Source: PENNSYLVANIA STATE UNIVERSITY submitted to NRP
ELECTROSPINNING OF REINFORCED AND FUNCTIONALIZED STARCH FIBERS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1005382
Grant No.
2015-67021-22994
Cumulative Award Amt.
$447,788.00
Proposal No.
2014-03672
Multistate No.
(N/A)
Project Start Date
Feb 1, 2015
Project End Date
Jan 31, 2019
Grant Year
2015
Program Code
[A1511]- Agriculture Systems and Technology: Nanotechnology for Agricultural and Food Systems
Recipient Organization
PENNSYLVANIA STATE UNIVERSITY
408 Old Main
UNIVERSITY PARK,PA 16802-1505
Performing Department
Food Science
Non Technical Summary
The development of bio-based materials from renewable resources to substitute for petroleum-based synthetics has been an area of interest, as well as, a primary research challenge for scientists. Dedicated research in this area will allow for conversion of agricultural commodities to high value-added materials at a very low cost and in a sustainable manner. One such application is nonwoven fibers. Because agriculture-derived biopolymers are generally biodegradable, biocompatible, and hydrophilic, fibers manufactured from them are regarded as suitable substitutes for petroleum-based synthetic polymers in textile, sanitary, and biomedical applications. Among the most attractive agriculture-derived biopolymers is starch. Starch, synthesized by plants via photosynthesis, is one of the most abundant biopolymers in nature and the least expensive on the market. In addition to its sustainable supply and inherent biodegradability, starch has functional advantages over synthetic polymers. Starch is more hydrophilic than synthetic polymers, and thus can be used for improving absorbency. Starch is an ideal material for making biomedical textiles since starch is biocompatible and bioabsorbable. Starch-based sanitary products could provide consumer-related benefits, e.g. easy disposability and flushability. Hence, many attempts to fabricate starch fibers are reported in the research and patent literature. Previous USDA funding resulted in the development of a novel method to produce pure starch fibers by an electro-wet-spinning technique that resulted in fibers with diameters ranging from hundreds of nanometers to tens of microns. Electrospinning employs electrostatic force to deform and elongate polymer melts or dispersions, and has gained much attention in the last decade, because it is currently the only known technique that can fabricate continuous nano-scale ?bers. However, starch fibers in nano-scale (< 100 nm) were not obtained within the experimental range using a simple electrospinning apparatus, and the pure starch fibers were mechanically weak and susceptible to moisture. This challenge has been confronted by many researchers when developing biopolymer-based products. Though some products are commercially available, biopolymer-based materials have not been widely accepted as replacements for their synthetic counterparts. To be competitive in the market, some properties of biopolymer-based materials, for instance, mechanical strength, compliance and moisture sensitivity, will need to be enhanced. For this reason, a new class of composite materials based on biopolymers and nanoclays has generated much attention. Nanoclays consist of two-dimensional nano-sized layers, the distance between which is also in the order of nanometers. Examples are naturally occurring layered mineral silicates, including montmorillonite (MMT), and synthetic layered double hydroxides (LDH). Awareness of the potential of polymer/clay nanocomposites has increased since the late 1980s when Toyota researchers showed that incorporation of as little as 5% nanoclay into nylons greatly increased their modulus and heat distortion temperature. Nanocomposites can drastically improve the mechanical properties, thermal stability, and barrier properties of polymers. In addition, nanoclays offer extra benefits, such as low density, low cost, and recyclability. Research activities involving starch and nanoclays have been conducted by many researchers mostly in thermoplastic starch compositions. This project will extend the advances made in the production of starch-based nano-fibers, with the goal of improving their functional properties through the use of nano-composites and production efficiencies. Biomedical applications of the starch-based nano-fibers will be explored as the most promising initial use.
Animal Health Component
40%
Research Effort Categories
Basic
25%
Applied
40%
Developmental
35%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
51174102020100%
Knowledge Area
511 - New and Improved Non-Food Products and Processes;

Subject Of Investigation
7410 - General technology;

