Difference between revisions of "Team:Madrid-OLM/HardawareMicrofluidics"

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         <title>First prototype of the device</title>
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         <title>Microfluidics part of the device</title>
 
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                         <a href="#firstass" class="inner-link" data-title="First assumptions"></a>
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                         <a href="#workflowPDMS" class="inner-link" data-title="Lab workflow for PDMS chips"></a>
 
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                         <a href="#howwork" class="inner-link" data-title="How it Works"></a>
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                         <a href="#manPMMA" class="inner-link" data-title="Manufacturing the PMMA chips"></a>
 
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                         <a href="#further" class="inner-link" data-title="Further Details"></a>
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                         <a href="#fluidmech" class="inner-link" data-title="Fluid Mechanics behaviour"></a>
 
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                         <a href="#meresult" class="inner-link" data-title="Measurement results"></a>
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                         <a href="#plamabond" class="inner-link" data-title="Plasma Bonding"></a>
 
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                         <a href="#learned" class="inner-link" data-title="Things we learned while doing"></a>
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                         <a href="#Injection" class="inner-link" data-title="Injection"></a>
 
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                        <a href="#improv" class="inner-link" data-title="Further improvements"></a>
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                             <h1 id="Teamtittle">First prototype</h1>
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                             <h1 id="Teamtittle">Microfluidics</h1>
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                             <p class="lead">The first design was conceived around a number of theoretical guesses that we needed to prove experimentally.</p>
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                             <p class="lead">When the need of moving microvolumes arise as a mandatory requirement of design, microfluidics pops up as the one and only solution. Although there is at hand a wide range of microfluidic commercial solutions, many of them are too expensive to start experimenting with. </p>
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                            <p class="lead">Our first prototype was born to test these assumptions. Some of them worked as expected, but many of them only served as an initial step towards a more concise device.</p>
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                             <p class="lead">That is why our method comes to give an alternative solution. The <a href="http://www.elveflow.com/microfluidic-tutorials/microfluidic-reviews-and-tutorials/the-poly-di-methyl-siloxane-pdms-and-microfluidics/">PDMS</a> manufacturing reveals itself as a tough rival with respect to other alternatives. PDMS was our initial choice, due to its reasonable price and ease of use. As DIY and digital manufacturing constitute the basis of our hardware, we built a workflow around the PDMS chip</p>
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                             <p class="lead">In the following paragraphs, we want to share our experience working with a new device, an initial prototype, designed by us, and tested to the limit. By learning how to set our prototype up, we were learning about every factor involved in the process. </p>
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                            <p class="lead">Designing, manufacturing, and testing our devices has been great. Engineering biodevices require theoretical and experimental skills. But what we have learned is the most simple lesson: there is no better way of doing things. The best way of doing anything is doing while learning.</p>
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                             <h2>First assumptions</h2>
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                             <h2>The lab workflow for PDMS chips</h2>
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                            <h4>Foto diagrama workflow</h4>
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                            <h6 class="lessmar">1-Molding of the upper half</h6>
 
