@article{liu_geng_zhao_zheng_yuan_2019, title={EFFECTS OF FORMIC AND LEVULINIC ACIDS ON BUTYRIC ACID SYNTHESIS BY CLOSTRIDIUM TYROBUTYRICUM IN XYLOSE MEDIA}, volume={62}, ISSN={["2151-0040"]}, DOI={10.13031/trans.13669}, abstractNote={Abstract. Weak acids released during hydrolysis of lignocellulosic biomass are potential inhibitors of microorganism fermentation. In this study, the effects of formic and levulinic acids on butyric acid synthesis by  were investigated. With the addition of 1.2 to 4.8 g L-1 of formic acid, increased lag time, decreased cell density, and lower butyric acid productivity were observed. Up to 15% and 56% reduction in peak cell density and butyric acid productivity, respectively, were caused by formic acid addition, whereas there was no significant difference in butyric acid yield between the control and formic acid treated groups (except for the 2.4 g formic acid L-1 treatment). Levulinic acid did not show any notable effects on  within the investigated concentration range (0 to 4.8 g L-1). Overall,  showed strong tolerance of both formic and levulinic acids, but neither of these acids could be metabolized by the microbe.}, number={6}, journal={TRANSACTIONS OF THE ASABE}, author={Liu, Y. and Geng, Y. and Zhao, R. and Zheng, H. and Yuan, W.}, year={2019}, pages={1803–1809} }
 @article{liu_shaw_dickey_genzer_2017, title={Sequential self-folding of polymer sheets}, volume={3}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.1602417}, abstractNote={We demonstrate an innovative strategy for sequentially self-folding 2D polymer sheets into 3D objects using light.}, number={3}, journal={SCIENCE ADVANCES}, publisher={American Association for the Advancement of Science (AAAS)}, author={Liu, Ying and Shaw, Brandi and Dickey, Michael D. and Genzer, Jan}, year={2017}, month={Mar} }
 @article{cooper_arutselvan_liu_armstrong_lin_khan_genzer_dickey_2017, title={Stretchable Capacitive Sensors of Torsion, Strain, and Touch Using Double Helix Liquid Metal Fibers}, volume={27}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201605630}, abstractNote={Soft and stretchable sensors have the potential to be incorporated into soft robotics and conformal electronics. Liquid metals represent a promising class of materials for creating these sensors because they can undergo large deformations while retaining electrical continuity. Incorporating liquid metal into hollow elastomeric capillaries results in fibers that can integrate with textiles, comply with complex surfaces, and be mass produced at high speeds. Liquid metal is injected into the core of hollow and extremely stretchable elastomeric fibers and the resulting fibers are intertwined into a helix to fabricate capacitive sensors of torsion, strain, and touch. Twisting or elongating the fibers changes the geometry and, thus, the capacitance between the fibers in a predictable way. These sensors offer a simple mechanism to measure torsion up to 800 rad m−1—two orders of magnitude higher than current torsion sensors. These intertwined fibers can also sense strain capacitively. In a complementary embodiment, the fibers are injected with different lengths of liquid metal to create sensors capable of distinguishing touch along the length of a small bundle of fibers via self‐capacitance. The three capacitive‐based modes of sensing described here may enable new sensing applications that employ the unique attributes of stretchable fibers.}, number={20}, journal={ADVANCED FUNCTIONAL MATERIALS}, publisher={Wiley}, author={Cooper, Christopher B. and Arutselvan, Kuralamudhan and Liu, Ying and Armstrong, Daniel and Lin, Yiliang and Khan, Mohammad Rashed and Genzer, Jan and Dickey, Michael D.}, year={2017}, month={May} }
 @misc{liu_genzer_dickey_2016, title={"2D or not 2D": Shape-programming polymer sheets}, volume={52}, ISSN={["1873-1619"]}, DOI={10.1016/j.progpolymsci.2015.09.001}, abstractNote={This review summarizes progress toward programming two-dimensional (2D) polymer sheets which respond to a variety of external stimuli to form three-dimensional (3D) shapes or topographical features on macroscopically planar sheets. Shape programming strategically adds value or function to 2D sheets, films, or coatings that can be created inexpensively. 