Field Of Science
2020 - Engineering;
Goals / Objectives
Long-term goal of the proposed researchTo understand the nanoscale science of nanoclay reinforced starch-based biofibers for replacing petroleum-based counterparts as well as providing additional functionalities over traditional biomedical, textile, and agricultural materials.Specific experimental objectivesObjective 1: Obtain a basic understanding of starch - nanoclay interactions in dispersions.Objective 2: Establish the rheology -spinnability relationship for starch/clay dispersions, and the structure - thermomechanical property relationship for the starch/filler nanocomposite fibers.Objective 3: Evaluate the disintegration, release and antimicrobial properties of cross-linked, annealed (crystallized) and iodine-loaded starch fibers.Objective 4: Determine the effect of alignment and drawing on thermomechanical properties of starch fibers. Objective 5: Assess the feasibility of using a multi-jet electrospinning setup to scale the electrospinning process for starch fiber production.
Project Methods
Objective 1: The starch materials include a native high amylose starch (Hylon VII) and starch acetate (Kofilm® 80 &Kofilm® 250), and two groups of nano-structured clays. Intensive mixing will be carried out by using a stirred pressure reactor (PAR-4592) at different levels of processing temperature and shear stress. A twin screw extruder (Haake Polylab OS) will be used to disperse the starch/clay composite. Mixed dispersions will be subject to oscillatory and steady shear rheological measurements. All rheological tests of the mixed composite dispersions will be performed on an strain-controlled rheometer, using 25 mm cone and plate geometry. The critical entanglement concentration of the starch/clay dispersions will be determined using steady shear viscometry. Dried starch/clay composites will be examined by X-ray diffraction (XRD) with an emphasis on changes of the interlayer distance of the clay. Transmission electron microscopy (TEM) images will be obtained as a complementary technique to observe the clay and composite morphologies.Objective 2: Electrospinnability of the starch/clay nanocomposite dispersions with exfoliated and/or intercalated morphologies will be evlauated. A laboratory scale electrospinning apparatus with ethanol coagulation bath will be used to spin the dispersions. The electrospinnability will be evaluated as described in our previous work. Dried fibers will be observed using an optical microscope and a scanning electron microscope. Thermomechanical properties of the fiber mats will be evaluated using dynamic mechanical analysis and differential scanning calorimetry. According to the ASTM D 5034-09, tensile properties of the fiber mats will be tested using a texture analyzer. Ultimate tensile stress and elongation at break will be resolved from the tensile test curves. Tensile properties will be normalized by the weight of the mats. We will use concentrated starch acetate/clay dispersions as a masterbatch and mix it with raw high amylose starch to the desired concentration. We will also evaluate the rheological behavior and electrospinnability of starch/clay/plasticizer systems: sorbitol, maltitol, and trehalose. For each selected plasticizer, a constrained 3-component mixture design will be used to evaluate the clay morphology, and thermomechanical and tensile properties of plasticized system, i.e. A: starch/clay (at a fixed ratio), B: plasticizer, and C: DMSO, will be defined to ensure electrospinnability. Based on preliminary experiments, an example of constraints can be written as: 10% < A < 20%, 0 < B < 20%, C > 70%, with A + B + C =100%.Objective 3: Nanocomposite fibers will be cross-linked by vapor-phase glutaraldehyde to varying degrees. The degree of cross-linking will be estimated by glutaraldehyde adsorption (weight increase). The fibers will be annealed in ethanol/water mixture to increase the degree of crystallinity. The degree of crystallinity will be resolved from XRD patterns. A 23 full factorial design will be employed to evaluate use of cross-linked and annealed nanocomposite fibers as biomedical scaffolds, according to ASTM standard guide F2150-07. The 2 factors are degree of cross-linking and degree of crystallinity, and each factor is set at three different levels. First, physical properties, including surface area and porosity, will be determined. Surface area will be measured by BET measurements of nitrogen adsorption using a surface area analyzer. According to ASTM standard guide F2450-10, SEM images using an image analysis software packages (FoveaPro) will be used to generate data concerning the shape of pores, their size and their distribution, and porosity. Tensile properties will be tested as aforementioned. Disintegration tests will be conducted by placing fiber mats in phosphate buffered saline pH 7.4 at 37 oC under constant shaking in an incubator. Weight of the soaked fiber mats (also indicates water holding capacity) and micrographs will be recorded at a fixed time interval during the disintegration process. Iodine will be loaded to form inclusion complex with starch helices by vapor phase exposure. By controlling the exposure time, iodine content will be 0.9% (w/w of starch fibers), same as that in commercial cadexomer iodine. Commercial cadexomer iodine dressing pads, Iodosorb® and Iodoflex® from Smith & Nephew, will be used as a control. Release study will be conducted using a dissolution apparatus (Sotax AT7) with baskets (containing fiber samples) rotating at constant low speed (25 rpm) at room temperature. Aliquots will be withdrawn at regular time intervals and the absorbance at 600nm will be measured using a spectrophotometer, and be converted into iodine concentrations with the help of calibration curve. The antimicrobial activity of the iodine-loaded starch fibers will be evaluated by zone of inhibition bioassays. Using starch fibers without iodine as a control and commercial cadexomer iodine dressing pads as comparisons, round pieces of samples that have the same weight and size will be placed onto the center of bioassay agar plates. After incubating at 37 oC for 24 hours, the diameter of inhibition zone around each sample will be measured. After measurement, the samples will be transferred aseptically to freshly inoculated agar plates, and the procedures repeated for 3 days.Objective 4: Fiber alignment and drawing will be achieved by collecting fibers using a rotating mandrel in the coagulation bath, designed to fit into the current electrospinning setup by the help of machine shops that are available on campus. The degree of alignment and drawing can be varied by controlling the rotation speed of the collection mandrel. Fiber diameter will be measured from the ESEM micrographs. The degree of alignment will be characterized by the angular standard deviation as described in the literature. Low angular standard deviations denote more strongly aligned fibers. The degree of molecular orientation will be determined using infrared dichroism of single fibers. Spectra recorded in the parallel and perpendicular modes of constrained starch samples showed clear difference. The dichroic ratio of certain band intensity that preferably aligned in the helical axis direction of starch can be used to quantify the degree of molecular orientation. Tensile anisotropy will be evaluated and compared with randomly oriented fibers.Objective 5: Starch fibers will be electrospun using multiple spinnerets in order to increase the production rate. The spinnerets will be designed and fabricated by the help of machine shops and/or the 3-D printing lab that are available on campus. Performance of two spinneret arrangements (i.e. linear and rectangular) and different inter-spinneret distances on the uniformity of fiber deposition will be evaluated. For each spinneret arrangement, the interaction of inter-spinneret spacing and electrospinning parameters (e.g. flow rate, applied voltage and spinning distance) will be evaluated using a fractional factorial design in a constrained region. The uniformity of fiber deposition will be quantified by the variability in the thickness and/or the light transmittance of a number of spots on the fiber mat. Tensile tests will also be performed to indicate the uniformity of the fiber mat. We will then design an X-Y motion stage to move the spinneret following a programmed route. The programmed motion should help cover all the area uniformly for fiber deposition

