Changes In Fiber Diameter Research Articles

Electrospinning and direct writing: why polymer melts are excellent fluids for 3D printing

Event Abstract Back to Event Electrospinning and direct writing: why polymer melts are excellent fluids for 3D printing Paul Dalton1, Tomasz Jungst1, Almoatazbellah Youssef1, Andrei Hrynevich2, Gernot Hochleitner1 and Jürgen Groll1 1 University of Würzburg, Functional Materials in Medicine and Dentistry, Germany 2 RWTH Aachen, Biomedical Engineering Science, Germany Introduction: Many different fluids have been used with nozzle-based direct writing techniques, including polyelectrolytes, colloidal inks, hydrogel inks and polymer solutions[1]. A key property of any material to be 3D printed is to maintain fidelity once delivered from the nozzle, and methods such as coagulation baths or rapid solvent evaporation are often used to preserve structural fidelity of the 3D printed object. Near field solution electrospinning has been used to direct write electrospun scaffolds[1], however the layer-by-layer accuracy of fiber placement and remains challenging. Here, the direct writing of non-conductive polymer melts[2] provides both the microscale fidelity and stacking capacity to 3D print objects. Materials and Methods: A custom-built, electrically-heated and pneumatically-driven melt electrospinning writing (MEW) device was used in combination with poly(ε-caprolactone) (PCL) (PURASORB PC12 Corbion). Instrument parameters included spinneret gauges of 22-25 G, spinneret to collector gaps of 6 mm, applied voltage of 4-6 kV, and operated at 85 °C. The speed where the fiber becomes straight, termed the “critical translation speed” (CTS), was determined for each of the samples by increasing the speed of the collector stage. No post-processing was performed. Results and Discussion: Molten PCL can be direct written readily using MEW. The fiber diameters range from 2 µm to 30 µm, depending on the instrument parameters. Figure 1 shows lines of fibers collected as speeds slower increase. The buckling due to viscoelastic forces generated patterns typical of falling fluids, and are sensitive to fluctuations in fiber diameter changes. Figure 1B-D shows very consistent fluid deposition over long time periods (hours). Figure 1: A) Schematic of the MEW jet, depicting the formation of a Taylor cone and the cooling of the melt jet during the direct writing process. B-E Increasing the stage speed shows structures typical of viscous fluids. The diameter of the fibers can also be finely controlled using stage movement. Figure 2A-B shows the electrified polymer melt above the CTS as it exits the spinneret and is drawn along the stage. Increasing the stage speed (Figure 2B), the fiber was mechanically pulled which allowed a reduction in filament diameter. A standard woodpile structure was made, and accurate stacking could be achieved up to 1mm in height, depending on the fiber spacing. Depending on the instrument parameters, suspended fibers between intersections were produced (Figure 2C), or fibers could be directly piled upon each other (Figure 2D). Figure 2: Photograph of the electrified melt electrospun jet as it exits the spinneret and is drawn onto a stage moving at A) 1000 mm/min and B) 6000 mm/min. C) A stereomicrograph of woodpile PCL structures printed under solidifying conditions while D) an SEM image shows the same structure printed where fibers “sag”. Conclusion: PCL melts were excellent fluids to direct write with using electrospinning direct writing technique. A rapid cooling of the electrified jet in combination with high viscosity and low conductivity allows the production of 3D scaffolds with microscale features. The hour-to-hour processing stability, stackability and solvent-free approach of manufacturing TE scaffolds allows MEW to be a considered an emerging additive manufacturing technique. We thank the European Research Council for funding under grant agreement no. 617989 (consolidator grant Design2Heal).

Extended Studies on Fibre Diameter Measurement with OFDA Instrument

OFDA 2000 is a widely used fibre diameter measurement instrument. The instrument can provide improved statistical accuracy measurements in comparison with traditional technology. In this paper, a new technique has been developed to enable fibre diameters to be measured in an aqueous environment using the OFDA 2000 instrument. This new technique was utilised to assess the effects of pH and temperature on the diameters of Merino wool fibres in aqueous environments. Significant changes in fibre diameter under aqueous conditions were found as a function of pH and temperature. It is also demonstrated in this paper that the fibre diameter measurement results can be affected by fibre colour. In both dry and aqueous conditions, variation in fibre diameter was observed on fibres with different colours. This could be due to an optical effect or more likely due to physical changes in the dyed fibres as a result of the presence of dyes. Apart from their physical bulk, dyes may also affect the water content of fibres and hence have an influence on the swelling of fibres when they are measured under ambient regain and wet conditions.

