Highly Elastic,Bioresorbable Polymeric Materials for Stretchable,Transient Electronic Systems

Substrates or encapsulants in soft and stretchable formats are key components for transient,bioresorbable electronic systems;however,elastomeric polymers with desired mechanical and biochemical properties are very limited compared to nontransient counterparts.Here,we introduce a bioresorbable elastomer,poly(glycolide-co-ε-caprolactone)(PGCL),that contains excellent material properties including high elongation-at-break(<1300%),resilience and toughness,and tunable dissolution behaviors.Exploitation of PGCLs as polymer matrices,in combination with conducing polymers,yields stretchable,conductive composites for degradable interconnects,sensors,and actuators,which can reliably function under external strains.Integration of device components with wireless modules demonstrates elastic,transient electronic suture system with on-demand drug delivery for rapid recovery of postsurgical wounds in soft,time-dynamic tissues.

Preparation,Rheological Properties and Primary Cytocompatibility of TPU/PLA Blends as Biomedical Materials

A polymer blends containing thermoplastic polyurethane（TPU） and poly（lactic acid）（PLA） as a biomedical material were prepared by a process of modifying thermally induced phase separation（MTIPS） and melt blending.The influences of composition,shear frequency,and temperature on the rheological behaviors of the blends were investigated by small amplitude oscillatory shear rheology.The results revealed that the addition of TPU into PLA significantly decreased the non-Newtonian index of the blends,and increased the sensitivity of the blends on shear rate,suggesting that optimization of the shear rate and temperature could improve the flowability of the blend melts in the extrusion process.In addition,the results of SEM images revealed that TPU distributed well into PLA matrix and showed good compatibility between the TPU and PLA,which made the blends with good toughness.The primary cytocompatibility of the blends was evaluated using C2C12 cells.The results suggested that the TPU/PLA blends did not affect cell growth,showing no cytotoxicity.In short,the TPU/PLA blends with excellent toughness had potential application as biomedical devices.

Macroencapsulation Devices for Cell Therapy

Macroencapsulation has been widely used in cell therapy due to its capability to provide immune-privileged sites for implanted allogeneic or xenogeneic cells.Macroencapsulation also serves to provide mechanical and physiochemical support for maintaining cell expansion and promoting therapeutic func-tions.Macroencapsulation devices such as membrane-controlled release systems,hydrogels,micronee-dle(MN)array patches,and three-dimensional(3D)stents have shown promising in-lab and preclinical results in the maintenance of long-term cell survival and the strengthening of treatment effi-cacy.Recent studies focus on expanding the applications of these devices to new cell-based areas such as chimeric antigen receptor(CAR)-T cell delivery,cardiovascular disease therapy,and the exploration of new materials,construction methods,and working principles to augment treatment efficacy and prolong therapy duration.Here,we survey innovative platforms and approaches,as well as translation outcomes,for advancing the performance and applications of macrodevices for cell-based therapies.A discussion and critique regarding future opportunities and challenges is also provided.

Optimization of Bio-Implantable Power Transmission Efficiency Based on Input Impedance

Recently,the inductive coupling link is the most robust method for powering implanted biomedical devices,such as micro-system stimulators,cochlear implants,and retinal implants.This research provides a novel theoretical and mathematical analysis to optimize the inductive coupling link efficiency driven by efficient proposed class-E power amplifiers using high and optimum input impedance.The design of the coupling link is based on two pairs of aligned,single-layer,planar spiral circular coils with a proposed geometric dimension,operating at a resonant frequency of 13.56 MHz.Both transmitter and receiver coils are small in size.Implanted device resistance varies from 200Ωto 500Ωwith 50Ωof stepes.When the conventional load resistance of power amplifiers is 50Ω,the efficiency is 45%;when the optimum resonant load is 41.89Ωwith a coupling coefficient of 0.087,the efficiency increases to 49%.The efficiency optimization is reached by calculating the matching network for the external LC tank of the transmitter coil.The proposed design may be suitable for active implantable devices.

