@article{miller_moorman_boehm_wolfley_chavez_baca_ashley_brener_narayan_polsku_2019, title={Fabrication of Hollow Metal Microneedle Arrays Using a Molding and Electroplating Method}, volume={4}, ISSN={["2059-8521"]}, DOI={10.1557/adv.2019.147}, abstractNote={The need for hollow microneedle arrays is important for both drug delivery and wearable sensor applications; however, their fabrication poses many challenges. Hollow metal microneedle arrays residing on a flexible metal foil substrate were created by combining additive manufacturing, micromolding, and electroplating approaches in a process we refer to as electromolding. A solid microneedle with inward facing ledge was fabricated with a two photon polymerization (2PP) system utilizing laser direct write (LDW) and then molded with polydimethylsiloxane. These molds were then coated with a seed layer of Ti/Au and subsequently electroplated with pulsed deposition to create hollow microneedles. An inward facing ledge provided a physical blocking platform to restrict deposition of the metal seed layer for creation of the microneedle bore. Various ledge sizes were tested and showed that the resulting seed layer void could be controlled via the ledge length. Mechanical properties of the PDMS mold was adjusted via the precursor ratio to create a more ductile mold that eliminated tip damage to the microneedles upon removal from the molds. Master structures were capable of being molded numerous times and molds were able to be reused. SEM/EDX analysis showed that trace amounts of the PDMS mold were transferred to the metal microneedle upon removal. The microneedle substrate showed a degree of flexibility that withstood over 100 cycles of bending from side to side without damaging. Microneedles were tested for their fracture strength and were capable of puncturing porcine skin and injecting a dye.}, number={24}, journal={MRS ADVANCES}, author={Miller, Philip R. and Moorman, Matthew and Boehm, Ryan D. and Wolfley, Steven and Chavez, Victor and Baca, Justin T. and Ashley, Carlee and Brener, Igal and Narayan, Roger J. and Polsku, Ronen}, year={2019}, pages={1417–1426} }
 @article{miller_boehm_skoog_edwards_rodriguez_brozik_brener_byrd_baca_ashley_et al._2015, title={Electrodeposited Iron as a Biocompatible Material for Microneedle Fabrication}, volume={27}, ISSN={["1521-4109"]}, DOI={10.1002/elan.201500199}, abstractNote={Abstract}, number={9}, journal={ELECTROANALYSIS}, author={Miller, Philip R. and Boehm, Ryan D. and Skoog, Shelby A. and Edwards, Thayne L. and Rodriguez, Mark and Brozik, Susan and Brener, Igal and Byrd, Thomas and Baca, Justin T. and Ashley, Carlee and et al.}, year={2015}, month={Sep}, pages={2239–2249} }
 @article{boehm_miller_daniels_stafslien_narayan_2014, title={Inkjet printing for pharmaceutical applications}, volume={17}, ISSN={["1873-4103"]}, DOI={10.1016/j.mattod.2014.04.027}, abstractNote={Miconazole is an imidazole used for treatment of fungal infections that exhibits poor solubility in polar solvents (e.g., aqueous solutions). Microneedles, small-scale lancet-shaped devices that are commonly used for delivery of pharmacologic agents and vaccines, were made out of an acid anhydride copolymer using visible light dynamic mask micro-stereolithography/micromolding and loaded with miconazole using a piezoelectric inkjet printer. The miconazole-coated microneedles showed biodegradation and antifungal activity against the organism Candida albicans (ATCC 90028) on Sabouraud dextrose agar using an in vitro agar plating method. The results of this study demonstrate that piezoelectric inkjet printing may be used load microneedles and other drug delivery devices with pharmacologic agents. Miconazole-loaded microneedles prepared by the visible light dynamic mask micro-stereolithography–micromolding–piezoelectric inkjet printing approach have potential use in transdermal treatment of cutaneous fungal infections.}, number={5}, journal={MATERIALS TODAY}, author={Boehm, Ryan D. and Miller, Philip R. and Daniels, Justin and Stafslien, Shane and Narayan, Roger J.}, year={2014}, month={Jun}, pages={247–252} }
