Poly L-lactic Acid Research Articles

Pilot-Scale Anaerobic Co-Digestion of Food Waste and Polylactic Acid

Bioplastics are frequently utilized in daily life, particularly for food packaging and carrier bags. They can be delivered to biogas plants through a separate collection of the organic fraction of municipal waste (OFMSW). The increased demand for and use of bioplastics aimed at mitigating plastic pollution raises significant questions concerning their life cycle and compatibility with waste management units. Anaerobic digestion (AD) in OFMSW is a valuable resource for biogas production. In this work, the valorization of poly-L-lactic acid (PLLA) composed of food waste within the Biowaste to Bioplastic (B2B) Project framework was studied in laboratory and pilot-scale anaerobic liquid conditions. Taking into account that the addition of PLLA to biowaste can increase biogas production, we performed laboratory-scale anaerobic tests on food waste enriched with different molecular-weight PLLAs produced from food waste or commercial PLLA at a mesophilic temperature of 37 °C. PLLA with the highest molecular weight was subjected to AD on the pilot scale to further validate our findings. The addition of PLLA increased biogas production and had no apparent negative impact on the operation of the reactors used in the laboratory or on the pilot scale. Biogas production was higher when using PLLA with the lowest molecular weight. In the pilot-scale experiments, co-digestion of FW with PLLA increased biogas production by 1.1 times. When PLLA was added to the feed, biomethane was 8% higher, while volatile solids (VS) and total chemical oxygen demand (TCOD) removal were almost the same. Importantly, no effect was observed in the operation of the digesters.

Mid-Term Outcomes of Novel Covered Stent with Biodegradable Membrane in Porcine Coronary Artery Perforation.

Currently, commercially covered stents are the main treatment for coronary artery perforation (CAP), but without satisfied late-term outcomes when compared to drug-eluting stents (DES). This study seeks to report a new covered stent to treat porcine CAP, which is manufactured with DES and a biodegradable membrane fabricated by poly-L-lactic acid (PLLA) polymer. Experimental swines experienced CAP in proximal-middle of right coronary artery (RCA) by non-compliant balloon burst, and covered stent was deployed in breach segment. Meanwhile, coronary angiography (CAG), optical coherence tomography (OCT), histological light microscopy and scan electron microscopy were performed to characterize the performance of covered stent. Seven swines were used for this study. Two swines were euthanasia at 14 days and 28 days after procedure, respectively. The remaining 5 kept alive until sacrifice at six months. CAG at six months showed total occlusion at the stented segment of RCA in all swines. The interventional revascularization of occlusion lesion was instituted in two swines. After recanalizing occlusion lesion, OCT examination visualized diffuse heterogeneous fibrous plaques, as well as organized thrombosis, lipid deposits and several neoatherosclerosis in the occluded segment. Serial histopathologic and electron microscopies at 14 days, 28 days and six months revealed gradual occlusive vessel lumen with diffuse heterogeneous fibroplasia, smooth muscle proliferation, inflammation response and local neoatherosclerosis, moreover with identification of PLLA polymer membrane degradability. The new covered stent with biodegradable membrane could seal urgent coronary breach and prevent experimental swines death, but with all stent occlusion in mid-term (six months) follow-up, which might be attributed to diffuse heterogeneous fibroplasia, smooth muscle proliferation, inflammation response and local neoatherosclerosis with the degradation of PLLA membrane.

Virus‐Engineered Microsol Electrospun Scaffold Promotes the Reprogramming of Fibroblasts to Neurons