Progress 02/01/15 to 01/31/19

Outputs
Target Audience:Academic and industrial researchers investigating manufactured fiber materials, especially those made from biopolymers via electrospinning for use as tissue scaffolds. Changes/Problems:We quickly established that starch-nanoclay composites proposed in Objectives 1 and 2 would not yield the improved mechanical properties anticipated. Therefore, we revised the objective to investigate starch-nanocellulose composites and to establish the rheology-spinnability relationship for these dispersions. Nanocellulose is another bio-based material and its inclusion is consistent with our original goals. During the course of the project we identified a unique starch-based material, originally described as a result of USDA ARS research, that could serve as a dope for spinning fibers directly from water, avoiding the use of organic solvents and making the process much "greener." We included further investigation of this material in our objectives. While we successfully built a multi-needle electrospinning apparatus, productivity was still low. We have initiated further investigation of needleless electrospinning for scale-up. What opportunities for training and professional development has the project provided?Lingyan Kong, a post-doctoral student trained by this project, secured a faculty position at the University of Alabama - Tuscaloosa. The project led to the awarding of one Ph.D. and one M.S. degree. The project provided training for three visiting Ph.D. scholars, one each from Mexico, Thailand and China, and one undergraduate researcher. How have the results been disseminated to communities of interest?The results of this project have been disseminated principally through peer-reviewed publications in the academic literature and presentations at academic conferences. A Penn State Newswire release (https://news.psu.edu/story/565492/2019/03/26/research/building-starch-backbones-lab-grown-meat-using-lego-pieces) was picked up by numerous newspapers and websites including: Science Daily, Daily Item (PA), LiveKindly, VegNews, MSN, Food Ingredients First, Food and Wine, Yahoo Finance, New Atlas, The Spoon, Mental Floss, Physics News, World News Buz, Brick Fanatics, Today Channel. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We have developed agriculturally-derived, bio-based materials from renewable resources in the form of non-woven fiber cloth from starch and starch-cellulose composites manufactured by electrospinning. Biodegradable, biocompatible and non-toxic bioabsorbable starch fiber cloth would be an ideal material for food and biomedical applications provided its strength and shape are appropriate. With this project we improved the mechanical strength of starch fiber cloth by adding a minor amount (<4%) of nano-cellulose and annealing the fibers at elevated relative humidity. We were able to replace the organic solvents used to dissolve the starch and prepare fibers from a water-based solution. The starch fibers were aligned by winding them onto a rotating drum. Aligned starch fiber cloth could be used as scaffolding in tissue engineering applications such as the regeneration of heart muscle or in cellular agriculture for the production of cell-based meat. Objective 1: Obtain a basic understanding of starch - nanoclay interactions in dispersions. Montmorillonite (MMT) nano-clay was easily dispersed into starch solutions containing dimethyl sulfoxide to prepare an electrospinning dope as evidenced by x-ray diffraction. Starch-MMT composite fibers were electrospun from this dope. However, we quickly established that starch-nanoclay composites proposed in Objectives 1 and 2 would not yield the improved mechanical properties anticipated. Therefore, we revised the objective to investigate starch-nanocellulose composites and to establish the rheology-spinnability relationship for these dispersions. Nanocellulose is another bio-based material and its inclusion is consistent with our original goals. Objective 2: Establish the rheology -spinnability relationship for starch/nano-cellulose dispersions, and the structure - thermomechanical property relationship for the starch/filler nanocomposite fibers. We enhanced the mechanical strength of electrospun starch-based fibers by using nanocellulose as a reinforcing filler and cationic starch as a binding agent. The potential ionic bonding between cationic starch and anionic nanocellulose, and the hydrogen bonding as well as macromolecular entanglement between the three components, are expected to improve the compatibility of polymers and the mechanical strength of their composite fibers. Rheological properties