The Effect of Surface Modification of Aligned Poly-L-Lactic Acid Electrospun Fibers on Fiber Degradation and Neurite Extension.

The surface of aligned, electrospun poly-L-lactic acid (PLLA) fibers was chemically modified to determine if surface chemistry and hydrophilicity could improve neurite extension from chick dorsal root ganglia. Specifically, diethylenetriamine (DTA, for amine functionalization), 2-(2-aminoethoxy)ethanol (AEO, for alcohol functionalization), or GRGDS (cell adhesion peptide) were covalently attached to the surface of electrospun fibers. Water contact angle measurements revealed that surface modification of electrospun fibers significantly improved fiber hydrophilicity compared to unmodified fibers (p < 0.05). Scanning electron microscopy (SEM) of fibers revealed that surface modification changed fiber topography modestly, with DTA modified fibers displaying the roughest surface structure. Degradation of chemically modified fibers revealed no change in fiber diameter in any group over a period of seven days. Unexpectedly, neurites from chick DRG were longest on fibers without surface modification (1651 ± 488 μm) and fibers containing GRGDS (1560 ± 107 μm). Fibers modified with oxygen plasma (1240 ± 143 μm) or DTA (1118 ± 82 μm) produced shorter neurites than the GRGDS or unmodified fibers, but were not statistically shorter than unmodified and GRGDS modified fibers. Fibers modified with AEO (844 ± 151 μm) were significantly shorter than unmodified and GRGDS modified fibers (p<0.05). Based on these results, we conclude that fiber hydrophilic enhancement alone on electrospun PLLA fibers does not enhance neurite outgrowth. Further work must be conducted to better understand why neurite extension was not improved on more hydrophilic fibers, but the results presented here do not recommend hydrophilic surface modification for the purpose of improving neurite extension unless a bioactive ligand is used.

Do price premiums for wool characteristics vary for different end products, processing routes and fibre diameter categories?

No Australian wool price hedonic studies have separated auction data into different end product-processing groups (PPR) on the basis of all fibre attributes that affect the suitability of wool sale lots for PPR. This study was conducted to assess: (1) whether including information about PPR groupings is more useful in understanding price than clustering by broad fibre diameter (FD) categories, and (2) if the ‘noise’ of macroeconomic effects on price can be reduced by using a clean price relative to the market indicator (RelPrice) formula or a log RelPrice formula compared with log price or clean price. Hedonic models using data derived from 369 918 Australian auction sale lots in 2010–2011 were estimated for these four dependent price variables. Linear FD models predicted less of price’s variance than quadratic or exponential models. Segmenting wool sale lots into 10 PPR before wool price analyses was found to increase the proportion of price variance explained and thus be worthwhile. The change in price with a change in FD, staple length and staple strength differs significantly between PPR. Calculating RelPrice or log RelPrice appears a better price parameter than clean price or log price. Comparing the RelPrice and clean price models, the mean absolute percentage errors were 6.3% and 16.2%, respectively. The differences in price sensitivity to FD, staple length and staple strength across PPR implies a complex set of price-setting mechanisms for wool as different users place different values on these wool properties. These price-setting mechanisms need to be incorporated in hedonic models for agricultural products that possess this characteristic. The wool price premiums can be used to estimate relative economic values when constructing sheep breeding selection indexes and can help determine the most profitable wool clip preparation strategies.

Effects of Molecular Weight and Temperature on Fiber Diameter of Poly(ε-caprolactone) Melt Electrospun Fiber

The 14k, 45k, and 70k Mw PCL have different crystallization temperatures and therefore have slightly different characteristics affecting the fiber diameter. To observe these behaviors, the fiber was produced at every step of 10oC for each molecular weights and the diameter was measured. Moreover, the fiber was fabricated over the cooled ground plate to observe the change in fiber diameter in comparison to the normal ground plate. In case of molecular Mw 14k PCL, the diameter increased as the temperature increased. For Mw 45k PCL, the fiber diameter decreased as the temperature increased. As of Mw 70k PCL, the fiber diameter decreased with increasing temperature as well. When the experiment was conducted over the cooled collector plate, the data did not change significantly from the previous lexperiments.

Improved time-resolved acousto-optic technique for optical fiber analysis of axial non-uniformities by using edge interrogation.

