Microfluidic Half Adder Chip Based on Spiking Neural P Systems

Transcription

1 doi: / Microfluidic Hlf Adder Chip Bsed on Spiking Neurl P Systems Yourui Hung* School of Electril nd Informtion Engineering, Anhui University of Science nd Technology, Huinn , Anhui, Chin *C(E-mil: hyr628@163.com) Jun Li, Jichng Xu School of Electricl nd Informtion Engineering, Anhui University of Science nd Technology, Huinn , Anhui, Chin Abstrct Spiking Neurl P systems (shortly clled SN P systems) re kind of distributed, extremely prllel nd nondeterministic bio-computing model, which is hotspot in the field of bio-computing reserch. Due to the limittion of the trditionl devices, the chrcteristics of membrne computing did not show up very well. This pper ttempts to chieve the most bsic function of the microprocessor using microfluidic chip s the hrdwre pltform of membrne computing, through combining the chrcteristics of minituriztion, integrtion nd prllelism of microfluidic. Arithmetic opertion nd logicl opertion re indispensble prts of clculting system. As the bsic unit of vrious kinds of rithmetic opertion, hlf dder directly ffects the performnce nd structure of computer. In this pper, polystryrene prticles insted of spikes complete opertions of membrne computing. Through Coulter counter nd dielectrophoresis seprtion complete the function of hlf dder. Key words: Spiking Neurl P System, Microfluidics, Hlf Adder, Coulter Counter, Dielectrophoresis. 1. INTRODUCTION The chrcteristics of modern science re minituriztion nd integrtion. As incrementl improvements were mde in the microelectronics technology, it is limited by physicl properties of the integrted circuit. When the chip size is reduced to certin extent, its performnce will become very unstble. In order to brek the limittions nd improve performnce of computers, people hve strted to py more ttention to non-trditionl computing models such s biologic computing nd quntum computing. Membrne computing is new brnch of nturl computing, firstly put forwrd by Păun in 1998 (Păun, 2000) to extrct computing models from structures nd functions of tissues or orgns tht composed of living cells. As membrne computing hs better computing performnce nd potentil ppliction vlues, it provided new thoughts to mny importnt nd difficult problems in mny fields. SN P systems re kind of bio-computing device in the field of membrne computing tht bsed on the biologicl phenomen tht one neuron sending spikes to other neurons, firstly put forwrd by Ionescu et l. (Ionescu et l., 2006). SN P system ws n ide tht inspired by distributed nd prllel computing device of spiking neurons. It hs not only good computing performnce but lso well simultes some mechnism of biologicl neurl system (Peng et l., 2013; Wng et l., 2013; Díz-Pernil et l., 2013; Song et l., 2013). Now both theoreticl reserch nd pplied reserch, the vst mjority of the reserch of SN P systems re on trditionl electronic devices. Due to the limittion of the trditionl devices, the chrcteristics of membrne computing did not show up very well. Microfluidic technology integrtes complete lb functions to one chip nd relizes functions through controlling of fluid tht inside the micro-chnnels. Microfluidic chip, the mjor crrier of the microfluidic technology, is widely pplied to prepre micro-chnnels, control nd test modules nd integrtion in nnoscle. Microfluidic chip is lso micro-nlytic system tht integrtes vrious precision functionl components to one chip. The controlled fluid psses through micro-chnnel network to relize functions of microfluidic chip tht integrtes vrious kinds of functions nd structures to relize prllel opertions to finish high throughput nd uto-control tests (Zheng et l., 2013; Frikin et l., 2011). Microfluidic hs been widely used in mny situtions (Cbello-Aguilr et l., 2014; Ning et l., 2014; Pethig, 2010; Li et l., 2014), since it hs the chrcteristics of smll volume, high integrtion nd prllelism. This technology gin dvntge in time nd spce by combining the prllel bility of membrne computing nd microfluidic. Microfluidic chip is different hrdwre pltform compred with the existing computer, nd it hs considerble prospects. Arithmetic opertion nd logicl opertion re indispensible prts in ll computer systems. To chieve the opertion of the microprocessor, the reliztion of the rithmetic opertion nd logicl opertion re essentil. 317

