3D printing used to make glass optical fiber preform

Researchers have developed a way to use 3D printing to create a preform that can be drawn into silica glass optical fibers, which form the backbone of the global telecommunications network. This new fabrication method could not only simplify production of these fibers but also enable designs and applications that weren't possible before.

A stretchable stopwatch lights up human skin

Imagine a runner who doesn't need to carry a stopwatch or cell phone to check her time: She could just gaze at the glowing stopwatch display on the back of her hand. Such human-machine interfaces are no longer science fiction, but they still have a way to go before becoming mainstream. Now, researchers have developed a stretchable light-emitting device that operates at low voltages and is safe for human skin.

Study shows ability to detect light from UV to the IR optical regimes using spin currents

The spin Seebeck effect (SSE) can be used to detect light across a broad optical range -- ultraviolet through visible to near-infrared. This has future implications on novel spin current-based technologies.

An electronic signal expands a material by a factor of 100

Researchers have discovered a material that can both increase and reduce its volume when exposed to a weak electrical pulse. In a sponge, or filter, the researchers can control the size of particles that pass through.

Intuitive virtual reality: Bimodal 'electronic skin' developed

Through the crafty use of magnetic fields, scientists have developed the first electronic sensor that can simultaneously process both touchless and tactile stimuli. Prior attempts have so far failed to combine these functions on a single device due to overlapping signals of the various stimuli. As the sensor is readily applied to the human skin, it could provide a seamless interactive platform for virtual and augmented reality scenarios.

Tungsten suboxide improves the efficiency of platinum in hydrogen production

Researchers presented a new strategy for enhancing catalytic activity using tungsten suboxide as a single-atom catalyst (SAC). This strategy, which significantly improves hydrogen evolution reaction (HER) in metal platinum (pt) by 16.3 times, sheds light on the development of new electrochemical catalyst technologies.

Giving valleytronics a boost

Physicists have revealed a new quantum process in valleytronics that can speed up the development of this fairly new technology.

Magnetics with a twist: Scientists find new way to image spins

Researchers have put a new spin on measuring and controlling spins in nickel oxide, with an eye toward improving electronic devices' speed and memory capacity.

Paving the way for sensor interfaces that are 30 times smaller

Researchers have invented a novel class of Digital-to-Analog (DAC) and Analog-to-Digital Converters (ADC) that can be entirely designed with a fully-automated digital design methodology.

Novel nanoprobes show promise for optical monitoring of neural activity

Researchers have developed ultrasensitive nanoscale optical probes to monitor the bioelectric activity of neurons and other excitable cells. This novel readout technology could enable scientists to study how neural circuits function at an unprecedented scale by monitoring large numbers of individual neurons simultaneously. It could also lead to high-bandwidth brain-machine interfaces with dramatically enhanced precision and functionality.

Flexible, wearable supercapacitors based on porous nanocarbon nanocomposites

Evening gowns with interwoven LEDs may look extravagant, but the light sources need a constant power supply from devices that are as well wearable, durable, and lightweight. Chinese scientists have manufactured fibrous electrodes for wearable devices that are flexible and excel by their high energy density. A microfluidic technology was key for the preparation of the electrode material was a microfluidic technology, as shown in the journal Angewandte Chemie.

Alignment of single-wall carbon nanotubes along common axis

The researchers used machine-vision automation and parallelization to simultaneously produce globally aligned, single-wall carbon nanotubes using pressure-driven filtration.

Researchers build a soft robot with neurologic capabilities

In work that combines a deep understanding of the biology of soft-bodied animals such as earthworms with advances in materials and electronic technologies, researchers have developed a robotic device containing a stretchable transistor that allows neurological function.

Controlling the charge state of organic molecule quantum dots in a 2D nanoarray

Researchers have fabricated a self-assembled, carbon-based nanofilm where the charge state (ie, electronically neutral or positive) can be controlled at the level of individual molecules. Molecular self-assembly on a metal results in a high-density, 2D, organic quantum-dot array with electric-field-controllable charge state, with the organic molecules used as 'nano-sized building blocks' in fabrication of functional nanomaterials. Achieved densities are an order of magnitude larger than conventional inorganic systems.

What is Negative Voltage?

I’m going to show you what negative voltage is by putting John into a hole. As you’ll quickly learn, it’s nothing weird or mystical.