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                                 <li><p class="lead">Immobilized aptamers on a PDMS surface. In order to create an electrostatic and mechanical trap for our targeted protein, we planned to work in a PDMS environment. PDMS is a well-known manufacturing material for electronics. So we could easily integrate PDMS in our device. </p></li>
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                                 <li><p class="lead"><u>Negative</u>: a laser cuts the tape that is adhered to an acetate. The remaining tape is removed carefully. The channels and the chambers, as well as the input and the output have been cutted and the negative has been created. More info about the protocols involved <a href="https://2018.igem.org/Team:Madrid-OLM/ProManufacturing#MoldM">here</a>.</p></li>
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                                 <li><p class="lead">Optical measurement sensor. The materials required to test our sensor were a 280nm UV LED emitter and an LDR.  The amount of light traversing the solution was quantified by a drop in voltage across the LDR: with higher protein concentrations, higher absorption is expected together with an increased drop in voltage. </p></li>
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                                 <li><p class="lead"><u>Molding box</u>: (Find the polymerization chamber in <a href="http://github.com/OpenLabMadrid/iGEM-Madrid-OLM/tree/master/CAD/Polymerization%20chamber">our github</a>). Once the negative has been created, it is time to align the acetate with the marks in the polymerization chamber. Depending on the chosen configuration, it might be worth to place the perforated base on the bottom of the acetate. </p></li>
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                                <li><p class="lead">Microfluidics: for channeling fluids through the chip. Microfluidics allows us to move microliters of samples, minimizing the dead volumes and the waste through the chip.</p></li>
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                                 <li><p class="lead">PDMS casting: PDMS casting was made inside an lab oven most of times. Curing time depended on the drying method selected. More info about the protocols involved <a href="https://2018.igem.org/Team:Madrid-OLM/ProManufacturing#PDMSCas">here</a>.</p></li>
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                                 <li><p class="lead">Modular design and normalization: We needed to standardize the protocols related to hardware to reduce the number of variables involved. This would restrict the design and manufacture and help us a lot when playing with certain design parameters. </p></li>
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                                <li><p class="lead">Enable the DIY: We had the need of developing everything in a way such that anyone, regardless his/her origin could replicate our experiments in an affordable and creative way.</p></li>
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                            <h6 class="lessmar">2-Molding of the lower half</h6>
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                            <p class="lead">The process is repeated without the negative.</p>
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                            <h6 class="lessmar">3-Fixing the two halves</h6>
 +
                            <p class="lead">The selected method for fixing both halves was plasma bonding.More info about the protocols involved <a href="https://2018.igem.org/Team:Madrid-OLM/ProManufacturing#PlamsB">here</a>.</p>
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                            <h6 class="lessmar">4-Creating the input and the outputs</h6>
 +
                            <p class="lead">We usually used to hole punch the PDMS inlet/outlet with a needle. But we cured the PDMS with a needle inside as another negative volume for molding.More info about the protocols involved <a href="https://2018.igem.org/Team:Madrid-OLM/ProManufacturing#Closingcir">here</a>.</p>
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                            <h6 class="lessmar">5-Injecting fluids into the chip</h6>
 +
                            <p class="lead">Automatic controlled microvolume pressure pumps have been developed specifically for our microfluidic chips. Specific plans of the pumps design can be found in <a href="http://github.com/OpenLabMadrid/iGEM-Madrid-OLM/tree/master/CAD/Pressure%20pump">our github</a>. </p>
 
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                            <h2>Manufacturing the PMMA chips</h2>
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                            <p class="lead">Although we are proud of having implemented an affordable workflow for developing functional PDMS chips, we manufactured PMMA chips with micromachining techniques. Our University has a Mechanical workshop that usually machines vacuum chambers, or metallic parts of machines, bending aluminum sheets, etc.</p>
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                            <p class="lead">We visited the workshop and asked the workers how to micromachine a PMMA chip with almost 0.2 mm height and 0.8 channel width. We purchased a 0.4 mm tip diameter and adapted the manufacturing to other available tools.</p>
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                            <p class="lead">The input and output needed to be modified, and we used 21G needles (0.8 mm) as inlet and outlet. The fitting was made with High Performance Liquid Chromatography (HPLC) 0.8 mm tubes. They fitted tight enough to avoid leaks. </p>
  