AbstractLentiviral‐vector‐based therapies, widely used for treating various diseases, face limitations because of release burst, rapid clearance, and immune activation. Herein, a lentiviral vector delivery platform is proposed utilizing a virus‐engineered microsol electrospun scaffold. Identifying a remarkable upregulation of polypyrimidine tract binding protein1 (PTB) in spinal cord injury (SCI) rats, a scaffold is constructed comprising a hyaluronic acid (HA) core encapsulating brain‐derived neurotrophic factor (BDNF) and a polydopamine (PDA)‐modified linear poly‐l‐lactic acid (PLLA) shell, with shPTB lentiviral vectors (LV‐shPTB) grafted via PDA. In vitro, the LV‐shPTB achieves an infection efficiency of 70%, and the oriented scaffolds significantly reduce the expression of inflammatory factors, induce the reprogramming of fibroblasts into neurons, and sustain the release of BDNF for over 2 weeks. In vivo, the scaffolds provide physical support and neural guidance, as well as released BDNF and LV‐shPTB. LV‐shPTB delivery leads to the reprogramming of fibroblasts into neurons, and the sustained BDNF delivery maintains the neurons’ proliferation and growth, which further promotes the recovery of neurological function in SCI rats. These results demonstrate the potential application of virus‐engineered delivery platforms in SCI treatment and other medical fields.

Osteogenic and antibacterial PLLA membrane for bone tissue engineering

Insufficient bone regeneration and bacterial infection are two major concerns of bone repair materials. Poly-L-lactic acid (PLLA) have been widely used in bone tissue engineering (BTE), however, lack of osteogenic and antibacterial properties have greatly limit its clinical application. Herein, PLLA membrane was firstly treated with polydopamine (PDA), and then modified with ε-polylysine (ε-PL) and alginate (ALG) via layer-by-layer method. The (ε-PL/ALG)n composite layer coated PLLA (PLLA@(ε-PL/ALG)n) could facilitates the adhesion and osteoblast differentiation of MC3T3-E1 cells. Furthermore, PLLA@(ε-PL/ALG)n presents an effective antibacterial efficacy against S. aureus and E. coli, and the bacterial survival rates of S. aureus and E. coli on PLLA@(ε-PL/ALG)10 were 21.5 ± 3.5 % and 13 ± 2.1 %, respectively. This work provides a promising method to design PLLA materials with osteogenic and antibacterial activity simultaneously. Furthermore, the method is also an optional choice to construct multifunctional coatings on the other substrate.

Poly-ε-caprolactone (PCL)/poly-l-lactic acid (PLLA) nanofibers loaded by nanoparticles-containing TGF-β1 with linearly arranged transforming structure as a scaffold in cartilage tissue engineering.

This study aimed to present a novel three-dimensional nanocomposite scaffold using poly-ε-caprolactone (PCL), containing transforming growth factor-beta 1 (TGF-β1)-loaded chitosan-dextran nanoparticles and poly-l-lactic acid (PLLA), to make use of nanofibers and nanoparticles simultaneously. The electrospinning method fabricated a bead-free semi-aligned nanofiber composed of PLLA, PCL, and chitosan-dextran nanoparticles containing TGF-β1. A biomimetic scaffold was constructed with the desired mechanical properties, high hydrophilicity, and high porosity. Transmission electron microscopy findings showed a linear arrangement of nanoparticles along the core of fibers. Based on the results, burst release was not observed. The maximum release was achieved within 4 days, and sustained release was up to 21 days. The qRT-PCR results indicated an increase in the expression of aggrecan and collagen type Ι genes compared to the tissue culture polystyrene group. The results indicated the importance of topography and the sustained release of TGF-β1 from bifunctional scaffolds in directing the stem cell fate in cartilage tissue engineering.

Laser-Assisted and Device-Assisted Filler Delivery: A Histologic Evaluation.

Lasers and devices are used to enhance transcutaneous delivery of fillers. However, little has been published on the histologic findings of this form of laser/device-assisted delivery to determine the optimal devices and fillers. To objectively evaluate the histological effects of laser-assisted and device-assisted filler delivery. Ex vivo human abdominoplasty skin samples were treated with fractional CO 2 laser (ECO 2 , 120 μm tip, 120 mJ), fractional radiofrequency microneedling (FRMN, Genius, 1.5 mm, 20 mJ/pin), and microneedling (2.0 mm). Immediately after poly- l -lactic acid (PLLA), hyaluronic acid gel, calcium hydroxylapatite, and black tissue marking dye were topically applied. After treatment, biopsies were collected for histologic evaluation. Histology revealed that PLLA and black dye were found in greatest abundance, hyaluronic acid was found to a lesser extent, and calcium hydroxylapatite was least found within channels created by fractional CO 2 laser. Microneedling was effective only at delivering black dye, whereas FRMN failed to show significant channel formation or delivery of the studied products. Among the devices and fillers studied, fractional CO 2 laser and PLLA proved to be the most effective combination for laser/device-assisted filler delivery. Neither microneedling nor FRMN was effective as devices to enhance filler delivery.

