Bionic refers to applying biological ways and systems seen in nature to design and study the engineering systems. A bionic human would refer to human whose worn out parts can be repaired and refitted into the body. We cannot say that the whole of the human body is replaceable, but most parts can find replacements.
There are replacements for human bones, teeth, vertebral discs. All these can be designed as per persons size and age. The tailored pants can be drawn in a few hours in a 3D printer to fit into the damaged parts. A device can even print a bone using a porous polymer that looks very real. The artificial bones may not be perfect and same as the natural bones. To give strength, we can add titanium powder with a laser. This would create pores on the bones, and the pores would be of different size and depth, making it look more natural, and these pores give strength and stiffness to the artificial bones.
There are ways even to improve implants enabling tissues and bones to regenerate. There are lab results showing cartilage growth through artificial ways in labs. By such a process even damages such as on knee area can be fixed. This process can be extended to ligaments connecting tissues between bone and the non-bones parts of the human body. The latest advancement in this filed is stem cell research. Through this field, any tissue can be grown without any prior organ being present. There are already results available to prove that complete organs can be regenerated. Many patients around the world already use artificially grown bladders.
Growing complete organs with complex, intricate blood vessel systems is still a future milestone which needs to achieve. There are even ways to ignore the complex problems involved in growing intricate blood vessel systems by directly using the organs from the donated body. Decellularisation process in which the cells are stripped just leaving the connective tissues along with blood vessels. This process was tested for a rat’s heart, and after a few electric shock, the rat’s heart started working as usual. Though this technique has worked for rats, it is still far from reaching for the human heart. The heart problems are usually cured by placing pacemakers. The pacemakers do the job of clumps of cells that can synchronize heart muscle with electricity. Recent inventions are powered by the heart itself, which prevents the operation from changing the battery very often.
Even the other parts, like the lymphatic system, are replaceable. Rats were tested for artificial lymph mode made out of collagen and cells and tissues taken from a newborn rat. The same can be applied to build an immune system against AIDS.
Brains complexity is known to all and very doubtful about recreating it in the labs, but some of the nervous system functions are already replaceable. There are medical fixes for helping blind people to see. For blind people, the retina and the optic nerve are stimulated.
There are chances of seeing a complete bionic man very soon.