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The main problem for the expansion of the use of microfluidic paper-based analytical devices and, thus, their mass production is their inherent lack of fluid flow control due to its uncontrolled fabrication protocols. To address this issue, the first step is the generation of uniform and reliable microfluidic channels. The most common paper microfluidic fabrication method is wax printing, which consists of two parts, printing and heating, where heating is a critical step for the fabrication of reproducible device dimensions. In order to bring paper-based devices to success, it is essential to optimize the fabrication process in order to always get a reproducible device. Therefore, the optimization of the heating process and the analysis of the parameters that could affect the final dimensions of the device, such as its shape, the width of the wax barrier and the internal area of the device, were performed. Moreover, we present a method to predict reproducible devices with controlled working areas in a simple manner.

The main problem for the expansion of the use of microfluidic paper-based analytical devices and, thus, their mass production is their inherent lack of fluid flow control due to its uncontrolled fabrication protocols. To address this issue, the first step is the generation of uniform and reliable microfluidic channels. The most common paper microfluidic fabrication method is wax printing, which consists of two parts, printing and heating, where heating is a critical step for the fabrication of reproducible device dimensions. In order to bring paper-based devices to success, it is essential to optimize the fabrication process in order to always get a reproducible device. Therefore, the optimization of the heating process and the analysis of the parameters that could affect the final dimensions of the device, such as its shape, the width of the wax barrier and the internal area of the device, were performed. Moreover, we present a method to predict reproducible devices with controlled working areas in a simple manner.

The main problem for the expansion of the use of microfluidic paper-based analytical devices and, thus, their mass production is their inherent lack of fluid flow control due to its uncontrolled fabrication protocols. To address this issue, the first step is the generation of uniform and reliable microfluidic channels. The most common paper microfluidic fabrication method is wax printing, which consists of two parts, printing and heating, where heating is a critical step for the fabrication of reproducible device dimensions. In order to bring paper-based devices to success, it is essential to optimize the fabrication process in order to always get a reproducible device. Therefore, the optimization of the heating process and the analysis of the parameters that could affect the final dimensions of the device, such as its shape, the width of the wax barrier and the internal area of the device, were performed. Moreover, we present a method to predict reproducible devices with controlled working areas in a simple manner.

Työn tarkoituksena oli kartoittaa paperipohjaisten, mikrofluidististen analyysilaitteistojen (engl. paper-based microfluidic devices, μPAD) käyttömahdollisuuksia farmaseuttisessa analytiikassa. Miniatyrisoiduissa kokonaisanalyysilaitteistoissa (engl. micro total-analysis system, μTAS) on mikrometrimittakaavan rakenteita, ja ne kykenevät suorittamaan kaikki analyysiketjun prosessit. Miniatyrisoinnin etuja ovat pienemmät reagenssi- ja näytetilavuudet sekä nopeammat analyysiajat. μTAS:t valmistetaan yleensä lasista, piistä tai polymeereistä ja niiden valmistaminen vaatii puhdastilatyöskentelyä sekä erikoislaitteita. Paperi tarjoaa edullisen ja monimuotoisen alustan μTAS:ien valmistamiseen. Neste liikkuu paperissa kapillaarivoimien vaikutuksesta eikä ulkoisia laitteita nesteen liikuttamiseen tarvita. μPAD:ien etuja perinteisiin μTAS:eihin nähden ovat niiden helppokäyttöisyys sekä edullinen ja yksinkertainen valmistus. μPAD:t valmistetaan tekemällä hydrofiiliseen paperiin hydrofobisten esteiden rajaama kuvio. μPAD:ien valmistusmenetelmiä on useita, kuten esim. fotolitografia, leikkaaminen sekä vahan käyttöön perustuvat menetelmät (syövytys, vahatulostus, vahaan upotus). Työhön valittiin μPAD:ien valmistusmenetelmäksi vahatulostus sen nopeuden, edullisuuden ja yksinkertaisuuden takia. Vaha toimii hydrofiilisessä paperissa hydrofobisena esteenä ohjaten nesteen virtausta. Haluttu vahakuvio tulostettiin paperiin Xerox Phaser 8560DN –kuumavahatulostimella, minkä jälkeen vaha sulatettiin paperin läpi kuumentamalla paperia 120 sekunnin ajan 150 °C:ssa kuumalevyllä. Paperin anisotrooppisuudesta johtuen vaha leviää paperissa kuumennuksen aikana myös horisontaalisesti, mikä heikentää vahakuvion resoluutiota eikä vahakuvio ole tarkkarajainen. Vahatulostus on edullinen ja yksinkertainen valmistusmenetelmä, joka soveltuu μPAD:ien valmistamiseen. Työssä tutkittiin myös nesteen virtausnopeutta paperissa ja virtausnopeuden säätelyä. Tuntemalla nesteen virtausnopeus voidaan varmistua, et, The aim of this research was to evaluate the use of microfluidic paper-based devices (μPAD) in drug analysis. Micro total analysis systems (μTAS) channels are in the range of a few micrometers and are capable of performing all steps of a chemical analysis. The advantages of miniaturization are lower sample consumption and faster analysis time. μTASs are usually fabricated of glass, silicon or polymers and their fabrication requires cleanroom facilities and specific equipment. Paper offers an inexpensive and versatile substrate for μTASs. Paper wicks liquids and no external pumps are required. μPADs advantages over μTAS are its ease of use and inexpensive and simple fabrication. μPADs are fabricated by patterning hydrophobic barriers in hydrophilic paper. There are several fabrication methods for μPADs such as photolithography, cutting and methods based on the application of wax (etching, wax printing, wax dipping). In this research wax printing was selected as the fabrication method because it’s simple, rapid and inexpensive. Wax was printed using Xerox Phaser 8560DN solid ink printer. After printing the wax was melted through the paper by heating the paper at 150 °C for 120 seconds on a hotplate. Thus the wax creates a hydrophobic barrier on the hydrophilic paper which channels the liquids flow. Owing to papers anisotropic nature the wax also spreads horizontally in the paper when heated, thus reducing the wax patterns resolution and making the pattern coarse. Wax printing is an inexpensive and simple fabrication method suitable for fabricating μPADs. Also liquids flow velocity and methods for controlling the flow rate were studied. By knowing the flow velocity, one can assure that the analytes and reagents reach the reaction site. Controlling the flow velocity enables the use of multiphase reactions or the use of multiple simultaneous reactions on the μPAD. The liquid flow velocity can be controlled by changing the hydrophilic channels width, reducing the average