Synthetic biology

For my very first class of Citizen science: Biotechnology we had to blindly pick chits from a randomized pool of topics which would be our subject of research for this course. I picked synthetic biology, or rather it picked me!

After spending an entire day watching simplified Youtube videos and reading popular science articles on synthetic biology, I can finally claim to have gotten my head around the subject and some of the jargon necessary to understand and communicate it. I feel I am now equipped to take on more serious literature and scientific papers.

Any discussion around synthetic biology and/or genetic engineering seldom takes place without touching upon ethics and necessary regulations around the technology and of course “designer babies!”. I am more interested in speculating on parallel applications of this technology than to really have an opinion on it’s ethics and practical concerns. After all the motivation behind synthetic biology is ethically positive, at least in the realm of therapeutics and nourishment rather than enhancement! The reality is that there are certain urgencies which are far more grave than the unclear ecological implications and potential risks with this technology. It is tempting to attack these urgencies with a piece of tech that shows promise than to fully think through its implications. But is it even possible to fully think through its implications without implementing it? Who would have imagined the internet when the first transistor was engineered?!

I am also pondering over how this technology could reflect in design and in-turn in our day to day life of using products. If we circumvent all the sensational “hot topics” around this technology and imagine a regular day in future, maybe 70 years from now, where synthetic biology is mainstream and has already proven to be immensely successful in treating several diseases; A future where men never go bald and everyone on the planet has enough food, what would our mundane day-to-day life look like? If biotech creates a market for new materials then how would it impact manufacturing and advertising and how will these new methods affect the way our everyday products look and function. What would our toothbrush look like? or the humble bar of soap? what kind of underwear will we be wearing? how would we redesign kitchen tools to work with new forms of food? how will it alter some of our everyday rituals like skin care and hygiene or using contraception?

These may not be very glamorous topics to discuss but certainly very important. The mundane everyday life is the grand reality for most of us and is directly related to a person’s sense of well-being. I may explore more along this track through the semester.



Modular soft robots_4

PART 4 of 4

For PART 1 click here
For PART 2 click here
For PART 3 click here

For the fourth iteration I built on the 3rd one but this time I inverted the shape of the inflation chamber. Made the walls thicker and and the inflation chambers much thinner and acute. Below is an image of the cross section of this actuator.

trial 5.PNG
This illustration shows the different approaches in trial 3 and 4
trial 4.PNG
cross section view of one segment of the mold. 

I only decided to print one segment of the mold to make de-molding easy.


Unfortunately the Silicone hadn’t cured even after 7hrs!

By the time I got to casting the silicone, the 00-50 grade which we had in class had gotten over. I bought the 00-30 variant since it had a cure time of 4hrs, only 1 more hour than the 00-50 grade. But even after 7+hrs or curing time it was still runny on the bottom end of the cast.

I have a feeling it probably has to do with the cooler temperature on the ITP floor. I think it cures faster at higher temperatures. I plan to recast this actuator on a slightly warmer day and continue this process through the summer break.

Modular soft robots_3

PART 3 of 3

For PART 1 click here
For PART 2 click here
For PART 4 click here

For the third iteration I wanted to model something after the accordion structure.
This video below shows the accordion shaped actuator extending linearly

I took inspiration from this but decided to add some solid chunks of silicone in between to add some stability to the actuation.

trial 3.PNG

As seen in the CAD model above, the cuboidal blocks of silicone do not inflate. They work as internal bracing elements. The blocks also serve as channels for the proposed external restraints to pass through.

trial 3 a.PNG
Mold design for the actuator with the outer part and inner core.
3D printed piece of the mold. The red wire seen on the left is to keep the cantilevered end of the inner core from touching the outer mold part.
I casted only one half of the actuator first and decided to color the other half.
Fully casted actuator, there were a few tears toward the end of the casted piece so I had to cut it in half. (6)

As you can see, this iteration achieves a good amount of linear extension but it inflates in a  rather ugly manner. Also it doesn’t inflate evenly. I later found out from Kari that silicone has a tendency to do that, maybe the wall thicknesses were slightly uneven and once it inflates beyond a threshold, it creates microscopic tears which irreversible alters the behavior of the actuator. (1).gif

I tried inflating the actuator with external restraints (white wire attached to the actuator). As you can see it did successfully turn linear motion into bending motion. I just needed to refine the inflation aesthetics in the following iterations.