of nanocellulose, cationic starch, and their mixtures were studied to understand their conformation and interaction in the DMSO dispersions. Then, the rheological properties of the ternary systems were studied and correlated with their electrospinnability and the tensile strength of the composite fiber mats. Our results suggested that nanocellulose-cationic starch at its percolation concentration (≈2%, w/w, of starch) has the most profound influence on fiber strength, and CS:NC ratios of 1:2 and 1:1 created improved intermolecular ionic bonding for reinforcing the fiber structure. The results were published in the peer-reviewed literature and presented at academic conferences. Objective 3: Evaluate the disintegration, release and antimicrobial properties of cross-linked, annealed (crystallized) and iodine-loaded starch fibers. Wet-electrospun starch fiber mats were subjected to post-drying conditioning at controlled equilibrium relative humidity and equilibration time. The weight-normalized ultimate tensile strength of starch fiber mats increased significantly with equilibration at relative humidity >0.75 after 28 days. Morphological observation and X-ray diffraction analysis excluded significant changes in fiber size or crystallinity, and thus we concluded that conglutination brought about by the plasticizing effect of water and observed microscopically was primarily responsible for this mechanical improvement. The results were published in the peer-reviewed literature and presented at academic conferences. Objective 4: Determine the effect of alignment and drawing on thermomechanical properties of starch fibers. This study comprehensively documented the feasibility of directed fiber deposition in wet-electrospinning and offered an inexpensive setup for laboratory investigation. Aligned starch fiber mats were produced and the effects of three operational parameters, i.e., rotational speed, drum location, and coagulation bath composition, were evaluated. The alignment of starch fibers was affected by the ethanol concentration in the coagulation bath and drum rotational speed. Coherent fibers could be obtained in all trials except for the one at the lowest ethanol concentration (60% v/v) and highest rotational speed (500 rpm) when the drum was below the liquid. The tensile strength was correlated with fiber alignment and influenced by the interaction of location and ethanol concentration, and that of rotational speed and ethanol concentration. This study set a promising example of making aligned biopolymer fiber mats and investigating fiber deposition in wet-electrospinning. The results were published in the peer-reviewed literature and presented at academic conferences. Objective 5: Assess the feasibility of using a multi-jet electrospinning setup to scale the electrospinning process for starch fiber production. A five-jet spinneret was designed, constructed, and used to electrospin pullulan fibers demonstrating technical feasibility. However, the productivity gain was insufficient and therefore we initiated work using needleless electrospinning. The results were presented at an academic conference. During the course of the project we identified a unique starch-based material, originally described as a result of USDA ARS research, that could serve as a dope for spinning fibers directly from water, avoiding the use of organic solvents and making the process much "greener." We included further investigation of this material in our objectives. A green method to fabricate starch-based nanofibers was developed. High-temperature (≈>1620 ºC) was used to destructure high-amylose starch in water. Sodium palmitate was added to enhance the stability of high-amylose starch in water at room temperature and increase the conductivity of the electrospinning dope. Flow properties and zeta potential of starch-palmitate dispersions were characterized by rheometer and dynamic light scattering, respectively. Pullulan was mixed in as a minor component of the starch-palmitate complex (starch:pullulan at a ca. 2:1 ratio) and the mixture electrospun. Pullulan hindered starch association and modified the dispersion properties, promoting molecular entanglement without gelation. The presence of sodium palmitate-starch inclusion complexes in the fiber was confirmed by differential scanning calorimetry and X-ray diffraction. Tensile strength of the nanofiber composite was found to be weaker than that of micro-sized pure starch fiber mats. This method provides future industry with lower cost by eliminating the use of organic chemicals. The results were published in the peer-reviewed literature and presented at academic conferences.

