A Nano Pressure Sensor 一种纳米压力传感器

Zinc-oxide nanowires that respond electrically when bent could be used to measure minute forces and pressures.

Twist, bend, or squeeze piezoelectric materials, and they produce electricity--an effect that is used in microphones and telephones. Now, taking advantage of the piezoelectric effect in zinc-oxide nanowires, researchers at Georgia Institute of Technology have made tiny devices that can measure extremely small forces--in the nano-to-piconewton range. That's about the force involved in interactions between two molecules, says Zhong Lin Wang, the materials-science and engineering professor at Georgia Tech who led the research.

Being able to measure such small forces might lead to devices that could be implanted in the body to measure minute blood-pressure changes continuously, Wang says. The sensors could also be installed on the wings of airplanes and spacecraft to monitor very small pressure fluctuations. And because the current flow through the nanowire responds quickly, it could be used to make a sensitive trigger for car air bags. "If it's subject to an external force, then it turns off within a microsecond," Wang says. 【移植体内测量血压，安装飞机或飞行器监视气流压力波动，激发汽车气囊】

By connecting the two ends of a zinc-oxide nanowire to electrodes, Wang's group has made devices similar to the transistors in electronic devices. In an electronic transistor, applying a voltage to the gate electrode controls the flow of current between the source and drain electrodes. In the new pressure-sensing transistor, the two electrodes that the nanowire is connected to act as the source and drain, but there is no gate. Instead of applying a voltage at the gate, one simply bends the wire.

When the nanowire bends, the stretched outer side of the bent wire becomes positively charged, while the compressed inner surface becomes negatively charged. The difference in charges creates a voltage that substitutes for the gate voltage.

Zinc oxide is biocompatible, so one could implant the nanowire pressure sensor in the arm to monitor blood pressure continuously, Wang says. The sensor could transmit the pressure reading to a receiver on one's watch that displays the data.

Because the device is based on the deformation in a single nanowire, "one could think that the sensitivity can be very high," says Yi Cui, professor of materials science and engineering at Stanford University.

The concept could also be applied to other types of sensing. One use for the device could be as a biosensor, Cui says. The principle is that molecules striking or sticking to the nanowires would deform the wire and change the current through it. Researchers could also develop a chemical sensor, in which the chemical reaction disturbs the nanowire, says RPI's Lu.

The idea is at a laboratory stage right now, and the researchers still need to come up with a design for a self-powered pressure-sensor device. This engineering challenge might not be easy, Lu says. "The basic idea is pretty good," he says. "Exactly how you would do it--putting it in the body and getting the response, figure out what's the signal, what's the noise--that's always challenging."【纳米电机供电】

Western Logic

西方人的“强者”逻辑：

第一，你必须有实力；
You should have power!

第二，你必须证明你有实力；
You should certificate your power!

第三，你必须让别人明白，你有勇气和决心在必要时使用你的实力。
You should let us know you have courage and resolution to employ your power if necessary!

Researchers bend nanowires to create new class of electronic components

Mar. 1, 2007 Small Times

Researchers at the Georgia Institute of Technology have taken advantage of the unique coupled semiconducting and piezoelectric properties of zinc oxide nanowires to create a new class of electronic components and devices that could provide the foundation for a broad range of new applications. So far, the researchers have demonstrated field-effect transistors, diodes, sensors, and current-producing nanogenerators that operate by bending zinc oxide nanowires and nanobelts. The new components take advantage of the relationship between the mechanical and electronic coupled behavior of piezoelectric nanomaterials, a mechanism the researchers call "nano-piezotronics."

注: " Nano Piezotronics" 源于 "Mechatronics"相同的构词法。

"Mechatronics" is the synergistic combination of mechanical engineering ("mecha" for mechanisms, i.e., machines that 'move'), electronic engineering ("tronics" for electronics), and software engineering. [Wikipedia]

"Nano-piezotronics utilizes the coupling of piezoelectric and semiconducting properties to fabricate novel electronic components," said Zhong Lin Wang, a Regents Professor in the School of Materials Science and Engineering. "These devices could provide the fundamental building blocks that would allow us to create a new area of electronics."

For example, in a nano-piezotronic transistor, bending a one-dimensional zinc oxide nanostructure alters the distribution of electrical charges, providing control over the current flowing through it. By measuring changes in current flow through them, piezotronic sensors can detect forces in the nano- or even pico-Newton range. Other piezotronic sensors can determine blood pressure within the body by measuring the current flowing through the nanostructures. And, an electrical connection made to one side of a bent zinc oxide nanostructure creates a piezotronic diode that limits current flow to one direction

The nano-piezotronic mechanism takes advantage of the fundamental property of nanowires or nanobelts made from piezoelectric materials: bending the structures creates a charge separation - positive on one side and negative on the other. The connection between bending and charge creation has also been used to create nanogenerators that produce measurable electrical currents when an array of zinc oxide nanowires is bent and then released.

Development of a piezotronic gated diode based on zinc oxide nanowires was reported February 13 in the online advance issue of the journal Advanced Materials. Other nano-piezotronic components have been reported in the journals Nano Letters and Science. The research has been sponsored by the National Science Foundation (NSF), Defense Advanced Research Projects Agency (DARPA), the National Institutes of Health (NHI) and NASA.

