Recent Advances in Paper-Based Analytical Devices: A Pivotal Step Forward in Building Next-Generation Sensor Technology

  • Charu Agarwal
  • Levente CsókaEmail author


Of late, the paper has attracted the significant attention of researchers as a substrate for sensing devices. Paper is a fibrous network of cellulose, a ubiquitous biopolymer, which is fast emerging as a sustainable raw material and replacing the non-renewable ones. Paper possesses many striking features such as hydrophilicity and low-cost, which make it an excellent choice for sensing platforms. Paper-based sensing devices are flexible, foldable, portable, economical, user-friendly and disposable. Recently, numerous works have reported the use of paper substrates for sensor fabrication in the fields of biomedical health care, environmental analysis, food and water quality, and forensics. The current chapter aims to present a concise overview of the recent developments in the area of paper-based sensing, particularly in the ongoing decade. It briefly discusses the sensing approach for the detection of various analytes and focuses on their applications in various sectors.


Paper-based sensing devices Biomedical Environmental Food safety Colorimetric Electrochemical Luminescence SERS 

List of Abbreviations


Microfluidic paper-based analytical devices




2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)


Alternating current voltammetry






Alkyl ketene dimer


Absorbent pad


Biogenic amines


Boron-doped diamond electrode




Bisphenol A


Carcinoma antigen 125


Carcinoma antigen 199


Carbon black


Carbohydrate binding molecule


Carcinoembryonic antigen


Colony forming units


Carbon nanocrystals


Chlorophenol red β-galactopyranoside


Cyanine 3








Enhanced green fluorescent protein


Enzyme linked immunosorbent assay


Förster resonance energy transfer




Gold nanoparticles


Gold nanorods


Graphene oxide


Glucose oxidase


Graphene quantum dots


Human papillomavirus


Horseradish peroxidase


Immunoglobulin G


Lateral flow immunoassay


Luminescence resonance energy transfer


Localized surface plasmon resonance


Micro-electro-mechanical systems


Molecularly imprinted polymers


Magnetic nanoparticles




Sodium 1,2-naphthoquinone-4-sulfonate


O-toluidine blue




Prussian blue


Phosphate buffered saline




Parylene C-coated paper














Quantum dots






Reduced graphene oxide




Scanning electron micrographs


Surface-enhanced Raman spectroscopy


Sample pad


Screen-printed carbon electrode


Square wave voltammetry


Thioctic acid


Tetrabromophenol blue








5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetraiodide










World health organization



CA is grateful to the Tempus Public Foundation (TPF) for providing financial assistance under the Stipendium Hungaricum Programme. This chapter was also made in frame of the “EFOP-3.6.1-16-2016-00018—Improving the role of research + development + innovation in the higher education through institutional developments assisting intelligent specialization in Sopron and Szombathely.”