2 Hlf dder is the most bsic computing unit, it is of high prcticbility nd cn be used to construct full dder, counter nd decoder. This pper ttempts to chieve the most bsic function of the microprocessor using microfluidic chip s the hrdwre pltform of membrne computing, through the combintion of the prllel opertion bility of microfluidic nd membrne computing. This microfluidic chip is simple in structure, nd chep nd cn be esily controller nd repetedly used. In this pper, polystryrene prticles insted of spike complete opertions of membrne computing to chieve hlf dder function by optimizing the structure of microfluidic chip. Rest of this rticle is structured s below: the second section introduces the hlf dder model bsed on SN P systems; the third section introduces the design of microfluidic hlf dder chip bsed on SN P systems; the fourth section describes the computing process of microfluidic hlf dder chip nd the finl fifth section summries this study. 2. HALF ADDER MODEL BASED ON SN P SYSTEMS Inspirtion of SN P systems come from the biologicl phenomenon tht neurons send spikes to other neurons for communiction. SN P system model is kind of distributed nd prllel computing model with complicted network structure nd good computing performnce. Different from trditionl computing models, informtion of SN P systems is encoded by unique sign. An SN P system of which hs following structure: In the formul: 1) is set of singleton lphbet nd refers to spike. 2) refers to tht there re neurons in system nd neuron is expressed s in which: (1) refers to the number of spikes included in neuron t the beginning of computtion. (2) refers to the finite set composed by ll rules in neuron nd it hs two forms: - Firing rule:. is regulr expression on. refers to time dely, tht is, the intervl between rule use nd spike relese. If there is (re) spike(s) nd mong which will be consumed fter the rule is being used. After time, one spike will be sent to surrounding neurons connected with this one. - Forgetting rule:.. In one neuron, firing rule nd forgetting rule cnnot be ctivted t the sme time. If the neuron hs spikes nd they will ll be consumed fter the rule being operted. 3) refers to the connection reltionships between neurons. To ech, there will be. 4) respectively refers to input neuron nd output neuron. Input λ 2 2 λ 3 C S Figure 1. Hlf dder model bsed on SN P systems 318

3 In SN P systems, bsic computing unit is clled neuron which cn be expressed by knots of digrph nd connection lines between knots refer to synpses. In this study, model of single-input neuron will be set up to relize the function of hlf dder. Figure 1 shows the detils of the model: Definition structure is s below: In the structure, (1) (2) (3) (4) (5) (6) (7) This model cn relize double-input computing nd ech input signl cn be expressed by. If the number of input is 1, neuron 1 will get 1 spike ( ). Otherwise, neuron 1 will get no spike ( ). In Figure 1, Input refers to dt input, S refers to sum nd C refers to the crry in multi-digit ddition. Dt will be input from Input to neuron 1. (1) When the inputted two numbers re both, it mens tht there re no input of both two numbers t current bit. Neurons 1, 2 nd 3 hve no rules running. The output of C nd S is 0. This mens tht the crry is 0 nd the sum is 0. (2) When the inputted two numbers re respectively, it mens tht one number hs input while the other not. Neuron 1 will run the rule. One spike in neuron 1 will be consumed nd will send one spike to neurons 2 nd 3 respectively. Thus, neurons 2 nd 3 will respectively hve one spike. Neurons 2 nd 3 will run rules nd t the sme time respectively nd then S will output one spike. Figure 2() shows tht there is no spike in neurons 1, 2, 3 nd C. The output of S is 1. This mens tht the crry is 0 nd the sum is 1. (3) When the two inputted numbers re both, it mens tht both two numbers hve input. Neuron 1 will run the rule. Two spike in neuron 1 will be consumed nd send two spikes respectively to neurons 2 nd 3. Thus, there will be two spikes in both neurons 2 nd 3. Neurons 2 nd 3 will run rules nd t the sme time respectively nd then C will output one spike. Figure 2(b) shows tht there is no spike in neurons 1, 2, 3 nd S. The output of C is 1. This mens tht the crry is 1 nd the sum is 0. Figure 2. () Output of hlf dder when the input is ; (b) Output of hlf dder when the input is Progrm with hlf dder functions is written s Figure 1 by using P-Lingu lnguge (Mcís-Rmos et l., 2011) nd simulted by MeCoSim (Pérez-Hurtdo et l., 2010). Results re shown in Figure DESIGN OF MICROFLUIDIC HALF ADDER CHIP BASED ON SN P SYSTEMS 319