Publications

  • Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Kong, L, Perez-Santos, DM,and Ziegler GR. Effect of Guest Structure on Amylose-Guest Inclusion Complexation. Food Hydrocolloids
  • Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Wang, H and Ziegler, GR. Electrospun nanofiber mats from aqueous starch-pullulan dispersions: optimizing dispersion properties for electrospinning. International J. Biological Macromolecules.
  • Type: Other Status: Other Year Published: 2019 Citation: Ziegler, GR. Functional Materials from Starch-Guest Inclusion Complexes. Penn State University, Department of Food Science Seminar, Feb. 7


Progress 02/01/18 to 01/31/19

Outputs
Target Audience:Academic and industrial researchers investigating manufactured fiber materials, especially those made by electrospinning. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?One M.S. and one Ph.D. were graduated during this reporting period. The project hosted one Ph.D.-seeking scientist from the South China University of Technology for 12 months. This individualhas gone on to complete her Ph.D. and accept a faculty position at Jimei University in Xiamen, China. Lingyan Kong, Ph.D., formerly a post-doc scholar on the project completed his first year as an assistant professor at the University of Alabama-Tuscaloosa in 2018. A PSU Millennium Scholar undergraduate student in Biomedical Engineering has been assisting with the project since starting Fall 2018. How have the results been disseminated to communities of interest?This reporting period the results have been disseminated largely through publication in peer-reviewed academic journals. What do you plan to do during the next reporting period to accomplish the goals?This is the last annual progress report. The final report will include publications and products completed after this reporting period.

Impacts
What was accomplished under these goals? A green method to fabricate starch-based nanofibers was developed. High-temperature (>160 ºC) was used to destructure high-amylose starch in water. Sodium palmitate was added to enhance the stability of high-amylose starch in water at room temperature and increase the conductivity of the electrospinning dope. Flow properties and zeta potential of starch-palmitate dispersions were characterized by rheometer and dynamic light scattering, respectively. Pullulan was mixed in as a minor component of the starch-palmitate complex (starch:pullulan at a ca. 2:1 ratio) and the mixture electrospun. Pullulan hindered starch association and modified the dispersion properties, promoting molecular entanglement without gelation. The presence of sodium palmitate-starch inclusion complexes in the fiber was confirmed by differential scanning calorimetry and X-ray diffraction. Tensile strength of the nanofiber composite was found to be weaker than that of micro-sized pure starch fiber mats. This method provides future industry with lower cost, environmentally-friendly process by eliminating the use of organic chemicals.

