Research

We manipulate matter on the smallest of scales to create materials with emergent properties, characterized by novel and sometimes surprising features arising from the interactions of multiple bodies.

By synthesizing, assembling, combining and organizing nanoscale building blocks, we design technologies that enhance the quality of human lives in the domains of health, energy, sensory augmentation and self-expression.

A tattoo is a body modification involving particles (typically pigments) embedded in the dermis layer of skin. Although tattooing has been practiced for thousands of years, innovations in particle science have not been brought to bear on this ancient technology. 

Our lab is re-thinking the tattoo ink as a way to permanently embed useful technologies in the skin. We are formulating tattoo inks that impart the skin with new properties. We hope to use these "tech tattoos" to power biomedical devices and wearable technologies, monitor and diagnose health issues, and augment human sensing and self-expression.

See our tattoo research featured on CNN, NPR, CBS News, Colorado Public Radio, KUNC, Chemical & Engineering News, Inked Magazine, CU Boulder Today, and the ATLAS Institute. Read Carson’s account of the rise of smart tattoos in The Conversation, listen to the conversation on The Disruptors podcast, or watch the TEDx talk:

We co-founded HYPRSKN with celebrity tattoo artist Bang Bang to bring our smart tattoo technologies to the market and make them available to those who want them, beginning with Magic Ink, the world’s first re-writable tattoo ink for body art. You can read more about this project in GQ, People, or the New York Post.

Further Reading:

1. JL Butterfield, JR Quigley, CJ Bruns.* Smart Tattoos from Intradermally Implantable Photochromic Nanosensors for Personal Ultraviolet Sensing and Dosimetry. Adv. Funct. Mater. 2024, 2405831.

2. JL Butterfield, GP Penoncello, KV Dikshit, CJ Bruns.* A Photochromic Intradermal Smart Tattoo Based on Diarylethene-Doped Polystyrene Nanoparticles for Personal γ-Ray Dosimetry. ACS Applied Nano Materials 2022, 5, 13840–13844.

3. JL Butterfield, SP Keyser, KV Dikshit, H Kwon, MI Koster, CJ Bruns.* Solar Freckles: Long-Term Photochromic Tattoos for Intradermal UV Radiometry. ACS Nano 2020, 14, 13619–13628.

The mechanical bond is a name we give to the interaction between parts that are entangled but not otherwise bonded, as in the links of a chain or a bead on a string. While it is easy to thread a bead on a string in the macroscopic world, this is not always the case on molecular, nano-, and microscopic length scales. 

We design molecules, macromolecules, and colloids that possess extra degrees of motional freedom attributable to the presence of mechanical bonds. These compounds form the basis of ultra-tiny machines and materials with unusual and potentially functional properties to suit a wide variety of applications in the domains of health and energy.  

Read The Nature of the Mechanical Bond, the definitive book on mechanically bonded molecules.

Further Reading:

1. KV Dikshit, AM Visal, F Janssen, A Larsen, CJ Bruns. Pressure-Sensitive Supramolecular Adhesives Based on Lipoic Acid and Bio-Friendly Dynamic Cyclodextrin and Polyrotaxane Cross-Linkers. ACS Appl. Mater. Interf. 2023, In Press.

2. KV Dikshit,CJ Bruns. Chemorheological Monitoring of Cross-Linking in Slide-Ring Gels Derived from a-Cyclodextrin Polyrotaxanes. Front. Chem. 2022, 10:923775.

3. KV Dikshit, CJ Bruns. Post-Synthesis Modification of Slide-Ring Gels for Thermal and Mechanical Reconfiguration. Soft Matter 2021, 17, 5248–5257.

4. CJ Bruns. Exploring and Exploiting the Symmetry-Breaking Effect of Cyclodextrins in Mechanomolecules. Symmetry 2019, 11, 1249–1271

Artificial Molecular Machines

Like the machines we encounter in everyday life, artificial molecular machines (AMMs) are nanoscale systems that consume energy to perform useful tasks. While AMMs are essential components of the photochromic smart tattoos (molecular switches) and slide-ring materials (molecular pulleys) we investigate, we are also interested in the fundamental science of AMMs. We aim to expand the library of synthons available for artificial molecular machinery by developing new structural motifs to control stimulus-responsive stereochemistry and dynamics.

Further Reading:

1. CJ Bruns. Moving Forward in Semantic Soup of Artificial Molecular Machine Taxonomy. Nature Nanotechnol. 2022, 17, 1231–1234.

2. H Kwon, B Newell, CJ Bruns. Redox-Switchable Host-Guest Complexes of Metallocenes and [8]Cycloparaphenylene. Nanoscale 2022, 14, 14276–14285.

3. H Kwon, CJ Bruns. All-Conjugated Cycloparaphenylene-Polycyclic Aromatic Hydrocarbon Host-Guest Complexes Stabilized by CH–π Interactions. Nano Research 2022, 15, 5545–5555.

Soft Shape-Shifters

Purnendu’s early work has employed HASEL (Hydraulically-Amplified Self-Healing ELectrostatic) actuators to create tangible interfaces for things like dynamic displays and haptic devices.

Further Reading:

1. Purnendu, J Hartcher-O’Brien, V Mehta, N Colonnese, A Gupta, CJ Bruns, P Agarwal.* Fingertip Wearable High Resolution Electro-Hydraulic Interface for Multi-modal Haptics. Technical Papers of the World Haptics Conference 2023. July 10–13, 2023.

2. Purnendu, S Novack, E Acome, M Alistar, C Keplinger, MD Gross, C Bruns, D Leithinger. Electriflow: Augmenting Books With Tangible Animation Using Soft Electrohydraulic Actuators SIGGRAPH ’21 Labs, August 09-13, 2021, Virtual, USA.

3. Purnendu, S Novack, E Acome, C Keplinger, M Alistar, MD Gross, C Bruns, D Leithinger. Electriflow: Soft Electrohydraulic Building Blocks for Prototyping Shape-changing Interfaces, In Designing Interactive Systems Conference 2021 (DIS ’21), June 28-July 2, 2021, Virtual Event. ACM, New York, NY, USA, 10 pages.

4. Purnendu, E Acome, C Keplinger, MD Gross, C Bruns, D Leithinger. Soft Electrohydraulic Actuators for Origami Inspired Shape-Changing Interfaces. In CHI Conference on Human Factors in Computing Systems Extended Abstracts (CHI '21 Extended Abstracts), May 8–13, 2021, Yokohama, Japan. ACM, New York, NY, USA, 6 pages.

Robochemistry

Robotics is the future of chemistry. Stay tuned for more info on our NSF-funded work on collaborative robochemists, automated lab helpers that make chemistry safer, faster, easier, and more fun!