 @article{miller_xiao_brener_burckel_narayan_polsky_2014, title={Microneedle-Based Transdermal Sensor for On-Chip Potentiometric Determination of K+}, volume={3}, ISSN={["2192-2659"]}, DOI={10.1002/adhm.201300541}, abstractNote={The determination of electrolytes is invaluable for point of care diagnostic applications. An ion selective transdermal microneedle sensor is demonstrated for potassium by integrating a hollow microneedle with a microfluidic chip to extract fluid through a channel towards a downstream solid‐state ion‐selective‐electrode (ISE). 3D porous carbon and 3D porous graphene electrodes, made via interference lithography, are compared as solid‐state transducers for ISE's and evaluated for electrochemical performance, stability, and selectivity. The porous carbon K+ ISE's show better performance than the porous graphene K+ ISE's, capable of measuring potassium across normal physiological concentrations in the presence of interfering ions with greater stability. This new microfluidic/microneedle platform shows promise for medical applications.}, number={6}, journal={ADVANCED HEALTHCARE MATERIALS}, author={Miller, Philip R. and Xiao, Xiaoyin and Brener, Igal and Burckel, D. Bruce and Narayan, Roger and Polsky, Ronen}, year={2014}, month={Jun}, pages={876–881} }
 @article{valdés-ramírez_li_kim_jia_bandodkar_nuñez-flores_miller_wu_narayan_windmiller_et al._2014, title={Microneedle-based self-powered glucose sensor}, volume={47}, ISSN={1388-2481}, url={http://dx.doi.org/10.1016/j.elecom.2014.07.014}, DOI={10.1016/j.elecom.2014.07.014}, abstractNote={A microneedle-based self-powered biofuel-cell glucose sensor is described. The biofuel cell sensor makes use of the integration of modified carbon pastes into hollow microneedle devices. The system displays defined dependence of the power density vs glucose concentration in artificial interstitialfluid. An excellent selectivity against common electroactive interferences and long-term stability are obtained. The attractive performance of the device indicates considerable promise for subdermal glucose monitoring.}, journal={Electrochemistry Communications}, publisher={Elsevier BV}, author={Valdés-Ramírez, Gabriela and Li, Ya-Chieh and Kim, Jayoung and Jia, Wenzhao and Bandodkar, Amay J. and Nuñez-Flores, Rogelio and Miller, Philip R. and Wu, Shu-Yii and Narayan, Roger and Windmiller, Joshua R. and et al.}, year={2014}, month={Oct}, pages={58–62} }
 @article{xiao_miller_narayan_brozik_wheeler_brener_wang_burckel_polsky_2014, title={Simultaneous Detection of Dopamine, Ascorbic Acid and Uric Acid at Lithographically-Defined 3D Graphene Electrodes}, volume={26}, ISSN={["1521-4109"]}, DOI={10.1002/elan.201300253}, abstractNote={Abstract}, number={1}, journal={ELECTROANALYSIS}, author={Xiao, Xiaoyin and Miller, Philip R. and Narayan, Roger J. and Brozik, Susan M. and Wheeler, David R. and Brener, Igal and Wang, Joseph and Burckel, D. Bruce and Polsky, Ronen}, year={2014}, month={Jan}, pages={52–56} }
 @article{cristescu_popescu_dorcioman_miroiu_socol_mihailescu_gittard_miller_narayan_enculescu_et al._2013, title={Antimicrobial activity of biopolymer-antibiotic thin films fabricated by advanced pulsed laser methods}, volume={278}, ISSN={["0169-4332"]}, DOI={10.1016/j.apsusc.2013.01.062}, abstractNote={Abstract We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer–drug composite thin film systems. A pulsed KrF* excimer laser source ( λ  = 248 nm, τ  = 25 ns, ν  = 10 Hz) was used to deposit composite thin films of poly( d , l -lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA–gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer–drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces.}, journal={APPLIED SURFACE SCIENCE}, author={Cristescu, R. and Popescu, C. and Dorcioman, G. and Miroiu, F. M. and Socol, G. and Mihailescu, I. N. and Gittard, S. D. and Miller, P. R. and Narayan, R. J. and Enculescu, M. and et al.}, year={2013}, month={Aug}, pages={211–213} }
