2009) 4 (22 المجلد مجلة ابن الھیثم للعلوم الصرفة والتطبیقیة شفاف كهرومیكانیكي) نیكـل-بولیمـر( تصنیع متحسس *صبیحة عبدالجبار بدن ، امیرة عبدالحمید الربیعي، عبدالحمید رحیم الصراف حسن اسماعیل دمبوس اوزارة العلوم والتكنولوجی/ دائرة علوم المواد جامعة بغداد ،كلیة التربیة ابن الهیثم ، قسم الفیزیاء * ةــالخالص موصلة للكهربائیة اموادبوصفها لكترونیة متعددة اتطبیقیة في مجاالت ألخیرة اةــاآلون يـــف راتـالبولیم تـاستخدم النیكل وق حمسحاویة على هملم واقل من) 1 (حضرت في هذا البحث أغشیة بولیمریة بسمك. ً للضوء معا)شفافة(ونافذة او لترتیب درجة مئویة120 بدرجة حرارة معدني وعولجت قبل تصلبها في مجال مغناطیسي داخل فرن مفرغ من الهواءال أظهرت هذه األغشیة قابلیتها .وتهیئته للنقل االتجاهي للكهربائیةتوجیه دقائق مسحوق النیكل في االساس البولیمري ).قوة لوحدة المساحة (ح سطالضع على للتحسس الى أي حمل یو ان استعمال االحمال الخفیفة ووضعها على وحدة الخلیة الكهربائیة لهذه االغشیة تمكننا من الحصول على .استخدامه في دوائر تحسس الكهربائیة التطبیقیة متحسس كهربائي شفاف، الذي من الممكن IBN AL- HAITHAM J . FO R PURE & APPL. SC I. VOL.22 (4) 2009 Forming Electro - Mechanical Transparent (Polymer -Ni) Sensor S. A. AL.Bedin, A .A . ALHame d, A. R. AL.Sarraf * , H.I.Dambus Ministry of Science and Technology, Iraq * Department of physics, College of Education Ibn Al-Haitham, Unive rsity of Baghdad Abstract Poly mers (Silicon elastomer) are used lately as a conductive material in electronic application in addition to be transp arent, to light. In this p ap er we p rep ared p olymer films about (1mm) thick and less which contain Ni- metal p owder cured in magnetic vacuu m furnaces at temp erature 120°C in order to arrange or to be or iented the p articles of the Ni- p owder through the p oly mer in such a way to be conductive for electric currents. We found that these films are sensitive to any loads on the surface (force p er unit area). Using light loads on a unit electric cell from these films, we get an electric transp arent sensor t hat could be used in sensin g app lications. Keywords: Polymers, Ni -powder, el ectrical sensor Introduction Opt ically transp arent but electrically conductive materials are usefu l for a variety of visual communication, sensor, and electronic device app lications. [1] Transp arent materials are in general electrical insulators or high resistively semiconductors because they have very low mobile char ge carriers. Although some comp osite materials (such as glass coated with thin transp arent metal) have bot h transp arency and electrical conductivity , which is useful for a variety of device app lications [2]. In order to create a transp arent sheet with vertical conducting p aths, we utilized magneti c field alignment of conductive ferromagnetic p articles in a transp arent matrix material. When ferromagnetic sp heres randomly disp ersed in a viscous medium are subjected to directional magnetic fields, they move and align themse lves into a chain configuration to minimize the magneto st atic energy . The matrix material such as glass, silicon elast omer, epoxy resin and so forth can be cured with a metal led to a comp osite structure that both op tically and electrically an isot rop ic [3, 4] . Experime ntal App roximately weight fraction 10-65% of Ni- p owder with an average diameter of about 20 um was thorou ghly mixed by rule of mixtures with op tically transp arent, uncured silicon elastome witch was p rovided by General Comp any of Chemical Indust ry . The mixture IBN AL- HAITHAM J . FO R PURE & APPL. SC I. VOL.22 (4) 2009 was sp read on a flat glass subst rate and a doctor blade was used to form a thin Lay er about (1mm) thick and less than; then it was heat -cur ed (120°C for 15min with 10 - 2 mbar vacuu m) in vacuum oven with the presence of vertical magnetic field of about 0.2 mT. T he cured sheet was p eeled off the substrate and tested for optical and electrical p rop erties [5, 6]. Results and Discussion We measured the electrical conductivity of the comp osite medium in the X – Y directions by using four p robe techniques. We found from the obtained r esults that the conductive material chan ges according to the f ilm thickness. That means when we use a thicker film, the conductive decr eases, due to the alignment of p articles inside the furnace through the magnetic ar ea in comp arison with t hickness. Fig (1-a) shows the structure of the electric unit cell circuit used