Publications

  • Type: Theses/Dissertations Status: Published Year Published: 2018 Citation: Wang, Jason. 2018. Enhancing the mechanical strength and water resilience of starch/gelatin-based electrospun nanofibers via nontoxic crosslinking with genipin. The Pennsylvania State University, M.S. thesis, 115 pp.
  • Type: Theses/Dissertations Status: Published Year Published: 2018 Citation: Wang, Hui. 2018. Electrospinning of reinforced starch fibers.The Pennsylvania State University, Ph.D. Dissertation, 148 pp.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Wang, H, Kong, LY, and Ziegler, GR. 2018. Fabrication of starch - Nanocellulose composite fibers by electrospinning. Food Hydrocolloids 90, 90-98
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Wang, H, Kong LY, and Ziegler, GR. 2018. Plasticization and conglutination improve the tensile strength of electrospun starch fiber mats. Food Hydrocolloids 83, 393-396
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Kong, LY, Yucel, U, Yoksan, R, Elias, RJ, and Ziegler, GR. 2018. Characterization of amylose inclusion complexes using electron paramagnetic resonance spectroscopy. Food Hydrocolloids 82, 82-88
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Gunenc, K, Kong, L, Elias, RJ, and Ziegler, GR. 2018. Inclusion complex formation between high amylose corn starch and alkylresorcinols from rye bran. Food Chemistry 259, 1-6
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Kong, L, Bhosale, R, and Ziegler, GR. 2018. Encapsulation and stabilization of ?-carotene by amylose inclusion complexes. Food Research International 105, 446-452
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Kong, L, Stapleton, JJ, and Ziegler, GR. 2018. Characterization of macromolecular orientation in ?-carrageenan fibers using polarized Fourier-transform infrared spectroscopy. Vibrational Spectroscopy 94, 61-65
  • Type: Journal Articles Status: Submitted Year Published: 2019 Citation: Shi, L, Hopfer, H, Ziegler, GR, and Kong, L. Starch-menthol inclusion complex: structure and release kinetics. Food Hydrocolloids
  • Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Ziegler, GR. Functional Materials from Starch-Guest Inclusion Complexes. Carbohydrate Symposium, South China University of Technology, Gunagzhou, China, December 19, 2018


Progress 02/01/17 to 01/31/18

Outputs
Target Audience:Academic and industrial researchers investigating manufactured fiber materials, especially those made by electrospinning. Changes/Problems:During our attendance at the Starch Round Table, we were exposed to a unique starch-based material that we felt could serve as a dope for spinning starch fibers directly from water, avoiding the use of organic solvents, and making the process much "greener." We followed up and were able to produce electrospun, nano-scale fibers directly from an aqueous solvent. Therefore, we've included further investigation of this system in our objectives. What opportunities for training and professional development has the project provided?Presently training two graduate students, one M.S. and one Ph.D. Additionally, the project is hosting one Ph.D.-seeking scientist from China. Furthermore, we have begun a collaboration with Dr. Huanyu (Larry) Cheng and his group in Engineering Science and Mechanics at PSU to employ our fibers as templates for ultrastretchable electronic materials. How have the results been disseminated to communities of interest?Principally through conferences. What do you plan to do during the next reporting period to accomplish the goals?We have already had success with spinnning nanoscale fibers from water-based dope vis-a-vis micro-scale fibers using our current DMSO dope. We intend to fully investigate this. Furthermore, we intend to establish the practical application of such fibers in a biological system.

Impacts
What was accomplished under these goals? Electrospinning is a cost-effective and versatile way to fabricate non-woven fibers with a fiber diameter at nano and micro scales. Electrospun starch fiber mat is a light-weight material with an enormous surface area and pores made from wet-electrospinning. As a material, the use of starch fiber depends on some crucial features like cost, scale-up feasibility, functional attributes, and mechanical properties. Currently, our research is focused on evaluating and improving the mechanical properties of starch fibers. In the past year, we established an inexpensive and facile setup to produce aligned fiber and addressed the influence of selected parameters and hypotheses in wet electrospinning. Our hypothesis is that fast rotation speed of the device would create uniform alignment perpendicular to the direction of deposition; increasing water fraction in the coagulation bath would slow the solidification process, resulting in better alignment and thinner fiber diameter. Also, unique to wet-electrospinning, we expected that the location of the drum in the coagulation bath would influence the drawing effect and solidification of spinning dope, therefore affecting fiber alignment. Our results showed that starch fibers can be collected by wet-electrospinning with an inexpensive drum system. The influence of selected parameters (rotation speed, coagulation bath composition, and drum location) on fiber formation, alignment and weight-normalized ultimate tensile strength were measured. Conditions optimizing fiber alignment (coagulation bath with 80% ethanol and drum speed at 500 rpm) were determined. Under these conditions, fiber diameter was not reduced by drum drawing, but improvement in tensile strength was observed due to fiber alignment. The effect of post-treatment on wet-electrospun starch fibers were also studied. As-spun starch fiber were subjected to post-drying conditioning at controlled equilibrium relative humidity and equilibration time. We hypothesized that a conglutination effect caused by exposure to water vapor would increase the tensile strength of electrospun starch fibers. To test this hypothesis, dried starch fibers were equilibrated at preselected relative humidity (RH) for varying periods of time, and their morphological, microstructural, and tensile properties were analysed. Both equilibration time and relative humidity significantly affected the weight-normalized ultimate tensile strength of the starch fibers. Conglutination at high RH was evidenced by scanning electron micrographs and coincided with a significant increase in weight-normalized tensile strength of the starch fibers. Since the diameter and crystallinity of starch fibers were not altered significantly, plasticization and conglutination are the likely cause for mechanical improvement. Our results also suggest the potential of using other plasticizers to enhance the mechanical properties of starch fibers.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Ziegler, GR, Kong, LY, Wang H, and Wang JJ. Electrospinning of Reinforced and Functionalized Starch Fibers, USDA Nanotechnology Grantees Annual Meeting, May 18, 2017, Washington, DC