The time-resolved acousto-optic technique demonstrated recently to be a very useful method for the analysis of fiber axial non-uniformities, able to detect variations of fiber diameter in the nanometric scale with a spatial resolution of few cm. An edge interrogation approach is proposed to improve further the performance of this technique. The detection of subnanometer fiber diameter changes or sub-ppm changes of the core refractive index is demonstrated.

Controlled release of titanocene into the hybrid nanofibrous scaffolds to prevent the proliferation of breast cancer cells

Electrospun hybrid nanofibrous scaffolds have gained much importance in the field of tissue engineering and drug delivery applications owing to its multifaceted properties. In this study, the properties of composite polycaprolactone (PCL)/silk fibroin (SF) nanofibrous scaffolds was investigated as a potential scaffold for cell growth and also a drug eluting mat to control the proliferation of MCF-7 cells. Titanocene dichloride was chosen as the model drug to study its antitumor efficacy on MCF-7 cell lines. Fascinating properties relating to crystallization of silk fibroin and binding of drug has also been discussed for the controlled release of drugs. The presence of amino acid residues in silk fibroin plays a big role in the cell-scaffold interaction, the nature of drug binding and also its release characteristics to control the cell proliferation. Studies on material properties for the hybrid nanofibrous scaffolds showed interrelated changes in fiber diameter and mechanical behavior for the drug loaded nanofibers. Significant decrease in fiber diameters from 352±52nm to 281±44.5nm and sharp increase in tensile stress from 4.5MPa to 50.3MPa was observed for 0.03% drug loaded scaffolds with respect to PCL fibers. Cell viability and cell morphology study was performed to analyze the effect of different concentrations of titanocene dichloride loaded on PCL/silk fibroin nanofibrous scaffolds. Maximum cell viability inhibition percentage of change 26.93% was obtained for 0.03% titanocene with respect to 0.01% on day 3. The obtained results proved that the drug loaded hybrid mat to control the proliferation of MCF-7 cells at different time points and serve as a model for cancer therapy.

Characterization of Electrospinning Polycarbosilane Fiber with the Concentration of N,N-Dimethylformamide 22%, 24%, 26%, 28% and 30%

Polycarbosilane (PCS) fibers have been made using a solvent which is a mixture of N,N-dimethylformamide (DMF) in toluene. Polycarbosilanes (PCS) obtained from NaBond with concentration 1.2 g/ml dissolved in solution toluene and N,N-dimethylformamide (DMF) was stirred gently for 24 h at ambient temperature. DMF was mixed with toluene at ratios 22%, 24%, 26%, 28% and 30%. Electrospinning apparatus (nanoE-Spinning) from NaBond was used. In a vertical electrospinning set up, the solution in a glass syringe delivered to the tip of a 6-gauge (0.5 mm inner diameter) stainless steel needle. The tip to collector distance was adjusted to 100 mm with applied high voltage at 10kV. A stainless steel plate with dimension 100 mm x 100 mm wrapped by aluminum foil was used as collector. The electrospinning non-woven fiber was cured at temperature 200°C (2°C/min), for 1h, 1.5h, and 2h, and fibers with DMF concentration 30% was also pyrolysis at 1000 °C for 3 h in inert atmosphere. The samples were tested and observed with FTIR spectroscopy, and SEM-EDS apparatus. The results showed that PCS fibers can be made from dissolving PCS with toluene with the addition of DMF to increase the polarity of the solvent and the formation of fibers is done by using electrospinning which is supported by the presence of voltage from the outside. Fiber curing is done at 200 °C to evaporate the toluene, the DMF, and resulting stronger fibers than before. The addition concentration of DMF in toluene and curing time will affect the composition of the resulting PCS fiber. Curing time on PCS fibers will affect the composition of solvents such as DMF and Si-H bond on which to assert their PCS fiber cross linking conditions. PCS fiber morphology is known of changes in fiber diameter and fiber uniformity. Smallest PCS fiber average diameter 4.81 μm resulted from 28% DMF with curing time 2 hours and the largest achieved from 22% DMF with curing time 1 hour around 14.22 μm. Composition of pyrolyzed fiber was SiO0.587C0.413, with average density 3.1033 g/cc and average diameter the fiber was 3.06 μm.

