scholarly journals Chronic Intracortical Recording and Electrochemical Stability of Thiol-ene/Acrylate Shape Memory Polymer Electrode Arrays

Micromachines ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 500 ◽  
Author(s):  
Allison Stiller ◽  
Joshua Usoro ◽  
Christopher Frewin ◽  
Vindhya Danda ◽  
Melanie Ecker ◽  
...  
Keyword(s):  
Shape Memory ◽  
Shape Memory Polymer ◽  
Polymer Materials ◽  
Clinical Implementation ◽  
Electrode Arrays ◽  
Neuroinflammatory Response ◽  
Order Of Magnitude ◽  
Intracortical Electrodes ◽  
Glial Scarring ◽  
Implanted Devices

Current intracortical probe technology is limited in clinical implementation due to the short functional lifetime of implanted devices. Devices often fail several months to years post-implantation, likely due to the chronic immune response characterized by glial scarring and neuronal dieback. It has been demonstrated that this neuroinflammatory response is influenced by the mechanical mismatch between stiff devices and the soft brain tissue, spurring interest in the use of softer polymer materials for probe encapsulation. Here, we demonstrate stable recordings and electrochemical properties obtained from fully encapsulated shape memory polymer (SMP) intracortical electrodes implanted in the rat motor cortex for 13 weeks. SMPs are a class of material that exhibit modulus changes when exposed to specific conditions. The formulation used in these devices softens by an order of magnitude after implantation compared to its dry, room-temperature modulus of ~2 GPa.

Thermo-mechanical Behavior of (Meth)Acrylate Shape-Memory Polymer Networks

2011 ◽  
Vol 1312 ◽  
Author(s):  
Carl P. Frick ◽  
Nishant Lakhera ◽  
Christopher M. Yakacki
Keyword(s):  
Shape Memory ◽  
Shape Memory Polymer ◽  
Polymer Network ◽  
Polymer Networks ◽  
Weight Fraction ◽  
Crosslinking Density ◽  
Mechanical Stiffness ◽  
Actuation Force ◽  
Order Of Magnitude ◽  
Cross Linker

ABSTRACTOur overall approach is based on developing a photocrosslinkable polymer network with a favorable shape-memory response, using polymer chemistry and crosslinking density to control thermo-mechanical properties. Three polymer networks were created and thermo-mechanically tested, each from tert-Butyl acrylate linear builder co-polymerized with a poly(ethylene glycol) dimethacrylate cross-linker. By systematically altering the molecular weight and the weight fraction of the cross-linker, it was possible to create three polymers that exhibited the same glass transition temperature, but varied by almost an order of magnitude in rubbery modulus. Therefore, the mechanical stiffness could be tailored to suit a given application. Recovery behavior of the polymers was characterized over a range of deformation temperatures. It has been implicitly assumed a linear relationship between Free-Strain (i.e. no actuation force) and Fixed-Stress (i.e. maximum actuation force), however, this has never been confirmed experimentally. The energy per unit volume performed by the shape-memory polymer was quantified, and observed to be a function of strain recovered. The maximum recoverable work was shown to increase with cross-linking density, although the overall efficiency is similar for all materials tested.

Shape Memory Polymer Based Reconfigurable Compliant Mechanisms: An Exploration

2009 ◽  
Author(s):  
Nilesh D. Mankame ◽  
Alan L. Browne ◽  
Anupam Saxena
Keyword(s):  
Shape Memory ◽  
High Temperatures ◽  
Compliant Mechanisms ◽  
Shape Memory Polymer ◽  
Shape Memory Polymers ◽  
Large Strains ◽  
Qualitative And Quantitative ◽  
Order Of Magnitude ◽  
Quantitative Changes

This paper explores the concept of reconfigurable compliant mechanisms. We define these to be fully or partially compliant mechanisms whose performance can be modified after they have been fabricated. Specifically, we are interested in the nature and extent of in situ reconfigurability in compliant mechanisms. In other words, we seek to understand the range of performance that can be achieved by these mechanisms without requiring significant reassembly. The material properties such as the storage modulus of a newly studied class of materials — shape memory polymers — vary by over an order of magnitude over a temperature range of 20 – 50 C. These polymers also allow the fixing of moderate to large strains (20 – 75%) experienced at high temperatures for extended periods of time, while retaining the ability to remember their original shape when reheated to the same high temperatures. These two properties make shape memory polymers a natural candidate for the fabrication of reconfigurable compliant mechanisms. We explore various means for introducing reconfigurability in compliant mechanisms, and from these, select a subset that is suitable for in situ reconfiguration. Quasi-static nonlinear finite element simulations are used to study the change in performance due to reconfiguration of four fully compliant mechanisms made of a shape memory polymer. Preliminary results indicate that noticeable qualitative and quantitative changes in performance can be achieved by these mechanisms.