Poly-l-lactide-co-ε-caprolactone (PLCL) and poly-l-lactic acid (PLLA)/gelatin electrospun subacromial spacer improves extracellular matrix (ECM) deposition for the potential treatment of irreparable rotator cuff tears

Biodegradable subacromial spacer implantation has become practicable for the treatment of irreparable rotator cuff tears (IRCT). However, the relative high degradation rate and inferior tissue regeneration properties of current subacromial spacer may lead to failure regards to long-term survival. It is reported that satisfactory clinical results lie in the surrounding extracellular matrix (ECM) deposition after implantation. This study aims to develop a biological subacromial spacer that would enhance tissue regeneration properties and results in better ECM deposition. Physicochemical properties were characterized on both poly-l-lactide-co-ε-caprolactone (PLCL) dip-coating spacer (monolayer spacer, MS) and PLCL dip-coating + Poly-l-Lactic Acid (PLLA)/Gelatin electrospun spacer (Bilayer Spacer, BS). Cytocompatibility, angiogenesis, and collagen inducibility were evaluated with tendon fibroblasts and endothelial cells. Ultrasonography and histomorphology were used to analyze biodegradability and surrounding ECM deposition after the implantation in vivo. BS was successfully fabricated with the dip-coating and electrospinning technique, based on the human humeral head data. In vitro studies demonstrated that BS showed a greater cytocompatibility, and increased secretion of ECM proteins comparing to MS. In vivo studies indicated that BS promoted ECM deposition and angiogenesis in the surrounding tissue. Our research highlights that BS exhibits better ECM deposition and reveals a potential candidate for the treatment of IRCT in future.

Characterization of Electrospun BDMC-Loaded PLA Nanofibers with Drug Delivery Function and Anti-Inflammatory Activity.

Controlled drug release systems are the subject of many investigations to achieve the therapeutic effect of drugs. They have numerous advantages, such as localized effects, lower side effects, and less onset of action. Among drug-delivery systems, electrospinning is a versatile and cost-effective method for biomedical applications. Furthermore, electrospun nanofibers are promising as drug carrier candidates due to their properties that mimic the extracellular matrix. In this work, electrospun fibers were made of Poly-L-lactic acid (PLA), one of the most widely tested materials, which has excellent biocompatible and biodegradable properties. A curcuminoid, bisdemethoxycurcumin (BDMC) was added in order to complete the drug delivery system. The PLA/BDMC membranes were characterized, and biological characteristics were examined in vitro. The results show that the average fiber diameter was reduced with the drug, which was mainly released during the first 24 h by a diffusion mechanism. It was seen that the use of our membranes loaded with BDMC enhanced the rate of proliferation in Schwann cells, the main peripheral neuroglial cells, and modulated inflammation by reducing NLRP3 inflammasome activation. Considering the results, the prepared PLA/BDMC membranes hold great potential for being used in tissue engineering applications.

Composites of Bacillus megaterium H16 derived poly-3-hydroxybutyrate as a biomaterial for skin tissue engineering

Composite films of Bacillus megaterium H16 derived PHB with 1%Poly-L-lactic acid (PLLA), 1%Poly-ε-caprolactone (PCL), and 0.3 % graphene nanoplatelets (GNP) were produced by solvent cast method. The composite films were characterized by SEM, DSC-TGA, XRD, and ATR-FTIR. The ultrastructure of PHB and its composites depicted an irregular surface morphology with pores after the evaporation of chloroform. The GNPs were seen to be integrated inside the pores. The B. megaterium H16 derived-PHB and its composites demonstrated good biocompatibility which was evaluated in vitro on HaCaT and L929 cells by MTT assay. The cell viability was best for PHB followed by PHB/PLLA/PCL > PHB/PLLA/GNP > PHB/PLLA. PHB and its composites were highly hemocompatible as it resulted in <1 % hemolysis. The PHB/PLLA/PCL and PHB/PLLA/GNP composites can serve as ideal biomaterials for skin tissue engineering.

