Jumat, 15 Februari 2008

ZnO nanogenerator II (lanjutan dari tulisan sebelumnya)

Bagaimana listrik dihasilkan dari nano wire

Oleh : Iwan

Prof Zhong Lin Wang dari Georgia Tech mengilustrasikan bahwa bila kita berjalan kaki, kita dapat menghasilkan daya 67 watt, gerakan jari2 kita menghsilkan 0.1 watt, pernapasan kita 1 watt. Nah bila kita mampu mengkonversikan fraksi dari daya tersebut, maka tubuh kita mampu menjadi sumber daya untuk sebuah divais. Secara konseptual lanjut Prof Zhong Lin Wang, dia mampu mendemostrasikan konversi daya yang mungkin untuk sebuah divais mencapai 17-30 persen dari total daya yang dihasilkan oleh tubuh kita.

Hasil dari penelitian di grup riset Prof Zhong Lin Wang dapat mengkonfirmasi sebuah teori bahwa: ZnO nanowire akan menunjukkan efek piezoelektrik yang sangat baik, yaitu menghasilkan sifat listrik dari respon tekanan mekanik. Biasanya muatan negative dan positif dari ion Zinc dan Oksigen di dalam kristal ZnO nanowire saling meniadakan. Namun ketika wire secara kimiawi tumbuh di permukaan elektroda, wire tersebut membengkok akibat adanya vibrasi external dari tip yang berskala nano. Tip tersebut adalah tip dari atomic force microscopy (AFM) yang terbuat dari bahan Si yang dilapisi oleh Pt. Pembengkokan dari ZnO nanowire menyebabkan terjadinya dipol listrik di dalam nanowire. Pada bagian yang mengalami kompresi bermuatan negatif sedangkan bagian yang terekpansi bermuatan positif. Hal itu disebabkan Zn2+ dan pole negatif akibat dari O-2. Maka dengan adanya kontak metal semikonduktor mengakibatkan adanya Schotcky barrier rectifyng dimana kontak antara tip AFM dengan pole yang bermuatan positif berlaku seperti forward bias sebaliknya tip AFM dengan pole negatif berlaku seperti reverse bias. Pada keadaan forward bias elektron akan mudah mengalir ke metal sebaliknya pada reverse bias elektron akan mengalami kesulitan. Fenomena itu dapat dilukiskan oleh grafik hubungan antara tegangan dan arus pada dioda, sedangkan mekanisme tranport-nya dapat diilustrasikan secara mudah dengan melihat diagram energi antara metal dan semikonduktor. Sebagai ilustrasi dari fenomena dihasilkannya arus listrik pada ZnO nanowire dapat di lihat pada gambar 2 dan 3.

Gambar 2. Nanowire dari ZnO yang mengkonversi energy mekanik menjadi listrik.

Gambar 3. Para peneliti menggunakan tip atomic force microscope (AFM) yang berbentuk
segitiga untuk mengaplikasikan gaya ke nanowire dan tegangan dapat diukur.

Prof Zhong Lin Wang menjelaskan pula bahwa, meskipun secara individual nanowire menghasilkan sebuah daya yang kecil, dengan banyaknya nanowire secara simultan akan menghasilkan jumlah daya yang besar. Beliau juga menjelaskan bahwa energi dari nanowire yang dikembangkan di laboratoriumnya disinyalir memiliki cukup energi untuk menjalankan implant medis berukuran kecil. Contoh dari implant tersebut adalah implant dari sensor gula darah di bawah permukaan kulit.
Sungguh luar biasa perkembangan nanoteknoloi saat ini, tidak terbayangkan bila hal itu terwujud maka dalam kurun waktu 5 tahun lagi dimungkinkan kita dapat mengcharge ipod melalui sepatu kita yang sudah difasilitasi dengan sumber listrik dari ZnO nanogenerator.

Sumber gambar :

Kamis, 14 Februari 2008

Analog-Digital. What’s the Difference?

Perhaps this article is useful for people who want to know at glance the different between analog and digital system.