4 According to the hlf dder model bsed on SN P systems shown in Figure 1, there re two prts to relize the function of hlf dder: one is running the corresponding rules ccording to the number of spikes within neurons, one is send corresponding number of spikes to connect neurons. We use Coulter counter nd dielectrophoresis seprtion to chieve these two prts in the microfluidic chip Structure of the Coulter counter In microfluidic chip functionl units, the Coulter counter (Rodriguez-Trujillo et l., 2014; Guo et l., 2014; Chen et l., 2015) is simple, rpid nd high precision functionl unit. In this pper, the Coulter counter is used to count the polystyrene prticles insted of the spikes complete opertions of membrne computing. The polystyrene prticles flowing through the sensing chnnel will led to the resistnce chnges of the sensing chnnel, becuse the prticles dischrge the volume of solution from the sensing chnnel. So the core of the Coulter counter theory is the reltionship between the resistnce chnges of the sensing chnnel nd the size of prticles nd the sensing chnnel. According to the principle of the Coulter counter mesuring the resistnce chnge of the sensing chnnel, the bis voltge will be pplied to the whole chnnel by pplying voltge of two electrodes on the inlet nd the outlet. A series of resistnce networks re formed in the microfluidic chnnels filled with electrolyte, so the voltge divider determines the sensing voltge. The sensing voltge cn be mesured by electrodes on the sensing chnnel. Inlet electrode R L V L R 0 R R V R Figure 3. Conceptul schemtics of the Coulter counter V g Outlet Figure 3 shows the conceptul schemtics of the Coulter counter. The bottom lyer is silicon, nd the upper lyer is polydimethylsiloxne. The fluid chnnel includes three prts: the sensing chnnel (with resistnce ) nd two microchnnels (with resistnce nd ) on two sides of the sensing chnnel. A voltge is pplied to the two electrodes in the vicinity of the inlet nd outlet. When the non conducting prticles flow into the microchnnels on both sides, the volume rtio of the prticle nd the fluid chnnel is smll, nd the totl resistnce chnge is negligible. However, when the non conducting prticles flow into the sensing chnnel, the electrolyte will be replced to increse the resistnce of the sensing chnnel. The volume rtio of the prticle nd the sensing chnnel is lrge, so the totl resistnce is not negligible. The chnge of sensing voltge nd the volume rtio of the prticle nd the sensing chnnel is proportionl. Assume tht the resistnce chnge is much smller thn the resistnce of the entire chnnel. In order to mximize the chnge of sensing voltge, we cn crry out the following opertions. First, incresing the bis voltge. Then, incresing the resistnce chnge. The chnge of resistnce is proportionl to the volume of electrolyte replced by the prticle in the sensing chnnel. When the prticle volume is the volume of the sensing chnnel, the output signl is the lrgest. The dimeter of the sensing chnnel should be s smll s possible in the cse of voiding blocking. Finlly, incresing the constnt. The constnt cn be mximized when. The length, width, nd height of the left microchnnel re 2000, 400, 30. The length, width, nd height of the right microchnnel re 666, 400, 30. And the dimensions of the sensing chnnel re 100 long, 30 wide, nd 30 deep. In our fluidic chnnel design, 320

5 nd. When the prticles flow into the sensing chnnel, the signls re mplified nd processed by the signl mplifier connected to the electrode on the sensing chnnel, nd then the dt cquisition re crried out, nd the size nd the number of the prticles through the sensing chnnel cn be obtined. In this pper, polystyrene prticles with 10 nd 15 re used s test smples. The sensing voltge chnges induced by 10 nd 15 polystyrene prticles were detected under the pproprite bis voltge (Chen et l., 2015). The number nd size of the prticles cn be clerly distinguished by the chnge of the sensing voltge Structure of the Dielectrophoresis Seprtion of dielectrophoresis (DEP) (Zhu et l., 2015; Alshreef et l., 2013; Jubery et l., 2014) is not in need of modifiction, non-intrusive, esily controllble nd with simple chip structure. The DEP force is relted to prticle size, electricl property, electricl property of surrounding medium nd intensity, field intensity chnge rte nd frequency of extr electric field. In the field of non uniform lternting electric field nd the phse of the electric field does not chnge, the DEP force of the electriclly neutrl polystyrene prticles suspended in the electrolyte is: It cn be concluded from the bove formul. First, when the prticles re plced in uniform electric field, it will not be subjected to the dielectric force. Then, the DEP force increses with the increse of the prticles size. Finlly, if, then prticles move to regions of highest field strength (positive DEP), or if, then prticles move to regions of lowest field strength (negtive DEP). Outlet D electrode Inlet B Outlet C 15µm 10µm Inlet A Figure 4. Conceptul schemtics of the dielectrophoresis seprtion As shown in Figure 4, width of bypss chnnels A, B, C, D nd the min chnnel is respectively 200, 100, 200, 200 nd 200. Heights of both min chnnel nd bypss chnnels re ll 30. Four electrodes re on the sidewll of the min chnnel nd their heights re sme to those of chnnels. Thus, sme AC field will be generted on the whole chnnel height so tht the DEP force on prticles t different heights will be the sme. When the conductivity of prticles equls to tht of the suspension liquid, polriztion degree of prticle under high frequency will be smller thn tht of the suspension fluid. In this cse, prticles will ber negtive DEP force. The polystyrene prticles of 10 nd 15 re pushed to weker field strength by pplying suitble AC signl on the four electrodes. The DEP force on 15 prticles during movement process is 3.4 times thn tht on 10 prticles so tht motion trils of two kinds of prticles inside chnnels will be different. In this cse, two kinds of prticles cn be seprted. Inlets A nd B re respectively dded with buffer solution nd prticle suspension fluid. When prticle suspension fluid enters into the min chnnel, it will be pressed by the buffer solution so tht prticles will move closely to the upside of the min chnnel. Then, when going through non-uniform electric field, the two different kinds of prticles will be seprted under influence of different DEP force (Mthew et l., 2015). As shown in Figure 4, 15 prticles flow out from outlet C while 10 prticles flow out from outlet D. 321

