The summit’s final technical session was the most philosophically unified of the four days: across soft lithography, exosome biosensing, bacterial cellulose fibre engineering, and biomimetic startups, a single principle recurred — that billions of years of evolutionary pressure have already solved most of the engineering problems we are only beginning to formulate.
Prof. Rabi Mukharji (IIT Kharagpur): The Physics of Making Patterns Taller Than Their Stamp
Prof. Rabi Mukharji of IIT Kharagpur’s Chemical Engineering Department opened the session with a talk that, by his own cheerful admission, had little to do with carbon — but which demonstrated, with characteristic elegance, how careful attention to the physics of viscoelastic materials can produce surface patterning capabilities unavailable through any other route. His subject was soft lithography: the ensemble of techniques developed by Whitesides and Chow in the early 1990s for creating micro- and nanoscale topographic and chemical patterns on polymer surfaces without the cost and rigidity of photolithography.
The canonical soft lithography process is familiar: a crosslinked polydimethylsiloxane (PDMS) stamp — the ‘magic material’ of the field — is cast from a master, thermally cured into a soft elastic solid, and used to create a negative replica of whatever pattern the master carries. What the group at Kharagpur asked was whether the physics of the curing transition itself — the transformation of a high-viscosity viscoelastic liquid into an elastic solid — could be exploited to create surface features not constrained to the stamp’s geometry.
The answer was yes, exploiting a phenomenon that Prof. Mukharji described with characteristic understated delight: when a stamp pressed against a partially cured PDMS film is retracted, adhesion-induced stretching during debonding creates features taller than the original stamp height. Using atomic force microscopy (AFM) to measure feature heights during the bonding and debonding phases — a measurement that surprisingly had never been made before, despite the phenomenon being observed in optical microscopy papers — the group documented that features with a stamp height of 150 nanometers could be stretched to 420 nanometers during retraction. A single stamp could generate structures of multiple heights simply by controlling the degree of precuring and the retraction geometry. The work was validated against theoretical predictions from the field of contact instability between soft elastic films — a body of theory to which Prof. Ashutosh Sharma, present in the audience, had himself contributed foundationally.
The applications of gradient topography surfaces are broad: structural colour through subwavelength diffraction gratings, superhydrophobic surfaces for self-cleaning solar panels, point-of-care diagnostic channels with controlled capillary geometry, and anti-reflection coatings — each requiring precisely controlled feature heights that single-stamp replication cannot achieve without the stretching mechanism the Kharagpur group has now characterised.
Prof. Chirashree Pramanick (IIEST Shibpur): Graphene-MXene FETs for Exosome-Based Cancer Screening
Prof. Chirashree Pramanick addressed one of the most pressing unmet needs in oncology: early-stage cancer detection, specifically for prostate cancer, through liquid biopsy — blood or urine testing — rather than invasive biopsy procedures. Her platform centres on exosomes: nanoscale extracellular vesicles (50–200 nm diameter) secreted by cells into body fluids, which carry molecular cargo (proteins, RNA, lipids) that reflects the metabolic and genetic state of their cell of origin. Tumour-derived exosomes carry surface proteins and nucleic acid profiles distinguishable from those of healthy-cell exosomes; detecting them in peripheral blood or urine at low concentrations could, in principle, identify prostate cancer at stages when treatment is most effective.
The engineering challenge is formidable. Exosomes are present in body fluids at picomolar to femtomolar concentrations amid a vast excess of proteins, lipids, and cellular debris. Conventional detection methods — ELISA, nanoparticle tracking analysis, electron microscopy — require sample processing steps that destroy the clinical workflow advantages of a rapid point-of-care test. Field-effect transistors (FETs) based on graphene offer an elegant alternative: when a target molecule binds to a functionalised graphene channel, it shifts the local electrostatic environment, producing a measurable change in the transistor’s drain-source current. The challenge is that real biological samples produce ‘device screening effects’ — the counterion screening of physiological salt concentrations prevents the electrostatic signal from a bound exosome from reaching the graphene channel.
Prof. Pramanick’s innovation was to integrate MXene (Ti₃C₂Tₓ) — a two-dimensional transition metal carbide with extraordinarily high electrical conductivity and a highly functional surface chemistry — with the graphene FET channel, creating a porous hybrid architecture that allows electrostatic signals to penetrate the counterion screening layer. The graphene-MXene composite FET, functionalised with antibodies specific to prostate cancer exosome surface markers, demonstrated detection sensitivity at clinically relevant exosome concentrations with minimal non-specific binding, using urine samples from patients at different disease stages. The transition from lab-scale proof of concept toward a manufacturable biosensor chip remains the primary engineering challenge, but the platform principle — porous 2D composite channels overcoming screening in high-ionic-strength biological fluids — is generalisable to other liquid biopsy targets.
Prof. Mudrika Khandelwal (IIT Hyderabad): First Form Film and the Secret of Bacterial Silk
Prof. Mudrika Khandelwal’s presentation on bacterial cellulose was the session’s most biochemically fascinating, centred on a single counter-intuitive discovery that she called the ‘First Form Film’ (FFF) technique: harvesting bacterial cellulose hydrogels after two days of fermentation rather than the standard fourteen days produces fibres with dramatically superior mechanical properties — approaching, on several parameters, the strength and toughness of natural silk.