 @article{boehm_miller_schell_perfect_narayan_2013, title={Inkjet Printing of Amphotericin B onto Biodegradable Microneedles Using Piezoelectric Inkjet Printing}, volume={65}, ISSN={["1543-1851"]}, DOI={10.1007/s11837-013-0574-7}, number={4}, journal={JOM}, author={Boehm, Ryan D. and Miller, Philip R. and Schell, Wiley A. and Perfect, John R. and Narayan, Roger J.}, year={2013}, month={Apr}, pages={525–533} }
 @article{boehm_miller_singh_shah_stafslien_daniels_narayan_2012, title={Indirect rapid prototyping of antibacterial acid anhydride copolymer microneedles}, volume={4}, ISSN={["1758-5082"]}, DOI={10.1088/1758-5082/4/1/011002}, abstractNote={Microneedles are needle-like projections with microscale features that may be used for transdermal delivery of a variety of pharmacologic agents, including antibacterial agents. In the study described in this paper, an indirect rapid prototyping approach involving a combination of visible light dynamic mask micro-stereolithography and micromolding was used to prepare microneedle arrays out of a biodegradable acid anhydride copolymer, Gantrez® AN 169 BF. Fourier transform infrared spectroscopy, energy dispersive x-ray spectrometry and nanoindentation studies were performed to evaluate the chemical and mechanical properties of the Gantrez® AN 169 BF material. Agar plating studies were used to evaluate the in vitro antimicrobial performance of these arrays against Bacillus subtilis, Candida albicans, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Large zones of growth inhibition were noted for Escherichia coli, S. aureus, Enterococcus faecalis and B. subtilis. The performance of Gantrez® AN 169 BF against several bacteria suggests that biodegradable acid anhydride copolymer microneedle arrays prepared using visible light dynamic mask micro-stereolithography micromolding may be useful for treating a variety of skin infections.}, number={1}, journal={BIOFABRICATION}, author={Boehm, Ryan D. and Miller, Philip R. and Singh, Ritika and Shah, Akash and Stafslien, Shane and Daniels, Justin and Narayan, Roger J.}, year={2012}, month={Mar} }
 @article{miller_skoog_edwards_lopez_wheeler_arango_xiao_brozik_wang_polsky_et al._2012, title={Multiplexed microneedle-based biosensor array for characterization of metabolic acidosis}, volume={88}, ISSN={["1873-3573"]}, DOI={10.1016/j.talanta.2011.11.046}, abstractNote={The development of a microneedle-based biosensor array for multiplexed in situ detection of exercise-induced metabolic acidosis, tumor microenvironment, and other variations in tissue chemistry is described. Simultaneous and selective amperometric detection of pH, glucose, and lactate over a range of physiologically relevant concentrations in complex media is demonstrated. Furthermore, materials modified with a cell-resistant (Lipidure®) coating were shown to inhibit macrophage adhesion; no signs of coating delamination were noted over a 48-h period.}, journal={TALANTA}, author={Miller, Philip R. and Skoog, Shelby A. and Edwards, Thayne L. and Lopez, Deanna M. and Wheeler, David R. and Arango, Dulce C. and Xiao, Xiaoyin and Brozik, Susan M. and Wang, Joseph and Polsky, Ronen and et al.}, year={2012}, month={Jan}, pages={739–742} }
 @article{cristescu_popescu_socol_visan_mihailescu_gittard_miller_martin_narayan_andronie_et al._2011, title={Deposition of antibacterial of poly(1,3-bis-(p-carboxyphenoxy propane)-co-(sebacic anhydride)) 20:80/gentamicin sulfate composite coatings by MAPLE}, volume={257}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2010.11.141}, abstractNote={We report on thin film deposition of poly(1,3-bis-(p-carboxyphenoxy propane)-co-sebacic anhydride)) 20:80 thin films containing several gentamicin concentrations by matrix assisted pulsed laser evaporation (MAPLE). A pulsed KrF* excimer laser was used to deposit the polymer–drug composite thin films. Release of gentamicin from these MAPLE-deposited polymer conjugate structures was assessed. Fourier transform infrared spectroscopy was used to demonstrate that the functional groups of the