2D substrates are common form factors that are compatible with ordinary 2D patterning techniques (i.e., inkjet, photolithography, roll-to-roll printing) and may be stored, packed, and shipped efficiently. Polymer materials are attractive due to their flexibility, light weight, low price, and compatibility with high throughput processing. This review highlights strategies for triggering shape change in planar polymeric materials. The strategies are divided into four broad categories: (1) 2D substrates with latent topography “programmed” using conventional microfabrication, (2) 2D substrates that form topography due to imposed or self-generated stress, (3) 2D substrates that form 3D shapes by out-of-plane bending, and (4) 2D substrates that use “hinges” to achieve out-of-plane folding. The review highlights all strategies while focusing primarily on last two approaches.}, journal={PROGRESS IN POLYMER SCIENCE}, publisher={Elsevier BV}, author={Liu, Ying and Genzer, Jan and Dickey, Michael D.}, year={2016}, month={Jan}, pages={79–106} }
 @article{mailen_liu_dickey_zikry_genzer_2015, title={Modelling of shape memory polymer sheets that self-fold in response to localized heating}, volume={11}, ISSN={["1744-6848"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84943141129&partnerID=MN8TOARS}, DOI={10.1039/c5sm01681a}, abstractNote={We conduct a nonlinear finite element analysis (FEA) of the thermo-mechanical shrinking and self-folding behavior of pre-strained polystyrene polymer sheets.}, number={39}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Mailen, Russell W. and Liu, Ying and Dickey, Michael D. and Zikry, Mohammed and Genzer, Jan}, year={2015}, pages={7827–7834} }
 @article{allensworth_liu_braun_genzer_dickey_2014, title={In-plane deformation of shape memory polymer sheets programmed using only scissors}, volume={55}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2014.07.042}, abstractNote={Abstract This paper describes an unconventional, yet simple method to program sheets of shape memory polymer into a variety of two dimensional (2D) structures. The final shape is “encoded” by physically cutting an initial design out of a pre-strained film. The orientation of the initial cut-out relative to the direction of strain and the subsequent relaxation of strain via heating defines the final shape. The appeal of the approach described here is that an easy, low-cost cutting method can achieve a similar shape memory effect attained by more complex processing techniques. Unlike conventional methods, where the final shape of a shape memory polymer must be defined a priori, the direction of cutting of the polymer defines its final shape without any complex pre-programmed strain profiles. A geometric model relating the resolved 2D polymer shape to the initial shape and strain orientation reveals linear correlation between the model-predicted and experimentally-observed shapes. In addition to demonstrating the principle with simple rectangular shapes, we suggest geometries related to encryption and high aspect ratio fibers.}, number={23}, journal={POLYMER}, publisher={Elsevier BV}, author={Allensworth, James R. and Liu, Ying and Braun, Hayley and Genzer, Jan and Dickey, Michael D.}, year={2014}, month={Nov}, pages={5948–5952} }
 @article{hayes_liu_genzer_lazzi_dickey_2014, title={Self-Folding Origami Microstrip Antennas}, volume={62}, ISSN={["1558-2221"]}, DOI={10.1109/tap.2014.2346188}, abstractNote={This communication presents antennas that incorporate self-folding polymer substrates that transform planar, two-dimensional structures into three-dimensional antennas when exposed to a light source. Pre-strained polystyrene sheets supporting a patterned copper foil form the light-activated structures. Black ink that is inkjet printed on the polymer substrate selectively absorbs light and controls the shape of the transformation. This approach represents a simple method to reconfigure the shape of an antenna and a hands-free method to assemble 3D antennas from many of the conventional methods that are used to pattern 2D metal foils. We demonstrate and characterize two embodiments that highlight this concept: a monopole antenna that transforms from a conventional microstrip transmission line and a microstrip patch antenna that converts within seconds into a monopole antenna.}, number={10}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Hayes, Gerard J. and Liu, Ying and Genzer, Jan and Lazzi, Gianluca and Dickey, Michael D.}, year={2014}, month={Oct}, pages={5416–5419} }