The bacterium in question is Acetobacter xylinum (also referred to in the literature as Komagataeibacter xylinus), a gram-negative organism that polymerises glucose into cellulose nanofibres as a metabolic by-product, producing a pure, highly crystalline three-dimensional network of nanocellulose ribbons arranged in a hydrogel matrix. This bacterial cellulose is among the most crystalline naturally occurring polymers — expected modulus of approximately 140 GPa, tensile strength approximately 6 GPa — and unlike plant cellulose, it requires no bleaching or chemical purification. The standard protocol for harvesting involves allowing the culture to grow for 14 days, producing a thick, dense pellicle.
“The bacteria had already done the hard work. We just had to listen to it — and harvest at exactly the right moment. Two days instead of fourteen changed everything.”
But the 14-day pellicle, when spun into fibres, yields only about 0.5 GPa tensile strength — far below what the nanofibre’s intrinsic crystallinity should produce. The problem, Prof. Khandelwal’s group realised through detailed rheological characterisation, is entanglement: by day 14, the nanocellulose fibres have formed a densely interconnected gel in which individual fibres are so thoroughly crosslinked with their neighbours that mechanical drawing cannot align them along the fibre axis. The crystalline units remain oriented randomly, cancelling each other’s contribution to axial strength.
The two-day culture produces a much more dilute gel — fewer crosslinks, more individual fibres, lower yield stress — that flows under moderate shear and can be drawn into axially oriented fibres by stretching. When these First Form Film fibres are benchmarked across five parameters (stiffness, strength, tenacity, specific strength, and toughness) against silk and against every other bacterial cellulose spinning method reported in the literature, they perform substantially better than the 14-day standard and occupy a position in materials property space close to natural silk. The crystalline Cellulose I structure (thermodynamically metastable relative to Cellulose II, the structure obtained when cellulose is dissolved and regenerated) is preserved throughout — because the fibres are never dissolved, only drawn, the natural crystallographic order established by the bacterium is retained rather than destroyed in a reconstitution step.
The applications are numerous: biomedical scaffolds (where the combination of strength, biocompatibility, and biodegradability is uniquely valuable), high-performance technical textiles, and reinforcement fibres for biodegradable composites. Most compellingly, the FFF process requires no toxic solvents, no high-temperature processing, and no complex equipment — it is, at its core, a matter of paying attention to what the bacterium is already doing, and harvesting at the moment when its output has the most useful mechanical character.
Dr. Srinath Mataparti (Karnavati Innovation and Incubation Foundation): What Pine Cones Know About Fire
Dr. Srinath Mataparti — a Carbon Lab PhD graduate of 2019, now Senior Manager at Karnavati Innovation and Incubation Foundation where he works with startups — delivered the session’s most accessible and, in its way, most inspiring presentation: a tour of real-world biomimetic innovations, aimed specifically at the large number of young researchers in the audience who had not yet thought about where their doctoral work might lead if translated commercially.
His central argument was simple and persuasive: nature, over billions of years, has solved most of the engineering problems that industrial civilisation is only now formulating — and it has solved them without heavy machinery, toxic chemicals, or energy-intensive processes. ‘Nature doesn’t use any complex heavy machines or toxic chemicals to solve any complex problem. It uses designs, textures, surfaces, and biodegradable materials.’ The discipline of biomimicry is not merely copying nature but, as Mataparti put it, ‘learning the language of nature, understanding its mechanisms, and trying to replicate those phenomena in artificial materials to solve real-time problems.’
His case studies ranged from the familiar (lotus leaf superhydrophobicity as the basis for self-cleaning surface coatings; mussel adhesive proteins as the inspiration for underwater adhesives used in marine engineering and medical wound closure) to the less obvious. Pine cones, he noted, are moisture-sensitive actuators: their scales open when dry and close when wet, a hygroscopic mechanism that controls seed dispersal without any cellular energy input. A startup has developed forest fire detection systems based on this principle — wax-coated biological materials that respond to the rapid drop in local humidity that precedes and accompanies a fire front, triggering an alarm before conventional smoke or heat detectors can respond. The system is passive, biodegradable, cheap, and sensitive at exactly the timescale relevant to early fire containment.
Pollia condensata — the Marble Berry, a tropical plant producing the most intense structural colour found in the biological world — produces iridescent blue colouration through cellulose nanofibre arrays arranged in a helicoidal photonic structure, with no pigment whatsoever. Prof. Khandelwal’s work on structural colours using bacterial cellulose nanocrystals directly draws from this model: a non-toxic, biodegradable, synthetic-pigment-free approach to structural colouration with applications in cosmetics, packaging, and photonic devices. Mataparti’s presentation of these examples to a room largely composed of materials chemists and electrochemists was a deliberate act of widening: the reminder that materials science has always drawn its deepest inspiration from the most patient and best-tested laboratory in existence.
– Sai Chaitanya Pulligadda