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                             <h2>How it works</h2>
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                             <h2>Fluid Mechanics behaviour inside the chip</h2>
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                            <h4>imagen 4 subsistemas</h4>
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                             <p class="lead">Once the workflow was designed and implemented, we focused on designing microfluidic concepts that could prove our system right. In this regard, there were some Fluid Mechanics concepts that we would love to experiment. This is why we created the following experiments:</p>
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                             <p class="lead">The device is divided into four parts. Every subsystem has been conceived to be integrated in a bigger organic whole: the device. </p>
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                                    <p class="lead nomargin">Electronics</p>
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                                        <li class="nomargin"><p class="lead">Custom modules oriented to experimentation.</p></li>
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                                        <li><p class="lead">Custom PCB created specifically for our device. </p></li>
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                                    <p class="lead nomargin">Microfluidics and aptasensor</p>
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                                        <li class="nomargin"><p class="lead">Affordable PDMS chip manufacturing.</p></li>
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                                        <li class="nomargin"><p class="lead">Input/output and chambers of measurement normalised for a chip design oriented to manufacture.</p></li>
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                                        <li><p class="lead">Immobilised aptamers on PDMS surface.</p></li>
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                                    <p class="lead nomargin">System of measurement</p>
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                                        <li class="nomargin"><p class="lead">Optic system of measurement based on protein absorbance at 280 nm of wavelength.</p></li>
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                                        <li><p class="lead">LDR as light receiver.</p></li>
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                                    <p class="lead nomargin">Pressure system</p>
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                                        <li><p class="lead">Pressure pump regulated manually</p></li>
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                            <p class="lead">From the point of view of the protein sample, the fluid would follow this stream: </p>
+
 
                             <ol class="ourlist">
 
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                                 <li class="nomargin"><p class="lead">The protein sample starts inside the syringe, suspended in a buffer solution. And it is manually pumped into the PDMS chip.</p></li>
+
                                 <li><p class="lead"><b>Our mixer:</b> Inside the chip, the fluid behaves in a laminar way. There are many <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4634658/">papers</a> on this topic.We wanted to test this experimentally. And that is why we created a mixer. We could study how the fluid behaves in the conditions of a mixer. Our mixer is just an example on how microfluidic components can be small enough to be modularly assembled in series or in parallel as an electronic component. </p></li>
−
                                <li class="nomargin"><p class="lead">From the inlet, it is displaced to the sensor chamber, where the surface is almost covered by aptamers. </p></li>
+
                                 <li><p class="lead"><b>Flow separation tests:</b> We have designed four experiments to study the behaviour of our flow under different circumstances. The flow circulates towards a triangle, a circle, a throat and the shape of a heart. This will show us how the flow behaves under certain circumstances. Its immediate consequences affect the design of chambers or any microchannel widening.</p></li>
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                                 <li class="nomargin"><p class="lead">The circulating proteins get trapped in the aptamers chamber.</p></li>
+
                                 <li><p class="lead"><b>Droplet generation tests:</b> Generating droplets is one of the milestones of microfluidics. Droplets are small volumes of sample moving as small drops in an arranged and harmonic way. It is much more than just beautiful. The main task of this chip is to study how a fluid and air pressure gradients can work together in the same room. The design pushes to the limit the available capabilities of our device. .</p></li>