L-Poly(lactic acid) Production by Microwave Irradiation of Lactic Acid Obtained from Lignocellulosic Wastes.

L-polylactic acid (PLA), a semi-crystalline aliphatic polyester, is one of the most manufactured biodegradable plastics worldwide. The objective of the study was to obtain L-polylactic acid (PLA) from lignocellulosic plum biomass. Initially, the biomass was processed via pressurized hot water pretreatment at a temperature of 180 °C for 30 min at 10 MPa for carbohydrate separation. Cellulase and the beta-glucosidase enzymes were then added, and the mixture was fermented with Lacticaseibacillus rhamnosus ATCC 7469. The resulting lactic acid was concentrated and purified after ammonium sulphate and n-butanol extraction. The productivity of L-lactic acid was 2.04 ± 0.18 g/L/h. Then, the PLA was synthesized in two stages. Firstly, lactic acid was subjected to azeotropic dehydration at 140 °C for 24 h in the presence of xylene, using SnCl2 (0.4 wt.%) as a catalyst, resulting in lactide (CPLA). Secondly, microwave-assisted polymerization was carried out at 140 °C for 30 min with 0.4 wt.% SnCl2. The resulting powder was purified with methanol to produce PLA with 92.1% yield. The obtained PLA was confirmed using electrospray ionization mass spectrometry, nuclear magnetic resonance, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. Overall, the resulting PLA can successfully replace the traditional synthetic polymers used in the packaging industry.

In Vitro Prototyping of a Nano-Organogel for Thermo-Sonic Intra-Cervical Delivery of 5-Fluorouracil-Loaded Solid Lipid Nanoparticles for Cervical Cancer

Solid lipid nanoparticles (SLNs) are used extensively to achieve site-specific drug delivery with improved bioavailability and reduced toxicity. This work focused on a new approach to provide site-specific stimuli-responsive delivery of SLNs loaded within thermo-sonic nano-organogel (TNO) variants to deliver the model chemotherapeutic agent 5-FU in treating cervical cancer. Pharmaceutically stable nanospherical SLNs comprising poly-L-lactic acid (PLA), palmitic acid (PA), and polyvinyl alcohol (PVA) were prepared and incorporated into TNO variants augmented by external thermal and ultrasound stimuli for release of 5-FU in the cervix. Results revealed that rate-modulated 5-FU release was achieved from SLNs (particle size =450.9 nm; PDI =0.541; zeta potential =−23.2 mV; %DL =33%) within an organogel upon exposure to either a single (thermo-) and/or both (thermo-sonic) stimuli. 5FU was released from all TNO variants with an initial burst on day 1 followed by sustained release over 14 days. TNO 1 provided desirable release over 15 days (44.29% vs. 67.13% under single (T) or combined (TU) stimuli, respectively). Release rates were primarily influenced by the SLN:TO ratio in tandem with biodegradation and hydrodynamic influx. Biodegradation by day 7 revealed that variant TNO 1 (1:5) released 5FU (46.8%) analogous to its initial mass than the other TNO variants (i.e., ratios of 2:5 and 3:5). FT-IR spectra revealed assimilation of the system components and corroborative with the DSC and XRD analysis (i.e., in ratios of PA:PLA 1:1 and 2:1). In conclusion, the TNO variants produced may be used as a potential stimuli-responsive platform for the site-specific delivery of chemotherapeutic agents such as 5-FU to treat cervical cancer.