"The future of nanotechnology research is in building integrated nanosystems from individual components," said Wang. "Piezotronic components based on zinc oxide nanowires and nanobelts have several important advantages that will help make such integrated nanosystems possible."

These advantages include:

1. Zinc oxide nanostructures can tolerate large amounts of deformation without damage, allowing their use in flexible electronics such folding power sources.
2. The large amount or deformation permits a large volume density of power output.
3. Zinc oxide materials are biocompatible, allowing their use in the body without toxic effects.
4. The flexible polymer substrate used in nanogenerators would allow implanted devices to conform to internal structures in the body.
5. Nanogenerators based on the structures could directly produce power for use in implantable systems.

优点: 大变形 大能量输出 生物兼容性 可移植 纳米发动机
In comparison to conventional electronic components, the nano-piezotronic devices operate much differently and exhibit unique characteristics. In conventional field-effect transistors, for instance, an electrical potential - called the gate voltage - is applied to create an electrical field that controls the flow of current between the device's source and its drain. In the piezotronic transistors developed by Wang and his research team, the current flow is controlled by changing the conductance of the nanostructure by bending it between the source and drain electrodes. The bending produces a "gate" potential across the nanowire, and the resulting conductance is directly related to the degree of bending applied.

"The effect is to reduce the width of the channel to carry the current, so you can have a 10-fold difference in the conductivity before and after the bending," Wang explained.

Diodes, which restrict the flow of current to one direction, have also been created through nano-piezotronic mechanisms to take advantage of a potential barrier created at the interface between the electrode and the tensile (stretched) side of the nanowire by mechanical bending. The potential barrier created by the piezoelectric effect limits the follow of current to one direction.

Nanogenerators, which were announced in the April 14, 2006 issue of the journal Science, harvest energy from the environment around them, converting mechanical energy from body movement, muscle stretching, fluid flow or other sources into electricity. By producing current from the bending and releasing of zinc oxide nanowires, these devices could eliminate the need for batteries or other bulky sources for powering nanometer-scale systems.

Piezotronic nanosensors can measure nano-Newton (10 -9) forces by examining the shape of the structure under pressure. Implantable sensors based on the principle could continuously measure blood pressure inside the body and relay the information wirelessly to an external device similar to a watch, Wang said. The device could be powered by a nanogenerator harvesting energy from blood flow.

Other nanosensors can detect very low levels of specific compounds by measuring the current change created when molecules of the target are adsorbed to the nanostructure's surface. "Utilizing this kind of device, you could potentially sense a single molecule because the surface area-to-volume ratio is so high," Wang said.

穷人富人的差异

1.自我认知穷人：很少想到如何去赚钱和如何才能赚到钱，认为自己一辈子就该这样，不相信会有什么改变。富人：骨子里就深信自己生下来不是要做穷人，而是要做富人，他有强烈的赚钱意识，这已是他血液里的东西，他会想尽一切办法使自己致富。

2.休闲穷人：在家看电视，为肥皂剧的剧情感动得痛哭流涕，还要仿照电视里的时尚打扮自己。富人：在外跑市场，即使打高尔夫球也不忘带着项目合同。

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4.学习穷人：学手艺。富人：学管理。

5. 时间穷人：一个享受充裕时间的人不可能挣大钱，要想悠闲轻松就会失去更多挣钱的机会。穷人的时间不值钱的，有时甚至多余，不知道怎么打发，怎么混起来才不 烦。如果你可以因为买一斤白菜多花了一毛钱而气恼不已，却不为虚度一天而心痛，这就是典型的穷人思维。富人：一个人无论以何种方式挣钱，也无论钱挣得是多 是少，都必须经过时间的积淀。富人的玩也是一种工作方式，是有目的的。富人的闲，闲在身体，修身养性，以利再战，脑袋一刻也没有闲着；穷人的闲，闲在思 想，他手脚都在忙，忙着去麻将桌上多摸几把。

6. 归属感穷人：是颗螺丝钉。穷人因为自身的卑微，缺少安全感，就迫切地希望自己从属并依赖于一个团体。于是他们以这个团体的标准为自己的标准，让自己的一切 合乎规范，为团体的利益而工作，奔波，甚至迁徙。对于穷人来说，在一个著名的企业里稳定地工作几十年，由实习生一直干到高级主管，那简直是美妙得不能再美 妙的理想了。富人：那些团体的领导者通常都是富人，他们总是一方面向穷人灌输：团结就是力量，如果你不从属于自己这个团体，你就什么都不是，一文不名。但 另一方面，他们却从来没有停止过招兵买马，培养新人，以便随时可以把你替换。

7. 投资及对待财富穷人：经典观点就是少用就等于多赚。比如开一家面馆，收益率是100%，投入2万，一年就净赚2万，对穷人来说很不错了。穷人即使有钱，也 舍不得拿出来，即使终于下定决心投资，也不愿冒风险，最终还是走不出那一步。穷人最津津乐道的就是鸡生蛋，蛋生鸡，一本万利……但是建筑在一只母鸡身上的 希望，毕竟是那样脆弱。富人：富人的出发点是万本万利。同样的开面馆，富人们会想，一家面馆承载的资本只有2万，如果有1亿资金，岂不是要开5000家面 馆？要一个一个管理好，大老板得操多少心，累白多少根头发呀？还不如投资宾馆，一个宾馆就足以消化全部的资本，哪怕收益率只有20%，一年下来也有 2000万利润啊