Meet John. He is 1.8 meters (6 feet) tall.

What does it mean that John is 1.8 m tall? Could you find his height by only looking at his head?

No. You have to compare the top of his head to the ground he is standing on to be able to find his height. That John is 1.8 m tall really means that the top of his head is 1.8 m higher than the ground that he stands on.

It’s the same thing with voltage. You can’t say anything about the voltage without comparing it to another point.

It’s common to define a zero point (0V), or ground, in a circuit.

In a simple battery circuit, the ground point is usually the minus terminal of the battery. So if someone says that “this point is 5V”, they usually mean it’s 5V compared to ground.

Putting John in a Hole

Back to John. What if we dig a hole of 1.8 meters, then put John into the hole. (Poor John).

His feet are now 1.8 meters below the ground.

Another way of saying this is that his feet are at MINUS 1.8 meters.

John is still the exact same person, he’s just placed differently compared to the ground. Therefore the position of his feet becomes negative.

It’s the same with voltage.

Creating Negative Voltage

For example, imagine two 9V batteries.

Remember – a battery being 9V means the plus terminal is 9V higher than the minus terminal.

Now, let’s take one battery and say that its minus terminal is going to be the ground (0V) in our circuit.

What happens if we connect the plus of the second battery to the minus of the first one (i.e. we connect it to ground)?

Nothing really happens with the batteries. They’re exactly the same as they were before connecting them.

And no current flows.

But what is the voltage on the minus terminal of the second battery?

Since the minus is 9V lower than the plus, and since the plus is connected to ground, the minus would have to be minus 9V.

So we have created a negative voltage of 9V.

Or have we?

If you look closely, we haven’t really created anything.

We’ve just labeled the plus of the second battery 0V.

And we’ve labeled the minus of the second battery -9V, because it’s 9V lower than 0V.

When Do You Need Negative Voltage?

It’s not so much that you “need” negative voltage. But sometimes you get negative voltage in a circuit, and it’s good to know what it is.

One example where you get negative voltage is in the astable multivibrator circuit.

Sometimes you see circuits that need a power supply with three connections, for example, +9V, 0V, and -9V. This is very common for amplifier circuits.

But they might as well have said that the circuit needs +18V, +9V, and 0V (GND). It would have been the exact same thing, just with different names.

Questions?

If you find these lessons useful, you should check out Ohmify. It’s an online academy for electronics where you learn everything from how voltage works to how you can design a microcontroller circuit.

And there are a bunch of project plans you can follow to build cool things like robots, traffic lights, amplifiers, a kitchen timer, music synthesizers and more.

Click here to learn more about Ohmify.

Do you have any questions about negative voltage? Let me know in the comments field below.

Copyright Build Electronic Circuits

How to control friction in topological insulators

Topological insulators are innovative materials that conduct electricity on the surface, but act as insulators on the inside. Physicists have begun investigating how they react to friction. Their experiment shows that the heat generated through friction is significantly lower than in conventional materials. This is due to a new quantum mechanism, the researchers report.

Creating 2D heterostructures for future electronics

New research integrates nanomaterials into heterostructures, an important step toward creating nanoelectronics.

'Electroadhesive' stamp picks up and puts down microscopic structures

New technique could enable assembly of circuit boards and displays with more minute components.

New soft actuators could make soft robots less bulky

Engineers have developed a way to build soft robots that are compact, portable and multifunctional. The advance was made possible by creating soft, tubular actuators whose movements are electrically controlled, making them easy to integrate with small electronic components. As a proof of concept, engineers used the new actuators to build an untethered, battery-powered, walking soft robot and a soft gripper.

Intelligent, shape-morphing, self-healing material for soft robotics

Advances in the fields of soft robotics, wearable technologies, and human/machine interfaces require a new class of stretchable materials that can change shape adaptively while relying only on portable electronics for power. Researchers have developed such a material that exhibits a unique combination of high electrical and thermal conductivity with actuation capabilities that are unlike any other soft composite.

Novel, high-performance diodes and transistors

Today's computer processors are increasingly pushed to their limits due to their physical properties. Novel materials could be the solution. Physicists have investigated if and how these materials might be developed. They have created, tested and filed a patent for a concept that utilizes the latest findings from the field of spintronics.

