LitCovid-sentences  

PMC:7143804 / 3449-9317 JSONTXT 11 Projects

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Id Subject Object Predicate Lexical cue
T28 0-4 Sentence denotes 1.1.
T29 5-21 Sentence denotes State-of-the-Art
T30 22-101 Sentence denotes In the past, several chip-based DNA and RNA amplification devices are reported.
T31 102-209 Sentence denotes It goes beyond the scope of this paper to discuss the state-of-the-art of DNA amplification chips in-depth.
T32 210-298 Sentence denotes There are several good review papers written on this topic [12,13,14,15,16,17,18,19,20].
T33 299-371 Sentence denotes Readers are referred to these for a comprehensive overview of the field.
T34 372-562 Sentence denotes In this paper, the state-of-the-art is divided into several discussion points, i.e., the heating method, the temperature control method, and the substrate material and fabrication technique.
T35 563-605 Sentence denotes These points will be discussed separately.
T36 606-672 Sentence denotes With respect to heat supply, different methods have been employed.
T37 673-785 Sentence denotes Almassian et al. give a comprehensive overview of different possible heating methods in their review paper [12].
T38 786-935 Sentence denotes Not all of the mentioned methods are easy to implement in low-cost and portable lab-on-a-chip devices due to their bulkiness or implementation costs.
T39 936-1045 Sentence denotes Examples of these rather difficult methods are using heating via induction, infrared, or microwave radiation.
T40 1046-1173 Sentence denotes Others are not useful due ot their challenging temperature control, like with heating up the system using exothermic reactions.
T41 1174-1257 Sentence denotes Within the field of DNA amplification, different mechanisms of amplification exist.
T42 1258-1343 Sentence denotes Some are based on thermo cycling processes, e.g., PCR, whereas others are isothermal.
T43 1344-1431 Sentence denotes The use of an isothermal amplification technique puts less requirements on the heaters.
T44 1432-1625 Sentence denotes Isothermal processes are either truly isothermal or consisting of three different temperatures, as they have a thermal denaturation step before and a termination step after the elongation step.
T45 1626-1775 Sentence denotes The switching between these temperature steps does not have to be as fast as with thermal cycling steps in, for example, PCR amplification reactions.
T46 1776-1908 Sentence denotes The use of less temperature variations makes it easier to maintain the set temperature as there is less heating an cooling involved.
T47 1909-2033 Sentence denotes Furthermore, it eliminates the use of a continuous flow approach in systems with low thermal conductivities, e.g., polymers.
T48 2034-2108 Sentence denotes Therefore, it is easier to implement within lab-on-a-chip devices [17,21].
T49 2109-2266 Sentence denotes Isothermal DNA amplification reactions can already be performed by putting the chip on a commercially available hotplate [22,23] or Peltier elements [24,25].
T50 2267-2328 Sentence denotes However, these heating systems are bulky and power-consuming.
T51 2329-2416 Sentence denotes Therefore, they are not useful for portable equipment or operation at remote locations.
T52 2417-2482 Sentence denotes Miniaturizing heaters lowers the bulkiness and power consumption.
T53 2483-2671 Sentence denotes Miniaturized heaters can be integrated as integrated resistive heaters, e.g., as deposited thin-film metal [26,27,28,29] or as laminated Cu foil [30], or as micro-Peltier elements [31,32].
T54 2672-2851 Sentence denotes These miniaturized heaters can be implemented directly onto the microfluidic chip [28] or on a different substrate and leter incorporated onto the microfluidic chip [33,34,35,36].
T55 2852-2975 Sentence denotes The geometry of such a heater contributes significantly to the uniformity of the heat distribution within the chip [26,37].
T56 2976-3102 Sentence denotes One method to accurately control the temperature is the use of a proportional-integral-derivative (PID) controlled thermostat.
T57 3103-3235 Sentence denotes These PID controllers are coupled to the electrical heaters and use a thermocouple as feedback-loop to the controller [22,23,24,25].
T58 3236-3345 Sentence denotes There are various materials that can be used to fabricate lab-on-a-chip devices for DNA or RNA amplification.
T59 3346-3481 Sentence denotes In the past 15 years, more than ten polymers, ceramic materials, and metals have successfully been used to fabricate such devices [15].
T60 3482-3561 Sentence denotes The major property playing a role here is the biocompatibility of the material.
T61 3562-3650 Sentence denotes The surface of the microfluidic structure should not inhibit the amplification reaction.
T62 3651-3804 Sentence denotes This biocompatibility can be an intrinsic property of the material or the surface can be modified or coated to achieve this [12,13,14,15,16,17,18,19,20].
T63 3805-3935 Sentence denotes One often used material is polydimethylsiloxane (PDMS) [22,23,31,32,34,35,38], which can be processed using soft lithography [39].
T64 3936-4053 Sentence denotes However, this is a fabrication technology used in academia and is not suitable for upscaling to mass production [40].
T65 4054-4157 Sentence denotes Fabrication methods suitable for mass production are thermoforming/embossing or injection molding [41].
T66 4158-4377 Sentence denotes One of the materials which is biocompatible and suitable for both industrial scale fabrication technologies is cyclic olefin copolymer (COC) [42], which is one of the materials used in the past as well [28,36,43,44,45].
T67 4378-4558 Sentence denotes Guckenberger et al. estimates the costs of injection molding of only 50 simple microfluidic devices on $47, but this becomes cheaper when the mass production stage is reached [41].
T68 4559-4632 Sentence denotes Another benefit of COC is the possibility to shape it using micromilling.
T69 4633-4746 Sentence denotes This technique is a rapid prototyping technology and therefore very useful within proof-of-concept projects [41].
T70 4747-4835 Sentence denotes Integrating resistive metal tracks onto a COC substrate have also been done in the past.
T71 4836-5055 Sentence denotes Some papers describe the use of a surface modification step done before metal deposition in order to enhance adhesion between the COC and the metal layer, like a pretreatment with plasma [46] or an organic solvent [47].
T72 5056-5138 Sentence denotes Other papers describe the direct deposition of metal onto the COC surface [28,48].
T73 5139-5238 Sentence denotes Chung et al. specifically, fabricated an amplification chip in COC with integrated Au heaters [28].
T74 5239-5369 Sentence denotes However, their system required heating from both sides as the used grade of COC has a glass transition temperature (Tg) of 130 °C.
T75 5370-5473 Sentence denotes This COC could not withstand the required heater temperatures to have enough heat flux into the system.
T76 5474-5608 Sentence denotes They had to heat up the heater to temperatures above 130 °C, which caused cracking of the heater tracks due to deformation of the COC.
T77 5609-5713 Sentence denotes With their double-sided heating they ensured that the reaction mixture had the desired PCR temperatures.
T78 5714-5868 Sentence denotes However, double-sided heating doubles the amount of metal required, increases the amount of fabrication steps, and therefore increases the price per chip.