  1. 1.
    Nayak S, Blumenfeld NR, Laksanasopin T, Sia SK (2017) Point-of-care diagnostics: recent developments in a connected age. Anal Chem 89:102–123CrossRefGoogle Scholar
  2. 2.
    Gong MM, Sinton D (2017) Turning the page: advancing paper-based microfluidics for broad diagnostic application. Chem Rev 117:8447–8480CrossRefGoogle Scholar
  3. 3.
    Sher M, Zhuang R, Demirci U, Asghar W (2017) Paper-based analytical devices for clinical diagnosis: recent advances in the fabrication techniques and sensing mechanisms. Expert Rev Mol Diagn 17:351–366CrossRefGoogle Scholar
  4. 4.
    Zarei M (2017) Portable biosensing devices for point-of-care diagnostics: recent developments and applications. Trends Anal Chem 91:26–41CrossRefGoogle Scholar
  5. 5.
    Martinez AW (2011) Microfluidic paper-based analytical devices: from POCKET to paper-based ELISA. Bioanalysis 3:2589–2592CrossRefGoogle Scholar
  6. 6.
    Martinez AW, Phillips ST, Whitesides GM, Carrilho E (2010) Diagnostics for the developing world: Microfluidic paper-based analytical devices. Anal Chem 82:3–10CrossRefGoogle Scholar
  7. 7.
    Morbioli GG, Mazzu-Nascimento T, Stockton AM, Carrilho E (2017) Technical aspects and challenges of colorimetric detection with microfluidic paper-based analytical devices (mPADs)—a review. Anal Chim Acta 970:1–22CrossRefGoogle Scholar
  8. 8.
    Tseng SC et al (2012) Eco-friendly plasmonic sensors: using the photothermal effect to prepare metal nanoparticle-containing test papers for highly sensitive colorimetric detection. Anal Chem 84:5140–5145CrossRefGoogle Scholar
  9. 9.
    Tao H et al (2011) Metamaterials on paper as a sensing platform. Adv Mater 23:3197–3201CrossRefGoogle Scholar
  10. 10.
    Martinez AW, Phillips ST, Butte MJ, Whitesides GM (2007) Patterned paper as a platform for inexpensive, low-volume, portable bioassays. Angew Chem Int Ed 46:1318–1320CrossRefGoogle Scholar
  11. 11.
    Parolo C, Merkoci A (2013) Paper-based nanobiosensors for diagnostics. Chem Soc Rev 42:450–457CrossRefGoogle Scholar
  12. 12.
    Ge S, Zhang L, Zhang Y, Lan F, Yan M, Yu J (2017) Nanomaterials-modified cellulose paper as a platform for biosensing applications. Nanoscale 9:4366–4382CrossRefGoogle Scholar
  13. 13.
    Alvarez-Diduk R, Orozco J, Merkoci A (2017) Paper strip-embedded graphene quantum dots: a screening device with a smartphone readout. Sci Rep 7:976–984CrossRefGoogle Scholar
  14. 14.
    Carrasquilla C, Little JR, Li Y, Brennan JD (2015) Patterned paper sensors printed with long-chain DNA aptamers. Chemistry 21:7369–7373CrossRefGoogle Scholar
  15. 15.
    Rat S et al (2016) Elastic coupling between spin-crossover particles and cellulose fibers. Chem Commun 52:11267–11269CrossRefGoogle Scholar
  16. 16.
    Lim WY, Goh BT, Khor SM (2017) Microfluidic paper-based analytical devices for potential use in quantitative and direct detection of disease biomarkers in clinical analysis. J Chromatogr B 1060:424–442CrossRefGoogle Scholar
  17. 17.
    Mahato K, Srivastava A, Chandra P (2017) Paper based diagnostics for personalized health care: emerging technologies and commercial aspects. Biosens Bioelectron 96:246–259CrossRefGoogle Scholar
  18. 18.
    Wang S, Chinnasamy T, Lifson MA, Inci F, Demirci U (2016) Flexible substrate-based devices for point-of-care diagnostics. Trends Biotechnol 34:909–921CrossRefGoogle Scholar
  19. 19.
    Meredith NA, Quinn C, Cate DM, Reilly TH 3rd, Volckens J, Henry CS (2016) Paper-based analytical devices for environmental analysis. Analyst 141:1874–1887CrossRefGoogle Scholar
  20. 20.
    Bulbul G, Hayat A, Andreescu S (2015) Portable nanoparticle-based sensors for food safety assessment. Sensors 15:30736–30758CrossRefGoogle Scholar
  21. 21.
    Hua M, Li S, Wang S, Lu X (2018) Detecting chemical hazards in foods using microfluidic paper-based analytical devices (μPADs): The real-world application. Micromachines 9:32–45CrossRefGoogle Scholar
  22. 22.
    Ansari N, Lodha A, Pandya A, Menon SK (2017) Determination of cause of death using paper-based microfluidic device as a colorimetric probe. Anal Methods 9:5632–5639CrossRefGoogle Scholar
  23. 23.
    Song Y, Gyarmati P, Araujo AC, Lundeberg J, Brumer H 3rd, Stahl PL (2014) Visual detection of DNA on paper chips. Anal Chem 86:1575–1582CrossRefGoogle Scholar
  24. 24.
    Ge S, Zhang L, Zhang Y, Liu H, Huang J, Yan M, Yu J (2015) Electrochemical K-562 cells sensor based on origami paper device for point-of-care testing. Talanta 145:12–19CrossRefGoogle Scholar
  25. 25.
    Nilghaz A, Guan L, Tan W, Shen W (2016) Advances of paper-based microfluidics for diagnostics—the original motivation and current status. ACS Sens 1:1382–1393CrossRefGoogle Scholar
  26. 26.
    Yamada K, Shibata H, Suzuki K, Citterio D (2017) Toward practical application of paper-based microfluidics for medical diagnostics: state-of-the-art and challenges. Lab Chip 17:1206–1249CrossRefGoogle Scholar
  27. 27.
    Tao X, Jia H, He Y, Liao S, Wang Y (2017) Ultrafast paper thermometers based on a green sensing ink. ACS Sens 2:449–454CrossRefGoogle Scholar
  28. 28.
    Yang J, Kwak TJ, Zhang X, McClain R, Chang WJ, Gunasekaran S (2016) Iridium oxide-reduced graphene oxide nanohybrid thin film modified screen-printed electrodes as disposable electrochemical paper microfluidic pH sensors. J Vis Exp 117:e53339–e53345Google Scholar
  29. 29.
    Balde M, Vena A, Sorli B (2015) Fabrication of porous anodic aluminium oxide layers on paper for humidity sensors. Sens Actuators B Chem 220:829–839CrossRefGoogle Scholar
  30. 30.
    Yuan Y, Zhang Y, Liu R, Liu J, Li Z, Liu X (2016) Humidity sensor fabricated by inkjet-printing photosensitive conductive inks PEDOT:PVMA on a paper substrate. RSC Adv 6:47498–47508CrossRefGoogle Scholar
