208: Chapter 208 Link Training

"This is the lower leg section," Li Wei said, pointing to the lower part of the prosthetic.

"The shell is a carbon fiber composite, with strength similar to aluminum alloy but only a third of the weight. Inside are the Drive Unit and Sensor Array, all sealed and waterproof."

She lightly flicked the prosthetic's ankle joint with her finger; the joint rotated about fifteen degrees before automatically returning to its position with an extremely faint "click."

"The ankle joint has two degrees of freedom," she said, "Plantarflexion and Dorsiflexion—the range for pointing and flexing the toes. The Drive Unit can provide a maximum torque of fifty Newton-meters, enough to support an adult standing and walking."

Lin Yue reached out and touched the shell of the prosthetic.

It felt warm to the touch, not cold, similar to body temperature.

He had expected the metal to be icy, but this wasn't.

"The surface has a Biomimetic Coating," Li Wei explained. "It conducts heat, so it doesn't feel cold. It also has a certain elasticity, so it won't scratch easily if it hits the ground."

Lin Yue's fingers moved to the knee joint. The structure there was more complex, with several layers of metal plates stacked together, sandwiching a translucent material through which fine circuitry was visible.

"The knee joint has four degrees of freedom," Li Wei said, "flexion and extension, rotation, lateral swing, and an axial adjustment of the lower leg relative to the thigh. The Drive Unit can provide a maximum torque of one hundred and twenty Newton-meters, enough to support running and jumping."

"Running?" Lin Yue looked up at her.

"Running," Li Wei nodded. "Of course, it requires an adaptation process. It starts with walking, then fast walking, then jogging. We have an experimental monkey that can already run on a treadmill at about eight kilometers per hour."

She took the prosthetic out of the box and held it in her hands. The entire limb weighed just over two kilograms, lighter than Lin Yue had imagined. Li Wei placed it on a chair by the bed, leaning it there.

"Once your wound heals and your nerve signals stabilize," she said, "we'll connect it. We'll start with static testing to see if signal transmission is normal. Then we'll do dynamic testing, starting from the simplest ankle movements and taking it step by step."

Lin Yue looked at the prosthetic on the chair.

It leaned there, its silver-gray shell shimmering softly under the light.

"Can I touch it?" he asked.

"Of course." Li Wei picked up the prosthetic and handed it to him.

Lin Yue took it; it was even lighter than he had imagined.

The shell was warm, and he could feel minute gaps at the joints; the texture felt slightly grainy to the touch, much like the sensation of real human fingerprints.

He turned the prosthetic over to look at its back.

There was a row of extremely fine interfaces, densely packed and thinner than a needle tip, arranged in a complex geometric pattern.

"These are the Neural Interfaces," Li Wei pointed to them. "They match the membrane on your residual limb. Once connected, signals will travel from your nerves to the prosthetic and back from the prosthetic to your brain."

Lin Yue turned the prosthetic back over to look at its front.

The streamlined shell looked beautiful under the light, silver-gray like the finish of a high-end sports car.

There were minute gaps at the joints where the internal mechanical structure was visible, but it was very clean, with no stray wire ends or burrs.

He put the prosthetic back in the box and closed the lid.

Lin Yue thought for a moment and said, "It looks good. But it doesn't look real."

"It doesn't need to look real," Li Wei said. "It isn't real. It's a tool. A useful tool doesn't need to disguise itself as a human organ."

Lin Yue was stunned for a moment, then laughed.

"True," he said.

On the fifth day after surgery, Li Wei came to perform the first signal test.

She attached several extremely fine wires to the outside of the gauze on Lin Yue's right leg and connected them to a device.

A row of waveforms appeared on the device's screen, similar to what Lin Yue had seen before but denser and more complex.

"Now, try to move your toes," Li Wei said.

"I don't have toes," Lin Yue said.

"I know. But your brain doesn't. Try to think—move the big toe of your right foot."

Lin Yue closed his eyes and tried to imagine the movement—the big toe of his right foot pressing down, like stepping on an accelerator.

He hadn't thought about that movement for a long time. For over two years, he had been trying to forget that leg and those movements. Now, trying to recall them was actually a bit difficult.

"Take your time," Li Wei said, "no rush. Just think about it."

Lin Yue continued to think. He remembered the feeling of his right foot pressing the accelerator while driving.

The toe pressing down, the pedal sinking, the car surging forward—the feeling was still there, just unused for a long time.

The waveform on the screen jumped.

"There it is!" Li Wei's voice carried a hint of excitement. "Look here."

Lin Yue opened his eyes and looked where she was pointing.

On the screen, one waveform suddenly spiked, several times higher than the others, like a mountain suddenly appearing.

"This is your motor signal," Li Wei said, "sent from the brain, traveling down the nerves, all the way to the interface."

"And then?" Lin Yue asked.

"Then it's received by the interface." Li Wei pointed to the part following the spike.

"Look here, the signal is still there after passing through the interface, without attenuation. It means your nerves and the interface have established a preliminary connection."

She recorded some data on her tablet and then said, "Try again. This time, try to move your ankle—flex your toes upward."

Lin Yue closed his eyes again.

Flexing the toes—he remembered that when driving, this was the movement for using the brake. The ankle lifting, the sole of the foot leaving the pedal.

The waveform on the screen jumped again. This time, it was even higher and more forceful.

"Very good," Li Wei said, "the signal strength is even greater than last time. Your nerves are recovering faster than expected."

Lin Yue opened his eyes and looked at the jumping waveforms on the screen.

They jumped rhythmically, high and low, as if saying something. He couldn't understand it, but he knew those were the signals from his leg.

Perhaps they had always been there, only visible through this kind of signal collection.

"Next," Li Wei said, "we will perform a signal test every day to record your nerve recovery. Once the signal is stable enough, we can attach the prosthetic for static testing."

"How long?" Lin Yue asked.

"At the current rate, about one to two weeks." Li Wei stood up and packed away the equipment. "Faster than expected."

She walked to the door and glanced back at Lin Yue. "Get some good rest. Your nerves are working; don't overexert them."

Lin Yue nodded.