Characterizations of Silicon Carbide Whisker-Filled in Benzoxazine-Epoxy Shape Memory Polymers

2015 ◽  
Vol 659 ◽  
pp. 373-377 ◽  
Author(s):  
Chutiwat Likitaporn ◽  
Sarawut Rimdusit
Keyword(s):  
Silicon Carbide ◽  
Shape Memory ◽  
Polymer Composites ◽  
Binary Systems ◽  
Glassy State ◽  
Shape Memory Polymer ◽  
Shape Memory Polymers ◽  
Polymer Materials ◽  
External Stimulation ◽  
Silicon Carbide Whisker

Shape memory polymers (SMPs) are polymer materials that can fix the temporary shape and then recover to their original permanent shape by external stimulation, i.e. applied heat. In this research, shape memory polymer composites (SMPCs) from benzoxazine (BA-a)-epoxy binary systems reinforced with adamantine silicon carbide whisker (SiCw) are investigated. The SiCw contents are controlled to be in range of 0 to 15% by weight. All specimens were fabricated by compression molding technique. The results revealed that the shape memory polymer composites showed higher glassy state storage modulus with increasing amount of the whisker suggesting substantial reinforcement effect of the whisker used. The glass transition temperature (Tg) was also improved from 102°C of the based polymer to the value about 122°C with the addition of about 15% by weight of the silicon carbide whisker. Finally, shape recovery stress systematically increased from the value about 1.5MPa of the unfilled polymer matrix to the value about 3.2MPa with an addition of 15% by weight of the silicon carbide whisker. The positive effect on thermal stability from SiCw addition is expected from the modification and will be reported in this work.

scholarly journals Non-woven shape-memory polymer blend actuators

MRS Advances ◽  
2021 ◽  
Author(s):  
Victor Izraylit ◽  
Matthias Heuchel ◽  
Karl Kratz ◽  
Andreas Lendlein
Keyword(s):  
Shape Memory ◽  
Bulk Material ◽  
Shape Memory Polymer ◽  
Polymer Materials ◽  
Design Approach ◽  
Structural Performance ◽  
Hierarchical Design ◽  
Soft Actuator ◽  
Processing Techniques ◽  
Effective Design

Abstract The hierarchical design approach provides various opportunities to adjust the structural performance of polymer materials. Electrospinning processing techniques give access to molecular orientation as a design parameter, which we consider here in view of the shape-memory actuation performance. The aim of this work is to investigate how the reversible strain $$\varepsilon^{\prime}_{{{\text{rev}}}}$$ ε rev ′ can be affected by a morphology change from a bulk material to an electrospun mesh. $$\varepsilon^{\prime}_{{{\text{rev}}}}$$ ε rev ′ could be increased from 5.5 ± 0.5% to 15 ± 1.8% for a blend from a multiblock copolymer with poly(ε-caprolactone) (PCL) and poly(L-lactide) (PLLA) segments with oligo(D-lactide) (ODLA). This study demonstrates an effective design approach for enhancing soft actuator performance, which can be broadly applied in soft robotics and medicine. Graphic abstract

scholarly journals Characterization of the Neuroinflammatory Response to Thiol-ene Shape Memory Polymer Coated Intracortical Microelectrodes

Micromachines ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 486 ◽  
Author(s):  
Andrew Shoffstall ◽  
Melanie Ecker ◽  
Vindhya Danda ◽  
Alexandra Joshi-Imre ◽  
Allison Stiller ◽  
...  
Keyword(s):  
Shape Memory ◽  
Room Temperature ◽  
Shape Memory Polymer ◽  
Biological Response ◽  
Material Surface ◽  
Neuroinflammatory Response ◽  
Precise Control ◽  
Silicon Devices ◽  
The Brain