  31. 31.
    Koren K, Kühl M (2015) A simple laminated paper-based sensor for temperature sensing and imaging. Sens Actuators B Chem 210:124–128CrossRefGoogle Scholar
  32. 32.
    Nagy V et al (2014) Cellulose fiber nanocomposites displaying spin-crossover properties. Colloids Surf A Physicochem Eng Asp 456:35–40CrossRefGoogle Scholar
  33. 33.
    Nagy V, Suleimanov I, Molnár G, Salmon L, Bousseksou A, Csóka L (2015) Cellulose–spin crossover particle composite papers with reverse printing performance: a proof of concept. J Mater Chem C 3:7897–7905CrossRefGoogle Scholar
  34. 34.
    Zhao H, Zhang T, Qi R, Dai J, Liu S, Fei T (2017) Drawn on paper: a reproducible humidity sensitive device by handwriting. ACS Appl Mater Interfaces 9:28002–28009CrossRefGoogle Scholar
  35. 35.
    Lopez-Ruiz N, Curto VF, Erenas MM, Benito-Lopez F, Diamond D, Palma AJ, Capitan-Vallvey LF (2014) Smartphone-based simultaneous pH and nitrite colorimetric determination for paper microfluidic devices. Anal Chem 86:9554–9562CrossRefGoogle Scholar
  36. 36.
    Lee C-Y, Lei KF, Tsai S-W, Tsang N-M (2016) Development of graphene-based sensors on paper substrate for the measurement of pH value of analyte. BioChip J 10:182–188CrossRefGoogle Scholar
  37. 37.
    Liu X, Mwangi M, Li X, O’Brien M, Whitesides GM (2011) Paper-based piezoresistive MEMS sensors. Lab Chip 11:2189–2196CrossRefGoogle Scholar
  38. 38.
    Lee J, Lee YJ, Ahn YJ, Choi S, Lee G-J (2018) A simple and facile paper-based colorimetric assay for detection of free hydrogen sulfide in prostate cancer cells. Sens Actuators B Chem 256:828–834CrossRefGoogle Scholar
  39. 39.
    Silva TG, de Araujo WR, Munoz RA, Richter EM, Santana MH, Coltro WK, Paixao TR (2016) Simple and sensitive paper-based device coupling electrochemical sample pretreatment and colorimetric detection. Anal Chem 88:5145–5151CrossRefGoogle Scholar
  40. 40.
    Cha R, Wang D, He Z, Ni Y (2012) Development of cellulose paper testing strips for quick measurement of glucose using chromogen agent. Carbohydr Polym 88:1414–1419CrossRefGoogle Scholar
  41. 41.
    Yamada K, Suzuki K, Citterio D (2017) Text-displaying colorimetric paper-based analytical device. ACS Sens 2:1247–1254CrossRefGoogle Scholar
  42. 42.
    Chen X, Chen J, Wang F, Xiang X, Luo M, Ji X, He Z (2012) Determination of glucose and uric acid with bienzyme colorimetry on microfluidic paper-based analysis devices. Biosens Bioelectron 35:363–368CrossRefGoogle Scholar
  43. 43.
    Chan SK, Lim TS (2016) A straw-housed paper-based colorimetric antibody–antigen sensor. Anal Methods 8:1431–1436CrossRefGoogle Scholar
  44. 44.
    Costa MN et al (2014) A low cost, safe, disposable, rapid and self-sustainable paper-based platform for diagnostic testing: lab-on-paper. Nanotechnology 25:094006–094017CrossRefGoogle Scholar
  45. 45.
    Tian T et al (2016) Integration of target responsive hydrogel with cascaded enzymatic reactions and microfluidic paper-based analytic devices (mPADs) for point-of-care testing (POCT). Biosens Bioelectron 77:537–542CrossRefGoogle Scholar
  46. 46.
    Wei X et al (2016) Microfluidic distance readout sweet hydrogel integrated paper-based analytical device (µDiSH-PAD) for visual quantitative point-of-care testing. Anal Chem 88:2345–2352CrossRefGoogle Scholar
  47. 47.
    Wei X et al (2015) Target-responsive DNA hydrogel mediated “stop-flow” microfluidic paper-based analytic device for rapid, portable and visual detection of multiple targets. Anal Chem 87:4275–4282CrossRefGoogle Scholar
  48. 48.
    Zhang Y et al (2016) Naked-eye quantitative aptamer-based assay on paper device. Biosens Bioelectron 78:538–546CrossRefGoogle Scholar
  49. 49.
    Santhiago M, Kubota LT (2013) A new approach for paper-based analytical devices with electrochemical detection based on graphite pencil electrodes. Sens Actuators B Chem 177:224–230CrossRefGoogle Scholar
  50. 50.
    Yao Y, Zhang C (2016) A novel screen-printed microfluidic paper-based electrochemical device for detection of glucose and uric acid in urine. Biomed Microdevices 18:92–100CrossRefGoogle Scholar
  51. 51.
    Narang J et al (2017) Lab on paper chip integrated with Si@GNRs for electroanalysis of diazepam. Anal Chim Acta 980:50–57CrossRefGoogle Scholar
  52. 52.
    Narang J, Malhotra N, Singhal C, Mathur A, Chakraborty D, Ingle A, Pundir CS (2017) Point of care with micro fluidic paper based device incorporated with nanocrys of Zeolite–GO for electrochemical sensing of date rape drug. Proc Technol 27:91–93CrossRefGoogle Scholar
  53. 53.
    Wang P, Ge L, Yan M, Song X, Ge S, Yu J (2012) Paper-based three-dimensional electrochemical immunodevice based on multi-walled carbon nanotubes functionalized paper for sensitive point-of-care testing. Biosens Bioelectron 32:238–243CrossRefGoogle Scholar
  54. 54.
    Teengam P, Siangproh W, Tuantranont A, Henry CS, Vilaivan T, Chailapakul O (2017) Electrochemical paper-based peptide nucleic acid biosensor for detecting human papillomavirus. Anal Chim Acta 952:32–40CrossRefGoogle Scholar
  55. 55.
    Wang Y et al (2016) A novel label-free microfluidic paper-based immunosensor for highly sensitive electrochemical detection of carcinoembryonic antigen. Biosens Bioelectron 83:319–326CrossRefGoogle Scholar
  56. 56.
    Kumar S et al (2015) Reduced graphene oxide modified smart conducting paper for cancer biosensor. Biosens Bioelectron 73:114–122CrossRefGoogle Scholar
  57. 57.
    Scida K, Cunningham JC, Renault C, Richards I, Crooks RM (2014) Simple, sensitive, and quantitative electrochemical detection method for paper analytical devices. Anal Chem 86:6501–6507CrossRefGoogle Scholar
  58. 58.