−
                                 <li class="nomargin"><p class="lead">A clean buffer solution is injected to the chip, to wipe any other molecule out.</p></li>
+
                                 <li><p class="lead"><b>Tree and mixer test:</b> We have designed a large PMMA chip to work as a sample on how fluid behaves when flow is separated into different branches of a tree. The aim of this experiment is to study the laminar flow, and how it behaves when it arrived to the central chamber. On the exact opposite side, a negative relative pressure will be generated to study how it behaves in an alternative “negative relative pressure” tree. In this experiment there are two sides of a chip. Both of them are experimentally equivalent. </p></li>
−
                                 <li class="nomargin"><p class="lead">A saline solution is pumped into the chip, to detach the protein from the aptamer. The process has been previously described in <a href="http://www.ncbi.nlm.nih.gov/pubmed/22736991"> this paper.</a></p></li>
+
                                 <li><p class="lead"><b>A chip adapted to Dropsens GNP110 electrode:</b> We manufactured via regular CNC milling, adapted to micromachining, the housing for a Dropsens GNP110 electrode. A paper proved our arrangement to be functional. We manufactured a two part chip. The upper side was micromilled with a 0.4 mm tool, with a custom made circuit for injecting the protein solution, ferricyanide and buffer solution. We integrated the Dropsens electrode, looking forward to replicating the results obtained in the laboratory:</p></li>
−
                                 <li class="nomargin"><p class="lead">The saline solution with the remaining protein is taken to another chamber, where absorbance is measured at the 280 nm wavelength.</p></li>
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                                 <a class="btn btn--primary-2 btn--sm type--uppercase" href="https://2018.igem.org/Team:Madrid-OLM/ElectrodeIntegration">
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                                 <li class="nomargin"><p class="lead">Once the measurement is taken, we get the information and analyze it. </p></li>
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                                    <span class="btn__text">
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                                <li class="nomargin"><p class="lead">The chip is cleaned and the process can start over again.</p></li>
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                                        Binding the aptamers to the electrode
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                             <h2>Further details</h2>
+
                             <h2>Plasma bonding</h2>
−
                             <h5>The caset</h5>
+
                             <p class="lead">After setting the microwave up for treating the chips with plasma, we got some results that might serve as an illustration of the process. Other documentation can be found <a href="http://arxiv.org/ftp/arxiv/papers/1807/1807.06784.pdf">here</a>. We used a 700W microwave, modded to fit our requirements, as we explain in the protocols section:</p>
−
                            <ol class="ourlist">
+
                            <a class="btn btn--primary-2 btn--sm type--uppercase" href="https://2018.igem.org/Team:Madrid-OLM/ProManufacturing#PlamsBn">
−
                                <li class="nomargin"><p class="lead">The caset is a two part PMMA structure, able to allow 4 fixed inputs (1 mm of diameter) and 4 fixed outputs (1 mm of diameter), 4 chambers for 280 nm UV LED modules and 4 chambers for LDR modules. An open module was designed for inserting other components if required by the user. Find more information on the modules in <a href="http://github.com/OpenLabMadrid/iGEM-Madrid-OLM/tree/master/Electronics/First%20prototype/Modules"> our GitHub.</a></p></li>
+
                                 <span class="btn__text">
−
                                <li class="nomargin"><p class="lead">The control electronics was designed to govern 4 LED modules and 4 LDR modules.</p></li>
+
                                    Plasma Bonding
−
                                <li class="nomargin"><p class="lead">It has a frame for the 40x40 mm PDMS chip, which relates to the bed of the laser cutter. PDMS chip should be 3 mm of thickness.</p></li>
+
                                 </span>
−
                                <li><p class="lead">These parts are fixed together with screws and spacers. Although not a large pressure is required.</p></li>
+
                             </a>
−
                            </ol>
+
                             <br/><br/>
−
                           