Physicists unlock the mystery of thermionic emission in graphene

Researchers discover a new theory that paves the way for the design of better graphene electronics and energy converters.

Picoscience and a plethora of new materials

The revolutionary tech discoveries of the next few decades may come from new materials so small they make nanomaterials look like lumpy behemoths. These materials will be designed and refined at the picometer scale, which is a thousand times smaller than a nanometer. A new study moves picoscience in a new direction: taking elements from the periodic table and tinkering with them at the subatomic level to tease out new materials.

Graphene turns 15 on track to deliver on its promises

Scientists analyze the current graphene landscape and market forecast for graphene over the following decade.

Why does the battery voltage change?

Today I got a question from Garry on the Ohmify community.

[GARRY]:
“When I measure the voltage of my 9V battery using my multimeter I get a reading of 9.06 when it is not connected to any circuit. When I hook the battery up to a simple circuit (i.e. 325 Ohm resistor in series with a red LED) and measure the voltage drop across the battery I get a reading of 8.65 V – why the difference?”

[OYVIND]:
Great observation! That’s the difference between an ideal battery that we often use to make calculations in a circuit and a real battery.

The reason for this is that a real battery has an internal resistance. The size of the internal resistance depends on the battery type.

So the voltage you can squeeze out of a battery actually depends on what you connect to it!

In the image above, the battery has an internal resistance of 1 ohm. If you connect that to something of 500 ohms, you can figure out the battery voltage by using the voltage divider formula:
V = 9V * 500 ohm / (1 ohm + 500 ohm) = 8.98 V

If you connect it to something of 50 ohms, you get:
V = 9V * 50 ohm / (1 ohm + 50 ohm) = 8.82V

So there you have it! Because of the internal resistance of the battery, the voltage from the battery will change depending on the load you connect to it.

If you want to learn electronics, check out the electronics academy Ohmify. One of the main benefits is the community forum – where you’ll be able to ask all these questions that come up when you experiment with circuits.

Learn more about Ohmify here:
https://ohmify.com/join/

Keep On Soldering!
Oyvind @ build-electronic-circuits.com

Copyright Build Electronic Circuits

Printed electronics open way for electrified tattoos and personalized biosensors

Electrical engineers have devised a fully print-in-place technique for printable electronics that is gentle enough to work on delicate surfaces ranging from paper to human skin. This can be accomplished without additional steps to bake, wash or powder-coat materials. The advance could enable technologies such as high-adhesion, embedded electronic tattoos and bandages with patient-specific biosensors.

Keeping cool with quantum wells

A research team has invented a semiconductor quantum well system that can efficiently cool electronic devices using established fabrication methods. This work can allow for smaller and faster smart devices that consume less power.

Researchers repurpose failed cancer drug into printable semiconductor

Many potential pharmaceuticals end up failing during clinical trials, but thanks to new research, biological molecules once considered for cancer treatment are now being repurposed as organic semiconductors for use in chemical sensors and transistors.

Tunable optical chip paves way for new quantum devices

Researchers have created a silicon carbide (SiC) photonic integrated chip that can be thermally tuned by applying an electric signal. The approach could one day be used to create a large range of reconfigurable devices such as phase-shifters and tunable optical couplers needed for networking applications and quantum information processing.

Ultra-fast optical way to extract critical information from quantum materials

Topological insulators are quantum materials, which, due to their exotic electronic structure, on surfaces and edges conduct electric current like metal, while acting as an insulator in bulk. Scientists have now demonstrated how to tell apart topological materials from their regular -- trivial -- counterparts within a millionth of a billionth of a second by probing it with ultra-fast laser light.

Shape affects performance of micropillars in heat transfer

A researcher has shown for the first time that the shape of a nanostructure has an effect on its ability to retain water. This has important ramifications for heat transfer, which is important when it comes to performance in small electronics.

Just add water: Simple step boosts polymer's ability to filter CO2 from mixed gases

Researchers have found it can significantly boost an existing polymer's ability to selectively remove carbon dioxide out of gas mixtures by first submerging the material in liquid water.

Chemicals for pharmaceuticals could be made cheaper and greener by new catalysts

High value chemicals used to make pharmaceuticals could be made much cheaper and quicker thanks to a series of new catalysts.