 @article{liu_mailen_zhu_dickey_genzer_2014, title={Simple geometric model to describe self-folding of polymer sheets}, volume={89}, ISSN={["1550-2376"]}, DOI={10.1103/physreve.89.042601}, abstractNote={Self-folding is the autonomous folding of two-dimensional shapes into three-dimensional forms in response to an external stimulus. This paper focuses on light-induced self-folding of prestrained polymer sheets patterned with black ink. The ink absorbs the light and the resulting heat induces the polymer beneath the ink to relax faster than the rest of the sheet. A simple geometric model captures both the folding angle and folding kinetics associated with this localized shrinkage. The model assumes that (1) the polymer in contact with the ink shrinks at a rate determined by the temporal temperature profile of the hinge surface; (2) the bottom of the sheet, which is cooler, does not shrink considerably; and (3) a linear gradient of strain relaxation exists across the film between these two extremes. Although there are more complex approaches for modeling folding, the appeal of this model is its simplicity and ease of use. Measurements of the macroscopic, thermally driven shrinkage behavior of the sheets help predict the kinetics of folding by determining how fast the top of the hinge shrinks as a function of temperature and time. These measurements also provide information about the temperature required to induce folding and offer indirect measurement of the glass transition temperature of the polymer that comprises the sheet.}, number={4}, journal={PHYSICAL REVIEW E}, publisher={American Physical Society (APS)}, author={Liu, Ying and Mailen, Russell and Zhu, Yong and Dickey, Michael D. and Genzer, Jan}, year={2014}, month={Apr} }
 @article{liu_miskiewicz_escuti_genzer_dickey_2014, title={Three-dimensional folding of pre-strained polymer sheets via absorption of laser light}, volume={115}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4880160}, DOI={10.1063/1.4880160}, abstractNote={Patterned light from a laser can induce rapid self-folding of pre-strained polymer sheets. Black ink coated on the sheet absorbs the light, which converts the photon energy into thermal energy that heats the sheet locally; the temperature of the sheet is highest at the surface where the light impinges on the sheet and decreases through the sheet thickness. The gradient of temperature induces a gradient of strain relaxation through the depth of the sheet, which causes folding within seconds of irradiation. The pattern of laser light that irradiates the compositionally homogeneous two-dimensional (2D) substrate dictates the resulting three-dimensional (3D) shape. Unlike most approaches to self-folding, the methodology described here requires no patterning of pre-defined hinges. It opens up the possibility of using a patterning technique that is inherently 2D to form 3D shapes. The use of lasers also enables systematic control of key process parameters such as power, intensity, and the pattern of light (i.e., beam width and shape). The rate of folding and folding angle measured with respect to these parameters provide an indirect quantification of heat loss in the sample and thereby identify the threshold power and power intensity that must be delivered to the hinge for folding to occur.}, number={20}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Liu, Ying and Miskiewicz, Matthew and Escuti, Michael J. and Genzer, Jan and Dickey, Michael D.}, year={2014}, month={May}, pages={204911} }
 @article{liu_boyles_genzer_dickey_2012, title={Self-folding of polymer sheets using local light absorption}, volume={8}, ISSN={["1744-6848"]}, DOI={10.1039/c1sm06564e}, abstractNote={This paper demonstrates experimentally and models computationally a novel and simple approach for self-folding of thin sheets of polymer using unfocused light. The sheets are made of optically transparent, pre-strained polystyrene (also known as Shrinky-Dinks) that shrink in-plane if heated uniformly. Black ink patterned on either side of the polymer sheet provides localized absorption of light, which heats the underlying polymer to temperatures above its glass transition. At these temperatures, the predefined inked regions (i.e., hinges) relax and shrink, and thereby cause the planar sheet to fold into a three-dimensional object. Self-folding is therefore achieved in a simple manner without the use of multiple fabrication steps and converts a uniform external stimulus (i.e., unfocused light) on an otherwise compositionally homogenous substrate into a hinging response. Modeling captures effectively the experimental folding trends as a function of the hinge width and support temperature and suggests that the hinged region must exceed the glass transition temperature of the sheet for folding to occur.}, number={6}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Liu, Ying and Boyles, Julie K. and Genzer, Jan and Dickey, Michael D.}, year={2012}, pages={1764–1769} }