+
                             <p class="lead">We finally configured the microwave to half of its power approximately, inserted a 100ml glass of water and 20 seconds of treatment. After these parameters were established, we got the following results.</p>
−
                            <h5>The chip design</h5>
+
                            <p class="lead">One of the indicators that show that plasma is treating the PDMS correctly is the modification of the surface tension of the water on a PDMS surface.</p>
−
                            <ol class="ourlist">
+
                            <h4>Foto de las gotas</h4>
−
                                <li class="nomargin"><p class="lead">The chip has dimensional restrictions (40 x 40 mm) due to the boundary condition of manufacturing: the laser cutter bed maximum dimensions.</p></li>
+
 
−
                                <li class="nomargin"><p class="lead">We created <a href="http://github.com/OpenLabMadrid/iGEM-Madrid-OLM/tree/master/CAD/Polymerization%20chamber">polymerization chambers</a> for this purpose.</p></li>
+
−
                                 <li class="nomargin"><p class="lead">The input and output have been fixed for manufacturing concerns.</p></li>
+
−
                                <li class="nomargin"><p class="lead">The last chip that we designed has two parallel circuits. Therefore, two inputs and two outputs and four chambers (two per circuit).</p></li>
+
−
                                 <li><p class="lead">The chambers were conceived to be surrounded by an emitter and a receiver, facing one another.</p></li>
+
−
                             </ol>
+
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+
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                             <h5>The electronics for an absorbance related measurement</h5>
+
−
                             <ol class="ourlist">
+
−
                                <li class="nomargin"><p class="lead">The electronics are governed by an Arduino Nano board. It links the analogue electronic board inside the device and the Arduino IDE. So the user can see the data related to the signal in the serial monitor. </p></li>
+
−
                                <li class="nomargin"><p class="lead">The light emitter is controlled by the Arduino through a 2N2222 transistor for providing the module with 6.5V and enough current. </p></li>
+
−
                                <li class="nomargin"><p class="lead">The circuit which receives the data related to the signal comes from the light receiver. When the protein sample contains a high concentration of protein, the voltage drops proportionally to the amount of protein. Then, the signal is amplified and corrected via an OpAmp and an Instrumental Amplifier.</p></li>
+
−
                                <li class="nomargin"><p class="lead">The voltage is measured by the built-in Arduino Analogue to digital converter.</p></li>
+
−
                                <li><p class="lead">Further information can be find in <a href="http://github.com/OpenLabMadrid/iGEM-Madrid-OLM/tree/master/Electronics/First%20prototype/PCB">our GitHub.</a></p></li>
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                             <h2>Measurement results</h2>
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                             <h2>Injection</h2>
−
                              
+
                             <p class="lead">One of the improvements of the second prototype with respect to the initial is centered in the pressure system. It has the capability of displacing liquid volumes in the order of microliters. Our pressure pump has an unique arrangement, and it has been designed to be affordable and precise enough to govern the physical parameters involved in microfluidics mechanics. </p> 
 +
                            <p class="lead">Further information can be found in <a href="http://github.com/OpenLabMadrid/iGEM-Madrid-OLM/tree/master/CAD/Pressure%20pump">our Github</a>. </p>
  
 
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                             <h2>Things we learned while doing</h2>
+
                             <h2>Further improvements</h2>
−
                             <ol class="ourlist">
+
                             <p class="lead">Although the microfluidic chip is quite similar to what we consider a final version, there are many situations that we want to warn about to anyone who wants to replicate our setup.</p>
−
                                <li class="nomargin"><p class="lead">The most important lesson we obtain was about the <b>system of measurement</b>. As we had no relevant results in this part, we proceed to change our approach, due to the following reasons:</p></li>
+
                            <p class="lead">Microfluidics does not always behave as we expect. DIY manufacturing is close to artisanry. Getting to a point in which replicability is expected is hard. It requires a lot of time and effort to master the technique.</p>
−
                                <p class="lead nomargin" style="margin-left:5%;">-  The sensor, at 280 nm, did not have a detection limit high enough for our necessities. It could not trace our concentrations.</p>
+
                            <p class="lead">PDMS has a very positive side for DIY manufacturers: it is affordable and resilient. It is easy to understand and a good way of learning microfluidics.</p>
−
                                <p class="lead nomargin" style="margin-left:5%;">-  Optical-based sensors are too sensitive to ambient conditions. So we should refuse to use it in our final design.</p>
+
                            <p class="lead">On the other hand, PMMA micromachining and precision manufacturing involve higher costs and a dependence to a mechanical workshop. You will not implement designs as fast as you can with the workflow that we have developed for PDMS, with the laser, the plasma bonding and the polymerization chamber.</p>
−
                                <p class="lead" style="margin-left:5%;">-  Optical-based sensors are too sensitive to metrologic precision parameters, as emitter-receiver alignment for instance. </p>
+
                            <p class="lead">We would love to share a project for anyone to replicate a microfluidics chip in the most affordable and optimal way. DIY tools are capricious and sometimes they do not behave as we expect them to do. </p>
−
                                <li class="nomargin"><p class="lead">The initial <b>PDMS chips</b> we made were very unstable. Troubleshooting leakages and integrating feasible input/output fittings require patience and creativity. We learnt the following: </p></li>
+
                            <p class="lead">By repairing and refining DIY tools, we have learn a lot of machine design, manufacturing and biodevices design. We consider that DIY is the best way of learning anything. This is the reason why we would love to share our spirit and encourage any interested person to overcome these difficulties and experience the satisfaction of designing, manufacturing and searching beyond the immediate reality.</p>
−
                                <p class="lead nomargin" style="margin-left:5%;">-  Our system should integrate a straightforward way of experimenting with microfluidics.</p>
+
−
                                <p class="lead" style="margin-left:5%;">-  We needed a smooth way of pumping microvolumes into the microfluidic system. PDMS is too sensitive to mechanical parameters, as pressure or input/output torques.</p>
+
−
                                <li><p class="lead"><b>Modular design</b> made our lives much easier.  Designing a chip, cutting it with the laser, curing the PDMS in the polymerization chamber and integrating the fittings was very easy, as we had developed an standard way of doing it.</p></li>
+
−
                                <li><p class="lead">It was not worth it <b>attaching aptamers to the PDMS surface</b>, as the range of detection of the sensor was too far from tracing our concentrations.</p></li>
+
−
                                <li><p class="lead"><b>DIY</b> was the way to go, as we could not spend time and money in buying commercial equipment and learning how to use it. /p></li>
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Revision as of 18:24, 15 October 2018

