional coatings. The simultaneous presence of positive and negative charges renders the zwitterion-based materials with electrostatically induced hydration properties, which enables a high resistance towards oily pollutants, nonspecific protein adsorption, bacterial adhesion and biofilm formation. This review starts from the working mechanism of zwitterions and covers the fabrication strategies of zwitterion-based functional coatings, namely the zwitterion-bearing binder route, the zwitterion-bearing additive route and the post-generation of coatings containing zwitterionic precursors. The applications of zwitterion-based functional coatings are discussed, including medical implants, marine antifouling and oil-resistant coatings, with focus on the relevant mechanisms of the zwitterion-containing coatings for a specific performance. Finally, some comments and perspectives on the current situation and future development of zwitterion-based functional coatings are given.

Polyhydroxyalkanoates： Current applications in the medical field

Polyhydroxyalkanoates （PHAs） are a class of biopolyesters that are synthesized intracellularly by microorganisms, mainly by different genera of eubacteria. These biopolymers have diverse physical and chemical properties that also classify them as biodegradable in nature and make them compatible to living systems. In the last two decades or so, PHAs have emerged as potential useful materials in the medical field for different applications owing to their unique properties. The lower acidity and bioactivity of PHAs confer them with minimal risk compared to other biopolymers such as poly-lactic acid （PLA） and poly-glycolic acid （PGA）. Therefore, the versatility of PHAs in terms of their non-toxic degradation products, biocompatibility, desired surface modifications, wide range of physical and chemical properties, cellular growth support, and attachment without carcinogenic effects have enabled their use as in vivo implants such as sutures, adhesion barriers, and valves to guide tissue repair and in regeneration devices such as cardiovascular patches, articular cartilage repair scaffolds, bone graft substitutes, and nerve guides. Here, we briefly describe some of the most recent innovative research involving the use of PHAs in medical applications. Microbial production of PHAs also provides the opportunity to develop PHAs with more unique monomer compositions economically through metabolic engineering approaches. At present, it is generally established that the PHA monomer composition and surface modifications influence cell responses.PHA synthesis by bacteria does not require the use of a catalyst （used in the synthesis of other polymers）, which further promotes the biocompatibility of PHA-derived polymers.

Secure Method for Software Upgrades for Implantable Medical Devices

A non-invasive software upgrade method for permanent implantable medical devices was developed to alleviate patients＇ suffering due to malfunctions because of software faults,which may cause serious adverse health consequences or require enhancements with new software.The programs distributed to the internal implantable pulse generator（IPG） from the external programmer have been developed so that the upgrade service program in the IPG is simplified with most complex functions executed by the external programmer.A bidirectional protocol including frame definition and transmission mode was designed to insure secure upgrades.A neuro-stimulator was used to verify the upgrade solution with no additional elements,to maintain the hardware reliability.This study emphasizes how to insure a secure and stable upgrade process and reduce power consumption for special wireless and life safety-critical applications.Tests on rhesus monkeys to evaluate the feasibility of the approach for an IPG used for brain stimulation evaluation show that the software upgrade can be implemented stably with good tolerance to the wireless data transmissions.

A high-efficiency charge pump in BCD process for implantable medical devices

This paper presents a high-efficiency charge pump circuit composed of cascaded cross-coupled voltage doublers implemented in an isolated bipolar-CMOS-DMOS（BCD） technology for implantable medical devices.Taking advantage of the transistor structures in the isolated BCD process, the leakage currents caused by the parasitic PNP transistors in the cross-coupled PMOS serial switches are eliminated by simply connecting the inside substrate terminal to the isolation terminal of each PMOS transistor. The simple circuit structure leads to small parasitic capacitance in the voltage doubler, which in turn ensures high efficiency of the overall charge pump. The proposed charge pump with 5 cascaded voltage doublers is fabricated in a 0.35-μm isolated BCD process. Measurement results with 2-V power supply, 1-MHz driving clock frequency and 40-μA current load show that an efficiency of 72.6% is achieved, and the output voltage can be pumped to about 11.5 V at zero load current. The chip area of the charge pump is 1.6 × 0.35 mm^2.

Analysis of intellectual properties on animalderived regenerative, implantable medical devices

This article analyses and summarizes issues of intellectual property involved in animal-derived regenerative,implantable medical devices(ADRIMD)in order to better understand global trends in patent applications and disclosures,the legal status of patent families(i.e.sets of patents filed in various countries to protect a single invention),and International Patent Classification topics such as main assignee and core expertise.Analysis of research trends will enhance and inform the decision-making capacity of researchers,investors,government regulators and other stake-holders as they undertake to develop,deploy,invest in or regulate ADRIMD.

An ultralow power wireless intraocular pressure monitoring system

This paper describes an ultralow power wireless intraocular pressure （IOP） monitoring system that is dedicated to sensing and transferring intraocular pressure of glaucoma patients. Our system is comprised of a capac- itive pressure sensor, an application-specific integrated circuit, which is designed on the SMIC 180 nm process, and a dipole antenna. The system is wirelessly powered and demonstrates a power consumption of 7.56 μW at 1.24 V during continuous monitoring, a significant reduction in active power dissipation compared to existing work. The input RF sensitivity is -13 dBm. A significant reduction in input RF sensitivity results from the reduction of mis- match time of the ASK modulation caused by FM0 encoding. The system exhibits an average error of-4- 1.5 mmHg in measured pressure. Finally, a complete IOP system is demonstrated in the real biological environment, showing a successful reading of the pressure of an eye.

Abnormal Blood Glucose Concentration on Degradation Behavior of AZ31 Magnesium Alloy

In order to evaluate the effect of blood glucose concentration on the reliability of AZ31 magnesium alloy medical implant,the corrosion of AZ31 alloy was studied in a simulated physiological saline solution.It is found that when the glucose concentration is in the normal range of ca.1g/L,the corrosion of AZ31 alloy can be inhibited However,when the glucose concentration becomes higher like that of diabetic patients,the degradation of AZ31 alloy is significantly accelerated.Therefore,for diabetic patients,the change in glucose concentration must be taken into consideration in order to ensure the reliability ofAZ31 medical implants.

Triboelectric nanogenerators for clinical diagnosis and therapy:A report of recent progress

Triboelectric nanogenerators(TENGs)are considered as an ideal platform for power harvesting for living organisms,thanks to their unique characteristics like flexibility,conversion efficient,and manufacturing cost.Recent advances in TENGs have brought innovative solutions for clinical healthcare.Particularly,TENGs offer novel solutions of continues power supply for wearable and implantable medical devices with lightweight,thinness,good biocompatibility,and excellent soft tissue conformability.In this review,we discuss(1)The working principle and representative structure of TENGs,(2)the material selection of TENGs,(3)the recent progression of application of TENG in the medical field of cardiovascular system,nervous system,respiratory system,microbial inactivation,antibiofouling,disinfection,and tissue repair,(4)challenges and future perspectives of TENG-based medical devices.The emerging TENGs and their applications in medicine cannot simply be seen as an alternative to conventional power supplies,it provides a revolutionary solution for wearable and implantable medical devices,and they will surely change the paradigm of disease diagnosis and treatment in the future.