taken from : http://telecom.hellodirect.com/docs/

by Paul Wotel

Analog phone lines. Analog signals. Digital security. Digital PBX. Analog-to-digital adapters. What does it all mean? In the telecom world, understanding analog versus digital isn't as simple as comparing one technology to another. It depends on what product—and in some cases, which product feature—you happen to be talking about.
Analog at a glanceAs a technology, analog is the process of taking an audio or video signal (in most cases, the human voice) and translating it into electronic pulses. Digital on the other hand is breaking the signal into a binary format where the audio or video data is represented by a series of "1"s and "0"s. Simple enough when it's the device—analog or digital phone, fax, modem, or likewise—that does all the converting for you.
Is one technology better than the other? Analog technology has been around for decades. It's not that complicated a concept and it's fairly inexpensive to use. That's why we can buy a $20 telephone or watch a few TV stations with the use of a well-placed antenna. The trouble is, analog signals have size limitations as to how much data they can carry. So with our $20 phones and inexpensive TVs, we only get so much.
Enter digital The newer of the two, digital technology breaks your voice (or television) signal into binary code—a series of 1s and 0s—transfers it to the other end where another device (phone, modem or TV) takes all the numbers and reassembles them into the original signal. The beauty of digital is that it knows what it should be when it reaches the end of the transmission. That way, it can correct any errors that may have occurred in the data transfer. What does all that mean to you? Clarity. In most cases, you'll get distortion-free conversations and clearer TV pictures.
You'll get more, too. The nature of digital technology allows it to cram lots of those 1s and 0s together into the same space an analog signal uses. Like your button-rich phone at work or your 200-plus digital cable service, that means more features can be crammed into the digital signal.
Compare your simple home phone with the one you may have at the office. At home you have mute, redial, and maybe a few speed-dial buttons. Your phone at work is loaded with function keys, call transfer buttons, and even voice mail. Now, before audiophiles start yelling at me through their PC screens, yes, analog can deliver better sound quality than digital…for now. Digital offers better clarity, but analog gives you richer quality.
But like any new technology, digital has a few shortcomings. Since devices are constantly translating, coding, and reassembling your voice, you won't get the same rich sound quality as you do with analog. And for now, digital is still relatively expensive. But slowly, digital—like the VCR or the CD—is coming down in cost and coming out in everything from cell phones to satellite dishes.
When you're shopping in the telecom world, you often see products touted as "all digital." Or warnings such as "analog lines only." What does it mean? The basic analog and digital technologies vary a bit in definition depending on how they're implemented. Read on.
Phone lines Analog lines, also referred to as POTS (Plain Old Telephone Service), support standard phones, fax machines, and modems. These are the lines typically found in your home or small office. Digital lines are found in large, corporate phone systems.
How do you tell if the phone line is analog or digital? Look at the back of the telephone connected to it. If you see "complies with part 68, FCC Rules" and a Ringer Equivalence Number (REN), then the phone and the line are analog. Also, look at the phone's dialpad. Are there multiple function keys? Do you need to dial "9" for an outside line? These are indicators that the phone and the line are digital.
A word of caution. Though digital lines carry lower voltages than analog lines, they still pose a threat to your analog equipment. If you're thinking of connecting your phone, modem, or fax machine to your office's digital phone system, DON'T! At the very least, your equipment may not function properly. In the worst case, you could zap your communications tools into oblivion.
How? Let's say you connect your home analog phone to your office's digital line. When you lift the receiver, the phone tries to draw an electrical current to operate. Typically this is regulated by the phone company's central office. Since the typical proprietary digital phone system has no facilities to regulate the current being drawn through it, your analog phone can draw too much current—so much that it either fries itself or in rare cases, damages the phone system's line card.
What to do? There are digital-to-analog adapters that not only let you use analog equipment in a digital environment, but also safeguard against frying the internal circuitry of your phone, fax, modem, or laptop. Some adapters manufactured by Konexx come designed to work with one specific piece of office equipment: phone, modem, laptop, or teleconferencer. Simply connect the adapter in between your digital line and your analog device. That's it. Or you can try a universal digital-to-analog adapter such as Hello Direct's LineStein®. It works with any analog communications device. Plus, it's battery powered so you're not running extra cords all over your office.
Cordless phones The very nature of digital technology—breaking a signal into binary code and recreating it on the receiving end—gives you clear, distortion-free cordless calls. Cordless phones with digital technology are also able to encrypt all those 1s and 0s during transmission so your conversation is safe from eavesdroppers. Plus, more power can be applied to digital signals and thus, you'll enjoy longer range on your cordless phone conversations.
The advantage to analog cordless products? Well, they're a bit cheaper. And the sound quality is richer. So unless you need digital security, why not save a few bucks and go with an analog phone? After all, in home or small office environments where you may be the only cordless user, you won't have any interference issues.
Keep in mind, when talking about digital and analog cordless phones, you're talking about the signals being transferred between the handset and its base. The phones themselves are still analog devices that can only be used on analog lines. Also, the range of your cordless phone—analog or digital—will always depend on the environment.
Cellular phones Perhaps the most effective use of the digital versus analog technology is in the booming cellular market. With new phone activations increasing exponentially, the limits of analog are quickly being realized. Digital cellular lets significantly more people use their phones within a single coverage area. More data can be sent and received simultaneously by each phone user. Plus, transmissions are more resistant to static and signal fading. And with the all-in-one phones out now—phone, pager, voice mail, internet access—digital phones offer more features than their analog predecessors.
Analog's sound quality is still superior—as some users with dual-transmission phones will manually switch to analog for better sound when they're not concerned with a crowded coverage area—but digital is quickly becoming the norm in the cellular market.
What to buy? The first thing to consider when buying analog or digital equipment is where you'll be using it. If you're buying for a proprietary PBX phone system, you'll need to get the digital phone designed for that particular system. Need to connect a conferencer on your digital system? Opt for a digital-to-analog adapter. Shopping for home office equipment? Most everything you'll consider is analog. Want an all-in-one cellular phone—paging, voice mail, web? A digital cellular phone will deliver it all. In fact, the only head-scratcher may be your cordless phone purchase. Looking for security and distortion-free conversations in your small office? Go with a digital 900 MHz or 2.4 GHz cordless phone. Using a cordless at home? An analog phone will give you the richest sound quality and usually enough range.

