digraph three_approaches {
  bgcolor="#1a1a2e"
  rankdir=TB
  node [fontname="Helvetica" fontsize=10 style=filled shape=box]
  edge [style=invis]

  label=<<B><FONT COLOR="#cccccc" POINT-SIZE="14">three approaches to hemp bioplastic</FONT></B>>
  labelloc=t

  subgraph cluster_a {
    label="A: CELLULOSE EXTRACTION\n(most documented)" fontcolor="#2196F3" fontsize=11 fontname="Helvetica Bold"
    color="#2196F3" style=dashed

    a1 [label="ret & decorticate stalks" fillcolor="#1565C0" fontcolor="white"]
    a2 [label="NaOH bath to dissolve lignin" fillcolor="#1976D2" fontcolor="white"]
    a3 [label="bleach & purify cellulose" fillcolor="#1E88E5" fontcolor="white"]
    a4 [label="mix with glycerol" fillcolor="#42A5F5" fontcolor="white"]
    a5 [label="hot press at 150°C" fillcolor="#64B5F6" fontcolor="#1a1a2e"]
    a_note [label="highest quality\nmost chemistry\n2-3 day process" fillcolor="#263238" fontcolor="#2196F3" shape=note]
    a1 -> a2 -> a3 -> a4 -> a5 -> a_note
  }

  subgraph cluster_b {
    label="B: FIBER + BIORESIN COMPOSITE\n(Robert Murray-Smith)" fontcolor="#4CAF50" fontsize=11 fontname="Helvetica Bold"
    color="#4CAF50" style=dashed

    b1 [label="prepare hemp fiber mat" fillcolor="#2E7D32" fontcolor="white"]
    b2 [label="make bioresin:\nseaweed + corn starch" fillcolor="#388E3C" fontcolor="white"]
    b3 [label="impregnate fiber with resin" fillcolor="#43A047" fontcolor="white"]
    b4 [label="dry at 150-200°C" fillcolor="#66BB6A" fontcolor="white"]
    b_note [label="simpler chemistry\ncomposite (not pure)\n1 day process" fillcolor="#263238" fontcolor="#4CAF50" shape=note]
    b1 -> b2 -> b3 -> b4 -> b_note
  }

  subgraph cluster_c {
    label="C: CITRIC ACID CROSSLINKING\n(Beluns et al. 2023)" fontcolor="#FF9800" fontsize=11 fontname="Helvetica Bold"
    color="#FF9800" style=dashed

    c1 [label="make hemp paper\nfrom chopped fiber" fillcolor="#E65100" fontcolor="white"]
    c2 [label="soak in glycerol +\ncitric acid solution" fillcolor="#F57C00" fontcolor="white"]
    c3 [label="cure at 140°C\nunder weight" fillcolor="#FF9800" fontcolor="white"]
    c_note [label="no NaOH needed\nsafest approach\nup to 70 MPa strength" fillcolor="#263238" fontcolor="#FF9800" shape=note]
    c1 -> c2 -> c3 -> c_note
  }
}