Exosomes derived from mesenchymal stromal cells promote bone regeneration by delivering miR-182–5p-inhibitor

Exosomes, small extracellular vesicles that function as a key regulator of cell-to-cell communication, are emerging as a promising candidate for bone regeneration. Here, we aimed to investigate the effect of exosomes from pre-differentiated human alveolar bone-derived bone marrow mesenchymal stromal cells (AB-BMSCs) carrying specific microRNAs on bone regeneration. Exosomes secreted from AB-BMSCs pre-differentiated for 0 and 7 days were cocultured with BMSCs in vitro to investigate their effect on the differentiation of the BMSCs. MiRNAs from AB-BMSCs at different stages of osteogenic differentiation were analyzed. BMSCs seeded on poly-L-lactic acid(PLLA) scaffolds were treated with miRNA antagonist-decorated exosomes to verify their effect on new bone regeneration. Exosomes pre-differentiated for 7 days effectively promoted the differentiation of BMSCs. Bioinformatic analysis revealed that miRNAs within the exosomes were differentially expressed, including the upregulation of osteogenic miRNAs (miR-3182, miR-1468) and downregulation of anti-osteogenic miRNAs (miR-182–5p, miR-335–3p, miR-382–5p), causing activation of the PI3K/Akt signaling pathway. The treatment of BMSC-seeded scaffolds with anti-miR-182–5p decorated exosomes demonstrated enhanced osteogenic differentiation and efficient formation of new bone. In conclusion, Osteogenic exosomes secreted from pre-differentiated AB-BMSCs were identified and the gene modification of exosomes provides great potential as a bone regeneration strategy. Data Availability StatementData generated or analyzed in this paper partly are available in the GEO public data repository(http://www.ncbi.nlm.nih.gov/geo).

Poly(1,3-Propylene Glycol Citrate) as a Plasticizer for Toughness Enhancement of Poly-L-Lactic Acid.

Despite the unique features of poly-L-lactic acid (PLLA), its mechanical properties, such as the elongation at break, need improvement to broaden its application scope. Herein, poly(1,3-propylene glycol citrate) (PO3GCA) was synthesized via a one-step reaction and evaluated as a plasticizer for PLLA films. Thin-film characterization of PLLA/PO3GCA films prepared via solution casting revealed that PO3GCA shows good compatibility with PLLA. The addition of PO3GCA slightly improves the thermal stability and enhances the toughness of PLLA films. In particular, the elongation at break of the PLLA/PO3GCA films with PO3GCA mass contents of 5%, 10%, 15%, and 20% increases to 172%, 209%, 230%, and 218%, respectively. Therefore, PO3GCA is promising as a plasticizer for PLLA.

Glutaeal remodelling protocol: Volumization with hyaluronic acid and collagen biostimulation with poly-L-lactic acid.

The purpose of this study is to develop an aesthetic treatment protocol for the glutes through the combination of poly-L-lactic acid (PLLA) and body hyaluronic acid (HA). Six female patients who aimed for glutaeal harmonisation were evaluated. Patients were treated with the combined protocol of Rennova Elleva® (poly-L-lactic acid) and Rennova Body Shape® (HA). The results were evaluated through quantitative and ultrasonographic analyses. The results showed that after 45-90days after treatment there was an increase in the glutaeal region of the treated patients. The improvement in glutaeal harmonisation was demonstrated through qualitative comparisons and analyses. Clinical evidence from these six cases suggests that the combined use of PLLA (Rennova Elleva®) and HA (Rennova Body Shape®) offers an excellent balance between efficacy and safety, with excellent aesthetic results.

Poly-L-Lactic Acid Fillers Improved Dermal Collagen Synthesis by Modulating M2 Macrophage Polarization in Aged Animal Skin.