Madrid-OLM

Microfluidics part of the device

Microfluidics

When the need of moving microvolumes arise as a mandatory requirement of design, microfluidics pops up as the one and only solution. Although there is at hand a wide range of microfluidic commercial solutions, many of them are too expensive to start experimenting with.

That is why our method comes to give an alternative solution. The PDMS manufacturing reveals itself as a tough rival with respect to other alternatives. PDMS was our initial choice, due to its reasonable price and ease of use. As DIY and digital manufacturing constitute the basis of our hardware, we built a workflow around the PDMS chip

The lab workflow for PDMS chips

Foto diagrama workflow

1-Molding of the upper half

  1. Negative: a laser cuts the tape that is adhered to an acetate. The remaining tape is removed carefully. The channels and the chambers, as well as the input and the output have been cutted and the negative has been created. More info about the protocols involved here.

  2. Molding box: (Find the polymerization chamber in our github). Once the negative has been created, it is time to align the acetate with the marks in the polymerization chamber. Depending on the chosen configuration, it might be worth to place the perforated base on the bottom of the acetate.

  3. PDMS casting: PDMS casting was made inside an lab oven most of times. Curing time depended on the drying method selected. More info about the protocols involved here.

2-Molding of the lower half

The process is repeated without the negative.

3-Fixing the two halves

The selected method for fixing both halves was plasma bonding.More info about the protocols involved here.

4-Creating the input and the outputs

We usually used to hole punch the PDMS inlet/outlet with a needle. But we cured the PDMS with a needle inside as another negative volume for molding.More info about the protocols involved here.

5-Injecting fluids into the chip

Automatic controlled microvolume pressure pumps have been developed specifically for our microfluidic chips. Specific plans of the pumps design can be found in our github.

Manufacturing the PMMA chips

Although we are proud of having implemented an affordable workflow for developing functional PDMS chips, we manufactured PMMA chips with micromachining techniques. Our University has a Mechanical workshop that usually machines vacuum chambers, or metallic parts of machines, bending aluminum sheets, etc.

We visited the workshop and asked the workers how to micromachine a PMMA chip with almost 0.2 mm height and 0.8 channel width. We purchased a 0.4 mm tip diameter and adapted the manufacturing to other available tools.

The input and output needed to be modified, and we used 21G needles (0.8 mm) as inlet and outlet. The fitting was made with High Performance Liquid Chromatography (HPLC) 0.8 mm tubes. They fitted tight enough to avoid leaks.