    Wang CC et al (2016) A paper-based “pop-up” electrochemical device for analysis of beta-hydroxybutyrate. Anal Chem 88:6326–6333CrossRefGoogle Scholar
  59. 59.
    Jagadeesan KK, Kumar S, Sumana G (2012) Application of conducting paper for selective detection of troponin. Electrochem Commun 20:71–74CrossRefGoogle Scholar
  60. 60.
    Yang M et al (2016) Flexible and disposable sensing platforms based on newspaper. ACS Appl Mater Interfaces 8:34978–34984CrossRefGoogle Scholar
  61. 61.
    Cunningham JC, Brenes NJ, Crooks RM (2014) Paper electrochemical device for detection of DNA and thrombin by target-induced conformational switching. Anal Chem 86:6166–6170CrossRefGoogle Scholar
  62. 62.
    Mirasoli M, Guardigli M, Michelini E, Roda A (2014) Recent advancements in chemical luminescence-based lab-on-chip and microfluidic platforms for bioanalysis. J Pharm Biomed Anal 87:36–52CrossRefGoogle Scholar
  63. 63.
    Liu W, Luo J, Guo Y, Kou J, Li B, Zhang Z (2014) Nanoparticle coated paper-based chemiluminescence device for the determination of L-cysteine. Talanta 120:336–341CrossRefGoogle Scholar
  64. 64.
    Liu F, Zhang C (2015) A novel paper-based microfluidic enhanced chemiluminescence biosensor for facile, reliable and highly-sensitive gene detection of Listeria monocytogenes. Sens Actuators B Chem 209:399–406CrossRefGoogle Scholar
  65. 65.
    Zhao M, Li H, Liu W, Guo Y, Chu W (2016) Plasma treatment of paper for protein immobilization on paper-based chemiluminescence immunodevice. Biosens Bioelectron 79:581–588CrossRefGoogle Scholar
  66. 66.
    Liu W, Cassano CL, Xu X, Fan ZH (2013) Laminated paper-based analytical devices (LPAD) with origami-enabled chemiluminescence immunoassay for cotinine detection in mouse serum. Anal Chem 85:10270–10276CrossRefGoogle Scholar
  67. 67.
    Chen Y, Wang J, Liu Z, Wang X, Li X, Shan G (2018) A simple and versatile paper-based electrochemiluminescence biosensing platform for hepatitis B virus surface antigen detection. Biochem Eng J 129:1–6CrossRefGoogle Scholar
  68. 68.
    Ge L, Yan J, Song X, Yan M, Ge S, Yu J (2012) Three-dimensional paper-based electrochemiluminescence immunodevice for multiplexed measurement of biomarkers and point-of-care testing. Biomaterials 33:1024–1031CrossRefGoogle Scholar
  69. 69.
    Ge S, Liang L, Lan F, Zhang Y, Wang Y, Yan M, Yu J (2016) Photoelectrochemical immunoassay based on chemiluminescence as internal excited light source. Sens Actuators B Chem 234:324–331CrossRefGoogle Scholar
  70. 70.
    Shi L, Li L, Li X, Zhang G, Zhang Y, Dong C, Shuang S (2017) Excitation-independent yellow-fluorescent nitrogen-doped carbon nanodots for biological imaging and paper-based sensing. Sens Actuators B Chem 251:234–241CrossRefGoogle Scholar
  71. 71.
    Cai Y, You J, You Z, Dong F, Du S, Zhang L (2018) Profuse color-evolution-based fluorescent test paper sensor for rapid and visual monitoring of endogenous Cu2+ in human urine. Biosens Bioelectron 99:332–337CrossRefGoogle Scholar
  72. 72.
    Samanta S, Halder S, Dey P, Manna U, Ramesh A, Das G (2018) A ratiometric fluorogenic probe for the real-time detection of SO32− in aqueous medium: Application in a cellulose paper based device and potential to sense SO32− in mitochondria. Analyst 143:250–257CrossRefGoogle Scholar
  73. 73.
    Thom NK, Lewis GG, Yeung K, Phillips ST (2014) Quantitative fluorescence assays using a self-powered paper-based microfluidic device and a camera-equipped cellular phone. RSC Adv 4:1334–1340CrossRefGoogle Scholar
  74. 74.
    Mei Q, Zhang Z (2012) Photoluminescent graphene oxide ink to print sensors onto microporous membranes for versatile visualization bioassays. Angew Chem Int Ed 51:5602–5606CrossRefGoogle Scholar
  75. 75.
    Derikvand F, Yin DT, Barrett R, Brumer H (2016) Cellulose-based biosensors for esterase detection. Anal Chem 88:2989–2993CrossRefGoogle Scholar
  76. 76.
    Li B, Zhou X, Liu H, Deng H, Huang R, Xing D (2018a) Simultaneous detection of antibiotic resistance genes on paper-based chip using [Ru(phen)2dppz]2+ turn-on fluorescence probe. ACS Appl Mater Interfaces. Scholar
  77. 77.
    Rosa AM, Louro AF, Martins SA, Inacio J, Azevedo AM, Prazeres DM (2014) Capture and detection of DNA hybrids on paper via the anchoring of antibodies with fusions of carbohydrate binding modules and ZZ-domains. Anal Chem 86:4340–4347CrossRefGoogle Scholar
  78. 78.
    Wang Y, Wang S, Ge S, Wang S, Yan M, Zang D, Yu J (2013) Facile and sensitive paper-based chemiluminescence DNA biosensor using carbon dots dotted nanoporous gold signal amplification label. Anal Methods 5:1328–1336CrossRefGoogle Scholar
  79. 79.
    Zhou F, Noor MO, Krull UJ (2014) Luminescence resonance energy transfer-based nucleic acid hybridization assay on cellulose paper with upconverting phosphor as donors. Anal Chem 86:2719–2726CrossRefGoogle Scholar
  80. 80.
    Oliveira MJ et al (2017) Office paper decorated with silver nanostars—an alternative cost effective platform for trace analyte detection by SERS. Sci Rep 7:2480–2493CrossRefGoogle Scholar
  81. 81.
    Hu SW, Qiao S, Pan JB, Kang B, Xu JJ, Chen HY (2018) A paper-based SERS test strip for quantitative detection of Mucin-1 in whole blood. Talanta 179:9–14CrossRefGoogle Scholar
  82. 82.
    Abbas A, Brimer A, Slocik JM, Tian L, Naik RR, Singamaneni S (2013) Multifunctional analytical platform on a paper strip: separation, preconcentration, and subattomolar detection. Anal Chem 85:3977–3983CrossRefGoogle Scholar
  83. 83.
    Banaei N, Foley A, Houghton JM, Sun Y, Kim B (2017) Multiplex detection of pancreatic cancer biomarkers using a SERS-based immunoassay. Nanotechnology 28:455101–455111CrossRefGoogle Scholar
  84. 84.