Modular soft robots_2

PART 2 of 4

For PART 1 click here
For PART 3 click here
For PART 4 click here

For the second iteration I wanted to test out a helical spring shape for the inner core of the actuator. The idea was to inflate a spring shaped hollow chamber to achieve linear extension, much like stretching a helical compression spring.

I quickly made a spring with thick aluminium wire coiled around a chisel
I put together a mold with these basic components, all picked up from the junk shop. The spring formed the inner core, the aluminium tube is the outer mold and the cardboard piece formed a conical end of the actuator for air inlet.
Actuator is casted and set aside for curing
And now the hardest part was demolding the inner spring. (5).gif
Again, with this one too, I did achieve linear actuation but the whole form was inflating much more than I liked. I was still happy with the overall form of this piece. I’d like to explore this aesthetically in the future. (7).gif

For PART 1 click here
For PART 3 click here
For PART 4 click here

Modular soft robots_1

PART 1 of 4

For PART 2 click here
For PART 3 click here
For PART 4 click here


For my finals for soft robotics class I want to make a system of modular soft actuators which can be combined together to perform different functions.

The soft modular system is an effort to create a plug and play system with soft robotics which is a very fabrication intensive process. I am also thinking of this system as working like an educational tool or toy to introduce kids and adults to the field of soft robotics. This will be to soft robotics, what K’nex is to mechanics or Little Bits is to electronics. Ideally, these blocks should also be compliant with other forms of robotics where they can be easily integrated.

Examples of similar systems

Modular soft robots by EPFL

The modular body

Modular robotic cubes



I had two approaches ahead of me

  1. Multiple modules for a common function
    This approach required me to fabricate multiple modules which would come together to carry out a single function. Like putting together the pieces of a puzzle.
  2. Same module, Multiple functions
    In this case I will make multiples of the same module which can perform differently with simple modifications or combinations. I found this approach to be more interesting and feasible, given the time frame of 3 weeks


The image below demonstrates my idea of a kit with different modular components.

The kit mainly comprises of linear silicone actuators, internal restraints, wheels, end caps, etc.


The different components can be fit together to create different robots or mechanisms as shown in the animation below.


clockwise from top left : Rope climbing robot, gripper, CG wheel, crawling robot.


The chart below explains the motivations and rationale behind the project.

Untitled presentation (2)


Most common actuation methods used in soft robotics are linear (forward and backward) and bending. I realized I need only design a linear actuator and use a mix of external and internal constraints to achieve different kinds of motions. So the actuator module remains same but the variety of motions is brought about by modular restraints.

Update : April 3rd

To test out the idea I designed a mold in Rhino to cast a basic actuator. I also wanted to test the coupler design which would enable the modularity and interfacing between different modules.

mould design.PNG
Dark grey part is the actuator and the light grey covering is a cross section of the mold design
mould design 2.PNG
Final molding assembly file ready for 3D printing



Shown in red in the image above is the coupler in hard plastic which is assembled with the actuator. The coupler has 4 arms which serve as hooks for different restraints. The coupler is slightly oversized to achieve a tight fit with the silicone actuator. In the final design the coupler should be in-molded with the silicone part. The 4 holes seen on the silicone part at the corners is the channel for the internal restraint to pass through.

Update : April 7th



Main body of the cast is ready for molding. I inserted two sticks in each half to form the channel for the restraint.



I also made small holes to let the air out and get the silicone moving more freely.


One half of the mold assembly. The green stick in the center forms the central inner air cavity.



Unfortunately the silicone started leaking from the bottom due to increasing pressure. I decided to let it sit and re-cast it the next day.

Update : April 8th


Was happy to see at least half of the actuator was casted. If anything it was a good run for testing the quality of the cast. Also gave me a much better idea for dis-assembly.


After de-molding, I reassembled the mold and plugged the holes and the edges with hot glue this time.



Parallely I cleaned up the half casted actuator for early testing of the actuation.


Tested assembling the coupler for fit.


I decided to plug one end of the actuator with more silicone and set it aside for casting.


3 hours later…

The actuator is sealed from one end

On the side, I injected more silicone into the mold which was still curing, to fill it up completely and compensate for some of the silicone which leaked at the bottom.


Update : April 9th


Final casted actuator. The red cable demonstrates the restraint mechanism. (6).gif
I was able to achieve some linear actuation but not without overall inflation.



For PART 2 click here
For PART 3 click here
For PART 4 click here