Fluid Mechanics behaviour inside the chip

Once the workflow was designed and implemented, we focused on designing microfluidic concepts that could prove our system right. In this regard, there were some Fluid Mechanics concepts that we would love to experiment. This is why we created the following experiments:

  1. Our mixer: Inside the chip, the fluid behaves in a laminar way. There are many papers on this topic.We wanted to test this experimentally. And that is why we created a mixer. We could study how the fluid behaves in the conditions of a mixer. Our mixer is just an example on how microfluidic components can be small enough to be modularly assembled in series or in parallel as an electronic component.

  2. Flow separation tests: We have designed four experiments to study the behaviour of our flow under different circumstances. The flow circulates towards a triangle, a circle, a throat and the shape of a heart. This will show us how the flow behaves under certain circumstances. Its immediate consequences affect the design of chambers or any microchannel widening.

  3. Droplet generation tests: Generating droplets is one of the milestones of microfluidics. Droplets are small volumes of sample moving as small drops in an arranged and harmonic way. It is much more than just beautiful. The main task of this chip is to study how a fluid and air pressure gradients can work together in the same room. The design pushes to the limit the available capabilities of our device. .

  4. Tree and mixer test: We have designed a large PMMA chip to work as a sample on how fluid behaves when flow is separated into different branches of a tree. The aim of this experiment is to study the laminar flow, and how it behaves when it arrived to the central chamber. On the exact opposite side, a negative relative pressure will be generated to study how it behaves in an alternative “negative relative pressure” tree. In this experiment there are two sides of a chip. Both of them are experimentally equivalent.

  5. A chip adapted to Dropsens GNP110 electrode: We manufactured via regular CNC milling, adapted to micromachining, the housing for a Dropsens GNP110 electrode. A paper proved our arrangement to be functional. We manufactured a two part chip. The upper side was micromilled with a 0.4 mm tool, with a custom made circuit for injecting the protein solution, ferricyanide and buffer solution. We integrated the Dropsens electrode, looking forward to replicating the results obtained in the laboratory:

    6. Binding the aptamers to the electrode

Plasma bonding

After setting the microwave up for treating the chips with plasma, we got some results that might serve as an illustration of the process. Other documentation can be found here. We used a 700W microwave, modded to fit our requirements, as we explain in the protocols section:

Plasma Bonding

We finally configured the microwave to half of its power approximately, inserted a 100ml glass of water and 20 seconds of treatment. After these parameters were established, we got the following results.

One of the indicators that show that plasma is treating the PDMS correctly is the modification of the surface tension of the water on a PDMS surface.

Foto de las gotas

Injection

One of the improvements of the second prototype with respect to the initial is centered in the pressure system. It has the capability of displacing liquid volumes in the order of microliters. Our pressure pump has an unique arrangement, and it has been designed to be affordable and precise enough to govern the physical parameters involved in microfluidics mechanics.

Further information can be found in our Github.

Further improvements

Although the microfluidic chip is quite similar to what we consider a final version, there are many situations that we want to warn about to anyone who wants to replicate our setup.

Microfluidics does not always behave as we expect. DIY manufacturing is close to artisanry. Getting to a point in which replicability is expected is hard. It requires a lot of time and effort to master the technique.

PDMS has a very positive side for DIY manufacturers: it is affordable and resilient. It is easy to understand and a good way of learning microfluidics.

On the other hand, PMMA micromachining and precision manufacturing involve higher costs and a dependence to a mechanical workshop. You will not implement designs as fast as you can with the workflow that we have developed for PDMS, with the laser, the plasma bonding and the polymerization chamber.

We would love to share a project for anyone to replicate a microfluidics chip in the most affordable and optimal way. DIY tools are capricious and sometimes they do not behave as we expect them to do.

By repairing and refining DIY tools, we have learn a lot of machine design, manufacturing and biodevices design. We consider that DIY is the best way of learning anything. This is the reason why we would love to share our spirit and encourage any interested person to overcome these difficulties and experience the satisfaction of designing, manufacturing and searching beyond the immediate reality.