    Kim W-S, Shin J-H, Park H-K, Choi S (2016) A low-cost, monometallic, surface-enhanced Raman scattering-functionalized paper platform for spot-on bioassays. Sens Actuators B Chem 222:1112–1118CrossRefGoogle Scholar
  85. 85.
    Liu Q et al (2014) Paper-based plasmonic platform for sensitive, noninvasive, and rapid cancer screening. Biosens Bioelectron 54:128–134CrossRefGoogle Scholar
  86. 86.
    Ngo YH, Li D, Simon GP, Garnier G (2012) Gold nanoparticle-paper as a three-dimensional surface enhanced Raman scattering substrate. Langmuir 28:8782–8790CrossRefGoogle Scholar
  87. 87.
    Tadepalli S et al (2015) Peptide functionalized gold nanorods for the sensitive detection of a cardiac biomarker using plasmonic paper devices. Sci Rep 5:16206–16216CrossRefGoogle Scholar
  88. 88.
    Noor MO, Krull UJ (2014) Camera-based ratiometric fluorescence transduction of nucleic acid hybridization with reagentless signal amplification on a paper-based platform using immobilized quantum dots as donors. Anal Chem 86:10331–10339CrossRefGoogle Scholar
  89. 89.
    Liu X, Yang Y, Li Q, Wang Z, Xing X, Wang Y (2018c) Portably colorimetric paper sensor based on ZnS quantum dots for semi-quantitative detection of Co2+ through the measurement of grey level. Sens Actuators B Chem. Scholar
  90. 90.
    Dhavamani J, Mujawar LH, El-Shahawi MS (2018) Hand drawn paper-based optical assay plate for rapid and trace level determination of Ag+ in water. Sens Actuators B Chem 258:321–330CrossRefGoogle Scholar
  91. 91.
    Yakoh A, Rattanarat P, Siangproh W, Chailapakul O (2018) Simple and selective paper-based colorimetric sensor for determination of chloride ion in environmental samples using label-free silver nanoprisms. Talanta 178:134–140CrossRefGoogle Scholar
  92. 92.
    Chaiyo S, Siangproh W, Apilux A, Chailapakul O (2015) Highly selective and sensitive paper-based colorimetric sensor using thiosulfate catalytic etching of silver nanoplates for trace determination of copper ions. Anal Chim Acta 866:75–83CrossRefGoogle Scholar
  93. 93.
    Hossain SM, Brennan JD (2011) b-Galactosidase-based colorimetric paper sensor for determination of heavy metals. Anal Chem 83:8772–8778CrossRefGoogle Scholar
  94. 94.
    Giokas DL, Tsogas GZ, Vlessidis AG (2014) Programming fluid transport in paper-based microfluidic devices using razor-crafted open channels. Anal Chem 86:6202–6207CrossRefGoogle Scholar
  95. 95.
    Kappi FA, Tsogas GZ, Christodouleas DC, Giokas DL (2017) Calibrant-loaded paper-based analytical devices for standard addition quantitative assays. Sens Actuators B Chem 253:860–867CrossRefGoogle Scholar
  96. 96.
    Cuartero M, Crespo GA, Bakker E (2015) Paper-based thin-layer coulometric sensor for halide determination. Anal Chem 87:1981–1990CrossRefGoogle Scholar
  97. 97.
    Ruecha N, Chailapakul O, Suzuki K, Citterio D (2017) Fully inkjet-printed paper-based potentiometric ion-sensing devices. Anal Chem 89:10608–10616CrossRefGoogle Scholar
  98. 98.
    Yoon JH et al (2017) Fabrication of newspaper-based potentiometric platforms for flexible and disposable ion sensors. J Colloid Interface Sci 508:167–173CrossRefGoogle Scholar
  99. 99.
    Zor E, Alpaydin S, Arici A, Saglam ME, Bingol H (2018) Photoluminescent nanopaper-based microcuvette for iodide detection in seawater. Sens Actuators B Chem 254:1216–1224CrossRefGoogle Scholar
  100. 100.
    Chen PC, Li YC, Ma JY, Huang JY, Chen CF, Chang HT (2016) Size-tunable copper nanocluster aggregates and their application in hydrogen sulfide sensing on paper-based devices. Sci Rep 6:24882–24890CrossRefGoogle Scholar
  101. 101.
    Zhang M, Ge L, Ge S, Yan M, Yu J, Huang J, Liu S (2013) Three-dimensional paper-based electrochemiluminescence device for simultaneous detection of Pb2+ and Hg2+ based on potential-control technique. Biosens Bioelectron 41:544–550CrossRefGoogle Scholar
  102. 102.
    Prabphal J, Vilaivan T, Praneenararat T (2018) Fabrication of a paper-based turn-off fluorescence sensor for Cu2+ ion from a pyridinium porphyrin. ChemistrySelect 3:894–899CrossRefGoogle Scholar
  103. 103.
    Sun T, Niu Q, Li Y, Li T, Hu T, Wang E, Liu H (2018) A novel oligothiophene-based colorimetric and fluorescent “turn on” sensor for highly selective and sensitive detection of cyanide in aqueous media and its practical applications in water and food samples. Sens Actuators B Chem 258:64–71CrossRefGoogle Scholar
  104. 104.
    Li B, Zhang Z, Qi J, Zhou N, Qin S, Choo J, Chen L (2017) Quantum dot-based molecularly imprinted polymers on three-dimensional origami paper microfluidic chip for fluorescence detection of phycocyanin. ACS Sens 2:243–250CrossRefGoogle Scholar
  105. 105.
    Zhao H, Zang L, Wang L, Qin F, Zhang Z, Cao W (2015) Luminescence ratiometric oxygen sensor based on gadolinium labeled porphyrin and filter paper. Sens Actuators B Chem 215:405–411CrossRefGoogle Scholar
  106. 106.
    Kim Y, Jang G, Lee TS (2015) New fluorescent metal-ion detection using a paper-based sensor strip containing tethered rhodamine carbon nanodots. ACS Appl Mater Interfaces 7:15649–15657CrossRefGoogle Scholar
  107. 107.
    Lee M, Oh K, Choi HK, Lee SG, Youn HJ, Lee HL, Jeong DH (2018) Subnanomolar sensitivity of filter paper-based SERS sensor for pesticide detection by hydrophobicity change of paper surface. ACS Sens 3:151–159CrossRefGoogle Scholar
  108. 108.
    Lee J-C, Kim W, Choi S (2017) Fabrication of a SERS-encoded microfluidic paper-based analytical chip for the point-of-assay of wastewater. Int J Precis Eng Manuf-Green Tech 4:221–226CrossRefGoogle Scholar
  109. 109.
    Bharadwaj S, Pandey A, Yagci B, Ozguz V, Qureshi A (2018) Graphene nano-mesh-Ag-ZnO hybrid paper for sensitive SERS sensing and self-cleaning of organic pollutants. Chem Eng J 336:445–455CrossRefGoogle Scholar
