http://hdl.handle.net/2289/149 2026-04-16T03:12:28Z 2026-04-16T03:12:28Z Chanda, Sayantan Chandeshwar, Misra Ranjini, Bandyopadhyay http://hdl.handle.net/2289/8707 2026-04-15T05:12:03Z 2026-03-18T00:00:00Z

Title: Investigating the roles of hydrophobicity and electrostatics in the particle-scale dynamics and rheology of dense microgel suspensions Authors: Chanda, Sayantan; Chandeshwar, Misra; Ranjini, Bandyopadhyay Abstract: Colloidal microgel particles such as poly(N-isopropylacrylamide) (PNIPAM) shrink reversibly in an aqueous medium due to the expulsion of water at a volume phase transition temperature (VPTT) ~ 33  * C. Romeo et al. [Adv. Mater. 2010, 22, 3441–3445] had previously shown that dense aqueous PNIPAM suspensions transformed from one viscoelastic solid-like phase to another when suspension temperature was increased, with an intermediate viscoelastic liquid-like phase near the VPTT. They attributed this observation to a change in the inter-particle interaction from hydrophilic to hydrophobic. Here, we show using a combination of experimental techniques that particle hydrophobicity can become significant even below the VPTT. We achieve this by incorporating dissociating additives such as sodium chloride and potassium chloride, or non-dissociating additives such as sucrose, into the aqueous medium. Above the VPTT, we observe that suspension rigidity is the highest in the presence of salts because of the combined effects of electrostatic and hydrophobic attractions. In the presence of non-dissociating sucrose, in contrast, the inter-microgel interaction remains hydrophobic across the VPTT. Such easy tunability of interactions by incorporating commonly available chemicals into the suspension medium opens up new avenues for the synthesis of novel metamaterials. Description: Open Access.

2026-03-18T00:00:00Z Marwah, Himanshu Bhatt, Hetarth Fartyal, Neeraj Nautiyal, Rohit Veer, Sukh Pullarkat, Pramod A Balakrishnan, Sreenath http://hdl.handle.net/2289/8702 2026-04-15T05:06:08Z 2026-04-06T00:00:00Z

Title: Biaxial stretcher with vision-based force sensing for estimating anisotropy of single cells Authors: Marwah, Himanshu; Bhatt, Hetarth; Fartyal, Neeraj; Nautiyal, Rohit; Veer, Sukh; Pullarkat, Pramod A; Balakrishnan, Sreenath Abstract: Mechanical properties of single cells offer insight into organismal development, disease progression, and mechanotransduction. Yet, estimating the complete mechanical state of single cells, involving multiple parameters, remains challenging due to limited deformation modes available in existing techniques and complex instrumentation. To address this gap, we are developing several compliant micromechanisms that together enable multiple modes of cell manipulation on a single chip. Building on an earlier uniaxial stretcher, here we demonstrate a biaxial stretching mechanism with vision-based force sensing. Because the mechanism uses elastic beams for actuation, stretching forces can be computed from optical displacement measurements using a closed-form analytical model derived from beam theory. This obviates the need for dedicated force sensors thereby simplifying device fabrication and operation. The force displacement relations were validated on macro- and microscale prototypes. The device is microfabricated out of SU-8 using a two-layer photolithography process, yielding an array of miniature stretchers that can be mounted on a coverslip for high-resolution imaging during manipulation. We stretch U87-MG human glioblastoma cells biaxially, compute bulk stiffness, stress and strain in orthogonal directions using microscopy and further fit 2D Fung’s model to investigate anisotropy. This biaxial stretcher can be combined with additional modules (e.g., for shear or twist) to realize a multimodal single-cell mechanophenotyping platform for comprehensive analysis of cellular mechanics. Such a versatile platform represents a new approach to single-cell mechanical characterization. Description: Restricted Access.

2026-04-06T00:00:00Z Sunithakumari, M Gagan, M U Dwarakanath, V Srinivasa, H T Devarajegowda, H C Palakshamurthy, B S http://hdl.handle.net/2289/8701 2026-04-15T05:05:09Z 2026-05-01T00:00:00Z

Title: Synthesis, crystal structure and Hirshfeld surface analysis of phenyl­methanaminium 2-oxo-2H-chromene-3-carboxyl­ate Authors: Sunithakumari, M; Gagan, M U; Dwarakanath, V; Srinivasa, H T; Devarajegowda, H C; Palakshamurthy, B S Abstract: The title salt, C7H10N+·C10H4O−, formed between 2-oxo-2H-chromene-3-carb­oxy­lic acid and benzyl­amine crystallizes in the triclinic space group P1. Proton transfer from 2-oxo-2H-chromene-3-carb­oxy­lic acid to the NH2 group of benzyl­amine results in a N—H⋯(O,O) hydrogen bond between cation and the carboxylate group of the anion. The 2-oxo-2H-chromene moiety is almost planar with a dihedral angle between the two fused rings of 1.48 (11)°. The dihedral angle between the rings of the anion and cation is 29.49 (10)°. In the crystal, N—H⋯O hydrogen-bonding inter­actions generate an R44(12) synthon parallel to the ac plane. The mol­ecules are linked by further C—H⋯π inter­actions, which consolidate the packing. In addition, π–π stacking inter­actions are observed with centroid-to-centroid distances of 3.5832 (14) and 3.8167 (15) Å. The two-dimensional fingerprint plots indicates that the most important contributions to the crystal packing are from H⋯H (39.7%), H⋯O/O⋯H (30.6%) and H⋯C/C⋯H (20.9%) contacts. The anti­bacterial activity, with MIC values of 30 µg ml−1 against S. aureus and 25 µg ml−1 against E. coli. The lower MIC against E. coli suggests that the compound is more effective against Gram-negative bacteria than Gram-positive bacteria. Description: Open Access.

2026-05-01T00:00:00Z Srinivasa, H T Roy, Arun http://hdl.handle.net/2289/8698 2026-03-25T06:15:54Z 2026-03-12T00:00:00Z

Title: Calamitic nematic liquid crystals synthesis and characterisation from bromo-chlorophenol and bromo-chlorobenzoic acid Authors: Srinivasa, H T; Roy, Arun Abstract: Insecticide-derived calamitic liquid crystals were synthesised and characterised using various analytical methods, including infrared and nuclear magnetic resonance spectroscopy. In this study, the liquid crystal properties of 4-bromo-2-chlorophenol and 4-bromo-2-chlorobenzoic acid derivatives were investigated. Out of 25 newly prepared compounds, 19 compounds exhibited nematic phase. A few middle-ordered compounds exhibit an extra nematic X phase. One molecule exhibits the SmA mesophase. The liquid crystal properties were confirmed by polarised optical microscopy, differential scanning calorimetry, and X-ray diffraction studies. Description: Restricted Access.

2026-03-12T00:00:00Z