Kegiatan awal bulan Februari 08....

oleh : Iwan (nulis aja daripada bengong)

Awal bulan Februari ini kegiatan utama saya masih sibuk mengurusi masalah sistem metal organic chemical vapor deposition (MOCVD). Sejak awal bulan Februari sistem belum bener2 fix untuk experiment. Dan kegiatan tersebut tertunda karena liburan imlek. Liburan imlek buat saya menjadikan moment yang berharga untuk bisa pulang ke Indonesia. Kebetulan di saat yang sama ada urusan administrasi di UNJ yang harus diselesaikan.Biasanya kalo saya pulang ke Indonesia saya selalu menyempatkan mengurus hobi saya beternak ayam jago bangkok, diskusi dengan Bapak Ibu, bercengkarama dengan sepupu2, berkunjung ke kantor di daerah Puri Jalan Sawangan Depok, mengurus mobil, dan sedikit meluangkan waktu ngobrol dengan tetangga di komplek. Selain itu, saya sempat juga main ke FMIPA UI pada hari Sabtu tanggal 9 Feb 08, disana saya hanya ngobrol saja dengan teman2 dekat saya.

Saya sedikit cerita tentang pengalaman baru saya di UNJ, saya kebetulan bergabung menjadi staf di jurusan Fisika FMIPA UNJ. Sudah diperkirakan bahwa keadaan di UNJ tentu jauh berbeda bila dibanding dengan UI. Namun demikian, bagi saya itu adalah tantangan untuk bisa memajukan Fisika UNJ atleast bisa exist di dalam riset level nasional. Bila itu dapat konsisten terwujud tidak dimungkinkan Fisika UNJ mampu berkompetisi riset di ajang internasional baik secara indvidual staf yang menggunakan nama UNJ atau secara institusional mampu mengadakan event seminar or conference level regional untuk melangkah ke internasional. Pada kesempatan liburan imlek, saya sempat melihat2 kondisi laboratorium yang dimiliki Fisika UNJ.
Secara pribadi saya memiliki harapan bahwa kelak Fisika UNJ bisa memberikan sebuah kontribusi yang baik terutama dalam memajukan Fisika dari dua sudut pandang yang tidak dapat dipisahkan, yaitu Fisika kependidikan dan non kependidikan. Sebuah perpaduan unik, namun hal itu bisa menjadi ujung tombak UNJ. Bila saya bandingkan dengan National Institute of Education (NIE) di Singapore, mereka juga lebih kurang memeliki sistem yang hampir sama dengan UNJ, yaitu ada dua program kependidikan dan non kependidikan. Namun cita-cita yang diarahkan adalah untuk menciptkan insan yang dapat memajukan dunia riset melalu jalur pendidikan. Mungkin perlu kiranya, institusi di Indonesia yang berkecimpung dalam riset kependidikan belajar dari NIE.

Sekembali dari Indonesia, saya kembali sibuk dengan urusan riset di nanoelecronics lab, sibuk dengan kuliah dan juga mengurus apartemen baru di daerah Jurong West. Ohya, ada hal menarik juga yang saya kerjakan dengan teman saya Yudhiakto yang saat ini sedang studi doktoral di USA. Saat ini kita sama2 mewujudkan sebuah media untuk menyiarkan informasi tentang sain teknologi dan pendidikan. Media tersebut merupakan sebuah reinkarnasi dari media sejenis yang terdistribusi untuk lingkungan sendiri. Dulu kita distribusikan hanya di lingkungan civitas Fisika UI. Media tersebut bernama Foton, nah kini kita menghadirkan media yang hampir sama namun ditujukan untuk semua kalangan dengan cakupan sain teknologi dan pendidikan. Media yang merupakan reinkarnasi dari Foton kami beri nama Exciton. Ada filosofi khusus dibalik pemilihan nama tersebut. Untuk lebih jelasnya kunjungi saja web exciton di :


At last but not least, sekian dulu informasi dari saya. Happy lunar new year and happy valentine day for all.