  110. 110.
    Jokerst JC, Adkins JA, Bisha B, Mentele MM, Goodridge LD, Henry CS (2012) Development of a paper-based analytical device for colorimetric detection of select foodborne pathogens. Anal Chem 84:2900–2907CrossRefGoogle Scholar
  111. 111.
    Alhogail S, Suaifan G, Zourob M (2016) Rapid colorimetric sensing platform for the detection of Listeria monocytogenes foodborne pathogen. Biosens Bioelectron 86:1061–1066CrossRefGoogle Scholar
  112. 112.
    Hakovirta M, Aksoy B, Hakovirta J (2015) Self-assembled micro-structured sensors for food safety in paper based food packaging. Mater Sci Eng, C 53:331–335CrossRefGoogle Scholar
  113. 113.
    Swerin A, Mira I (2014) Ink-jettable paper-based sensor for charged macromolecules and surfactants. Sens Actuators B Chem 195:389–395CrossRefGoogle Scholar
  114. 114.
    Kong Q, Wang Y, Zhang L, Ge S, Yu J (2017) A novel microfluidic paper-based colorimetric sensor based on molecularly imprinted polymer membranes for highly selective and sensitive detection of bisphenol A. Sens Actuators B Chem 243:130–136CrossRefGoogle Scholar
  115. 115.
    Liu C-C, Wang Y-N, Fu L-M, Chen K-L (2018) Microfluidic paper-based chip platform for benzoic acid detection in food. Food Chem 249:162–167CrossRefGoogle Scholar
  116. 116.
    Ma L, Nilghaz A, Choi JR, Liu X, Lu X (2018) Rapid detection of clenbuterol in milk using microfluidic paper-based ELISA. Food Chem 246:437–441CrossRefGoogle Scholar
  117. 117.
    Gao N, Huang P, Wu F (2018) Colorimetric detection of melamine in milk based on Triton X-100 modified gold nanoparticles and its paper-based application. Spectrochim Acta A Mol Biomol Spectrosc 192:174–180CrossRefGoogle Scholar
  118. 118.
    Ha N-R, Jung I-P, Kim S-H, Kim AR, Yoon M-Y (2017) Paper chip-based colorimetric sensing assay for ultra-sensitive detection of residual kanamycin. Process Biochem 62:161–168CrossRefGoogle Scholar
  119. 119.
    Xiao L, Zhang Z, Wu C, Han L, Zhang H (2017) Molecularly imprinted polymer grafted paper-based method for the detection of 17b-Estradiol. Food Chem 221:82–86CrossRefGoogle Scholar
  120. 120.
    Nouanthavong S, Nacapricha D, Henry CS, Sameenoi Y (2016) Pesticide analysis using nanoceria-coated paper-based devices as a detection platform. Analyst 141(5):1837–1846CrossRefGoogle Scholar
  121. 121.
    Liu C-C, Wang Y-N, Fu L-M, Yang D-Y (2017) Rapid integrated microfluidic paper-based system for sulfur dioxide detection. Chem Eng J 316:790–796CrossRefGoogle Scholar
  122. 122.
    Busa LS, Mohammadi S, Maeki M, Ishida A, Tani H, Tokeshi M (2016) A competitive immunoassay system for microfluidic paper-based analytical detection of small size molecules. Analyst 141:6598–6603CrossRefGoogle Scholar
  123. 123.
    Lopez Marzo AM, Pons J, Blake DA, Merkoci A (2013) All-integrated and highly sensitive paper based device with sample treatment platform for Cd2+ immunodetection in drinking/tap waters. Anal Chem 85:3532–3538CrossRefGoogle Scholar
  124. 124.
    Nath P, Arun RK, Chanda N (2014) A paper based microfluidic device for the detection of arsenic using a gold nanosensor. RSC Adv 4:59558–59561CrossRefGoogle Scholar
  125. 125.
    Cinti S, Basso M, Moscone D, Arduini F (2017) A paper-based nanomodified electrochemical biosensor for ethanol detection in beers. Anal Chim Acta 960:123–130CrossRefGoogle Scholar
  126. 126.
    Chaiyo S, Apiluk A, Siangproh W, Chailapakul O (2016) High sensitivity and specificity simultaneous determination of lead, cadmium and copper using μPAD with dual electrochemical and colorimetric detection. Sens Actuators B Chem 233:540–549CrossRefGoogle Scholar
  127. 127.
    Bi X-M, Wang H-R, Ge L-Q, Zhou D-M, Xu J-Z, Gu H-Y, Bao N (2018) Gold-coated nanostructured carbon tape for rapid electrochemical detection of cadmium in rice with in situ electrodeposition of bismuth in paper-based analytical devices. Sens Actuators B Chem. Scholar
  128. 128.
    Koskela J et al (2015) Monitoring the quality of raw poultry by detecting hydrogen sulfide with printed sensors. Sens Actuators B Chem 218:89–96CrossRefGoogle Scholar
  129. 129.
    Mraovic M, Muck T, Pivar M, Trontelj J, Pletersek A (2014) Humidity sensors printed on recycled paper and cardboard. Sensors 14:13628–13643CrossRefGoogle Scholar
  130. 130.
    Morales-Narváez E, Naghdi T, Zor E, Merkoçi A (2015) Photoluminescent lateral-flow immunoassay revealed by graphene oxide: highly sensitive paper-based pathogen detection. Anal Chem 87:8573–8577CrossRefGoogle Scholar
  131. 131.
    Guzman JMCC, Tayo LL, Liu C-C, Wang Y-N, Fu L-M (2018) Rapid microfluidic paper-based platform for low concentration formaldehyde detection. Sens Actuators B Chem 255:3623–3629CrossRefGoogle Scholar
  132. 132.
    Liu C-C, Wang Y-N, Fu L-M, Huang Y-H (2018) Microfluidic paper-based chip platform for formaldehyde concentration detection. Chem Eng J 332:695–701CrossRefGoogle Scholar
  133. 133.
    Zhang Y, Zuo P, Ye BC (2015) A low-cost and simple paper-based microfluidic device for simultaneous multiplex determination of different types of chemical contaminants in food. Biosens Bioelectron 68:14–19CrossRefGoogle Scholar
  134. 134.
    Jin SQ, Guo SM, Zuo P, Ye BC (2015) A cost-effective Z-folding controlled liquid handling microfluidic paper analysis device for pathogen detection via ATP quantification. Biosens Bioelectron 63:379–383CrossRefGoogle Scholar
  135. 135.
    Mirasoli M, Buragina A, Dolci LS, Simoni P, Anfossi L, Giraudi G, Roda A (2012) Chemiluminescence-based biosensor for fumonisins quantitative detection in maize samples. Biosens Bioelectron 32:283–287CrossRefGoogle Scholar
  136. 136.