Effect of Aniline Oligomer on the Electrosynthesis of Polyaniline Fibres

In this paper, polyaniline (PANI) fibres were prepared by electrochemical polymerization from the solutions of aniline and hydrochloric acid in the presence of different concentrations of aniline oligomer. The influences of adding a small amount of aniline oligomeric additives, such as p-aminodiphenylamine (PADPA), p-phenylenediamine (PPDA) to the electrochemical polymerization system of aniline on polyaniline fibres have been investigated. Change in fibre diameter with the concentration of aniline oligomer were investigated. Morphologies of PANI fibres were characterized by scanning electron microscopy (SEM). Electrochemical behaviors of PANI fibres were studied by cyclic voltammetry (CV). The results show that with the addition of PADPA, PPDA to aniline polymerization system, the rate of polymerization increases greatly, and more lower potentials can be applied to generate electroactive PANI fibres with more finer and uniform structure.

Au ion irradiation of various silicon carbide fiber-reinforced SiC matrix composites

Silicon carbide fiber-reinforced SiC matrix composites are promising candidates as fuel cladding for several concepts of Generation IV reactors and as structural materials for fusion reactors. The composites used in this study were composed of a SiC matrix obtained by chemical vapor infiltration associated with various fiber types (Tyranno Type-S, Tyranno SA Grade-3 and Hi-Nicalon Type-S) and with a PyC layer as the interphase. 12MeV Au ions were used for irradiation up to 0.05 and 1 displacement per atom (dpa) fluences at room temperature and 800°C. Analysis of both microstructure and composition of composites were performed by scanning electron microscopy (SEM), electron probe microanalysis and Raman spectroscopy. At room temperature and low fluence, Raman spectroscopy results showed that irradiation induces a disordered/distorted state into fibers and matrix. With increasing fluence, a total amorphization of these constituents occurs. The increase in the irradiation temperature leads to a damage recovery and partial recrystallization of samples. Image analysis performed from SEM micrographs highlights no significant change in fiber diameter and shape. However, SEM analysis suggests a longitudinal shrinkage of Tyranno Type-S fibers for the composite irradiated at 1dpa at room temperature and 800°C. These results are in complete agreement with conclusions from neutron irradiations suggesting an appropriate relevance of irradiations with 12MeV Au.

Influences of moisture absorption and chemical treatments on the resin flow characteristics of natural fibre nonwoven mats

A major challenge for the use of natural fibres in polymeric composites is their incompatibility with commonly used matrices, causing weak interfaces of the final composites. Many surface treatments to natural fibres have been proposed to eliminate or reduce these problems. In this paper, we evaluate the influences of three commonly used natural fibre chemical treatments on the resin flow characteristics of flax fibre nonwoven mats in a vacuum-assisted resin transfer moulding process. The alkalization treatment significantly increases the in-plane permeability and flow anisotropy of the natural nonwoven mat due to changes in fibre diameter, fibre surface tension and mat structure. The effects of silane and acetylation treatments on resin flow are much smaller. It is well known that in comparison with glass fibre, natural fibres can absorb a large amount of moisture from surrounding air. The absorption of moisture causes a considerable reduction in the in-plane permeability of natural fibre nonwoven mats.

Nanofiber diameter‐dependent MAPK activity in osteoblasts

The major challenge for bone tissue engineering lies in the fabrication of scaffolds that can mimic the extracellular matrix and promote osteogenesis. Electrospun fibers are being widely researched for this application due to high porosity, interconnectivity, and mechanical strength of the fibrous scaffolds. Electrospun poly methyl methacrylate (PMMA, 2.416 ± 0.100 μm) fibers were fabricated and etched using a 60% propylene glycol methyl ether acetate (PGMEA)/limonene (vol/vol) solution to obtain fiber diameters ranging from 2.5 to 0.5 μm in a time-dependent manner. The morphology of the fibrous scaffolds was evaluated using scanning electron microscopy and cellular compatibility with etchant-treated scaffold was assessed using immunoflurescence. Mitogen-activated protein kinases (MAPK) activation in response to different fiber diameter was evaluated with western blot as well as quantitative in-cell western. We report that electrospun micro-fibers can be etched to 0.552 ± 0.047 μm diameter without producing beads. Osteoblasts adhered to the fibers and a change in fiber diameter played a major role in modulating the activation of extracellular signal-regulated kinase (ERK) and p38 kinases with 0.882 ± 0.091 μm diameter fibers producing an inverse effect on ERK and p38 phosphorylation. These results indicate that nanofibers produced by wet etching can be effectively utilized to produce diameters that can differentially modulate MAPK activation patterns.