MAPLE-transferred materials were not changed by the deposition process nor were new functional groups formed. Scanning electron microscopy confirmed that MAPLE may be used to fabricate thin films of good morphological quality. The activity of gentamicin-doped films against Escherichia coli and Staphylococcus aureus bacteria was demonstrated using disk diffusion and antibacterial drop test. Our studies indicate that deposition of polymer–drug composite thin films prepared by MAPLE is a suitable technique for performing controlled drug delivery. Antimicrobial thin film coatings have several medical applications, including use for indwelling catheters and implanted medical devices.}, number={12}, journal={APPLIED SURFACE SCIENCE}, author={Cristescu, R. and Popescu, C. and Socol, G. and Visan, A. and Mihailescu, I. N. and Gittard, S. D. and Miller, P. R. and Martin, T. N. and Narayan, R. J. and Andronie, A. and et al.}, year={2011}, month={Apr}, pages={5287–5292} }
 @article{gittard_miller_jin_martin_boehm_chisholm_stafslien_daniels_cilz_monteiro-riviere_et al._2011, title={Deposition of antimicrobial coatings on microstereolithography-fabricated microneedles}, volume={63}, ISSN={["1543-1851"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000291610800011&KeyUID=WOS:000291610800011}, DOI={10.1007/s11837-011-0093-3}, number={6}, journal={JOM}, author={Gittard, Shaun D. and Miller, Philip R. and Jin, Chunming and Martin, Timothy N. and Boehm, Ryan D. and Chisholm, Bret J. and Stafslien, Shane J. and Daniels, Justin W. and Cilz, Nicholas and Monteiro-Riviere, Nancy A. and et al.}, year={2011}, month={Jun}, pages={59–68} }
 @article{windmiller_zhou_chuang_valdes-ramirez_santhosh_miller_narayan_wang_2011, title={Microneedle array-based carbon paste amperometric sensors and biosensors}, volume={136}, ISSN={["0003-2654"]}, DOI={10.1039/c1an00012h}, abstractNote={The design and characterization of a microneedle array-based carbon paste electrode towards minimally invasive electrochemical sensing are described. Arrays consisting of 3 × 3 pyramidal microneedle structures, each with an opening of 425 µm, were loaded with a metallized carbon paste transducer. The renewable nature of carbon paste electrodes enables the convenient packing of hollow non-planar microneedles with pastes that contain assorted catalysts and biocatalysts. Smoothing the surface results in good microelectrode-to-microelectrode uniformity. Optical and scanning electron micrographs shed useful insights into the surface morphology at the microneedle apertures. The attractive performance of the novel microneedle electrode arrays is illustrated in vitro for the low-potential detection of hydrogen peroxide at rhodium-dispersed carbon paste microneedles and for lactate biosensing by the inclusion of lactate oxidase in the metallized carbon paste matrix. Highly repeatable sensing is observed following consecutive cycles of packing/unpacking the carbon paste. The operational stability of the array is demonstrated as well as the interference-free detection of lactate in the presence of physiologically relevant levels of ascorbic acid, uric acid, and acetaminophen. Upon addressing the biofouling effects associated with on-body sensing, the microneedle carbon paste platform would be attractive for the subcutaneous electrochemical monitoring of a number of physiologically relevant analytes.}, number={9}, journal={ANALYST}, author={Windmiller, Joshua Ray and Zhou, Nandi and Chuang, Min-Chieh and Valdes-Ramirez, Gabriela and Santhosh, Padmanabhan and Miller, Philip R. and Narayan, Roger and Wang, Joseph}, year={2011}, pages={1846–1851} }