    Liu W, Guo Y, Luo J, Kou J, Zheng H, Li B, Zhang Z (2015) A molecularly imprinted polymer based a lab-on-paper chemiluminescence device for the detection of dichlorvos. Spectrochim Acta A Mol Biomol Spectrosc 141:51–57CrossRefGoogle Scholar
  137. 137.
    Liu W, Kou J, Xing H, Li B (2014) Paper-based chromatographic chemiluminescence chip for the detection of dichlorvos in vegetables. Biosens Bioelectron 52:76–81CrossRefGoogle Scholar
  138. 138.
    Li D, Ma Y, Duan H, Deng W, Li D (2018) Griess reaction-based paper strip for colorimetric/fluorescent/SERS triple sensing of nitrite. Biosens Bioelectron 99:389–398CrossRefGoogle Scholar
  139. 139.
    Zhu Y, Li M, Yu D, Yang L (2014) A novel paper rag as ‘D-SERS’ substrate for detection of pesticide residues at various peels. Talanta 128:117–124CrossRefGoogle Scholar
  140. 140.
    Tseng SY, Li SY, Yi SY, Sun AY, Gao DY, Wan D (2017) Food quality monitor: Paper-based plasmonic sensors prepared through reversal nanoimprinting for rapid detection of biogenic amine odorants. ACS Appl Mater Interfaces 9:17307–17317Google Scholar
  141. 141.
    Gonzalez CM, Iqbal M, Dasog M, Piercey DG, Lockwood R, Klapotke TM, Veinot JG (2014) Detection of high-energy compounds using photoluminescent silicon nanocrystal paper based sensors. Nanoscale 6:2608–2612CrossRefGoogle Scholar
  142. 142.
    Sablok K, Bhalla V, Sharma P, Kaushal R, Chaudhary S, Suri CR (2013) Amine functionalized graphene oxide/CNT nanocomposite for ultrasensitive electrochemical detection of trinitrotoluene. J Hazard Mater 248–249:322–328CrossRefGoogle Scholar
  143. 143.
    Peters KL, Corbin I, Kaufman LM, Zreibe K, Blanes L, McCord BR (2015) Simultaneous colorimetric detection of improvised explosive compounds using microfluidic paper-based analytical devices (μPADs). Anal Methods 7:63–70CrossRefGoogle Scholar
  144. 144.
    Aparna RS, Anjali Devi JS, Sachidanandan P, George S (2018) Polyethylene imine capped copper nanoclusters-fluorescent and colorimetric onsite sensor for the trace level detection of TNT. Sens Actuators B Chem 254:811–819CrossRefGoogle Scholar
  145. 145.
    Nergiz SZ, Gandra N, Farrell ME, Tian L, Pellegrino PM, Singamaneni S (2013) Biomimetic SERS substrate: peptide recognition elements for highly selective chemical detection in chemically complex media. J Mater Chem A 1:6543–6549CrossRefGoogle Scholar
  146. 146.
    Hughes S, Dasary SS, Begum S, Williams N, Yu H (2015) Meisenheimer complex between 2,4,6-trinitrotoluene and 3-aminopropyltriethoxysilane and its use for a paper-based sensor. Sens Biosensing Res 5:37–41CrossRefGoogle Scholar
  147. 147.
    Pesenti A, Taudte RV, McCord B, Doble P, Roux C, Blanes L (2014) Coupling paper-based microfluidics and lab on a chip technologies for confirmatory analysis of trinitro aromatic explosives. Anal Chem 86:4707–4714CrossRefGoogle Scholar
  148. 148.
    Huang S, He Q, Xu S, Wang L (2015) Polyaniline-based photothermal paper sensor for sensitive and selective detection of 2,4,6-trinitrotoluene. Anal Chem 87:5451–5456CrossRefGoogle Scholar
  149. 149.
    da Silva GO, de Araujo WR, Paixao T (2018) Portable and low-cost colorimetric office paper-based device for phenacetin detection in seized cocaine samples. Talanta 176:674–678CrossRefGoogle Scholar
  150. 150.
    Narang J, Malhotra N, Singhal C, Mathur A, Pn AK, Pundir CS (2017) Detection of alprazolam with a lab on paper economical device integrated with urchin like Ag@ Pd shell nano-hybrids. Mater Sci Eng, C 80:728–735CrossRefGoogle Scholar
  151. 151.
    Hu J, Wang S, Wang L, Li F, Pingguan-Murphy B, Lu TJ, Xu F (2014) Advances in paper-based point-of-care diagnostics. Biosens Bioelectron 54:585–597CrossRefGoogle Scholar
  152. 152.
    Zhu W-J, Feng D-Q, Chen M, Chen Z-D, Zhu R, Fang H-L, Wang W (2014) Bienzyme colorimetric detection of glucose with self-calibration based on tree-shaped paper strip. Sens Actuators B Chem 190:414–418CrossRefGoogle Scholar
  153. 153.
    Malekghasemi S, Kahveci E, Duman M (2016) Rapid and alternative fabrication method for microfluidic paper based analytical devices. Talanta 159:401–411CrossRefGoogle Scholar
  154. 154.
    Kannan B, Jahanshahi-Anbuhi S, Pelton RH, Li Y, Filipe CD, Brennan JD (2015) Printed paper sensors for serum lactate dehydrogenase using pullulan-based inks to immobilize reagents. Anal Chem 87:9288–9293CrossRefGoogle Scholar
  155. 155.
    Pardee K et al (2016) Rapid, low-cost detection of Zika virus using programmable biomolecular components. Cell 165:1255–1266CrossRefGoogle Scholar
  156. 156.
    Sharpe E, Frasco T, Andreescu D, Andreescu S (2013) Portable ceria nanoparticle-based assay for rapid detection of food antioxidants (NanoCerac). Analyst 138:249–262CrossRefGoogle Scholar
  157. 157.
    Guan L, Tian J, Cao R, Li M, Cai Z, Shen W (2014) Barcode-like paper sensor for smartphone diagnostics: an application of blood typing. Anal Chem 86:11362–11367CrossRefGoogle Scholar
  158. 158.
    Khatri V, Halasz K, Trandafilovic LV, Dimitrijevic-Brankovic S, Mohanty P, Djokovic V, Csoka L (2014) ZnO-modified cellulose fiber sheets for antibody immobilization. Carbohydr Polym 109:139–147CrossRefGoogle Scholar
  159. 159.
    Noiphung J, Songjaroen T, Dungchai W, Henry CS, Chailapakul O, Laiwattanapaisal W (2013) Electrochemical detection of glucose from whole blood using paper-based microfluidic devices. Anal Chim Acta 788:39–45CrossRefGoogle Scholar
  160. 160.
    Wang P, Cheng Z, Chen Q, Qu L, Miao X, Feng Q (2018) Construction of a paper-based electrochemical biosensing platform for rapid and accurate detection of adenosine triphosphate (ATP). Sens Actuators B Chem 256:931–937CrossRefGoogle Scholar
  161. 161.
    Li X, Liu X (2016) A microfluidic paper-based origami nanobiosensor for label-free, ultrasensitive immunoassays. Adv Healthc Mater 5:1326–1335CrossRefGoogle Scholar
