Biotech

"the integration of natural sciences and engineering sciences in order to achieve the application of organisms and their parts for products and services."
This field of technology focuses on bringing together what nature created and what man can create and turn it into something better. No material is better then the one used by the mother nature. After all she created life.
As such most of the practitioners of this tech type tend to lean towards its use for creating artificial life forms.
But it doesn't mean that there aren't uses for it in other fields as well.
You can make exoskeletons with organic muscles and shells from creatures to provide defense.
Or image capturing devices with the eyes of creatures.
Guns are probably the second most common area where this tech is used after artificial life.
You can also turn a creature into a vehicle.
One must not forget the limits of ethic as many abused of this tech during the age of terror. This technology barely escaped being prohibited when the age ended.

Biotech for Battle Engineer

To choose biotech you need Medicine and Nature skill proficiencies.

Materials

Although the materials for biotechnology are relatively common they are hard to harvest. You can harvest parts of creatures and plants (or entire creatures in case for vehicles).
The player should roll a Medicine Check using the DC determined either by the material if it has one or by the DM. On a success, the player is able to harvest the material. On a failure, the material cannot be harvested (either because the character is not skilled enough, or because the material is ruined).
The materials might have an expiration, and can not be sold or used after the expiration has passed.

Sources of energy

Being alive the tech needs nutrition. In other words you'll have to feed it in some way. So don't forget to build a mouth or something in your device or it will quickly starve and stop working.
Your creation needs the same type of nutrition as the thing it is made of. Carnivore = meat, Herbivore = Plant matter, Omnivore = either, Plant = Carbon dioxide, water and sunlight. If the creature had a special diet like a specific plant, creature or substance it eats, you must respect that diet.
However being transformed with technology its feeding frequency and quantities are different. lb of food for creature based creations and is equal to number of hours in contact with nutritive elements for plant based. (it takes 1 minute for the creature based creation to consume its nutrition)

Size	Food per 3 uses or per week
Tiny	0.25 lb
Small	0.5 lb
Medium	1 lb
Large	4 lb
Huge	16 lb
Gargantuan	50 lb

Particularities

You start with Biologist's kit instead of tinkering tools as your starting equipment and proficiency.
Biotech creations are treated as both creatures and objects.
You can not repair a heavily damaged biotech.

Exoskeleton example
Gadget example
Gun example
Vehicle example