Peripheral nerve lengthening as a regenerative strategy

Peripheral nerve injury impairs motor, sensory, and autonomic function, incurring substantial financial costs and diminished quality of life. For large nerve gaps, proximal lesions, or chronic nerve injury, the prognosis for recovery is particularly poor, even with autografts, the current gold standard for treating small to moderate nerve gaps. In vivo elongation of intact proximal stumps towards the injured distal stumps of severed peripheral nerves may offer a promising new strategy to treat nerve injury. This review describes several nerve lengthening strategies, including a novel internal fixator device that enables rapid and distal reconnection of proximal and distal nerve stumps.

Accelerated neutral atom beam(ANAB)and gas clustered ion beam(GCIB)treatment of implantable device polymers leads to decreased bacterial attachment in vitro and decreased inflammation in vivo

Infections at the placement site of biomaterial-based devices and subsequent scar formation results in morbidity,which may require revision surgery.Biomaterials intended for permanent implantation in the body need to be biologically inert to avoid excessive foreign body response and to reduce bacterial attachment.In this study,we show that polymeric materials commonly used in medical devices,including polyetheretherketone(PEEK)and polypropylene,treated by gas cluster ion beam(GCIB)or by accelerated neutral atom beam(ANAB)result in a nanoscale-modified surface topography that changes the ability of extracellular proteins to bind.This leads to decreased bacterial attachment and an attenuated inflammatory response using both in vitro and in vivo assays.Differential adsorption of extracellular proteins to the polymeric surface improved the competitive attachment of osteoblasts over bacteria,without resorting to growth factor of antibiotic use.

An overview of graphene-based hydroxyapatite composites for orthopedic applications

Hydroxyapatite(HA)is an attractive bioceramic for hard tissue repair and regeneration due to its physicochemical similarities to natural apatite.However,its low fracture toughness,poor tensile strength and weak wear resistance become major obstacles for potential clinical applications.One promising method to tackle with these problems is exploiting graphene and its derivatives(graphene oxide and reduced graphene oxide)as nanoscale reinforcement fillers to fabricate graphene-based hydroxyapatite composites in the form of powders,coatings and scaffolds.The last few years witnessed increasing numbers of studies on the preparation,mechanical and biological evaluations of these novel materials.Herein,various preparation techniques,mechanical behaviors and toughen mechanism,the in vitro/in vivo biocompatible analysis,antibacterial properties of the graphene-based HA composites are presented in this review.

An implantable neurostimulator with an integrated high-voltage inductive powerrecovery frontend

This paper present a highly-integrated neurostimulator with an on-chip inductive power-recovery fron- tend and high-voltage stimulus generator. In particular, the power-recovery frontend includes a high-voltage full- wave rectifier （up to 100 V AC input）, high-voltage series regulators （24/5 V outputs） and a linear regulator （1.8/ 3.3 V output） with bandgap voltage reference. With the high voltage output of the series regulator, the proposed neurostimulator could deliver a considerably large current in high electrode-tissue contact impedance. This neu- rostimulator has been fabricated in a CSMC 1 μm 5/40/700 V BCD＇process and the total silicon area including pads is 5.8 mm2. Preliminary tests are successful as the neurostimulator shows good stability under a 13.56 MHz AC supply. Compared to previously reported works, our design has advantages of a wide induced voltage range （26-100 V）, high output voltage （up to 24 V） and high-level integration, which are suitable for implantable neu- rostimulators.

CMOS implementation of a low-power BPSK demodulator for wireless implantable neural command transmission

A new BPSK demodulator was presented.By using a clock multiplier with very simple circuit structure to replace the analog multiplier in the traditional BPSK demodulator,the circuit structure of the demodulator became simpler and hence its power consumption became lower.Simpler structure and lower power will make the designed demodulator more suitable for use in an internal single chip design for a wireless implantable neural recording system.The proposed BPSK demodulator was implemented by Global Foundries 0.35μm CMOS technology with a 3.3 V power supply.The designed chip area is only 0.07 mm;and the power consumption is 0.5 mW.The test results show that it can work correctly.