Needleless electrospinning: influences of fibre generator geometry

The fibre generator shape and dimension are key factors affecting the needleless electrospinning process and fibre fineness. In this work, cylinder with rounded rim, disc and ball were used as spinnerets to electrospin polyvinyl alcohol and polyacrylonitrile solutions. A finite element method was used to analyse how the spinneret geometry affected the electric field generated during electrospinning and the associated changes in fibre diameter and productivity. For cylinder spinnerets, increasing the rim radius reduced the discrepancy of electric field intensity between the cylinder end and middle area, which affected the fibre productivity. The electrospinning failed to operate when the rim radius was over 20 mm. With decreasing cylinder diameter, the electric field intensity in the middle area increased, improving the fibre productivity. Thinner disc spinnerets increased the electric field intensity, resulting in finer nanofibres and higher productivities. Ball spinnerets produced evenly distributed electric field, but failed to electrospin fibres when the diameters were below 60 mm. It has been found that strong and narrowly distributed electric field in the fibre-generating area can significantly facilitate the mass production of quality nanofibres.

Rapid fibre diameter measurement in aqueous solutions with OFDA 2000

In this paper, a new technique has been developed to enable fibre diameters to be measured in an aqueous environment using the OFDA 2000 instrument. The existing OFDA instrument has only been used to measure diameters of animal fibres under dry conditions. This new technique was utilised to assess the effects of pH and temperature on the diameters of merino wool fibres in aqueous environments. Significant changes in fibre diameter under aqueous conditions were found as a function of pH and temperature. Wool fibre diameters were at a minimum close to the wool isoelectric point (pH 4.8) and increased at both lower and higher pHs. Swelling of merino wool fibres was observed to increase linearly by around 15% as the temperature rose from ambient to 70°C.

Physician-writers in the age of blogging

Muscle atrophy, fiber-type shifting, reduced contractility, metabolic alterations, capillarization defect, and mitochondrial modifications are important adaptations in COPD. Skelatal muscle dysfunction is one of the most devastating systemic manifestations of COPD which eventually leads to increase in morbidity and mortality. In this study we aimed to demonstrate the effects of COPD on both muscles and nerves in neurologically normal patients with different degrees of airflow limitations, using current electrophysiological methods.Electrophysiological examinations were performed using a Keypoint EMG machine with subjects lying supine on a bed at a room temperature. Tests were nerve conduction studies, motor unit potential (MUP) analysis, interference pattern (IP) analysis and macro EMG (mEMG) analysis on the right side in the upper and lower extremities. Multi-motor unit potential (m-MUP) analysis and interference pattern (IP) analysis revealed some changes in biceps brachii (BB) and tibialis anterior (TA) muscles, but macro EMG (mEMG) analysis was similar except for increased fiber density at TA muscles in COPD patients. Increased ulnar and sural sensory latency, decreased ulnar sensory velocity, and increased ulnar motor latency values were found in COPD. There was increased motor unit potential (MUP) turn and phase values in BB muscles and increased MUP turn and decreased MUP duration, area, area/amplitude ratio and size index values in TA muscles in COPD patients. As a conclusion, in COPD more nerve conduction abnormalities and more MUP abnormalities which reflected muscle fiber diameter changes were observed by the use of electrophysiological methods including multi MUP - IP analysis and mEMG analysis.

The Effect of pH on Wool Fiber Diameter and Fabric Dimensions

Wool fabrics are often treated under conditions of varying pH in dyeing and finishing processes. It is known that in air the dimensions of wool fabrics change with the amount of fiber swelling at different regain. In this work, it has been shown that a similar relationship between fiber swelling and fabric dimensions existed in water at different pH values. The diameters of Merino and Corriedale wool fibers in water at different pH values were measured with an OFDA 2000 fiber diameter analyzer, fitted with a specially constructed accessory liquid cell. The results showed that the mean diameters of swollen wool fibers in water varied with pH. Minimum swelling was obtained in the range pH 5-7. It was found that the dimensions of wool fabric in water were dependent on the pH. The changes in fiber diameter in water could be attributed to changes in ionic interactions between charged acid and basic groups in wool protein with variations in pH.