Progress 02/01/16 to 01/31/17

Outputs
Target Audience:The target audience during this period consisted of colleagues in the nanoscale science and technology program. Changes/Problems:The major change was the move away from nanoclays as reinforcement as they were ineffective in preliminary experiments. Instead we have employed the addition of other biopolymers, including gelatin and a unique blend of cationic starch and nanocellulose. We continue to investigate the spinning from water alone as a solvent, as this would dramatically improve the environmental sustainability of the process. What opportunities for training and professional development has the project provided?Two graduate students, one Ph.D. and one M.S., are supported on this project. The Ph.D. candidate has passed her comprehensive exams. One post-doc scholar was supported for this reporting period. That post-doc has now accepted a faculty position at University of Alabama. How have the results been disseminated to communities of interest?The results were principally dissmeinated through the annual Project Director's Meeting, which we at Penn State hosted this reporting period. What do you plan to do during the next reporting period to accomplish the goals?Complete manuscript on reinforcementof starch fibers with nanocellulose/cationic starch blends. Initiate research on antimicrobial properties of iodine loaded fibers. Continue to develop a means for drawing spun fibers. Complete work on crosslinking techniques and outcomes.

Impacts
What was accomplished under these goals? Preliminary results indicated that clay nano-particles did not improve mechanical properties of starch fibers as anticipated. Therefore, nanocellulose fibers wereselected and successfully incorporated into the starch fiber. Starch/nanocellulose fibers have significantly improved the tensile strength of the fiber mat as compared with as-spun starch-only fiber. Cationic starch is used as a mediator between nanocellulose and high amylose starch. During nanocellulose processing, sulfuric acid and hydrochloric acid are used to hydrolyze amorphous regions. Sulfate group esterification takes place during the reaction, resulting in a negatively charged surface of nanocellulose (Lee, Hamid, and Zain 2014). As a positively charged polymer, cationic starch serves as a binding agent between starch and nanocellulose. The ionic bonding between cationic starch and nanocellulose, and hydrogen bonding as well as entanglement between cationic starch and high amylose starch, contributed to increasing nanocellulose and starch compatibility. The interaction between nanocellulose and cationic starch was demonstratedby rheological study. Flow curves of cationic starch (CS), nanocellulose (NC) and CS-NC mixtures in pure DMSO solutions were examined. CS-NC mixture ratios were1:1, 1:2, 2:1 at different total polymer concentrations of 0.25, 0.75, 1, 2, and 4%. Entanglement concentrations of CS and NC were analyzed. CS-NC mixtures have higher viscosity than CS and NC alone under the same total concentrations. In addition, theCS-NC mixtures showed more shear thinning properties. CS-NC mixtures were then added into high-amylose starchsolution before stirring overnight. The finial mixture contained12% w/v of high-amylosestarch and five levels of CS/NC master mix (0.25, 0.5, 1, 2, 4, 8%, w/w to high-amylose starch) atseveralratios (CS:NC, 1:1, 1:2, 2:1) in pure DMSO. Starch fibers made from high-amylose starch(12%, w/v) in pure DMSO wereused as the control. Spinnability of all samples has been tested. Proper electrospinning operation parameters were recorded. Scanning electron microscopy images were used to analyze the morphology of the fiber mat. As the mixture incorporation increased, more beads were found in the fiber mat. The diameter distribution of fibers was analyzed by DiameterJ. The distribution of NC in the fiber is observed using energy dispersive spectroscopy (EDS). The tensile properties of the fiber mat were evaluated after equilibrium in an environmental chamber. Normalized tensile strength by weight was used in the statistical analysis. The equilibrium time and concentration of CS-NC mixture were found to significantly affect the normalized tensile strength. Further investigation on the function and mechanics of starch accretion during equilibrium is still ongoing. A manuscript entitled "Fabrication of Starch and Nanocellulose Composite Fibers by Electrospinning" is in preparation.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Kong, L, Wang, H, Wang, J, Ziegler, GR. Electrospinning of Reinforced and Functionalized Starch Fibers, AFRI Nanoscale Science and Technology Project Director's Meeting, June 6, University Park, PA