Thiol-ene based shape memory polymers (SMPs) have been developed for use as intracortical microelectrode substrates. The unique chemistry provides precise control over the mechanical and thermal glass-transition properties. As a result, SMP substrates are stiff at room temperature, allowing for insertion into the brain without buckling and subsequently soften in response to body temperatures, reducing the mechanical mismatch between device and tissue. Since the surface chemistry of the materials can contribute significantly to the ultimate biocompatibility, as a first step in the characterization of our SMPs, we sought to isolate the biological response to the implanted material surface without regards to the softening mechanics. To accomplish this, we tightly controlled for bulk stiffness by comparing bare silicon ‘dummy’ devices to thickness-matched silicon devices dip-coated with SMP. The neuroinflammatory response was evaluated after devices were implanted in the rat cortex for 2 or 16 weeks. We observed no differences in the markers tested at either time point, except that astrocytic scarring was significantly reduced for the dip-coated implants at 16 weeks. The surface properties of non-softening thiol-ene SMP substrates appeared to be equally-tolerated and just as suitable as silicon for neural implant substrates for applications such as intracortical microelectrodes, laying the groundwork for future softer devices to improve upon the prototype device performance presented here.

Controlling the Physical Properties of Random Network Based Shape Memory Polymer Foams

2010 ◽  
Vol 1274 ◽  
Author(s):  
Pooja Singhal ◽  
Thomas S Wilson ◽  
Duncan J Maitland
Keyword(s):  
Shape Memory ◽  
Random Network ◽  
Shape Memory Polymer ◽  
Shape Memory Polymers ◽  
Low Density ◽  
Polymer Foams ◽  
Glass Transitions ◽  
Shape Memory Behavior ◽  
Monomer Composition ◽  
Implanted Devices

AbstractShape memory polymers (SMPs) are increasingly being considered for use in minimally invasive medical devices. For safe deployment of implanted devices it is important to be able to precisely control the actuation temperature of the device. In this study we report the effect of varying monomer composition on the glass transitions/actuation temperatures (Tg) of novel low density shape memory foams. The foams were based on hexamethylenediisocyanate (HDI), triethanolamine (TEA) and tetrakis (2-hydroxyl propyl) ethylenediamine (HPED), and were produced via a combination of chemical and physical blowing process. The process for post-foaming cleaning was also varied. Foams were characterized by DSC, DMA, and for shape memory. No clear trends were observed for foam samples without cleaning, and this was attributed to process chemicals acting as plasticizers. In foams cleaned via washing and/or sonication, the Tg was observed to decrease for compositions that were higher in the TEA content. Also, no change in shape memory behavior was observed for varying compositions. This work demonstrates the ability to tailor actuation transition temperature while maintaining shape memory behavior for low density foams suitable for aneurysm treatment.

Design of Multistimuli-Responsive Shape-Memory Polymer Materials by Reactive Extrusion

2014 ◽  
Vol 26 (20) ◽  
pp. 5860-5867 ◽  
Author(s):  
Florence Pilate ◽  
Rosica Mincheva ◽  
Julien De Winter ◽  
Pascal Gerbaux ◽  
Linbo Wu ◽  
...  
Keyword(s):  
Shape Memory ◽  
Shape Memory Polymer ◽  
Reactive Extrusion ◽  
Polymer Materials

A Thermo-Mechanical Constitutive Model of Glassy Shape Memory Polymers

2016 ◽  
Vol 853 ◽  
pp. 96-100 ◽  
Author(s):  
Jian Li ◽  
Shi Yu Dong ◽  
Qian Hua Kan ◽  
Guo Zheng Kang ◽  
Wen Yi Yan
Keyword(s):  
Constitutive Model ◽  
Shape Memory ◽  
Evolution Equations ◽  
Model Simulation ◽  
Shape Memory Polymer ◽  
Three Dimensional ◽  
Shape Memory Polymers ◽  
Nonlinear Evolution Equations ◽  
Polymer Materials ◽  
Extended Model

Glassy shape memory polymer materials are applied successfully in biomedical fields due to their large recovery deformation, excellent biocompatibility and unique biodegradability. To predict the thermo-mechanical behavior of glassy shape memory polymers in biomedical devices accurately, a reasonably three-dimensional thermo-mechanical constitutive model must be established firstly. A one-dimensional linear-elastic constitutive model proposed by Tobushi et. al. (1997) was extended to capture the loading level dependent degradation of shape memory effect by introducing new nonlinear evolution equations with threshold values. Comparisons between experiments and simulations were carried to validate the extended model. Simulation results agree with experiments well, especially for the high loading levels.

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