Poly-L-lactic acid (PLLA) fillers correct cutaneous volume loss by stimulating fibroblasts to synthesize collagen and by augmenting the volume. PLLA triggers the macrophage-induced activation of fibroblasts that secrete transforming growth factor-β (TGF-β). However, whether M2 macrophage polarization is involved in PLLA-induced collagen synthesis via fibroblast activation in aged skin is not known. Therefore, we evaluated the effect of PLLA on dermal collagen synthesis via M2 polarization in an H2O2-induced cellular senescence model and aged animal skin. H2O2-treated macrophages had increased expression levels of the M1 marker CD80 and decreased expression levels of the M2 marker CD163, which were reversed by PLLA. The expression levels of interleukin (IL)-4 and IL-13, which mediate M2 polarization, were decreased in H2O2-treated macrophages and increased upon the PLLA treatment. CD163, IL-4, and IL-13 expression levels were decreased in aged skin, but increased after the PLLA treatment. The expression levels of TGF-β, pSMAD2/SMAD2, connective tissue growth factor (CTGF), alpha-smooth muscle actin (α-SMA), collagen type 1A1 (COL1A1), and COL3A1 were also decreased in aged skin, but increased after the PLLA treatment. Moreover, PLLA upregulated phosphatidylinositol 3-kinase p85α (PI3-kinase p85α)/protein kinase B (AKT) signaling, leading to fibroblast proliferation. PLLA decreased the expression of matrix metalloproteinase (MMP) 2 and MMP3, which destroy collagen and elastin fibers in aged skin. The amount of collagen and elastin fibers in aged skin increased following the PLLA treatment. In conclusion, PLLA causes M2 polarization by increasing IL-4 and IL-13 levels and upregulating TGF-β expression and collagen synthesis in aged skin.

Sculptra®—History and how it is best used today

AbstractIntroductionSculptra® is an injectable biostimulatory soft tissue filler containing microparticles of poly‐L‐lactic acid (PLLA) that is FDA‐approved for the correction of HIV‐associated facial lipoatrophy and nasolabial fold contour deficiencies and other facial wrinkles in immunocompetent patients. Injectable PLLA has been shown to provide gradual improvement in cutaneous thickness by inciting a subclinical inflammatory response that stimulates increased collagen deposition in the dermis, with results lasting up to 2 years.DiscussionThe utilization of Sculptra® in aesthetics has expanded to many off‐label indications including panfacial revolumization, improvement in skin quality, and use in various non‐facial sites such as the neck/décolleté, abdomen, arms, hands, thighs, and gluteal area. Clinical experience and scientific investigation have driven changes in the way PLLA is used. Simpler methods of product preparation, improved injection techniques, and attention to appropriate patient selection have led to improved outcomes and ease of use.ConclusionPLLA's long safety history and ability to produce subtle yet significant results through a biostimulatory mechanism make it an attractive and versatile option for cutaneous volume augmentation.

Application of Intraoperative CT-Ultrasound Fusion Imaging in Hip Endoscopy for Treatment of Iatrogenic Impingement Due to PLLA Screw: A Novel Surgical Technique

Ultrasound-assisted surgery is becoming an established tool in the medical field. The addition of imagery to ultrasound-assisted surgery may enable one to perform a procedure in a safer and more accurate manner. This can be achieved through fusion imaging (fusion), a technology that synchronizes MRI or CT images with ultrasound images. We describe intraoperative CT-ultrasound fusion-guided (or -assisted) hip endoscopy for the removal of an impinging poly L-lactic acid screw, which was difficult to identify on fluoroscopy during surgery. The fusion technology enables merging two advantages of ultrasound: the real-time guidance capabilities and CT or MRI and the bird's eye view that makes minimally invasive arthroscopic and endoscopic surgery less invasive, precise, and safe.

A small-diameter vascular graft immobilized peptides for capturing endothelial colony-forming cells.