 @article{gubbins_liu_moore_palmer_2011, title={The role of molecular modeling in confined systems: impact and prospects}, volume={13}, ISSN={["1463-9084"]}, DOI={10.1039/c0cp01475c}, abstractNote={Molecular modeling at the electronic and atomistic levels plays an important and complementary role to experimental studies of confinement effects. Theory and atomistic simulation can provide fundamental understanding, determine the limits of well known macroscopic laws such as Kelvin's equation, provide predictions for systems that are difficult to study via experiment (e.g. adsorption of highly toxic gases), and can be used to gain detailed molecular level information that may not be accessible in the laboratory (e.g. the local structure and composition of confined phases). We describe the most important and useful methods that are based firmly on quantum mechanics and statistical mechanics, including ab intio and classical density functional theories, and Monte Carlo and molecular dynamics simulation. We discuss their strengths and limitations. We then describe examples of applications of these methods to adsorption and equilibrium properties, including testing the Kelvin equation, determination of pore size distributions and capillary phenomena. Applications to self and transport diffusion, including single-file and anomalous diffusion, and viscous flow in nanoporous materials are described. The use of these methods to understand confinement effects on chemical reactions in heterogeneous media is treated, including effects on reaction equilibria, rates and mechanism. Finally we discuss the current status of molecular modeling in this area, and the outlook and future research needs for the next few years. The treatment is suitable for the general technical reader.}, number={1}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Gubbins, Keith E. and Liu, Ying-Chun and Moore, Joshua D. and Palmer, Jeremy C.}, year={2011}, pages={58–85} }
 @article{moore_palmer_liu_roussel_brennan_gubbins_2010, title={Adsorption and diffusion of argon confined in ordered and disordered microporous carbons}, volume={256}, ISSN={["0169-4332"]}, DOI={10.1016/j.apsusc.2009.12.071}, abstractNote={We use a combination of grand canonical Monte Carlo and microcanonical molecular dynamics simulations to study the adsorption and diffusion of argon at 77 K and 120 K confined in previously generated models of a disordered bituminous coal-based carbon, BPL, and an ordered carbon replica of Faujasite zeolite (C-FAU). Both materials exhibit a maximum in the diffusion coefficient as well as anomalous (sub-diffusive) behavior in the mean-squared displacements at short times at some relative pressures. In BPL, the anomalous diffusion occurs at low relative pressures, due to the trapping of argon atoms in small pores. In C-FAU, the anomalous diffusion occurs at high relative pressures, due to competitive diffusion of atoms traveling through windows and constrictions which interconnect the pores. All diffusion eventually tends to Fickian diffusion at longer times.}, number={17}, journal={APPLIED SURFACE SCIENCE}, author={Moore, Joshua D. and Palmer, Jeremy C. and Liu, Ying-Chun and Roussel, Thomas J. and Brennan, John K. and Gubbins, Keith E.}, year={2010}, month={Jun}, pages={5131–5136} }
 @article{liu_moore_roussel_gubbins_2010, title={Dual diffusion mechanism of argon confined in single-walled carbon nanotube bundles}, volume={12}, ISSN={["1463-9076"]}, DOI={10.1039/b927152j}, abstractNote={The adsorption and diffusion mechanisms of argon at 120 K were examined in a (25,0) single-walled carbon nanotube (SWCNT) bundle using a combination of Grand Canonical Monte Carlo and microcanonical molecular dynamics simulations. Interstices between the SWCNTs provided the most energetically favorable adsorption sites and filled completely at low relative pressure, followed by adsorption in the SWCNTs. We calculated the self-diffusivities from the average mean squared displacements of argon molecules. In both flexible and rigid bundles, we observed a bimodal diffusion mechanism, with single-file diffusion occurring in the interstitial sites and Fickian diffusion in the SWCNTs. Strong system size effects were observed in our simulations. The largest system sizes showed very little influence of the nanotube flexibility on the diffusion of argon even at the lowest pressures studied.}, number={25}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Liu, Ying-Chun and Moore, Joshua D. and Roussel, Thomas J. and Gubbins, Keith E.}, year={2010}, pages={6632–6640} }