Progress 02/01/15 to 01/31/16

Outputs
Target Audience:The primary target audience is academic and industrial scientists and engineers working in bio-based materials science, especially nanomaterials based on biopolymers. Academic and industrial scientists and engineers interested in electrospinning are a secondary target audience. Companies interested in commercializing bio-based nanofiber technology may also be interested. Changes/Problems:Two new directions have been initiated: in addition to nanoclays, we are reinforcing the starch-based fibers with other bio-based polymers, e.g. gelatin and chitosan, and in an effort to make the spinning process less costly and more sustainable, we are investigating techniques for spinning from water alone (without DMSO). What opportunities for training and professional development has the project provided?Two graduate students, one Ph.D. and one M.S., are supportedon this project. In addition,a visiting scholar from Thailand and one from Mexico collaborated on the project for 3 and 12 months, respectively. How have the results been disseminated to communities of interest?Poster presentations were made at a Gordon conference and at the Starch Round Table. What do you plan to do during the next reporting period to accomplish the goals?Major goals for the coming period are to develop a method for drawing (aligning and stretching) the spun fibers and determining its effect on their mechanical properties. This requires the development and validation of testing methodology. Work will begin on Objective 3 and the multineedle spinneret built during this last period will be evaluated. We will sponsor the PDs meeting for the NIFA nanoscale science and technology program.

Impacts
What was accomplished under these goals? Previously, electrospun fibers with pure starches have been fabricated. In order to further improve the properties of as-spun starch fibers, nano-composites were prepared. Based on literature reviews, clays include Montmorillonite (MMT) and Layered Double Hydroxides (LDH), chitosan, and gelatin were selected in the preliminary tests. Electrospinning results indicated the potential of fabricate starch/clay, starch/chitosan, and starch/gelatin fiber composites. In the following investigation, gelatin/starch mixtures with various concentration combinations were tested for the electrospinnibility in 90% DMSO solution. Fiber formation ability was categorized based on the morphology characterization. Practicable combinations of starch/gelatin concentration were concluded. The viscosity properties in starch/gelatin dopes were also measured in order to understand the effect of additions on the rheology properties. Shear thinning was observed for all mixtures. Potential phase separations are still under investigation. Another goal of this project is to scale up the electrospinning process for starch fiber production. Designing and building a proper multineedle spinneret is one of the approaches. There are several concerns with multineedle spinneret for electrospinning use. First, high voltage is one the important character of electrospinning. Isolation properties of the material should be considered. Second, the interference of electric field among needles should be prevented. Third, the flow rate of needles should be the same in order to generate uniform fibers. Also, precise control of temperature maybe needed for future experiment. Based on those considerations, we have designed and built a multineedle spinneret.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Wang, H, Kong, L and Ziegler, GR. Electrospinning of Reinforced and Functionalized Starch Fibers. Gordon Research Conference on Nanoscale Science & Engineering for Agriculture & Food Systems, June 7-12, Bentley University, Waltham, MA
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Wang, H, Kong, L and Ziegler, GR. Electrospinning of Reinforced and Functionalized Starch Fibers. Starch Round Table, Oct. 15-17, Minneapolis, MN
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Perez-Santos, D, Kong, L and Ziegler, GR. Starch complexation as a function of guest molecule features. Starch Round Table, Oct. 15-17, Minneapolis, MN