Combining synthetic polymers and biomacromolecules prevents the occurrence of thrombogenicity and intimal hyperplasia in small-diameter vascular grafts (SDVGs). In the present study, an electrospinning poly (L)-lactic acid (PLLA) bilayered scaffold is developed to prevent thrombosis after implantation by promoting the capture and differentiation of endothelial colony-forming cells (ECFCs). The scaffold consists of an outer PLLA scaffold and an inner porous PLLA biomimetic membrane combined with heparin (Hep), peptide Gly-Gly-Gly-Arg-Glu-Asp-Val (GGG-REDV), and vascular endothelial growth factor (VEGF). Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle goniometry were performed to determine successful synthesis. The tensile strength of the outer layer was obtained using the recorded stress/strain curves, and hemocompatibility was evaluated using the blood clotting test. The proliferation, function, and differentiation properties of ECFCs were measured on various surfaces. Scanning electronic microscopy (SEM) was used to observe the morphology of ECFCs on the surface. The outer layer of scaffolds exhibited a similar strain and stress performance as the human saphenous vein via the tensile experiment. The contact angle decreased continuously until it reached 56° after REDV/VEGF modification, and SEM images of platelet adhesion showed a better hemocompatibility surface after modification. The ECFCs were captured using the REDV + VEGF + surface successfully under flow conditions. The expression of mature ECs was constantly increased with the culture of ECFCs on REDV + VEGF + surfaces. SEM images showed that the ECFCs captured by the REDV + VEGF + surface formed capillary-like structures after 4weeks of culture. The SDVGs modified by REDV combined with VEGF promoted ECFC capture and rapid differentiation into ECs, forming capillary-like structures in vitro. The bilayered SDVGs could be used as vascular devices that achieved a high patency rate and rapid re-endothelialization.

A new insight into the mechanical properties of nanobiofibers and vibrational behavior of atomic force microscope beam considering them as the samples

Nowadays, the utilization and production of polymeric nanofibers are expanding rapidly due to their unique and exclusive properties. The current study examined silk fibroin nanofibers, poly-L lactic acid (PLLA), and polycaprolactone (PCL) as three widely-used biopolymers. In the first section, the mechanical properties of nanobiofibers, including elastic modulus as the first research variable, were investigated using atomic force microscopy (AFM)-based nanoindentation and tensile testing (through a universal testing machine). The results indicated that increasing the concentration of the biopolymer solution increased its elastic modulus. The total amount of elastic modulus for silk fibroin (SF), PCL, and PLLA nanofibers with random and aligned scaffold formats ranged from 1.207 MPa to 3.71 MPa. Based on the molecular weight and concentrations of the solutions, PLLA, PCL, and silk fibroin nanofibers yielded the highest elastic modulus, respectively. In addition, the elastic modulus was greater in an aligned scaffold as opposed to a random format and in retraction as opposed to an extended stroke. During the second section of the study, resonant frequencies as the second research variable and the amplitude of the FRF of the AFM beam's vertical movements using nanobiopolymers with various scaffolds as the samples were investigated theoretically (using the Finite Element Method [FEM]) and experimentally (using AFM). For the first to third modes, the resonant frequency of the AFM beam considering biopolymer nanofibers as samples varied from 12658.43 Hz to 241208.4 Hz. The results revealed that increasing the elastic modulus of the samples increases the resonant frequency. The mechanical and vibrational properties of nanofibers calculated by various methods were subsequently compared separately. Overall, the comparison indicated good agreement between the properties.

Skin‐Adhesive Flexible Force Sensors Based on Piezoelectric Poly(l‐lactic acid) for Human Behavior Recognition

AbstractThe application of biodegradable films based on the piezoelectric effect of poly‐l‐lactic acid (PLLA) in sensors, transducers, actuators, and so on has gradually become one of the emerging research focuses. In this work, a flexible PLLA sensor with UV‐curable acrylate film packaging is proposed for human behavior recognition. The acrylic films with different proportions have different mechanical and surface properties, showing good flexibility, ductility, and skin adhesion. The morphology and crystal structure of the PLLA films and UV curable substrate obtained under the various postprocessing conditions and different proportions are examined by scanning electron microscopy, X‐ray diffraction, Raman, and ATR‐FTIR spectroscopy. In addition, by comparing six groups of PLLA films with different treatment conditions, the device made on film stretched four times and annealed for 8 h has the best performance. This sensor has good response ability to impact, vibration, and bending strain, and can be applied to human behavior recognition, such as touch, wrist bending, and swallowing.