for the composite film. The comp osite sheet was sandwiched between two circuit boards ( myler sheet) coated with Al. Avominal pressure (we use this term to determine the affected pressure on the film, whi ch is a p ressure resulted fro m a local p ressure as a h ead p en or a thumb)as in fig (1-b) was applied durin g the measure ment to ensure good contacts between metal sp heres so the average through resistance of the comp osite medium was measured so small between 1 and 2 p oints [7]. Fig. (2) indicates the changing of electrical conductive by outside p ressure (load) on the Nickel p articles, which get a conductive we can use in film sensors. We noticed that the electrical condu ctivity increases due to the decreas of electrical resistance when increasing the load to a p articular value, which d epends on the film thickness and its method of p rep aring. Thus, bey ond this value, this film will lose its feature. The p henomenon of p articles align ment or Nickel atoms in the medium of insulated p oly mers which is called (p ercolation eff ect) that leads t o the chan ge of Nickel – p olymer to a conductive medium because the p olymer here should characterize with a sort of flexibility , so the atoms can move and return to the zero p oint (the beginnin g) when the external effect vanishes. The weight fraction of Nick el in polymer (as a volume) p lay s a role in determining the value of electrical conductive of the p rep ared film. In fig. (3), the optical microscope p icture indicates the effect range of Nickel concentration in the medium of p olymers up on the film transp arency to light in addition to conductive. We found that there was a relation between Nickel concentration and its distribution inside the film on the electrical – mechanical conductive. The increasing of Nickel concentration does not mean increasing of conductive unless the atoms ali gnment allow to electrical si gn to p ass through an external load that p ushes t he atoms closer and deletes the internal gaps, and that leads to gett ing the electrical sign. That depends on the Nickel atoms array of the film inside the furnace after the thermal treating. Conclusion An opt ically transp arent, Z- direction conductive med ium such as described here may be useful as a p ressure sensor for visual communication devices such as a write pads or finger – touch sensitivity disp lay screens. T he feasibility of the device dep ends on the concentrations of comp osite medium containing about 1% by volume of the p articles. IBN AL- HAITHAM J . FO R PURE & APPL. SC I. VOL.22 (4) 2009 Re ference 1.Eur, J. (1999) “Self – Assembled M onolyers as Interface for Organic Op to-Electronic Devices”. Phy s. Bll 505:512 . 2.Nicast ro, A. J. (1983) “Demonstrations of Some Op tical Prop erties of Liquid Cry st als”. Phys. Tech. 21: 181. 3.M artin, S. J. ; Kambili, A. and Walker, A. (1977) “ Temp erature and Field Dep endence of the M obility in liquid Cry stal-Cryst alline Conju gated Poly mer Films”, Advances in Electrically Conductive M aterials, Calverton Down, UK 4.Berger, K. E. and Donald, S.D. (1988) “ Journal of M aterials Science”, 23(4) : 1368 5. Collins,P. J. (1990), “Liquid Crystals Nature Delicate Phase of M atter”, Princton University , Press, Princton. 6.Kleja, P. U. (1987) “ Liquid Cryst al Phy sics”, Encyclop edia of Phy sical Scienmce and Technologe, Academic Press 7:365. 7.Braum, D.; Cherobon, H. ; Reh ahn, M .; Riher, H. and Voits, B. (2005) “Poly mer Sy nthesis Theory and Practice”, Sp ringer-verlay Berlin Heidber g,, P.154 . Fig. (1): Diagram of e lectric unit cell circuit used the (polyme r – Ni) film (a): before and (b): after a local pressure applied IBN AL- HAITHAM J . FO R PURE & APPL. SC I. VOL.22 (4) 2009 Fig. (2): Shows the relation between the average resistance and a local load applied for the three different thickness films 0 5 10 15 20 0 50 100 15 0 Load (gm) R a ve t=50 (K W ) (mm) 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 140 Load (gm) R a v e t = 400 (K W ) (mm) 0 100 200 300 400 500 600 700 800 0 10 20 30 40 50 Load (gm) R a v e t=700 (K W ) (mm) IBN AL- HAITHAM J . FO R PURE & APPL. SC I. VOL.22 (4) 2009 Fig. (3): The E.M. picture of the film transparency at different weight fraction of Ni in silicon elstomer (a) Ni =65% Ni = 53% Ni = 43% (e ) Ni = 27% Ni = 60% (d) (b) (c)