 @article{boehm_miller_hayes_monteiro-riviere_narayan_2011, title={Modification of microneedles using inkjet printing}, volume={1}, ISSN={2158-3226}, url={http://dx.doi.org/10.1063/1.3602461}, DOI={10.1063/1.3602461}, abstractNote={In this study, biodegradable acid anhydride copolymer microneedles containing quantum dots were fabricated by means of visible light dynamic mask micro-stereolithography-micromolding and inkjet printing. Nanoindentation was performed to obtain the hardness and the Young's modulus of the biodegradable acid anhydride copolymer. Imaging of quantum dots within porcine skin was accomplished by means of multiphoton microscopy. Our results suggest that the combination of visible light dynamic mask micro-stereolithography-micromolding and inkjet printing enables fabrication of solid biodegradable microneedles with a wide range of geometries as well as a wide range of pharmacologic agent compositions.}, number={2}, journal={AIP Advances}, publisher={AIP Publishing}, author={Boehm, R D and Miller, P R and Hayes, S L and Monteiro-Riviere, N A and Narayan, R J}, year={2011}, pages={022139} }
 @article{gittard_miller_boehm_ovsianikov_chichkov_heiser_gordon_monteiro-riviere_narayan_2011, title={Multiphoton microscopy of transdermal quantum dot delivery using two photon polymerization-fabricated polymer microneedles}, volume={149}, ISSN={["1364-5498"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000285924900015&KeyUID=WOS:000285924900015}, DOI={10.1039/c005374k}, abstractNote={Due to their ability to serve as fluorophores and drug delivery vehicles, quantum dots are a powerful tool for theranostics-based clinical applications. In this study, microneedle devices for transdermal drug delivery were fabricated by means of two-photon polymerization of an acrylate-based polymer. We examined proliferation of cells on this polymer using neonatal human epidermal keratinocytes and human dermal fibroblasts. The microneedle device was used to inject quantum dots into porcine skin; imaging of the quantum dots was performed using multiphoton microscopy.}, journal={FARADAY DISCUSSIONS}, author={Gittard, Shaun D. and Miller, Philip R. and Boehm, Ryan D. and Ovsianikov, Aleksandr and Chichkov, Boris N. and Heiser, Jeremy and Gordon, John and Monteiro-Riviere, Nancy A. and Narayan, Roger J.}, year={2011}, pages={171–185} }
 @article{koroleva_schlie_fadeeva_gittard_miller_ovsianikov_koch_narayan_chichkov_2010, title={Microreplication of laser-fabricated surface and three-dimensional structures}, volume={12}, ISSN={["2040-8986"]}, DOI={10.1088/2040-8978/12/12/124009}, abstractNote={The fabrication of defined surface topographies and three-dimensional structures is a challenging process for various applications, e.g. in photonics and biomedicine. Laser-based technologies provide a promising approach for the production of such structures. The advantages of femtosecond laser ablation and two-photon polymerization for microstructuring are well known. However, these methods cannot be applied to all materials and are limited by their high cost and long production time. In this study, biomedical applications of an indirect rapid prototyping, molding microreplication of laser-fabricated two- and three-dimensional structures are examined. We demonstrate that by this method any laser-generated surface topography as well as three-dimensional structures can be replicated in various materials without losing the original geometry. The replication into multiple copies enables fast and perfect reproducibility of original microstructures for investigations of cell–surface interactions. Compared to unstructured materials, we observe that microstructures have strong influence on morphology and localization of fibroblasts, whereas neuroblastoma cells are not negatively affected.}, number={12}, journal={JOURNAL OF OPTICS}, author={Koroleva, Anastasia and Schlie, Sabrina and Fadeeva, Elena and Gittard, Shaun D. and Miller, Philip and Ovsianikov, Aleksandr and Koch, Juergen and Narayan, Roger J. and Chichkov, Boris N.}, year={2010}, month={Dec} }
 @article{miller_aggarwal_doraiswamy_lin_lee_narayan_2009, title={Laser micromachining for biomedical applications}, volume={61}, ISSN={["1047-4838"]}, DOI={10.1007/s11837-009-0130-7}, number={9}, journal={JOM}, author={Miller, Philip R. and Aggarwal, Ravi and Doraiswamy, Anand and Lin, Yi Jen and Lee, Yuan-Shin and Narayan, Roger J.}, year={2009}, month={Sep}, pages={35–40} }