Effect of blend composition on the morphology development of electrospun fibres based on PAN/PMMA blends

AbstractBACKGROUND: The aim of the work presented was to determine the morphology development and relevant change in fibre diameter of a binary polymer blend system during an electrospinning process. The size of the fibre diameter is one of the important factors determining the general properties of non‐woven mats formed from electrospun fibres.RESULTS: The morphology and diameter of electrospun polyacrylonitrile (PAN)/poly(methyl methacrylate) (PMMA) blends were investigated as a function of blend ratio using scanning electron microscopy. The diameter of the electrospun PAN/PMMA fibres decreased with increasing PMMA content up to 50 wt%, and then increased again with further increase of PMMA. After thermal treatment, the fibres shrank, and an irregularly shaped morphology was observed.CONCLUSION: The electrospinning of incompatible PAN/PMMA blends leads to a microphase‐separation morphology of fibres. A phase inversion occurs at a PMMA content of between 50 and 75 wt%. Due to the phase inversion, the fibre diameter shows a minimum value at the relevant composition. Copyright © 2008 Society of Chemical Industry

Taking Advantage of Tailored Electrostatics and Complementary Hydrogen Bonding in the Design of Nanostructures for Biomedical Applications

AbstractFour‐armed, star‐shaped poly(D,L‐lactide) (PDLLA) was synthesized and terminally‐functionalized with either adenine or thymine complementary hydrogen bonding groups (PDLLA‐A and PDLLA‐T, respectively). The strong hydrogen bonding led to increased viscosity below the dissociation temperature of the hydrogen bonds. Rheology confirmed that these bonds were thermally reversible, with a sharp reduction in viscosity near 100 °C. PDLLA, PDLLA‐A, and PDLLA‐T were melt electrospun with no significant change in fiber diameter (all between 3.6 and 4.0 µm). However, a blend of PDLLA‐A and PDLLA‐T formed fibers with an average diameter of 9.8 ± 2.0 µm, resulting from the hydrogen bond associations. Also, the phospholipid 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphoethanolamine (POPE) was melt electrospun at 200 °C and formed uniform fibers with average fiber diameter of 6.5 ± 2.0 µm.

The modified‐single fiber test: A methodology for monitoring ballistic performance

AbstractA minimally invasive testing methodology was developed to monitor the in‐service performance of soft body armor. In the spirit of the single fiber test standard, ASTM C 1557‐03, the fiber diameter was measured at five equally spaced locations along a 6‐cm gauge length specimen. In addition, the single fiber test specimen was modified by placing reflecting tape just outside the specimen gauge length to allow the use of a laser extensometer for directly measuring fiber displacement and hence, strain. This modified testing methodology was found to be reproducible and provide data that was normally distributed based on descriptive statistics when variations in the fiber diameters along the length of the specimen were considered. The abnormality in the data, identified using Pierce's outlier criterion, may be associated with processing variations during the fiber manufacture and/or the woven fabrics and not associated with the testing methodology. Furthermore, the failure strain was found to be drastically reduced when the minimum fiber diameter along the length of the test specimen was less than 11 μm. This suggests that a methodology that accurately profiles fiber diameter changes along the gauge length of the fiber may be useful in analyzing single fiber test results. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Tissue inhibitor of metalloproteinase‐2 (TIMP‐2) regulates neuromuscular junction development via a β1 integrin‐mediated mechanism

Extracellular matrix (ECM) molecules play critical roles in muscle function by participating in neuromuscular junction (NMJ) development and the establishment of stable, cytoskeleton-associated adhesions required for muscle contraction. Matrix metalloproteinases (MMPs) are neutral endopeptidases that degrade all ECM components. While the role of MMPs and their inhibitors, the tissue inhibitor of metalloproteinases (TIMPs), has been investigated in many tissues, little is known about their role in muscle development and mature function. TIMP-2 -/- mice display signs of muscle weakness. Here, we report that TIMP-2 is expressed at the NMJ and its expression is greater in fast-twitch (extensor digitorum longus, EDL) than slow-twitch (soleus) muscle. EDL muscle mass is reduced in TIMP-2-/- mice without a concomitant change in fiber diameter or number. The TIMP-2-/- phenotype is not likely due to increased ECM proteolysis because net MMP activity is actually reduced in TIMP-2-/- muscle. Most strikingly, TIMP-2 colocalizes with beta1 integrin at costameres in the wild-type EDL and beta1 integrin expression is significantly reduced in TIMP-2-/- EDL. We propose that reduced beta1 integrin in fast-twitch muscle may be associated with destabilized ECM-cytoskeletal interactions required for muscle contraction in TIMP-2-/- muscle; thus, explaining the muscle weakness. Given that fast-twitch fibers are lost in muscular dystrophies and age-related sarcopenia, if TIMP-2 regulates mechanotransduction in an MMP-independent manner it opens new potential therapeutic avenues.