  162. 162.
    Scordo G, Moscone D, Palleschi G, Arduini F (2018) A reagent-free paper-based sensor embedded in a 3D printing device for cholinesterase activity measurement in serum. Sens Actuators B Chem 258:1015–1021CrossRefGoogle Scholar
  163. 163.
    Lee SH, Lee JH, Tran V-K, Ko E, Park CH, Chung WS, Seong GH (2016) Determination of acetaminophen using functional paper-based electrochemical devices. Sens Actuators B Chem 232:514–522CrossRefGoogle Scholar
  164. 164.
    Adkins JA, Noviana E, Henry CS (2016) Development of a quasi-steady flow electrochemical paper-based analytical device. Anal Chem 88:10639–10647CrossRefGoogle Scholar
  165. 165.
    da Costa TH, Song E, Tortorich RP, Choi J-W (2015) A paper-based electrochemical sensor using inkjet-printed carbon nanotube electrodes. ECS J Solid State Sci Technol 4:S3044–S3047CrossRefGoogle Scholar
  166. 166.
    Cinti S, Minotti C, Moscone D, Palleschi G, Arduini F (2017) Fully integrated ready-to-use paper-based electrochemical biosensor to detect nerve agents. Biosens Bioelectron 93:46–51CrossRefGoogle Scholar
  167. 167.
    Nantaphol S, Channon RB, Kondo T, Siangproh W, Chailapakul O, Henry CS (2017) Boron doped diamond paste electrodes for microfluidic paper-based analytical devices. Anal Chem 89:4100–4107CrossRefGoogle Scholar
  168. 168.
    Zhang H, Zhao Z, Lei Z, Wang Z (2016) Sensitive detection of polynucleotide kinase activity by paper-based fluorescence assay with l exonuclease-assistance. Anal Chem 88:11358–11363CrossRefGoogle Scholar
  169. 169.
    Jiang P, He M, Shen L, Shi A, Liu Z (2017) A paper-supported aptasensor for total IgE based on luminescence resonance energy transfer from upconversion nanoparticles to carbon nanoparticles. Sens Actuators B Chem 239:319–324CrossRefGoogle Scholar
  170. 170.
    Liang L et al (2016) Aptamer-based fluorescent and visual biosensor for multiplexed monitoring of cancer cells in microfluidic paper-based analytical devices. Sens Actuators B Chem 229:347–354CrossRefGoogle Scholar
  171. 171.
    Saha B, Baek S, Lee J (2017) Highly sensitive bendable and foldable paper sensors based on reduced graphene oxide. ACS Appl Mater Interfaces 9:4658–4666CrossRefGoogle Scholar
  172. 172.
    Gong MM, Nosrati R, San Gabriel MC, Zini A, Sinton D (2015) Direct DNA analysis with paper-based ion concentration polarization. J Am Chem Soc 137:13913–13919CrossRefGoogle Scholar
  173. 173.
    Davaji B, Lee CH (2014) A paper-based calorimetric microfluidics platform for bio-chemical sensing. Biosens Bioelectron 59:120–126CrossRefGoogle Scholar
  174. 174.
    Chen GH, Chen WY, Yen YC, Wang CW, Chang HT, Chen CF (2014) Detection of mercury (II) ions using colorimetric gold nanoparticles on paper-based analytical devices. Anal Chem 86:6843–6849CrossRefGoogle Scholar
  175. 175.
    Sicard C et al (2015) Tools for water quality monitoring and mapping using paper-based sensors and cell phones. Water Res 70:360–369CrossRefGoogle Scholar
  176. 176.
    Wang B, Lin Z, Wang M (2015) Fabrication of a paper-based microfluidic device to readily determine nitrite ion concentration by simple colorimetric assay. J Chem Educ 92:733–736CrossRefGoogle Scholar
  177. 177.
    Rattanarat P, Dungchai W, Cate D, Volckens J, Chailapakul O, Henry CS (2014) Multilayer paper-based device for colorimetric and electrochemical quantification of metals. Anal Chem 86:3555–3562CrossRefGoogle Scholar
  178. 178.
    Cho YB, Jeong SH, Chun H, Kim YS (2018) Selective colorimetric detection of dissolved ammonia in water via modified Berthelot’s reaction on porous paper. Sens Actuators B Chem 256:167–175CrossRefGoogle Scholar
  179. 179.
    Lamas-Ardisana PJ et al (2017) Disposable electrochemical paper-based devices fully fabricated by screen-printing technique. Electrochem Commun 75:25–28CrossRefGoogle Scholar
  180. 180.
    Qin Y, Pan S, Howlader MM, Ghosh R, Hu NX, Deen MJ (2016) Paper-based, hand-drawn free chlorine sensor with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). Anal Chem 88:10384–10389CrossRefGoogle Scholar
  181. 181.
    Cinti S, Talarico D, Palleschi G, Moscone D, Arduini F (2016) Novel reagentless paper-based screen-printed electrochemical sensor to detect phosphate. Anal Chim Acta 919:78–84CrossRefGoogle Scholar
  182. 182.
    Li H, Wang W, Lv Q, Xi G, Bai H, Zhang Q (2016) Disposable paper-based electrochemical sensor based on stacked gold nanoparticles supported carbon nanotubes for the determination of bisphenol A. Electrochem Commun 68:104–107CrossRefGoogle Scholar
  183. 183.
    Chouler J, Cruz-Izquierdo A, Rengaraj S, Scott JL, Di Lorenzo M (2018) A screen-printed paper microbial fuel cell biosensor for detection of toxic compounds in water. Biosens Bioelectron 102:49–56CrossRefGoogle Scholar
  184. 184.
    Zhang R, Zhang C-J, Song Z, Liang J, Kwok RTK, Tang BZ, Liu B (2016) AIEgens for real-time naked-eye sensing of hydrazine in solution and on a paper substrate: structure-dependent signal output and selectivity. J Mater Chem C 4:2834–2842CrossRefGoogle Scholar
  185. 185.
    Fraiwan A, Lee H, Choi S (2016) A paper-based cantilever array sensor: monitoring volatile organic compounds with naked eye. Talanta 158:57–62CrossRefGoogle Scholar
  186. 186.
    Bulbul G, Eskandarloo H, Abbaspourrad A (2018) A novel paper based colorimetric assay for the detection of TiO2 nanoparticles. Anal Methods 10:275–280CrossRefGoogle Scholar

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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Institute of Wood Based Products and TechnologiesUniversity of SopronSopronHungary

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