6 4. COMPUTING PROCESS OF MICROFLUIDIC HALF ADDER CHIP Due to the model of the hlf dder bsed on SN P systems, the structure of the microfluidic chip is designed, which is shown in Figure 5. In this study, 10 nd 15 polystyrene prticles re used respectively to express two input signls to chieve the opertion of microfluidic chip. First, the number of polystyrene prticles entering the Coulter counter through the inlet 1 is detected. And then through the open nd closed microvlves to control the fluid chnnel. Finlly, the seprtion of the prticles is relized by the dielectrophoresis seprtion. According to the rules of the hlf dder model bsed on SN P systems, the output of different number of prticles in different outlets cn relize the function of the hlf dder. And the microvlves re closed t the beginning of the clcultion. (1) If no prticles re detected by the Coulter counter, it mens tht there is no input signl. Two micro-vlves will open t the sme time nd outlets S, C nd 1 will hve no outflow of prticle, which mens the crry is 0 nd the sum is 0 s well. (2) If one prticle is detected by the Coulter counter, it mens tht one bit hs input signl. Neurons 2 nd 3 will get 1 spike, but the neuron 2 hs forgetting rule, nd there will be no output. So micro-vlve 1 will open while micro-vlve 2 will close. The prticle will flow out from outlet S nd there is no prticle t outlets C nd 1, which mens the crry is 0 while the sum is 1. (3) If two prticles re detected by the Coulter counter, it mens tht both two bits hve input signls. Neurons 2 nd 3 will get 2 spikes, but the neuron 3 hs forgetting rule, nd there will be no output. So micro-vlve 1 will close while micro-vlve 2 will open. Prticles in two different sizes enter into the process of seprtion by dielectrophoresis. When prticle suspension fluid enters into the min chnnel, it will be pressed by the buffer solution so tht prticles will move closely to the upside of the min chnnel. Then, when going through non-uniform electric field, the DEP force on 15 prticle during movement process is 3.4 times thn tht on 10 prticle so tht two kinds of prticles cn be seprted. Outlet S will hs no outflow of prticle. 10 prticle will flow out from outlet C nd 15 prticle will flow out from outlet 1. This mens tht the crry is 1 while the sum is 0. Therefore, function of hlf dder chip cn be relized. The output cn be used for the next clcultion, nd cn lso be detected by the Coulter counter. Inlet 1 Outlet S Outlet C Outlet 1 microvlve 1 microvlve 2 Inlet 2 5. CONCLUSIONS Figure 5. Conceptul schemtics of the hlf dder chip In this pper, polystryrene prticles insted of spikes complete opertions of membrne computing. Due to forgetting rules, the structure of microfluidic chip ws optimized. Through Coulter counter nd dielectrophoresis seprtion chieve membrne computing nd complete the clcultion of hlf dder. The hlf dder bsed on microfluidic technology tht we get in this study hs simple structure other thn the complicted logic gte structure in trditionl hlf dders. Microfluidic chip is used s hrdwre pltform of membrne computing. By combining prllel opertion cpbility of membrne computing nd microfluidic, the function of most simple, most bsic nd most importnt of microprocessor is relized. So we cn design nd implement more complex functions nd components, such s the logicl opertions nd rithmetic opertions of the bsic function of the microprocessor. ACKNOWLEDGEMENTS This reserch ws supported by the Ntionl Nturl Science Foundtion of Chin ( nd ). 322

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